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1
Liu, Congcong, Yuanfang Chai, Boyuan Zhu, Yunping Yang, Jinyun Deng, and Yong Hu. "River regulation and resilience: an approach for the Yangtze watershed." Water Supply 21, no. 4 (2021): 1817–33. http://dx.doi.org/10.2166/ws.2021.035.
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Abstract Many studies have focused on analyzing variation characteristics of the watershed resilience based on different indicators, while few efforts have been made to quantificationally evaluate contributions of climatic and anthropogenic factors to the varied resilience. In this study, we investigate changes in the seasonal runoff resilience of the entire Yangtze River basin during 1961–2014 by using a convex model and a resilience indicator (Pi). The MIKE 11HD model and the regression method were adopted to further differentiate effects of climate variations and human activities. Results show that climate variation (especially droughts and floods) and human activities exert negative and positive effects, respectively, and become primary reasons for falling and increasing trends in entire watershed resilience. These impacts grow with time under the gradually intensified climate variability and human activity. HIGHTLIGHTS Effects of climatic and anthropogenic factors on the varied watershed runoff resilience are quantificationally estimated. Investigating the changes in the watershed resilience in the entire Yangtze River.
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Ervinia, A., J. Huang, and Z. Zhang. "Land-use changes reinforce the impacts of climate change on annual runoff dynamics in a southeast China coastal watershed." Hydrology and Earth System Sciences Discussions 12, no. 6 (2015): 6305–25. http://dx.doi.org/10.5194/hessd-12-6305-2015.
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Abstract. Study on runoff dynamics across different physiographic regions is fundamentally important to formulate the sound strategies for water resource management especially in the coastal watershed where peoples heavily concentrated and relied on water resources. The L−R diagram, a conceptual model by which the land-changes evapotranspiration (ΔL) was estimated as the difference between actual and climate evapotranspiration to identify the specific impact of land-use changes on annual runoff changes (ΔR), was developed using the 53-year hydro-climatic data of Jiulong River Watershed, a typical medium-sized subtropical coastal watershed in China. This study found that land-use changes have reinforced the impact of climatic changes on runoff changes where nearly all points were scattered in II and IV quadrant. Deforestation and expansion of built up area has diminished the water retention capacity in a catchment as well as evapotranspiration thus produce extra runoff accounting for 12–183 % of total runoff increase. In contrast, reforestation makes the significant contribution to decreasing annual runoff for about 21–82 % of total runoff loss. This study revealed the river runoff has become more vulnerable to intensive anthropogenic disturbances under the context of climate changes in a coastal watershed.
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Gnjato, Slobodan, Tatjana Popov, Dragutin Adžić, Marko Ivanišević, Goran Trbić, and Davorin Bajić. "Influence of climate change on river discharges over the Sava River watershed in Bosnia and Herzegovina." Időjárás 125, no. 3 (2021): 449–62. http://dx.doi.org/10.28974/idojaras.2021.3.5.
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The paper examines changes in air temperature, precipitation, and river discharges on seasonal and annual scale over the Sava River watershed in Bosnia & Herzegovina during the period 1961–2016. Based upon data gathered from 11 meteorological stations and 3 hydrological stations, hydroclimatic variables trends were established by utilizing the nonparametric Mann-Kendall test and the nonparametric Sen’s slope estimator. The results show significant positive seasonal and annual trends (expect for autumn, during which upward trends were insignificant) in air temperature, whereas both positive and negative insignificant seasonal and annual precipitation trends are shown where determined for the entire watershed. Most prominent upward trends in air temperature were found in summer and afterwards in winter and spring, indicating a pronounced warming tendency over the Sava River watershed. Trends in river discharge displayed a negative tendency in all seasons. Nevertheless, a majority of estimated trends of river discharges were weak and statistically insignificant. Throughout the year, river discharges showed significant positive correlation with precipitation, whilst connection with air temperature was mostly significant and negative. The study results suggest that climate is an important factor affecting river regimes, as well as that changes in river discharges are reflecting recent abrupt changes in climatic variables.
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Bawden, Allison J., Donald H. Burn, and Terry D. Prowse. "Recent changes in patterns of western Canadian river flow and association with climatic drivers." Hydrology Research 46, no. 4 (2014): 551–65. http://dx.doi.org/10.2166/nh.2014.032.
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Climatic variability and change can have profound impacts on the hydrologic regime of a watershed, especially in regions that are sensitive to changes in climate, such as the northern latitudes and alpine-fed regions of western Canada. Quantifying historical spatial and temporal changes in hydrological data can provide useful information as to how water resources are affected by climatic and atmospheric forcings, as well as create an understanding of potential future variability. Trends in western Canadian runoff are examined for the period of 1976–2010. Regional patterns of spatial variability are quantified using a principal component analysis (PCA) that results in the identification of three hydrological regions. Both watershed-scale and PCA trend results show increased runoff in the northern-most watersheds, while decreased water availability has generally affected the mid-latitude basins. The southern watersheds show increases and decreases in runoff with no significant trends. Runoff is shown to be positively correlated with precipitation. Runoff in some regions of western Canada is shown to be influenced by the Pacific Decadal Oscillation and Pacific North American (PNA) modes of atmospheric variability. The results of this analysis provide water managers with an indication of the direction and magnitude of changing water availability in western Canada.
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Gao, Yuqin, Zichen Guo, Dongdong Wang, Zhenxing Zhang, and Yunping Liu. "Multivariate Flood Risk Analysis at a Watershed Scale Considering Climatic Factors." Water 10, no. 12 (2018): 1821. http://dx.doi.org/10.3390/w10121821.
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Based on the constructed SWAT model in the Qinhuai River Basin, the hydrological response of flooding under different scenarios of temperature and rainfall change is analyzed. The Copula function is then used to calculate and analyze the multivariate flood risk. The results show that the flood peaks increase with the increase of precipitation and decrease with the increase of temperature. The hydrological response of light floods to temperature changes is stronger than that of medium and heavy floods. Additionally, the temperature drop and the precipitation increase lead to a higher flood risk. The flood risk of flood peaks is more sensitive to changes in precipitation.
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Pandey, Vishnu Prasad, Dibesh Shrestha, Mina Adhikari, and Shristi Shakya. "Streamflow Alterations, Attributions, and Implications in Extended East Rapti Watershed, Central-Southern Nepal." Sustainability 12, no. 9 (2020): 3829. http://dx.doi.org/10.3390/su12093829.
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Streamflow alteration and subsequent change in long-term average, seasonality, and extremes (e.g., floods and droughts) may affect water security, which is a major concern in many watersheds across the globe. Both climatic and anthropogenic activities may contribute to such changes. Therefore, this study assesses: (i) Streamflow and precipitation trends to identify streamflow alterations in the Extended East Rapti (EER) watershed in central-southern Nepal; (ii) relationship of the alterations to climatic and anthropogenic sources; and (iii) implications of streamflow changes to the socio-environmental system. The trends in streamflow were analyzed for pre-and post-1990 periods considering the abrupt shift in temperature trend in 1990. Results showed a general decreasing trends in discharge post-1990 in the EER watershed. Human activities have significantly contributed in altering streamflow in the EER. Human-induced streamflow alterations have affected the water availability, food security, river health, aquatic biodiversity, and groundwater abstraction in the EER watershed.
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Kalu, Ikechukwu, Christopher E. Ndehedehe, Onuwa Okwuashi, and Aniekan E. Eyoh. "Assessing Freshwater Changes over Southern and Central Africa (2002–2017)." Remote Sensing 13, no. 13 (2021): 2543. http://dx.doi.org/10.3390/rs13132543.
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In large freshwater river basins across the globe, the composite influences of large-scale climatic processes and human activities (e.g., deforestation) on hydrological processes have been studied. However, the knowledge of these processes in this era of the Anthropocene in the understudied hydrologically pristine South Central African (SCA) region is limited. This study employs satellite observations of evapotranspiration (ET), precipitation and freshwater between 2002 and 2017 to explore the hydrological patterns of this region, which play a crucial role in global climatology. Multivariate methods, including the rotated principal component analysis (rPCA) were used to assess the relationship of terrestrial water storage (TWS) in response to climatic units (precipitation and ET). The use of the rPCA technique in assessing changes in TWS is warranted to provide more information on hydrological changes that are usually obscured by other dominant naturally-driven fluxes. Results show a low trend in vegetation transpiration due to deforestation around the Congo basin. Overall, the Congo (r2 = 76%) and Orange (r2 = 72%) River basins maintained an above-average consistency between precipitation and TWS throughout the study region and period. Consistent loss in freshwater is observed in the Zambezi (−9.9 ± 2.6 mm/year) and Okavango (−9.1 ± 2.5 mm/year) basins from 2002 to 2008. The Limpopo River basin is observed to have a 6% below average reduction in rainfall rates which contributed to its consistent loss in freshwater (−4.6 ± 3.2 mm/year) from 2006 to 2012.Using multi-linear regression and correlation analysis we show that ET contributes to the variability and distribution of TWS in the region. The relationship of ET with TWS (r = 0.5) and rainfall (r = 0.8) over SCA provides insight into the role of ET in regulating fluxes and the mechanisms that drive precipitation in the region. The moderate ET–TWS relationship also shows the effect of climate and anthropogenic influence in their interactions.
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Talib, Ammara, and Timothy O. Randhir. "Climate change and land use impacts on hydrologic processes of watershed systems." Journal of Water and Climate Change 8, no. 3 (2017): 363–74. http://dx.doi.org/10.2166/wcc.2017.064.
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Land use, land cover and climate change (CC) can significantly influence the hydrologic balance and biogeochemical processes of watershed systems. These changes can alter interception, evapotranspiration (ET), infiltration, soil moisture, water balance, and biogeochemical cycling of carbon, nitrogen, and other elements. The need to evaluate the combined effect of land use change and CC of watershed systems is a focus of this study. We simulated watershed processes in the SuAsCo River watershed in MA, USA, using a calibrated and validated Hydrological Simulation Program Fortran model. Climatic scenarios included downscaled regional projections from Global Climate Model models. The Land Transformation Model was used to project land use. Combined change in land cover and climate reduce ET with loss of vegetation. Changes in climate and land cover increase surface runoff significantly by 2100 as well as stream discharge. Combined change in land cover and climate cause 10% increase in peak volume with 7% increase in precipitation and 75% increase in effective impervious area. Climate and land use changes can intensify the water cycle and introduce seasonal changes in watershed systems. Understanding dynamic changes in watershed systems is critical for mitigation and adaptation options. We propose restoration strategies that can increase the resilience of watershed systems.
