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1
Jedd, Theresa, Deborah Bathke, Duane Gill, Bimal Paul, Nicole Wall, Tonya Bernadt, Jacob Petr, Anthony Mucia, and Milan Wall. "Tracking Drought Perspectives: A Rural Case Study of Transformations Following an Invisible Hazard." Weather, Climate, and Society 10, no. 4 (August 15, 2018): 653–72. http://dx.doi.org/10.1175/wcas-d-17-0067.1.
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Abstract Rural towns are especially susceptible to the effects of drought because their economies are dependent on natural resources. However, they are also resilient in many ways to natural hazards because they are rich in civic engagement and social capital. Because of the diverse nature of drought’s impacts, understanding its complex dynamics and its effects requires a multidisciplinary approach. To study these dynamics, this research combines appreciative inquiry, the Community Capitals Framework, and a range of climatological monitoring data to assess the 2012–14 Great Plains drought’s effect on McCook, Nebraska. Community coping measures, such as water-use reduction and public health programs, were designed to address the immediate effects of heat and scant rainfall during the initial summer and the subsequent years. Residents generally reported the community was better prepared than in previous droughts, including the persistent multiyear early-2000s drought. However, the results highlight wide variation in community perspectives about the drought’s severity and impacts, as well as divergent experiences and coping responses. Despite these factors, we find evidence of the transformative potential of moving from drought coping to drought mitigation. We attribute the city’s resilience to the ability to draw upon prior experience with droughts, having a formal municipal plan, and strong human and social capital to coordinate individual knowledge and expertise across agencies. We suggest that droughts have served a catalytic function, prompting the community to transform land-use practices, water conservation planning, and built infrastructure in lasting ways.
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Nasir, Muhammad Waqar, and Zoltan Toth. "Effect of Drought Stress on Potato Production: A Review." Agronomy 12, no. 3 (March 4, 2022): 635. http://dx.doi.org/10.3390/agronomy12030635.
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Potato is the third most consumed crop globally after rice and wheat. It is a short-duration crop, versatile in use, suitable for growing in a wide range of environments, and its production is increasing rapidly. The modern potato is considered a drought-sensitive crop, and it is susceptible to yield loss because of drought stress. Unfortunately, drought severity, frequency, and extent have been increasing around the globe because of climate change. Potato drought susceptibility has primarily been attributed to its shallow root system. However, several studies in past decades have suggested that drought susceptibility of potato also depends upon the type, developmental stage, and the morphology of the genotype, and the duration and severity of drought stress. They have been overlooked, and root depth is considered the only significant cause of potato drought susceptibility. This review combines these studies to understand the varying response of potato genotypes. This review also explores the current potato production scenario and the effect of varying degrees of drought stress on potatoes’ growth, development, and yield. In the absence of drought-tolerant genotypes, agronomic practices should be improved to mitigate drought stress. Late maturing cultivars, nutrient management, mulching, and foliar application of plant growth regulators can be used during prolonged droughts. Irrigation at tuber initiation and the tuber bulking stage during early droughts can reduce the adverse effects of drought.
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KANWAL, VINITA, SMITA SIROHI, and PREM CHAND. "Effect of drought on livestock enterprise: Evidence from Rajasthan." Indian Journal of Animal Sciences 90, no. 1 (February 18, 2020): 94–98. http://dx.doi.org/10.56093/ijans.v90i1.98229.
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Livestock act as a cushion against vagaries of nature and augment income of the farmers, particularly in drought prone Rajasthan. However, to what extent it withheld the adverse climatic situation has been a less probed area at least at macro-level. This paper studies the impact of drought on milk and meat enterprises in the drought prone state of Rajasthan using district level secondary data for the period of 1983/84 to 2015/16. Standardized Precipitation Index (SPI) was used to determine drought years. Results indicated that although the sector has been able to absorb the minor shocks of droughts, the major droughts affect the livestock adversely. The drought prone districts of western Rajasthan were found to be much prepared for drought than the southern and south eastern districts. Study recommends that the strategies followed by western districts such as stock of fodder, fodder bank, perennial grasses, etc. should be promoted in rest of the areas of the state for sustainable livestock production.