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Trammell, Jamie, Meagan Krupa, Paula Williams, and Andrew Kliskey. "Using Comprehensive Scenarios to Identify Social–Ecological Threats to Salmon in the Kenai River Watershed, Alaska." Sustainability 13, no. 10 (2021): 5490. http://dx.doi.org/10.3390/su13105490.
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Environmental changes caused by climate change in Alaska pose a serious threat to the food, energy and water systems that support the culturally diverse communities statewide. The fishing industry, watershed managers and other stakeholders struggle with understanding and predicting the rates, magnitude and location of changes occurring in their regions primarily because of the significant range of uncertainty inherent in these changes. With the guidance of stakeholders, we demonstrate a scenario analysis methodology to elucidate the interactions among various components and uncertainties within the food, energy and water systems of the Kenai River Watershed. Alternative scenario analysis provided stakeholders with a venue and process to consider plausible futures in which rates of change in critical uncertainties were modeled to elucidate potential responses. Critical uncertainties ranged from climatic impacts on freshwater systems, to new energy development proposals, to changes in sport and personal use fisheries. Working together, stakeholders developed narratives that reflected different combinations of future uncertainty to guide potential management actions now and in the future. Five scenarios were developed by stakeholders that capture the complex interactions in the Kenai River Watershed as a social–ecological system. This process provides a way for managers and stakeholders to plan for the future in a richer way than extrapolating trends for obvious drivers of change. We present this framework as a platform for integrating climate, landscape and cultural change data into actionable decisions, crafted by stakeholders, to improve future food, energy and water resource management at the watershed scale.
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Tamrakar, Naresh Kazi, and Ramita Bajracharya. "Basinal and planform characteristics of the Kodku and the Godavari Rivers, Kathmandu, Central Nepal." Bulletin of the Department of Geology 15 (January 21, 2013): 15–22. http://dx.doi.org/10.3126/bdg.v15i0.7414.
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The rivers of the Kathmandu Basin are vulnerable to flash floods and disturbances caused by anthropogenic as well as climatic changes. Two southern tributaries of the Bagmati River: the Kodku and the Godavari Rivers, have been considered for their (i) watershed-scale geomorphic parameters such as relative relief, drainage texture and stream order, (ii) stretchscale planform parameters such as sinuosity (K), meander belt width (Wblt), meander wavelength (Lm) and radius of curvature (Rc), and (ii) longitudinal profiles and slopes. Both Kodku and the Godavari Rivers are elongate basins with wide ranges of the watershed-scale parameters. The Godavari River is longer, larger and more sinuous compared to the Kodku River. The development of the patterns of the fifth order main stem stretches of both rivers with respect to the stream slopes, and asymmetric patterns of the meander loops indicate anomalous growth of the river stretches. DOI: http://dx.doi.org/10.3126/bdg.v15i0.7414 Bulletin of the Department of Geology, Vol. 15, 2012, pp. 15-22
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Mentzafou, Angeliki, George Varlas, Elias Dimitriou, Anastasios Papadopoulos, Ioannis Pytharoulis, and Petros Katsafados. "Modeling the Effects of Anthropogenic Land Cover Changes to the Main Hydrometeorological Factors in a Regional Watershed, Central Greece." Climate 7, no. 11 (2019): 129. http://dx.doi.org/10.3390/cli7110129.
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In this study, the physically-based hydrological model MIKE SHE was employed to investigate the effects of anthropogenic land cover changes to the hydrological cycle components of a regional watershed in Central Greece. Three case studies based on the land cover of the years 1960, 1990, and 2018 were examined. Copernicus Climate Change Service E-OBS gridded meteorological data for 45 hydrological years were used as forcing for the model. Evaluation against observational data yielded sufficient quality for daily air temperature and precipitation. Simulation results demonstrated that the climatic variabilities primarily in precipitation and secondarily in air temperature affected basin-averaged annual actual evapotranspiration and average annual river discharge. Nevertheless, land cover effects can locally outflank the impact of climatic variability as indicated by the low interannual variabilities of differences in annual actual evapotranspiration among case studies. The transition from forest to pastures or agricultural land reduced annual actual evapotranspiration and increased average annual river discharge while intensifying the vulnerability to hydrometeorological-related hazards such as droughts or floods. Hence, the quantitative assessment of land cover effects presented in this study can contribute to the design and implementation of successful land cover and climate change mitigation and adaptation policies.
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Chi, Kaige, Bo Pang, Lizhuang Cui, et al. "Modelling the Vegetation Response to Climate Changes in the Yarlung Zangbo River Basin Using Random Forest." Water 12, no. 5 (2020): 1433. http://dx.doi.org/10.3390/w12051433.
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Vegetation coverage variation may influence watershed water balance and water resource availability. Yarlung Zangbo River, the longest river on the Tibetan Plateau, has high spatial heterogeneity in vegetation coverage and is the main freshwater resource of local residents and downstream countries. In this study, we proposed a model based on random forest (RF) to predict the Normalized Difference Vegetation Index (NDVI) of the Yarlung Zangbo River Basin and explore its relationship with climatic factors. High-resolution datasets of NDVI and monthly meteorological observation data from 2000 to 2015 were used to calibrate and validate the proposed model. The proposed model was then compared with artificial neural network and support vector machine models, and principal component analysis and partial correlation analysis were also used for predictor selection of artificial neural network and support vector machine models for comparative study. The results show that RF had the highest model efficiency among the compared models. The Nash–Sutcliffe coefficients of the proposed model in the calibration period and verification period were all higher than 0.8 for the five subzones; this indicated that the proposed model can successfully simulate the relationship between the NDVI and climatic factors. By using built-in variable importance evaluation, RF chose appropriate predictor combinations without principle component analysis or partial correlation analysis. Our research is valuable because it can be integrated into water resource management and elucidates ecological processes in Yarlung Zangbo River Basin.
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Dibike, Yonas B., Rajesh R. Shrestha, Colin Johnson, Barrie Bonsal, and Paulin Coulibaly. "Assessing Climatic Drivers of Spring Mean and Annual Maximum Flows in Western Canadian River Basins." Water 13, no. 12 (2021): 1617. http://dx.doi.org/10.3390/w13121617.
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Flows originating from cold and mountainous watersheds are highly dependent on temperature and precipitation patterns, and the resulting snow accumulation and melt conditions, affecting the magnitude and timing of annual peak flows. This study applied a multiple linear regression (MLR) modelling framework to investigate spatial variations and relative importance of hydroclimatic drivers of annual maximum flows (AMF) and mean spring flows (MAMJflow) in 25 river basins across western Canada. The results show that basin average maximum snow water equivalent (SWEmax), April 1st SWE and spring precipitation (MAMJprc) are the most important predictors of both AMF and MAMJflow, with the proportion of explained variance averaging 51.7%, 44.0% and 33.5%, respectively. The MLR models’ abilities to project future changes in AMF and MAMJflow in response to changes to the hydroclimatic controls are also examined using the Canadian Regional Climate Model (CanRCM4) output for RCP 4.5 and RCP8.5 scenarios. The results show considerable spatial variations depending on individual watershed characteristics with projected changes in AMF ranging from −69% to +126% and those of MAMJflow ranging from −48% to +81% by the end of this century. In general, the study demonstrates that the MLR framework is a useful approach for assessing the spatial variation in hydroclimatic controls of annual maximum and mean spring flows in the western Canadian river basins. However, there is a need to exercise caution in applying MLR models for projecting changes in future flows, especially for regulated basins.
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Sun, Rui, Xueqin Zhang, Yang Sun, Du Zheng, and Klaus Fraedrich. "SWAT-Based Streamflow Estimation and Its Responses to Climate Change in the Kadongjia River Watershed, Southern Tibet." Journal of Hydrometeorology 14, no. 5 (2013): 1571–86. http://dx.doi.org/10.1175/jhm-d-12-0159.1.
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Abstract Runoff estimation and its response to climate change in ungauged or poorly gauged basins based on hydrological models are frontier research issues of the hydrological cycle. For the Kadongjia River watershed (KRW), a poorly gauged watershed located in southern Tibet, China, the Soil and Water Assessment Tool (SWAT) was adapted to model streamflow and its responses to climate change. The average annual streamflow was simulated to be roughly 124.6 mm with relatively small interannual variation during 1974–2010. The seasonal distribution of streamflow was uneven with a maximum in summer and a minimum in winter. Snowmelt, which was mainly produced in April–May, accounted for 4.0% of annual streamflow. Correlations and regression analysis between the interannual variations of major climatic and hydrological variables indicated that precipitation (temperature) had positive (negative) influence on the annual streamflow variation. For the interannual streamflow variations, warmer temperature was slightly more important than the variation of winter precipitation. Comparing streamflow changes in the current years (1980–99) with the future (2030–49), streamflow variations were more sensitive to changing climate in winter and spring than in the other two seasons. Model improvement is expected to enhance the simulation efficiency of SWAT and the analyses of hydrological responses to climatic change in KRW, thus supporting the model's credibility for hydrological cycle research in alpine regions.
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Soum, Savoeurn, Peng Bun Ngor, Thomas E. Dilts, et al. "Spatial and Long-Term Temporal Changes in Water Quality Dynamics of the Tonle Sap Ecosystem." Water 13, no. 15 (2021): 2059. http://dx.doi.org/10.3390/w13152059.
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Tonle Sap lake-river floodplain ecosystem (TSE) is one of the world’s most productive freshwater systems. Changes in hydrology, climate, population density, and land use influence water quality in this system. We investigated long term water quality dynamics (22 years) in space and time and identified potential changes in nutrient limitation based on nutrient ratios of inorganic nitrogen and phosphorus. Water quality was assessed at five sites highlighting the dynamics in wet and dry seasons. Predictors of water quality included watershed land use, climate, population, and water level. Most water quality parameters varied across TSE, except pH and nitrate that remained constant at all sites. In the last decade, there is a change in the chemical nutrient ratio suggesting that nitrogen may be the primary limiting nutrient across the system. Water quality was strongly affected by development in the watershed i.e., flooded forest loss, climatic variation, population growth, and change in water level. Seasonal variations of water quality constituents were driven by precipitation and hydrology, notably the Mekong’s distinct seasonal flood pulse.
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Giles-Hansen, Krysta, Qiang Li, and Xiaohua Wei. "The Cumulative Effects of Forest Disturbance and Climate Variability on Streamflow in the Deadman River Watershed." Forests 10, no. 2 (2019): 196. http://dx.doi.org/10.3390/f10020196.
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Climatic variability and cumulative forest cover change are the two dominant factors affecting hydrological variability in forested watersheds. Separating the relative effects of each factor on streamflow is gaining increasing attention. This study adds to the body of literature by quantifying the relative contributions of those two drivers to the changes in annual mean flow, low flow, and high flow in a large forested snow dominated watershed, the Deadman River watershed (878 km2) in the Southern Interior of British Columbia, Canada. Over the study period of 1962 to 2012, the cumulative effects of forest disturbance significantly affected the annual mean streamflow. The effects became statistically significant in 1989 at the cumulative forest disturbance level of 12.4% of the watershed area. The modified double mass curve and sensitivity-based methods consistently revealed that forest disturbance and climate variability both increased annual mean streamflow during the disturbance period (1989–2012), with an average increment of 14 mm and 6 mm, respectively. The paired-year approach was used to further investigate the relative contributions to low and high flows. Our analysis showed that low and high flow increased significantly by 19% and 58%, respectively over the disturbance period (p < 0.05). We conclude that forest disturbance and climate variability have significantly increased annual mean flow, low flow and high flow over the last 50 years in a cumulative and additive manner in the Deadman River watershed.
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Fang, Gonghuan, Jing Yang, Yaning Chen, et al. "Climate Change Impact on the Hydrology of a Typical Watershed in the Tianshan Mountains." Advances in Meteorology 2015 (2015): 1–10. http://dx.doi.org/10.1155/2015/960471.
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To study the impact of future climatic changes on hydrology in the Kaidu River Basin in the Tianshan Mountains, two sets of future climatic data were used to force a well-calibrated hydrologic model: one is bias-corrected regional climate model (RCM) outputs for RCP4.5 and RCP8.5 future emission scenarios, and the other is simple climate change (SCC) with absolute temperature change of −1~6°C and relative precipitation change of −20%~60%. Results show the following: (1) temperature is likely to increase by 2.2°C and 4.6°C by the end of the 21st century under RCP4.5 and RCP8.5, respectively, while precipitation will increase by 2%~24%, with a significant rise in the dry season and small change in the wet season; (2) flow will change by −1%~20%, while evapotranspiration will increase by 2%~24%; (3) flow increases almost linearly with precipitation, while its response to temperature depends on the magnitude of temperature change and flow decrease is significant when temperature increase is greater than 2°C; (4) similar results were obtained for simulations with RCM outputs and with SCC for mild climate change conditions, while results were significantly different for intense climate change conditions.
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Thienpont, Joshua R., Brian K. Ginn, Brian F. Cumming, and John P. Smol. "An Assessment of Environmental Changes in Three Lakes from King's County (Nova Scotia, Canada) Using Diatom-Based Paleolimnological Techniques." Water Quality Research Journal 43, no. 2-3 (2008): 85–98. http://dx.doi.org/10.2166/wqrj.2008.012.
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Abstract Paleolimnological approaches using sedimentary diatom assemblages were used to assess water quality changes over the last approximately 200 years in three lakes from King's County, Nova Scotia. In particular, the role of recent shoreline development in accelerating eutrophication in these systems was assessed. Sediment cores collected from each lake were analyzed for their diatom assemblages at approximately 5-year intervals, as determined by 210Pb dating. Analyses showed that each system has changed, but tracked different ecosystem changes. Tupper and George lakes recorded shifts, which are likely primarily related to climatic warming, with diatom assemblages changing from a preindustrial dominance by Aulacoseira spp. to present-day dominance by Cyclotella stelligera. In addition to the recent climatic-related changes, further diatom changes in the Tupper Lake core between approximately 1820 and 1970 were coincident with watershed disturbances (farming, forestry, and construction of hydroelectric power infrastructure). Black River Lake has recorded an increase in diatom-inferred total phosphorus since about 1950, likely due to impoundment of the Black River system for hydroelectric generation and subsequent changes in land runoff. Before-and-after (i.e., top-bottom) sediment analyses of six other lakes from King's County provided further evidence that the region is being influenced by climatic change (decreases in Aulacoseira spp., increases in planktonic diatom taxa), as well as showing other environmental stressors (e.g., acidification). However, we recorded no marked increase in diatom-inferred nutrient levels coincident with shoreline cottage development in any of the nine study lakes. Paleolimnological studies such as these allow lake managers to place the current limnological conditions into a long-term context, and thereby provide important background data for effective lake management.
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Krajewski, Adam, Anna Sikorska-Senoner, Roberto Ranzi, and Kazimierz Banasik. "Long-Term Changes of Hydrological Variables in a Small Lowland Watershed in Central Poland." Water 11, no. 3 (2019): 564. http://dx.doi.org/10.3390/w11030564.
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Climate-induced changes in small watersheds are still not well researched because long-term datasets are usually missing for these watersheds. Such studies can, however, improve our understanding of the watershed response to climatic changes at such a small scale being transparent. In this study, we investigate trends in temperature, precipitation and river-flow characteristics in a small watershed, typical for Central Poland, with 53 years of observations (1963–2015) using the Mann-Kendall test. Particularly, we examine whether any trends in hydro-meteorological variables can be identified, and if any associated changes in water resources in this region can already be observed. We found that this short period already allows for detecting some changes in hydro-meteorological variables. These changes could be characterized by a significant increase in the mean annual air temperature on a daily basis, and a significant decrease in the mean annual discharge on a daily basis and in the minimum annual discharge on a daily basis. Yet, no significant trend could be detected for the total annual precipitation, the maximum summer rainfall, and the maximum annual discharge on a daily basis. These findings indicate that water resources are decreasing in this region, which affects natural habitats, agriculture and local communities.
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Zhan, Yunjun, Jiemeng Fan, Tingting Meng, et al. "Analysis on vegetation cover changes and the driving factors in the mid-lower reaches of Hanjiang River Basin between 2001 and 2015." Open Geosciences 13, no. 1 (2021): 675–89. http://dx.doi.org/10.1515/geo-2020-0259.
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Abstract The mid-lower reaches of the Hanjiang River Basin, located in the core of economic development in Hubei Province, is an integral part of the Yangtze River Economic Belt. In recent years, the watershed ecosystem has become more sensitive to climate changes and human activities, thus affecting the regional vegetation cover. To maintain a stable watershed ecosystem, it is critical to analyze and evaluate the vegetation change and its response to temperature, precipitation, and human activities in this region. This study, based on the trend analysis, partial correlation analysis, and residual analysis, evaluated the change characteristics of vegetation cover as well as the corresponding driving factors in the basin from 2001 to 2015. The results showed that (1) the overall spatial pattern of vegetation cover in the study area was “high in the west and north, lower on both sides of Hanjiang River, and lowest in the center and southeast,” and the pattern changed parabolically with the increasing elevation. (2) Over the 15 years, vegetation cover in the basin showed an increasing trend, and the increased and decreased areas were 90.72 and 9.23%, respectively. (3) The response of vegetation cover to climatic factors varies greatly depending on the increasing elevation. That is, the lag effect under the impact of temperature disappeared gradually, while it became more evident under the impact of precipitation. (4) On the whole, human activities had a positive effect on the regional vegetation cover. The negative effect in the areas around the Nanyang Basin and the positive effect in most parts of the Jianghan Plain were gradually decreased.
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Tian, Lei, Jiming Jin, Pute Wu, and Guo-yue Niu. "Quantifying the Impact of Climate Change and Human Activities on Streamflow in a Semi-Arid Watershed with the Budyko Equation Incorporating Dynamic Vegetation Information." Water 10, no. 12 (2018): 1781. http://dx.doi.org/10.3390/w10121781.
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Understanding hydrological responses to climate change and land use and land cover change (LULCC) is important for water resource planning and management, especially for water-limited areas. The annual streamflow of the Wuding River Watershed (WRW), the largest sediment source of the Yellow River in China, has decreased significantly over the past 50 years at a rate of 5.2 mm/decade. Using the Budyko equation, this study investigated this decrease with the contributions from climate change and LULCC caused by human activities, which have intensified since 1999 due to China’s Grain for Green Project (GFGP). The Budyko parameter that represents watershed characteristics was more reasonably configured and derived to improve the performance of the Budyko equation. Vegetation changes were included in the Budyko equation to further improve its simulations, and these changes showed a significant upward trend due to the GFGP based on satellite data. An improved decomposition method based on the Budyko equation was used to quantitatively separate the impact of climate change from that of LULCC on the streamflow in the WRW. Our results show that climate change generated a dominant effect on the streamflow and decreased it by 72.4% in the WRW. This climatic effect can be further explained with the drying trend of the Palmer Severity Drought Index, which was calculated based only on climate change information for the WRW. In the meantime, although human activities in this watershed have been very intense, especially since 1999, vegetation cover increase contributed a 27.6% decline to the streamflow, which played a secondary role in affecting hydrological processes in the WRW.
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Legesse, D., T. A. Abiye, C. Vallet-Coulomb, and H. Abate. "Streamflow sensitivity to climate and land cover changes: Meki River, Ethiopia." Hydrology and Earth System Sciences 14, no. 11 (2010): 2277–87. http://dx.doi.org/10.5194/hess-14-2277-2010.
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Abstract. Impacts of climate and land cover changes on streamflow were assessed using a hydrological modeling. The precipitation runoff modeling system of the US Geological Survey was modified in order to consider wetlands as a separate hydrological response unit. Initial model parameters were obtained from a previously modeled adjacent catchment and subsequent calibration and validation were carried out. The model calibration and validation periods were divided into three. The calibration period was a five years period (1981–1986). The validation period was divided into two: validation 1 (1986–1991) and validation 2 (1996–2002). Model performance was evaluated by using joint plots of daily and monthly observed and simulated runoff hydrographs and different coefficients of efficiency. The model coefficients of efficiency were 0.71 for the calibration period and 0.69 and 0.66 for validation periods 1 and 2, respectively. A "delta-change" method was used to formulate climatic scenarios. One land cover change scenario was also used to assess the likely impacts of these changes on the runoff. The results of the scenario analysis showed that the basin is more sensitive to increase in rainfall (+80% for +20%) than to a decrease (−62% for −20%). The rainfall elasticity is 4:1 for a 20% increase in rainfall while it is 3:1 for a 20% reduction. A 1.5°c increase in temperature resulted in a 6% increase in potential evapotranspiration and 13% decrease in streamflow. This indicates that the watershed is more elastic to rainfall increase than temperature. The proposed land cover scenario of converting areas between 2000 to 3000 m a.s.l. to woodland also resulted in a significant decrease in streamflow (11.8%). The study showed that properly calibrated and validated models could help understand likely impacts of climate and land cover changes on catchment water balance.