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Ritson, Jonathan P., Richard E. Brazier, Nigel J. D. Graham, Chris Freeman, Michael R. Templeton, and Joanna M. Clark. "The effect of drought on dissolved organic carbon (DOC) release from peatland soil and vegetation sources." Biogeosciences 14, no. 11 (June 16, 2017): 2891–902. http://dx.doi.org/10.5194/bg-14-2891-2017.
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Abstract. Drought conditions are expected to increase in frequency and severity as the climate changes, representing a threat to carbon sequestered in peat soils. Downstream water treatment works are also at risk of regulatory compliance failures and higher treatment costs due to the increase in riverine dissolved organic carbon (DOC) often observed after droughts. More frequent droughts may also shift dominant vegetation in peatlands from Sphagnum moss to more drought-tolerant species. This paper examines the impact of drought on the production and treatability of DOC from four vegetation litters (Calluna vulgaris, Juncus effusus, Molinia caerulea and Sphagnum spp.) and a peat soil. We found that mild droughts caused a 39.6 % increase in DOC production from peat and that peat DOC that had been exposed to oxygen was harder to remove by conventional water treatment processes (coagulation/flocculation). Drought had no effect on the amount of DOC production from vegetation litters; however large variation was observed between typical peatland species (Sphagnum and Calluna) and drought-tolerant grassland species (Juncus and Molinia), with the latter producing more DOC per unit weight. This would therefore suggest the increase in riverine DOC often observed post-drought is due entirely to soil microbial processes and DOC solubility rather than litter layer effects. Long-term shifts in species diversity may, therefore, be the most important impact of drought on litter layer DOC flux, whereas pulses related to drought may be observed in peat soils and are likely to become more common in the future. These results provide evidence in support of catchment management which increases the resilience of peat soils to drought, such as ditch blocking to raise water tables.
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Gevaert, Anouk I., Ted I. E. Veldkamp, and Philip J. Ward. "The effect of climate type on timescales of drought propagation in an ensemble of global hydrological models." Hydrology and Earth System Sciences 22, no. 9 (September 6, 2018): 4649–65. http://dx.doi.org/10.5194/hess-22-4649-2018.
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Abstract. Drought is a natural hazard that occurs at many temporal and spatial scales and has severe environmental and socioeconomic impacts across the globe. The impacts of drought change as drought evolves from precipitation deficits to deficits in soil moisture or streamflow. Here, we quantified the time taken for drought to propagate from meteorological drought to soil moisture drought and from meteorological drought to hydrological drought. We did this by cross-correlating the Standardized Precipitation Index (SPI) against standardized indices (SIs) of soil moisture, runoff, and streamflow from an ensemble of global hydrological models (GHMs) forced by a consistent meteorological dataset. Drought propagation is strongly related to climate types, occurring at sub-seasonal timescales in tropical climates and at up to multi-annual timescales in continental and arid climates. Winter droughts are usually related to longer SPI accumulation periods than summer droughts, especially in continental and tropical savanna climates. The difference between the seasons is likely due to winter snow cover in the former and distinct wet and dry seasons in the latter. Model structure appears to play an important role in model variability, as drought propagation to soil moisture drought is slower in land surface models (LSMs) than in global hydrological models, but propagation to hydrological drought is faster in land surface models than in global hydrological models. The propagation time from SPI to hydrological drought in the models was evaluated against observed data at 127 in situ streamflow stations. On average, errors between observed and modeled drought propagation timescales are small and the model ensemble mean is preferred over the use of a single model. Nevertheless, there is ample opportunity for improvement as substantial differences in drought propagation are found at 10 % of the study sites. A better understanding and representation of drought propagation in models may help improve seasonal drought forecasting as well as constrain drought variability under future climate scenarios.
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Chen, Zhong Lin, Su Nan Xu, Yue Li, Shi Xie, Li Xia Fan, and Li Hong Zhang. "The Effect of Different Drought Stress on Antioxidant Enzymes and Lipid Peroxidation on Zoysia japonica." Advanced Materials Research 518-523 (May 2012): 5489–92. http://dx.doi.org/10.4028/www.scientific.net/amr.518-523.5489.