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Rottler, Erwin, Till Francke, Gerd Bürger, and Axel Bronstert. "Long-term changes in central European river discharge for 1869–2016: impact of changing snow covers, reservoir constructions and an intensified hydrological cycle." Hydrology and Earth System Sciences 24, no. 4 (2020): 1721–40. http://dx.doi.org/10.5194/hess-24-1721-2020.
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Abstract. Recent climatic changes have the potential to severely alter river runoff, particularly in snow-dominated river basins. Effects of changing snow covers superimpose with changes in precipitation and anthropogenic modifications of the watershed and river network. In the attempt to identify and disentangle long-term effects of different mechanisms, we employ a set of analytical tools to extract long-term changes in river runoff at high resolution. We combine quantile sampling with moving average trend statistics and empirical mode decomposition and apply these tools to discharge data recorded along rivers with nival, pluvial and mixed flow regimes as well as temperature and precipitation data covering the time frame 1869–2016. With a focus on central Europe, we analyse the long-term impact of snow cover and precipitation changes along with their interaction with reservoir constructions. Our results show that runoff seasonality of snow-dominated rivers decreases. Runoff increases in winter and spring, while discharge decreases in summer and at the beginning of autumn. We attribute this redistribution of annual flow mainly to reservoir constructions in the Alpine ridge. During the course of the last century, large fractions of the Alpine rivers were dammed to produce hydropower. In recent decades, runoff changes induced by reservoir constructions seem to overlap with changes in snow cover. We suggest that Alpine signals propagate downstream and affect runoff far outside the Alpine area in river segments with mixed flow regimes. Furthermore, our results hint at more (intense) rainfall in recent decades. Detected increases in high discharge can be traced back to corresponding changes in precipitation.
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Dahal, Ngamindra, Uttam Shrestha, Anita Tuitui, and Hemant Ojha. "Temporal Changes in Precipitation and Temperature and their Implications on the Streamflow of Rosi River, Central Nepal." Climate 7, no. 1 (2018): 3. http://dx.doi.org/10.3390/cli7010003.
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Nepal has experienced recent changes in two crucial climatic variables: temperature and precipitation. Therefore, climate-induced water security concerns have now become more pronounced in Nepal as changes in temperature and precipitation have already altered some hydrological processes such as the river runoff in some river systems. However, the linkage between precipitation patterns and streamflow characteristics are poorly understood, especially in small rivers. We analysed the temporal trends of temperature, precipitation, and extreme indices of wet and dry spells in the Rosi watershed in Central Nepal, and observed the temporal patterns of the streamflow of the Rosi river. We also examined the linkages between the average and extreme climate indices and streamflow. We found that the area has warmed up by an average of 0.03 °C/year, and has seen a significant decline in precipitation. The dry spell as represented by the maximum length of the dry spell (CDD) and the magnitude of dryness (AII) has become more pronounced, while the wet spell as represented by the number of heavy rainfall days (R5D) and the precipitation intensity on wet days (SDII) has diminished significantly. Our analysis shows that recent changes in precipitation patterns have affected the streamflow of the Rosi river, as manifested in the observed decline in annual and seasonal streamflows. The decrease in the availability of water in the river is likely to have severe consequences for water security in the area.
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Russell, Hazen A. J., Robert W. C. Arnott, and David R. Sharpe. "Stratigraphic Architecture and Sediment Facies of the Western Oak Ridges Moraine, Humber River Watershed, Southern Ontario*." Glacial History 58, no. 2-3 (2006): 241–67. http://dx.doi.org/10.7202/013141ar.
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Abstract The Oak Ridges Moraine in southern Ontario is a ca. 160 km long east-west trending ridge of sand and gravel situated north of Lake Ontario. Study of the Oak Ridges Moraine in the Humber River watershed was undertaken to assess its role in the groundwater system of the buried Laurentian Valley. The Oak Ridges Moraine is interpreted to have been deposited in three stages. Stage I records rapid deposition from hyperconcentrated flows where tunnel channels discharged into a subglacial lake in the Lake Ontario basin. Low-energy basin sedimentation of Stage II was in a subglacial and ice-contact setting of a highly crevassed ice sheet. Stage III sedimentation is characterized by rapid facies changes associated with esker, subaqueous fan, and basinal sedimentation. Detailed sediment analysis challenges the concept that the Oak Ridges Moraine was deposited principally from seasonal meltwater discharges, climatic modulated ice-marginal fluctuations, or in an interlobate position. Instead it is interpreted to have formed in response to late-glacial ice sheet events associated with subglacial meltwater ponding, episodic and catastrophic subglacial meltwater discharge, and subsequent seasonal meltwater discharge. The moraine probably formed as the glacial-hydraulic system re-equilibrated to the presence of a thinned, grounded ice shelf and a subglacial lake in the Lake Ontario basin.
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Makhtoumi, Yashar, Simeng Li, Victor Ibeanusi, and Gang Chen. "Evaluating Water Balance Variables under Land Use and Climate Projections in the Upper Choctawhatchee River Watershed, in Southeast US." Water 12, no. 8 (2020): 2205. http://dx.doi.org/10.3390/w12082205.
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Changes in water balance variables are essential in planning and management. Two major factors affecting these variables are climate change and land use change. Few researches have been done to investigate the combined effect of the land use change and climate change using projections. In this study the hydrological processes in Upper Choctawhatchee River Watershed were modeled using the Soil and Water Assessment Tool (SWAT) to investigate the impacts of climate and land use change. We integrated land use projection based in the Shared Socioeconomic Pathways with future climate data to study the combined effects on Hydrological response of the watershed. Future rainfall and temperature, for two time periods, were obtained using General Climate Models to provide SWAT with the climatic forcing in order to project water balance variables. The simulation was carried out under two radiative forcing pathways of RCP4.5 and RCP6.0. Land use change focused on urbanization dominated the climate changes. Impacts on water balance variables differed seasonally. Results showed surface runoff experienced major changes under both emissions scenarios in some months up to 5 times increase. Among the water balance variables, evapotranspiration (ET) as the least dominant pathway for water loss showed the modest changes with the largest decrease during fall and summer. Projection indicated more frequent extreme behavior regarding water balance during midcentury. Discharge was estimated to increase through the year and the highest changes were projected during summer and fall with 186.3% increase in November under RCP6.0. Relying on rainfall for farming along with reduced agricultural landuse (11.8%) and increased urban area (47%) and population growth would likely make the water use efficiency critical. The model demonstrated satisfactory performance, capturing the hydrologic parameters. It thus can be used for further modelling of water quality to determine the sustainable conservation practices and extreme weather events such as hurricane and tropical storms.
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Peng, Huanhua, Haonan Xia, Hao Chen, Panding Zhi, and Zhonglin Xu. "Spatial variation characteristics of vegetation phenology and its influencing factors in the subtropical monsoon climate region of southern China." PLOS ONE 16, no. 4 (2021): e0250825. http://dx.doi.org/10.1371/journal.pone.0250825.
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Understanding the response mechanism of ecosystems to climate change and human disturbance can be improved by analyzing the spatial patterns of vegetation phenology and its influencing factors. Because the diverse phenological patterns are impacted by cloud cover contamination issues in the satellite observations, there are few remote sensing phenological research data in subtropical monsoon climate regions. To better understand the horizontal and vertical changes of vegetation phenology in these regions and how it may be affected by climatic factors and topographical features, we first extracted vegetation phenological information (such as start of growth season (SOS), end of growth season (EOS) and length of growth season (LEN)) from a reconstructed MODIS EVI time-series data. We then used geographic detectors to identify the influencing factors of phenology in different elevation zoning areas. We have found that in the Xiangjiang River Basin: 1) gradual changes in the longitudinal or latitudinal gradient of vegetation phenology were not obvious. Instead of horizontal changes, the variation pattern of phenology was similar to the striped river network of the Xiangjiang River. Earlier SOS mainly appeared in the areas far away from the river; later SOS appeared in the midstream and downstream reaches.2) Elevation played an important role in the regional differentiation of phenology. Boundaries at elevations of 320 m and 520 m distinctly separated the region into plain, hilly, and mountain vegetation phenological characteristics. 3) The impacts of climatic factors were quite different in the three vertical zoning areas. Precipitation was the most crucial factor affecting SOS both in plain and mountain areas. There was no significant factor affecting EOS in the plain area, but temperature had an essential effect on EOS in the mountain area. The hilly areas had a concentrated growth period with no significant factors affecting phenology. These findings highlight the importance of elevation in phenology at a watershed scale, enhance our understanding of the impact of climate changes on subtropical ecosystems, and provide a reference for further land-use change monitoring.
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Zhao, Liang, Yu Liu, and Yong Luo. "Assessing Hydrological Connectivity Mitigated by Reservoirs, Vegetation Cover, and Climate in Yan River Watershed on the Loess Plateau, China: The Network Approach." Water 12, no. 6 (2020): 1742. http://dx.doi.org/10.3390/w12061742.
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Hydrologic connectivity is related to the water-mediated transport of matter, energy, and organisms within or between elements of the hydrologic cycle. It reflects the hydrological consequences caused by topographic, land cover, and climatic factors, and is an important tool to characterize and predict the hydrological responses to climate and landscape change. In the Loess Plateau region, a large number of reservoirs have been constructed to trap sediment and storage water for drinking, irrigation, and industries. The land cover has been significantly reshaped in the past decades. These changes may alter the watershed hydrological connectivity. In this study, we mapped the spatial pattern of hydrological connectivity with consideration of reservoir impedances, mitigation of climate, and land cover in the Yan River watershed on the Loess Plateau by using the network index (NI) approach that is based on topographical wetness index. Three wetness indices were used, i.e., topographical wetness index (TWI), SAGA (System for Automated Geoscientific Analyses) wetness index (WIS), and wetness index adopted aridity index (AI) determined by precipitation and evapotranspiration (WIPE). In addition, the effective catchment area (ECA) was also employed to reveal the connectivity of reservoirs and river networks to water source areas. Results show that ECA of reservoirs and rivers account for 35% and 65%, respectively; the hydrological connectivity to the reservoir was lower than that to the river networks. The normalized hydrological connectivity revealed that the connectivity to river channels maintained the same distribution pattern but with a decreased range after construction of reservoirs. As revealed by comparing the spatial patterns of hydrological connectivity quantified by NI based on WIS and WIPE respectively, vegetation cover patterns had significantly alternated watershed hydrological connectivity. These results imply a decreased volume of flow in river channels after reservoir construction, but with same temporal period of flow dynamic. It is illustrated that the network index (NI) is suitable to quantify the hydrological connectivity and it is dynamic in the context of human intervention and climate change.
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Sokolova, Galina, Andrei Verkhoturov, and Hiroshi Hayasaka. "Hydrological consequences of changes forest cover on watersheds of the Amur river basin." E3S Web of Conferences 192 (2020): 04011. http://dx.doi.org/10.1051/e3sconf/202019204011.
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Observing the geographic environment change of watersheds is very important for understanding problem of influence on streamflow, which ranks fourth out of 23 hydrological problems highlighted at Vienna Catchment Science Symposium in April 2018. Watersheds of the Middle and Lower Amur, where main part of streamflow is formed, are covered with forests of various structures. Annual forest fires in the Amur basin lead to sharp decrease in transpiration and summarize evaporation, an increase in volume and rate of surface streamflow (slope) into river beds and, as a consequence an increase in river runoff. An increase frequency of fires entails a change in forest species composition. Despite fact that species of the stand within watershed grow up in same conditions (environment, climate, weather, fires) – total value of the areas of coniferous forests has a decrease, in contrast to deciduous species. This is consistent with the conclusions of Russian hydrologists about shift in Russia of the boundaries of middle taiga on north, which is justified by them using climatic models. Reduction of coniferous forests, which have a deeper root system and larger area of contact with atmospheric precipitation, contributes to a faster runoff of rainwater, contributing an increase streamflow. Moreover, a positive trend is also noted in synchronous dynamics of peaks of rain floods on the Amur near Khabarovsk. This corresponds to assessment of spatio-temporal variations of global terrestrial water storage changes of the Amur according measurements of the Earth’s gravitational fields by GRACE satellite, carried out by foreign researchers. It has been suggested that with a descending trend in areas of coniferous forests, conditions will persist, contributing to increase in streamflow during the period of monsoon and frontal cyclonic rains.
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Burenina, T., and A. Onuchin. "SPATIAL-TEMPORAL ASPECTS OF THE HYDROLOGICAL REGIME IN CATCHMENTS AFTER CLEARCUTTING." ASJ 1, no. 48 (2021): 24–35. http://dx.doi.org/10.31618/asj.2707-9864.2021.1.48.91.
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This article discusses the spatial and temporal aspects of hydrological processes in catchments after logging for different landscape conditions of Central Siberia. For this discussion, the results of our own research in the Sayan Mountains, the Yenisei Ridge, the Angara River basin, the Khamar-Daban ridge and literature data were involved. It analyzed the impact of felling area to change the river flow and development of the erosion at the catchment area. The annual runoff, its seasonal structure and sediment discharge change significantly in dependence on as area of clearcutting so area of river basin. The authors analyzed the results of observations of the restoration of the water balance in the experimental logging sites of small catchments and the dynamics of runoff in large rivers. Research has shown the vegetation cover structure changes continuously on logged sites during post-logging forest regeneration and future post-cutting hydrologic regime scenarios are determined both by further climatic changes and by vegetation succession trajectories. The role of the time as a factor to decrease erosion at watershed after logging depends of many regional and local features of landscapes and of initial soil mineralized by logging. For the forests of Khamar-Daban mountainous in Baikal basin the model of soil erosion at watersheds after logging was developed.
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Ndiaye, Papa Malick, Ansoumana Bodian, Lamine Diop, et al. "Trend and Sensitivity Analysis of Reference Evapotranspiration in the Senegal River Basin Using NASA Meteorological Data." Water 12, no. 7 (2020): 1957. http://dx.doi.org/10.3390/w12071957.
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Understanding evapotranspiration and its long-term trends is essential for water cycle studies, modeling and for water uses. Spatial and temporal analysis of evapotranspiration is therefore important for the management of water resources, particularly in the context of climate change. The objective of this study is to analyze the trend of reference evapotranspiration (ET0) as well as its sensitivity to climatic variables in the Senegal River basin. Mann-Kendall’s test and Sen’s slope were used to detect trends and amplitude changes in ET0 and climatic variables that most influence ET0. Results show a significant increase in annual ET0 for 32% of the watershed area over the 1984–2017 period. A significant decrease in annual ET0 is observed for less than 1% of the basin area, mainly in the Sahelian zone. On a seasonal scale, ET0 increases significantly for 32% of the basin area during the dry season and decreases significantly for 4% of the basin during the rainy season. Annual maximum, minimum temperatures and relative humidity increase significantly for 68%, 81% and 37% of the basin, respectively. However, a significant decrease in wind speed is noted in the Sahelian part of the basin. The wind speed decrease and relative humidity increase lead to the decrease in ET0 and highlight a “paradox of evaporation” in the Sahelian part of the Senegal River basin. Sensitivity analysis reveals that, in the Senegal River basin, ET0 is more sensitive to relative humidity, maximum temperature and solar radiation.
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He, C., L. Zhang, L. Fu, Y. Luo, L. Li, and C. DeMarchi. "Streamflow allocation in arid watersheds: a case study in Northwestern China." Hydrology and Earth System Sciences Discussions 9, no. 7 (2012): 8941–78. http://dx.doi.org/10.5194/hessd-9-8941-2012.
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Abstract. This paper proposes a framework for allocating water resources among the upper, middle, and lower reaches of arid watersheds to meet the multiple demands for water, including rehabilitation of downstream ecosystem. The framework includes: (1) hydrologic simulation of distribution of water resources in the study watershed; (2) development of water allocation criteria; and (3) implementation of the water allocation plan. The advantages of the proposed framework are: (1) spatial integration; (2) multiple objectives; (3) incorporation of local needs through participatory decision making; and (4) dynamic evaluation. The framework was applied to the Heihe watershed, a large inland (terminal lake) watershed with a drainage area of over 128 000 km2 in Northwestern China. Simulation of the daily river flows for the period of 1990–2000 by the Distributed Large Basin Runoff Model shows that Qilian Mountain in the upper reach produced most of the runoff in the watershed, and the increased withdrawals of water for agricultural irrigation, industrial development, and municipal supplies at the middles reach oasis reduced the annual mean discharge by approximately 0.18 × 109 m3 over the simulation period, making the middle reach unable to deliver the mandated amount of 0.95 × 109 m3 water downstream by the State Council, under normal climatic conditions. Changes in land use practices need to be implemented to achieve the mandated water allocation plan. The paper suggests that a participatory watershed planning approach involving multiple stakeholders in the water allocation process be undertaken to address key questions regularly, including how much water should be allocated to what uses and for whom and at what price?
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Sokolova, Galina V., Andrei L. Verkhoturov, and Sergei P. Korolev. "Impact of Deforestation on Streamflow in the Amur River Basin." Geosciences 9, no. 6 (2019): 262. http://dx.doi.org/10.3390/geosciences9060262.
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In the basin of the Amur River in the Russian Far East, the influence of watershed areas covered by forests on the river basin has a complex nature, and no strict functional dependency has been established yet between these two factors. A study of the Amur River watershed in the current conditions, between 2000 and 2016 (climate, forest coverage, fires, and felling), has been conducted using the ground and satellite observations. The purpose of the study was to identify their influence on the river behaviour (flow, flooding, and levels of water). The study of hydrological regime of rivers was conducted in conjunction with the analysis of the dynamics of forest and burns areas over the synchronised periods of time. A special attention was given to the changing nature of the species composition of the forests (coniferous and deciduous forests separately) from 2000 to 2016, and climatic parameters over thirty years (atmospheric temperature, dew point, precipitation). New facts have been obtained, which provide an explanation of the reasons for predominant prolonged trends in the dynamics of the summer streamflow. In the view of the general tendency toward increased forest coverage combining all species of forest stand, the trend in the dynamics of the coniferous species areas is negative. Therefore, a conclusion can be made, that one of the major factors in the increase of the river flood flow (alongside the atmospheric precipitation), is deforestation of primary coniferous forests on the watershed areas, in contrast with the deciduous forests, where the trend is positive. Practicability of such conclusions can be justified, as different types of forests have different root systems, which mellow the ground and facilitate partial loss of the atmospheric precipitation and its transformation into the groundwater flow. Besides, coniferous forests attract more frequent and intensive fires, more subjected to felling, have longer regeneration period, and also, use larger volumes of ground waters for growing and functioning. Consequently, with their disappearance, an increase in streamflow should be expected. No changes in surface temperature and humidity of the forest cover in the watersheds during 1980-2016 despite global warming. Therefore, annual variability of forested areas of watersheds is greatly influenced by fires and felling. There are reasons to assume, that because of the tendency for decreasing areas of coniferous forests, the conditions contributing to the increases in rivers’ flood flow and flood risks during monsoon and frontal cyclonic rainfalls will remain.
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Jiang, Junchao, Leting Lyu, Yuechi Han, and Caizhi Sun. "Effect of Climate Variability on Green and Blue Water Resources in a Temperate Monsoon Watershed, Northeastern China." Sustainability 13, no. 4 (2021): 2193. http://dx.doi.org/10.3390/su13042193.
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Over 80% of global grain production relies on green water, water from precipitation that is stored in unsaturated soil and supports plant growth. Blue water, precipitation that turns into surface water and groundwater, is also a vital surface water resource, and it can be directly utilized. The Tanghe River Basin is a typical temperate continental monsoon watershed in Northern China where residents and crops rely on blue and green water resources. In this study, the spatiotemporal distributions of water resources in the Tanghe River Basin were simulated using the soil and water assessment tool (SWAT) model for the period between 1970 and 2015. The results demonstrate that the Nash–Sutcliffe efficiency and coefficient of determination were both higher than 0.64 during the calibration and validation periods at all hydrological stations, indicating high simulation accuracy. The average annual water resources of the Tanghe River Basin are 759.37 mm. Green and blue water account for 68% and 32% of the total water resources, respectively. The study period was divided into the reference period (1970–1976) and the variation period (1977–2015), to explore the impact of climate change on the green and blue water resources of the Tanghe River Basin water resources. Compared with the reference period, the average green and blue water resources in the variation period decreased by 78.48 and 35.94 mm/year, and their rate changes were −13.45% and −13.17%, respectively. The water resource relative change rates were high in the south and low in the north, and they were predominantly affected by precipitation. This study improves our understanding of the hydrological processes as well as the availability of blue and green water in the study region, and can prove beneficial in promoting the sustainable development of small basins and the integrated watershed management in areas with similar climatic conditions.