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The objective of this study was to understand the effects of mild, moderate and severe drought stress on zoysiagrass(Zoysia japonica). Superoxide dismutase (SOD), guaiacol peroxidase (POD), catalase (CAT), and malondialdehyde (MDA) content were investigated. Mild drought(60%-70% of field capacity), moderate drought(45%-55% of field capacity), and severe drought (25%-35% of field capacity) were remained for 16 days. A gradual increase was observed in SOD activity of Zoysiagrass from 1 to13 days of drought stress in all treatments. POD and CAT activity, and lipid peroxidation increased in all treatments, and maximum change was happened in severe drought group. Severe drought has more serious damage to Zoysia japonica than mild drought and moderate drough. This suggests that Zoysiagrass has excellent drought tolerance and its ability to survive in the drought environment is very strong.
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Lucas-Borja, Manuel Esteban, Arun K. Bose, Enrique Andivia, David Candel-Pérez, Pedro A. Plaza-Álvarez, and Juan C. Linares. "Assessing Tree Drought Resistance and Climate-Growth Relationships under Different Tree Age Classes in a Pinus nigra Arn. ssp. salzmannii Forest." Forests 12, no. 9 (August 27, 2021): 1161. http://dx.doi.org/10.3390/f12091161.
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The magnitude of drought impact in forest ecosystems depends on which group of trees are more severely affected; greater mortality of smaller trees can modulate the trajectories of succession, while the mortality of larger trees can disproportionately offset the ecosystem’s carbon balance. Several studies have documented a greater vulnerability of large trees to extreme droughts while some other studies reported a greater growth reduction in smaller trees during droughts. We tested these hypotheses by comparing tree basal area increment (BAI), drought resistance (i.e., magnitude of growth decline during drought), and resilience (i.e., magnitude of growth recovery after drought) across five different age-classes in black pine (Pinus nigra Arn. ssp. salzmannii) forests in Spain. Our results showed that the BAI patterns, drought resistance, and resilience were strongly influenced by tree age-classes. In addition, the effect of climatic water balance (precipitation minus potential evapotranspiration) on BAI significantly varied among age-classes. The effect of water balance on BAI was lower for younger age-classes (1–39 years of age) compared to older age-classes. We observed a greater growth reduction (i.e., lower resistance) in older trees (>40 years of age) during droughts compared to younger trees (<40 years of age). However, all trees, irrespective of their ages, were able to recover the growth rates after the drought. In general, younger trees showed a greater capacity in recovering the growth rate (i.e., more resilient) than older trees. We detected no significant effects of stand basal area and stand density on BAI, drought resistance, and resilience. Overall, our results indicated that growth of older trees was more negatively affected during drought. Therefore, these older/larger trees can be selected for commercial thinning, or can be released from competition, which can minimize the potential impacts of future droughts in black pine forests in Spain.
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Krishna Prabhakar, Sivapuram Venkata Rama. "Implications of Regional Droughts and Transboundary Drought Risks on Drought Monitoring and Early Warning: A Review." Climate 10, no. 9 (August 23, 2022): 124. http://dx.doi.org/10.3390/cli10090124.
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Regional droughts are increasing in frequency and climate change projections indicate an exacerbation in the occurrence of regional droughts in the future. Droughts are complex hydrometeorological events, and the complexity of cause-and-effect relationships across administrative and political borders can make drought management a challenge. While countries are largely focused on assessing drought impacts within their borders, thereby providing focused information for the relevant administration, the impact on communities, industries, and countries that are distantly connected with the affected location must also be taken into consideration. If not considered, drought impacts can be underestimated, and adaptation actions undertaken may not completely address the drought risks. Understanding transboundary drought risks is an important and integral part of drought risk reduction and it will grow in importance as the world experiences more integration at regional and global levels on multiple fronts. To address drought risks comprehensively, the new paradigm demands that the impacts of regional droughts are fully understood, that this understanding is incorporated into drought monitoring and early warning systems, and that drought early warning information is provided to all stakeholders, including those beyond the boundaries of the affected region, thereby eliciting appropriate action.
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Wossenyeleh, Buruk Kitachew, Kaleb Asnake Worku, Boud Verbeiren, and Marijke Huysmans. "Drought propagation and its impact on groundwater hydrology of wetlands: a case study on the Doode Bemde nature reserve (Belgium)." Natural Hazards and Earth System Sciences 21, no. 1 (January 8, 2021): 39–51. http://dx.doi.org/10.5194/nhess-21-39-2021.