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Wine, Michael L., Sarah E. Null, R. Justin DeRose, and Wayne A. Wurtsbaugh. "Climatization—Negligent Attribution of Great Salt Lake Desiccation: A Comment on Meng (2019)." Climate 7, no. 5 (2019): 67. http://dx.doi.org/10.3390/cli7050067.
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A recent article reviewed data on Great Salt Lake (Utah) and concluded falsely that climate changes, especially local warming and extreme precipitation events, are primarily responsible for lake elevation changes. Indeed climatically influenced variation of net inflows contribute to huge swings in the elevation of Great Salt Lake (GSL) and other endorheic lakes. Although droughts and wet cycles have caused lake elevation changes of over 4.5 m, they have not caused a significant long-term change in the GSL stage. This recent article also suggests that a 1.4 °C rise in air temperature and concomitant increase in the lake’s evaporative loss is an important reason for the lake’s decline. However, we calculate that a 1.4 °C rise may have caused only a 0.1 m decrease in lake level. However, since 1847, the lake has declined 3.6 m and the lake area has decreased by ≈50%, despite no significant change in precipitation (p = 0.52) and a slight increase, albeit insignificant, in river flows above irrigation diversions (p = 0.085). In contrast, persistent water extraction for agriculture and other uses beginning in 1847 now decrease water flows below diversions by 39%. Estimates of consumptive water use primarily for irrigated agriculture in the GSL watershed suggest that approximately 85% (2500 km2) of the reduced lake area can be attributed to human water consumption. The recent article’s failure to calculate a water budget for the lake that included extensive water withdrawals misled the author to focus instead on climate change as a causal factor for the decline. Stable stream flows in GSL’s headwaters, inadequate temperature increase to explain the extent of its observed desiccation, stable long-term precipitation, and the magnitude of increased water consumption from GSL together demonstrate conclusively that climatic factors are secondary to human alterations to GSL and its watershed. Climatization, in which primarily non-climatic processes are falsely attributed to climatic factors, is a threat to the credibility of hydrological science. Despite a recent suggestion to the contrary, pressure to support Earth’s rising human population—in the form of increasing consumption of water in water-limited regions, primarily to support irrigated agriculture—remains the leading driver of desiccation of inland waters within Earth’s water-limited regions.
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Vybernaite-Lubiene, Irma, Mindaugas Zilius, Laura Saltyte-Vaisiauske, and Marco Bartoli. "Recent Trends (2012–2016) of N, Si, and P Export from the Nemunas River Watershed: Loads, Unbalanced Stoichiometry, and Threats for Downstream Aquatic Ecosystems." Water 10, no. 9 (2018): 1178. http://dx.doi.org/10.3390/w10091178.
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The Curonian Lagoon, the largest in Europe, suffers from nuisance cyanobacterial blooms during summer, probably triggered by unbalanced nutrient availability. However, nutrient delivery to this system was never analysed in detail. During 2012–2016, we analysed the monthly discharge, nutrient loads, and ecological stoichiometry at the closing section of the Nemunas River, the main nutrient source to the lagoon. The aim of this study was to investigate seasonal and annual variations of nitrogen (N), silica (Si), and phosphorous (P) with respect to discharge, climatic features, and historical trends. The nutrient loads varied yearly by up to 50% and their concentrations underwent strong seasonality, with summer N and Si limitation. The river discharge (16 ± 4 km3·yr−1) was lower than the historical average (21.8 km3·yr−1). Changes in agricultural practices resulted in similar N export from the river watershed compared to historical data (1986–2002), while sewage treatment plant improvements led to a ~60% decrease of P loads. This work contributes new data to the scattered available information on the most important nutrient source to the Curonian Lagoon. Further P reduction is needed to avoid unbalanced dissolved inorganic nitrogen and phosphorus (DIN:DIP~10) ecological stoichiometry in summer, which may stimulate undesired cyanobacterial blooms.
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Yigzaw, Wondmagegn, Faisal Hossain, and Alfred Kalyanapu. "Comparison of PMP-Driven Probable Maximum Floods with Flood Magnitudes due to Increasingly Urbanized Catchment: The Case of American River Watershed." Earth Interactions 17, no. 8 (2013): 1–15. http://dx.doi.org/10.1175/2012ei000497.1.
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Abstract Since historical (predam) data are traditionally the sole criterion for dam design, future (postdam) meteorological and hydrological variability due to land-use and land-cover change cannot be considered for assessing design robustness. For example, postdam urbanization within a basin leads to definite and immediate increase in direct runoff and reservoir peak inflow. On the other hand, urbanization can strategically (i.e., gradually) alter the mesoscale circulation patterns leading to more extreme rainfall rates. Thus, there are two key pathways (immediate or strategic) by which the design flood magnitude can be compromised. The main objective of the study is to compare the relative contribution to increase in flood magnitudes through direct effects of land-cover change (urbanization and less infiltration) with gradual climate-based effects of land-cover change (modification in mesoscale storm systems). The comparison is cast in the form of a sensitivity study that looks into the response to the design probable maximum flood (PMF) from probable maximum precipitation (PMP). Using the American River watershed (ARW) and Folsom Dam as a case study, simulated peak floods for the 1997 (New Year's) flood event show that a 100% impervious watershed has the potential of generating a flood that is close to design PMF. On the other hand, the design PMP produces an additional 1500 m3 s−1 peak flood compared to the actual PMF when the watershed is considered 100% impervious. This study points to the radical need for consideration future land-cover changes up front during the dam design and operation formulation phase by considering not only the immediate effects but also the gradual climatic effects on PMF. A dynamic dam design procedure should be implemented that takes into account the change of land–atmospheric and hydrological processes as a result of land-cover modification rather than relying on historical records alone.
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Koch, Hagen, Ana Lígia Chaves Silva, Stefan Liersch, José Roberto Gonçalves de Azevedo, and Fred Fokko Hattermann. "Effects of model calibration on hydrological and water resources management simulations under climate change in a semi-arid watershed." Climatic Change 163, no. 3 (2020): 1247–66. http://dx.doi.org/10.1007/s10584-020-02917-w.
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AbstractSemi-arid regions are known for erratic precipitation patterns with significant effects on the hydrological cycle and water resources availability. High temporal and spatial variation in precipitation causes large variability in runoff over short durations. Due to low soil water storage capacity, base flow is often missing and rivers fall dry for long periods. Because of its climatic characteristics, the semi-arid north-eastern region of Brazil is prone to droughts. To counter these, reservoirs were built to ensure water supply during dry months. This paper describes problems and solutions when calibrating and validating the eco-hydrological model SWIM for semi-arid regions on the example of the Pajeú watershed in north-eastern Brazil. The model was calibrated to river discharge data before the year 1983, with no or little effects of water management, applying a simple and an enhanced approach. Uncertainties result mainly from the meteorological data and observed river discharges. After model calibration water management was included in the simulations. Observed and simulated reservoir volumes and river discharges are compared. The calibrated and validated models were used to simulate the impacts of climate change on hydrological processes and water resources management using data of two representative concentration pathways (RCP) and five earth system models (ESM). The differences in changes in natural and managed mean discharges are negligible (< 5%) under RCP8.5 but notable (> 5%) under RCP2.6 for the ESM ensemble mean. In semi-arid catchments, the enhanced approach should be preferred, because in addition to discharge, a second variable, here evapotranspiration, is considered for model validation.
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Lattaud, Julie, Denise Dorhout, Hartmut Schulz, et al. "The C<sub>32</sub> alkane-1,15-diol as a proxy of late Quaternary riverine input in coastal margins." Climate of the Past 13, no. 8 (2017): 1049–61. http://dx.doi.org/10.5194/cp-13-1049-2017.
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Abstract. The study of past sedimentary records from coastal margins allows us to reconstruct variations in terrestrial input into the marine realm and to gain insight into continental climatic variability. There are numerous organic proxies for tracing terrestrial input into marine environments but none that strictly reflect the input of river-produced organic matter. Here, we test the fractional abundance of the C32 alkane 1,15-diol relative to all 1,13- and 1,15-long-chain diols (FC32 1, 15) as a tracer of input of river-produced organic matter in the marine realm in surface and Quaternary (0–45 ka) sediments on the shelf off the Zambezi and nearby smaller rivers in the Mozambique Channel (western Indian Ocean). A Quaternary (0–22 ka) sediment record off the Nile River mouth in the eastern Mediterranean was also studied for long-chain diols. For the Mozambique Channel, surface sediments of sites most proximal to Mozambique rivers showed the highest F1, 15 − C32 (up to 10 %). The sedimentary record shows high (15–35 %) pre-Holocene F1, 15 − C32 and low (< 10 %) Holocene F1, 15 − C32 values, with a major decrease between 18 and 12 ka. F1, 15 − C32 is significantly correlated (r2 = 0.83, p < 0.001) with the branched and isoprenoid tetraether (BIT) index, a proxy for the input of soil and river-produced organic matter in the marine environment, which declines from 0.25 to 0.60 for the pre-Holocene to < 0.10 for the Holocene. This decrease in both FC32 1, 15 and the BIT is interpreted to be mainly due to rising sea level, which caused the Zambezi River mouth to become more distal to our study site, thereby decreasing riverine input at the core location. Some small discrepancies are observed between the records of the BIT index and FC32 1, 15 for Heinrich Event 1 (H1) and the Younger Dryas (YD), which may be explained by a change in soil sources in the catchment area rather than a change in river influx. Like for the Mozambique Channel, a significant correlation between FC32 1, 15 and the BIT index (r2 = 0.38, p < 0.001) is observed for the eastern Mediterranean Nile record. Here also, the BIT index and FC32 1, 15 are lower in the Holocene than in the pre-Holocene, which is likely due to the sea level rise. In general, the differences between the BIT index and FC32 1, 15 eastern Mediterranean Nile records can be explained by the fact that the BIT index is not only affected by riverine runoff but also by vegetation cover with increasing cover leading to lower soil erosion. Our results confirm that FC32 1, 15 is a complementary proxy for tracing riverine input of organic matter into marine shelf settings, and, in comparison with other proxies, it seems not to be affected by soil and vegetation changes in the catchment area.
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Qin, Jun, Ailin Shi, Guoyu Ren, et al. "Severe Historical Droughts Carved on Rock in the Yangtze." Bulletin of the American Meteorological Society 101, no. 6 (2020): E905—E916. http://dx.doi.org/10.1175/bams-d-19-0126.1.
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Abstract The White Crane Ridge (WCR) Rock Fish, now submerged under the backwater of the Three Gorges Reservoir in the Yangtze River, are affirmed as one of the earliest hydrologic observations ever made in any large river in the world. The usually in-water monument provides highly valuable historical records of severe droughts in the upper Yangtze over the last 1,200 years. This article updated the historical drought chronology previously developed based on the WCR inscriptions, which can be applied in assessment of extreme climatic and hydrological risks, and also made a preliminary analysis of changes of the severe drought frequency during the last thousand years in the upper Yangtze. The analysis shows that the severe droughts occurred more frequently during the Medieval Climate Anomaly (MCA), relatively less so during the Little Ice Age (LIA), and once again more often under the background of modern global warming. It was suggested that a generally warmer Euro-Asian continent during the MCA was in favor of the stronger East Asian summer monsoon, and the resulting less precipitation and more severe droughts of the Yangtze and the lower water level at the Three Gorges area on the centennial scale, and vice versa for the period of the LIA. The results would help in understanding the causes and mechanisms of the regional climate change and variability, and also in taking measures in the fields of the watershed management to cope with the long-term change in climatic and hydrologic droughts.
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Mustafa, Mamoon, Brad Barnhart, Meghna Babbar-Sebens, and Darren Ficklin. "Modeling Landscape Change Effects on Stream Temperature Using the Soil and Water Assessment Tool." Water 10, no. 9 (2018): 1143. http://dx.doi.org/10.3390/w10091143.
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Stream temperature is one of the most important factors for regulating fish behavior and habitat. Therefore, models that seek to characterize stream temperatures, and predict their changes due to landscape and climatic changes, are extremely important. In this study, we extend a mechanistic stream temperature model within the Soil and Water Assessment Tool (SWAT) by explicitly incorporating radiative flux components to more realistically account for radiative heat exchange. The extended stream temperature model is particularly useful for simulating the impacts of landscape and land use change on stream temperatures using SWAT. The extended model is tested for the Marys River, a western tributary of the Willamette River in Oregon. The results are compared with observed stream temperatures, as well as previous model estimates (without radiative components), for different spatial locations within the Marys River watershed. The results show that the radiative stream temperature model is able to simulate increased stream temperatures in agricultural sub-basins compared with forested sub-basins, reflecting observed data. However, the effect is overestimated, and more noise is generated in the radiative model due to the inclusion of highly variable radiative forcing components. The model works at a daily time step, and further research should investigate modeling at hourly timesteps to further improve the temporal resolution of the model. In addition, other watersheds should be tested to improve and validate the model in different climates, landscapes, and land use regimes.
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Cozzi, Stefano, Carles Ibáñez, Luminita Lazar, Patrick Raimbault, and Michele Giani. "Flow Regime and Nutrient-Loading Trends from the Largest South European Watersheds: Implications for the Productivity of Mediterranean and Black Sea’s Coastal Areas." Water 11, no. 1 (2018): 1. http://dx.doi.org/10.3390/w11010001.
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In the last century, large watersheds in Southern Europe have been impacted by a combination of anthropogenic and climatic pressures, which have rapidly evolved to change the ecological status of freshwater and coastal systems. A comparative analysis was performed for Ebro, Rhône, Po and Danube rivers, to investigate if they exhibited differential dynamics in hydrology and water quality that can be linked to specific human and natural forces acting at sub-continental scales. Flow regime series were analyzed from daily to multi-decadal scales, considering frequency distributions, trends (Mann–Kendall and Sen tests) and discontinuities (SRSD Method). River loads of suspended matter, nutrients and organic matter and the eutrophication potential of river nutrients were estimated to assess the impact of river loads on adjacent coastal areas. The decline of freshwater resources largely impacted the Ebro watershed on annual (−0.139 km3 yr−1) and seasonal (−0.4% yr−1) scales. In the other rivers, only spring–summer showed significant decreases of the runoff coupled to an exacerbated flow variability (0.1–0.3% yr−1), which suggested the presence of an enhanced regional climatic instability. Discontinuities in annual runoff series (every 20–30 years) indicated a similar long-term evolution of Rhône and Po rivers, differently from Ebro and Danube. Higher nutrient concentrations in the Ebro and Po (+50%) compared to Rhône and Danube and distinct stoichiometric nutrient ratios may exert specific impacts on the growth of plankton biomass in coastal areas. The overall decline of inorganic phosphorus in the Rhône and Po (since the 1980s) and the Ebro and Danube (since the 1990s) mitigated the eutrophication in coastal ecosystems inducing, however, a phase in which the role of organic phosphorus loads (Po > Danube > Rhône > Ebro) on coastal productivity could be more relevant. Overall, the study showed that the largest South European watersheds are differently impacted by anthropogenic and climatic forces and that this will influence their vulnerability to future changes of flow regime and water quality.
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Ashu, Agbortoko Bate, and Sang-Il Lee. "Assessing Climate Change Effects on Water Balance in a Monsoon Watershed." Water 12, no. 9 (2020): 2564. http://dx.doi.org/10.3390/w12092564.
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Understanding the changes on future water resources resulting from climate variations will assist in developing effective management strategies for a river basin. Our area of interest is the Osan watershed in South Korea, where the summer monsoon contributes approximately 60–70% of the annual runoff and precipitation for the country. We determined the effects that future climatic changes have on this area. To accomplish this, we made use of global climate models (GCMs). A total of 10 GCMs were downscaled with the help of climate information production tools. Coupled with the GCMs and the Soil and Water Assessment (SWAT) model, three periods were used to assess these climate impacts. The baseline, mid-century (MC), and end-century (EC) periods include 1993–2018, 2046–2065, and 2081–2099, respectively. The entire process was performed using two scenarios (4.5 and 8.5) from the representative concentration pathways (RCPs). Some of the statistical metrics used for model calibration and validation were p-factor, r-factor, percent bias, root-mean-square error (RMSE), and Nash–Sutcliffe model efficiency. Their respective values were 0.88, 0.88, 8.3, 0.91, and 0.91 for calibration, and 1.16, 0.85, 7.9, 0.88, and 0.87 for validation. For the MC and EC periods under both scenarios, we projected an increase in temperature and precipitation of approximately 2–5 °C and 15–30%, respectively. A predicted rise in precipitation, surface flow, lateral flow, and water yield were noted for the month of June. Subsequently, a decline in July followed during the summer monsoon season. Summer monsoon rains will fluctuate more sharply, with heavy rainfall in June, lower rainfall in July, and more rain in the late summer, leading to the possibility of both flooding and drought within a given period. Annual precipitation, surface flow, lateral flow, and water yield will increase whereas evapotranspiration would decrease in both periods under both scenarios during the summer monsoon period, which will lead to wetter conditions in the future.
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Islam, Siraj Ul, Charles L. Curry, Stephen J. Déry, and Francis W. Zwiers. "Quantifying projected changes in runoff variability and flow regimes of the Fraser River Basin, British Columbia." Hydrology and Earth System Sciences 23, no. 2 (2019): 811–28. http://dx.doi.org/10.5194/hess-23-811-2019.
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Abstract. In response to ongoing and future-projected global warming, mid-latitude, nival river basins are expected to transition from a snowmelt-dominated flow regime to a nival–pluvial one with an earlier spring freshet of reduced magnitude. There is, however, a rich variation in responses that depends on factors such as the topographic complexity of the basin and the strength of maritime influences. We illustrate the potential effects of a strong maritime influence by studying future changes in cold season flow variability in the Fraser River Basin (FRB) of British Columbia, a large extratropical watershed extending from the Rocky Mountains to the Pacific Coast. We use a process-based hydrological model driven by an ensemble of 21 statistically downscaled simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5), following the Representative Concentration Pathway 8.5 (RCP 8.5). Warming under RCP 8.5 leads to reduced winter snowfall, shortening the average snow accumulation season by about one-third. Despite this, large increases in cold season rainfall lead to unprecedented cold season peak flows and increased overall runoff variability in the VIC simulations. Increased cold season rainfall is shown to be the dominant climatic driver in the Coast Mountains, contributing 60 % to mean cold season runoff changes in the 2080s. Cold season runoff at the outlet of the basin increases by 70 % by the 2080s, and its interannual variability more than doubles when compared to the 1990s, suggesting substantial challenges for operational flow forecasting in the region. Furthermore, almost half of the basin (45 %) transitions from a snow-dominated runoff regime in the 1990s to a primarily rain-dominated regime in the 2080s, according to a snowmelt pulse detection algorithm. While these projections are consistent with the anticipated transition from a nival to a nival–pluvial hydrologic regime, the marked increase in FRB cold season runoff is likely linked to more frequent landfalling atmospheric rivers in the region projected in the CMIP5 models, providing insights for other maritime-influenced extratropical basins.
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Tundisi, JG, T. Matsumura-Tundisi, and DS Abe. "The ecological dynamics of Barra Bonita (Tietê River, SP, Brazil) reservoir: implications for its biodiversity." Brazilian Journal of Biology 68, no. 4 suppl (2008): 1079–98. http://dx.doi.org/10.1590/s1519-69842008000500015.
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Barra Bonita reservoir is located in the Tietê River Basin - São Paulo state - 22° 29" to 22° 44" S and 48° 10° W and it is the first of a series of six large reservoirs in this river. Built up in 1963 with the aim to produce hydroelectricity this reservoir is utilized for several activities such as fish production, irrigation, navigation, tourism and recreation, besides hydroelectricity production. The seasonal cycle of events in this reservoir is driven by the hydrological features of the basin with consequences on the retention time and on the limnological functions of this artificial ecosystem. The reservoir is polymitic with short periods of stability. Hydrology of the basin, retention time of the reservoir and cold fronts have an impact in the vertical and horizontal structure of the system promoting rapid changes in the planktonic community and in the succession of species. Blooms of Microcystis sp. are common during periods of stability. Superimposed to the climatological and hydrological forcing functions the human activities in the watershed produce considerable impact such as the discharge of untreated wastewater, the high suspended material contributions and fertilizers from the sugar cane plantations. The fish fauna of the reservoir has been changed extent due to the introduction of exotic fish species that exploit the pelagic zone of the reservoir. Changes in the primary productivity of phytoplankton in this reservoir, in the zooplankton community in the diversity and organization of trophic structure are a consequence of eutrophication and its increase during the last 20 years. Control of eutrophication by treating wastewater from urban sources, adequate agricultural practices in order to diminish the suspended particulate matter contribution, revegetation of the watershed and riparian forests along the tributaries are some possible restoration measures. Another action that can be effective is the protection of wetlands in the main tributaries as an effort to control eutrophication and particulate material load. Hydrology, climatic forcing and retention time are major forcing functions that promote the circulation (vertical and horizontal) in the reservoir and probably have a strong effect on dissolved and particulate material distribution. The 114 tributaries are systems that enhance spatial heterogeneity promoting diversity throughout ecological niches. Switches of control systems of this artificial ecosystem seems to be related with physical - physical forces; physical - biological forces during short periods of time, and biological - biological interactions at varying degrees during the seasonal cycle.