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Abstract. Drought can be described as a temporary decrease in water availability over a significant period that affects both surface and groundwater resources. Droughts propagate through the hydrological cycle and may impact vulnerable ecosystems. This paper investigates drought propagation in the hydrological cycle, focusing on assessing its impact on a groundwater-fed wetland ecosystem. Meteorological drought indices were used to analyze meteorological drought severity. Moreover, a method for assessing groundwater drought and its propagation in the aquifer was developed and applied. Groundwater drought was analyzed using the variable threshold method. Furthermore, meteorological drought and groundwater drought on recharge were compared to investigate drought propagation in the hydrological cycle. This research is carried out in the Doode Bemde wetland in central Belgium. The results of this research show that droughts are attenuated in the groundwater system. The number and severity of drought events on groundwater discharge were smaller than for groundwater recharge. However, the onset of both drought events occurred at the same time, indicating a quick response of the groundwater system to hydrological stresses. In addition, drought propagation in the hydrological cycle indicated that not all meteorological droughts result in groundwater drought. Furthermore, this drought propagation effect was observed in the wetland.
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Wossenyeleh, Buruk Kitachew, Kaleb Asnake Worku, Boud Verbeiren, and Marijke Huysmans. "Drought propagation and its impact on groundwater hydrology of wetlands: a case study on the Doode Bemde nature reserve (Belgium)." Natural Hazards and Earth System Sciences 21, no. 1 (January 8, 2021): 39–51. http://dx.doi.org/10.5194/nhess-21-39-2021.
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Abstract. Drought can be described as a temporary decrease in water availability over a significant period that affects both surface and groundwater resources. Droughts propagate through the hydrological cycle and may impact vulnerable ecosystems. This paper investigates drought propagation in the hydrological cycle, focusing on assessing its impact on a groundwater-fed wetland ecosystem. Meteorological drought indices were used to analyze meteorological drought severity. Moreover, a method for assessing groundwater drought and its propagation in the aquifer was developed and applied. Groundwater drought was analyzed using the variable threshold method. Furthermore, meteorological drought and groundwater drought on recharge were compared to investigate drought propagation in the hydrological cycle. This research is carried out in the Doode Bemde wetland in central Belgium. The results of this research show that droughts are attenuated in the groundwater system. The number and severity of drought events on groundwater discharge were smaller than for groundwater recharge. However, the onset of both drought events occurred at the same time, indicating a quick response of the groundwater system to hydrological stresses. In addition, drought propagation in the hydrological cycle indicated that not all meteorological droughts result in groundwater drought. Furthermore, this drought propagation effect was observed in the wetland.
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Robroek, Bjorn J. M., Vincent E. J. Jassey, Boudewijn Beltman, and Mariet M. Hefting. "Diverse fen plant communities enhance carbon-related multifunctionality, but do not mitigate negative effects of drought." Royal Society Open Science 4, no. 10 (October 2017): 170449. http://dx.doi.org/10.1098/rsos.170449.
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Global change, like droughts, can destabilize the carbon sink function of peatlands, either directly or indirectly through changes in plant community composition. While the effects of drought and plant community composition on individual carbon (C) related processes are well understood, their effect on multiple C-related processes simultaneously—multifunctionality—is poorly known. We studied the effect of drought on four C-related processes (net and gross CO 2 exchange, methane fluxes, and dissolved organic carbon content) in a plant removal experiment. Plant functional type (PFT) removal (graminoids, herbs, Polytrichum spp., incl. combinations) negatively affected multifunctionality; most markedly when all PFTs were removed. Our results corroborate a negative drought effect on C-related multifunctionality. Drought reduced multifunctionality, and this reduction was again largest when all PFTs were removed. Our data further indicate that much of these negative drought effects were carried over and maintained from the initial removal treatment. These results suggest that while a high diversity in plant functional types is associated to high C-related multifunctionality, plant community assembly does not drive the ability of peatlands to withstand the negative impacts of drought on multifunctionality. Hence, to safeguard the carbon cycling function in intact peatlands, the effects of climate change on the functional composition of the peatland plant community needs to be minimized.
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Sharif, Asim, and Utsab Thapa. "Effect of Water Stress in Soil Nitrogen Dynamics under Intercropping System with Maize and Sorghum." Forestry: Journal of Institute of Forestry, Nepal 15 (July 31, 2018): 1–12. http://dx.doi.org/10.3126/forestry.v15i0.24916.
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Global warming, one of the most persistent threats to nature, is expected to result in severe droughts in many parts of the world. Droughts are supposed to effect individual plants and/or plant communities by changing their a/ biotic interactions. The objective of this study was to elucidate drought effects on soil nitrogen allocation in different aggregate sizes. This was done by growing Zea mays and Sorghum bicolor in monoculture and mixture. Nitrogen allocation under drought stress was traced using nitrogen stable isotope 15N. Drought disintegrated soil aggregates into finer aggregates for sorghum monoculture and decreased the aggregate proportion in small macro-aggregate fraction for maize monoculture. For plant mixture, drought increased total nitrogen content in micro-aggregate fraction and uptake of added 15N in bulk soil. Hence, the study showed that mix planting maize and sorghum offer better resistance against changes in plant biomass and nitrogen content which suggests its effectiveness in nitrogen conservation during water stress. Moreover, intergrowing maize and sorghum under agroforestry systems also produce advantageous results.
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Hu, Qi, Jose Abraham Torres-Alavez, and Matthew S. Van Den Broeke. "Land-Cover Change and the “Dust Bowl” Drought in the U.S. Great Plains." Journal of Climate 31, no. 12 (June 2018): 4657–67. http://dx.doi.org/10.1175/jcli-d-17-0515.1.
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The North American Dust Bowl drought during the 1930s had devastating environmental and societal impacts. Comprehending the causes of the drought has been an ongoing effort in order to better predict similar droughts and mitigate their impacts. Among the potential causes of the drought are sea surface temperature (SST) anomalies in the tropical Pacific Ocean and strengthened local sinking motion as a feedback to degradation of the land surface condition leading up to and during the drought. Limitations on these causes are the lack of a strong tropical SST anomaly during the drought and lack of local anomaly in moisture supply to undercut the precipitation in the U.S. Great Plains. This study uses high-resolution modeling experiments and quantifies an effect of the particular Great Plains land cover in the 1930s that weakens the southerly moisture flux to the region. This effect lowers the average precipitation, making the Great Plains more susceptible to drought. When drought occurs, the land-cover effect enhances its intensity and prolongs its duration. Results also show that this land-cover effect is comparable in magnitude to the effect of the 1930s large-scale circulation anomaly. Finally, analysis of the relationship of these two effects suggests that while lowering the precipitation must have contributed to the Dust Bowl drought via the 1930s land-cover effect, the initiation of and recovery from that drought would likely result from large-scale circulation changes, either of chaotic origin or resulting from combinations of weak SST anomalies and other forcing.
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Vidal, J. P., E. Martin, N. Kitova, J. Najac, and J. M. Soubeyroux. "Evolution of spatio-temporal drought characteristics: validation, projections and effect of adaptation scenarios." Hydrology and Earth System Sciences Discussions 9, no. 2 (February 3, 2012): 1619–70. http://dx.doi.org/10.5194/hessd-9-1619-2012.
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Abstract. Drought events develop in both space and time and they are therefore best described through summary joint spatio-temporal characteristics, like mean duration, mean affected area and total magnitude. This paper addresses the issue of future projections of such characteristics of drought events over France through three main research questions: (1) are downscaled climate projections able to reproduce spatio-temporal characteristics of meteorological and agricultural droughts in France over a present-day period? (2) How such characteristics will evolve over the 21st century? (3) How to use standardized drought indices to represent theoretical adaptation scenarios? These questions are addressed using the Isba land surface model, downscaled climate projections from the ARPEGE General Circulation Model under three emissions scenarios, as well as results from a previously performed 50-yr multilevel and multiscale drought reanalysis over France. Spatio-temporal characteristics of meteorological and agricultural drought events are computed using the Standardized Precipitation Index and the Standardized Soil Wetness Index, respectively, and for time scales of 3 and 12 months. Results first show that the distributions of joint spatio-temporal characteristics of observed events are well reproduced by the downscaled hydroclimate projections over a present-day period. All spatio-temporal characteristics of drought events are then found to dramatically increase over the 21st century, with stronger changes for agricultural droughts. Two theoretical adaptation scenarios are eventually built based on hypotheses of adaptation to evolving climate and hydrological normals, either retrospective or prospective, and by taking advantage of the statistical properties of the standardized drought indices. The perceived spatio-temporal characteristics of drought events derived from these theoretical adaptation scenarios show much reduced changes, but they call for more realistic scenarios at both the catchment and national scale in order to accurately assess the combined effect of local-scale adaptation and global-scale mitigation.