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Wolfe, Jared D., Kevin R. Shook, Chris Spence, and Colin J. Whitfield. "A watershed classification approach that looks beyond hydrology: application to a semi-arid, agricultural region in Canada." Hydrology and Earth System Sciences 23, no. 9 (2019): 3945–67. http://dx.doi.org/10.5194/hess-23-3945-2019.
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Abstract. Classification and clustering approaches provide a means to group watersheds according to similar attributes, functions, or behaviours, and can aid in managing natural resources. Although they are widely used, approaches based on hydrological response parameters restrict analyses to regions where well-developed hydrological records exist, and overlook factors contributing to other management concerns, including biogeochemistry and ecology. In the Canadian Prairie, hydrometric gauging is sparse and often seasonal. Moreover, large areas are endorheic and the landscape is highly modified by human activity, complicating classification based solely on hydrological parameters. We compiled climate, geological, topographical, and land-cover data from the Prairie and conducted a classification of watersheds using a hierarchical clustering of principal components. Seven classes were identified based on the clustering of watersheds, including those distinguishing southern Manitoba, the pothole region, river valleys, and grasslands. Important defining variables were climate, elevation, surficial geology, wetland distribution, and land cover. In particular, three classes occur almost exclusively within regions that tend not to contribute to major river systems, and collectively encompass the majority of the study area. The gross difference in key characteristics across the classes suggests that future water management and climate change may carry with them heterogeneous sets of implications for water security across the Prairie. This emphasizes the importance of developing management strategies that target sub-regions expected to behave coherently as current human-induced changes to the landscape will affect how watersheds react to change. The study provides the first classification of watersheds within the Prairie based on climatic and biophysical attributes, with the framework used being applicable to other regions where hydrometric data are sparse. Our findings provide a foundation for addressing questions related to hydrological, biogeochemical, and ecological behaviours at a regional level, enhancing the capacity to address issues of water security.
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Records, R. M., M. Arabi, S. R. Fassnacht, W. G. Duffy, M. Ahmadi, and K. C. Hegewisch. "Climate change and wetland loss impacts on a Western river's water quality." Hydrology and Earth System Sciences Discussions 11, no. 5 (2014): 4925–69. http://dx.doi.org/10.5194/hessd-11-4925-2014.
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Abstract. An understanding of potential stream water quality conditions under future climate is critical for the sustainability of ecosystems and protection of human health. Changes in wetland water balance under projected climate could alter wetland extent or cause wetland loss. This study assessed the potential climate-induced changes to in-stream sediment and nutrients loads in the historically snow melt-dominated Sprague River, Oregon, Western United States. Additionally, potential water quality impacts of combined changes in wetland water balance and wetland area under future climatic conditions were evaluated. The study utilized the Soil and Water Assessment Tool (SWAT) forced with statistical downscaling of general circulation model (GCM) data from the Coupled Model Intercomparison Project 5 (CMIP5) using the Multivariate Adaptive Constructed Analogs (MACA) method. Our findings suggest that in the Sprague River (1) mid-21st century nutrient and sediment loads could increase significantly during the high flow season under warmer-wetter climate projections, or could change only nominally in a warmer and somewhat drier future; (2) although water quality conditions under some future climate scenarios and no wetland loss may be similar to the past, the combined impact of climate change and wetland losses on nutrient loads could be large; (3) increases in stream total phosphorus (TP) concentration with wetland loss under future climate scenarios would be greatest at high-magnitude, low-probability flows; and (4) loss of riparian wetlands in both headwaters and lowlands could increase outlet TP loads to a similar degree, but this could be due to distinctly different mechanisms in different parts of the watershed.
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Cheng, Lizhen, Meixue Yang, Xuejia Wang, and Guoning Wan. "Spatial and Temporal Variations of Terrestrial Evapotranspiration in the Upper Taohe River Basin from 2001 to 2018 Based on MOD16 ET Data." Advances in Meteorology 2020 (August 28, 2020): 1–17. http://dx.doi.org/10.1155/2020/3721414.
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Evapotranspiration (ET) is an essential component of watershed hydrological cycle. Spatial-temporal variations analyses of evapotranspiration and potential evapotranspiration (PET) have remarkable theoretical and practical significances for understanding the interaction between climate changes and hydrological cycle and optimal allocation of water resources under global warming background. The MODIS-estimated ET agreed well with basin evapotranspiration from water balance principle methods in the study. The spatiotemporal variations results based on MOD16 ET data showed the following: (1) multiyear mean ET and PET were 464.2 mm and 1192.2 mm, and annual ET showed an upward trend at a rate of 3.48 mm/a, while PET decreased significantly at a rate of −8.18 mm/a. The annual ET trend showed a complemental relationship with PET; (2) at the seasonal scale, ET was highest in summer and least in winter, while PET was higher in spring and summer. The change of ET and PET in spring and summer had a great contribution to the annual variations; (3) ET and PET in the northern part were significantly stronger than those in the western and southern parts; (4) ET in cropland increased significantly, while PET decreased obviously in grass and forest; (5) changes of ET and PET were closely related to climatic factors. The rise in temperature caused the increase in ET and the decrease of wind speed contributed more to the decrease in PET. The results can provide a scientific basis for water resources planning and management.
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Khilchevskyi, V. K., and S. M. Kurylo. "A RESEARCH OF THE TRANSFORMATION OF THE CHEMICAL COMPOSITION OF SURFACE WATERS USING THE MODERNIZED CLASSIFICATION OF ALEKIN." Hydrology, hydrochemistry and hydroecology, no. 1 (56) (2020): 6–14. http://dx.doi.org/10.17721/2306-5680.2020.1.1.
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Climatic changes and value of anthropogenic load of watershed of the rivers can be main reasons. The article researched long-term changes in the chemical composition of rivers in Ukraine. Long-term changes in the chemical composition of the river waters of Ukraine were analyzed using the modernized Alekin classification (modernization was proposed by V.K. Khilchevskyi and S.M. Kurylo). The additions introduced by the authors to the basic classification of O.A.Alekin allow fixing the dynamics of changes in the chemical composition of natural waters by cations at the group level, as well as at a more detailed level, revealing quantitative changes in the relative content of class-forming anions (at the level of subtypes). Taking it into account for the most relevant tasks which arise for hydrologists and hydrochemicals are considered to be determination of modern regularities of streamflow and hydrochemical regime in conditions of warming which happens and assessments of such changes for the perspective. The mineralization of water and concentration of the main ions in river waters change for many reasons. Studying has been executed on the Udaj river, Tur`ya river, Sula river. The trend of increasing salinity of river water is detection. Main changes are taking place in the spring. During period of supervisions there was growth of mineralization of water: Sula – from 440 to 1125 mg/dm3.The main factor there is an increased part of groundwater flow. In favor of this conclusion the following results of researches serve. The special executed calculations showed dependence between part of ground flow and chemical composition of water of the rivers. Different classifications are used to systematize natural waters by chemical composition. Attempts to classify water in accordance with the general conditions by which their chemical composition is formed are known. For analysis of long-term changes of the hydrochemical regime in different phases of the water was found and application of the classification of Alekin (modernizated). Modernization does not touch the highest trait – class, but concerns groups and types, with the introduction of a new taxon – subtype. Modernization to the basic classification of Alekhin allow to fixed in detail the dynamics of changes in the chemical composition of natural waters by cations at the group level. At a detailed level, quantitative changes in the relative content of anions (at the level of proposed subtypes) can be fixed. Verification of the modernized classification of O.A. Alekhin, made on 25 rivers of the Dnipro river basin. Rivers are located in different environmental zones, have different anthropogenic pressure and term of observations (40 – 60 years). An attempt was made to apply the modernized classification to other types of natural waters – groundwater and atmospheric.
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Records, R. M., M. Arabi, S. R. Fassnacht, W. G. Duffy, M. Ahmadi, and K. C. Hegewisch. "Climate change and wetland loss impacts on a western river's water quality." Hydrology and Earth System Sciences 18, no. 11 (2014): 4509–27. http://dx.doi.org/10.5194/hess-18-4509-2014.
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Abstract. An understanding of potential stream water quality conditions under future climate is critical for the sustainability of ecosystems and the protection of human health. Changes in wetland water balance under projected climate could alter wetland extent or cause wetland loss (e.g., via increased evapotranspiration and lower growing season flows leading to reduced riparian wetland inundation) or altered land use patterns. This study assessed the potential climate-induced changes to in-stream sediment and nutrient loads in the snowmelt-dominated Sprague River, Oregon, western US. Additionally, potential water quality impacts of combined changes in wetland water balance and wetland area under future climatic conditions were evaluated. The study utilized the Soil and Water Assessment Tool (SWAT) forced with statistical downscaling of general circulation model (GCM) data from the Coupled Model Intercomparison Project 5 (CMIP5) using the Multivariate Adaptive Constructed Analogs (MACA) method. Our findings suggest that, in the Sprague River, (1) mid-21st century nutrient and sediment loads could increase significantly during the high-flow season under warmer, wetter climate projections or could change only nominally in a warmer and somewhat drier future; (2) although water quality conditions under some future climate scenarios and no wetland loss may be similar to the past, the combined impact of climate change and wetland losses on nutrient loads could be large; (3) increases in stream total phosphorus (TP) concentration with wetland loss under future climate scenarios would be greatest at high-magnitude, low-probability flows; and (4) loss of riparian wetlands in both headwaters and lowlands could increase outlet TP loads to a similar degree, but this could be due to distinctly different mechanisms in different parts of the watershed.