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Liu, Tingting, Richard Krop, Tonya Haigh, Kelly Helm Smith, and Mark Svoboda. "Valuation of Drought Information: Understanding the Value of the US Drought Monitor in Land Management." Water 13, no. 2 (January 6, 2021): 112. http://dx.doi.org/10.3390/w13020112.
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Droughts affect recreation and tourism, grazing, forests, and timber, and can have important indirect effects for the ecosystems and species that rely on water. Despite its importance, the effect of drought in the land management sector is less understood than in other water-intensive sectors, such as agriculture and public water supplies. This study presents the first-ever estimates of the economic valuation of the information provided by the U.S. Drought Monitor using the avoided cost method. These estimates are based on the time and labor saved by using the U.S. Drought Monitor rather than compiling drought-related information from other sources, or using other sources for tracking/monitoring droughts, communicating drought conditions, and dealing with drought-related issues. The results reflect rational behavior—the more time needed to compile or collect drought information provided by the U.S. Drought Monitor, the higher the dollar value in avoided cost. This dollar amount also varies by institution and organization, which indicates respondents from different organizations value the information from the U.S. Drought Monitor differently. For example, compared to the state offices, the field offices in the Bureau of Land Management value more of the information provided by the U.S. Drought Monitor. These estimates can be used to estimate the societal benefits and help policy makers evaluate the U.S. Drought Monitor in different sectors.
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Phavaphutanon, L., F. T. Davies, and S. A. Duray. "Effect of Mycorrhiza on Growth Recovery of Neem Plants after Drought Exposure." HortScience 31, no. 4 (August 1996): 647d—647. http://dx.doi.org/10.21273/hortsci.31.4.647d.
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Growth recovery of mycorrhizal (VAM) and nonmycorrhizal (non-VAM) neem plants after drought exposure were followed under low phosphorus conditions. Drought significantly decreased plant growth regardless of mycorrhiza. Relative growth rate of droughted plants was greater than nondroughted plants during the growth recovery period, and compensated the loss of growth during the previous drought. VAM increased plant growth and improved regeneration of new roots outside the original root balls, particularly in plants previously exposed to drought. New roots of VAM plants were readily colonized by the VAM fungi, while those of non-VAM plants remained uncolonized. VAM growth enhancement after drought exposure was associated with greater uptake of phosphorus and other nutrients, and improved root regeneration.
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Van Tiel, Marit, Adriaan J. Teuling, Niko Wanders, Marc J. P. Vis, Kerstin Stahl, and Anne F. Van Loon. "The role of glacier changes and threshold definition in the characterisation of future streamflow droughts in glacierised catchments." Hydrology and Earth System Sciences 22, no. 1 (January 22, 2018): 463–85. http://dx.doi.org/10.5194/hess-22-463-2018.
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Abstract. Glaciers are essential hydrological reservoirs, storing and releasing water at various timescales. Short-term variability in glacier melt is one of the causes of streamflow droughts, here defined as deficiencies from the flow regime. Streamflow droughts in glacierised catchments have a wide range of interlinked causing factors related to precipitation and temperature on short and long timescales. Climate change affects glacier storage capacity, with resulting consequences for discharge regimes and streamflow drought. Future projections of streamflow drought in glacierised basins can, however, strongly depend on the modelling strategies and analysis approaches applied. Here, we examine the effect of different approaches, concerning the glacier modelling and the drought threshold, on the characterisation of streamflow droughts in glacierised catchments. Streamflow is simulated with the Hydrologiska Byråns Vattenbalansavdelning (HBV-light) model for two case study catchments, the Nigardsbreen catchment in Norway and the Wolverine catchment in Alaska, and two future climate change scenarios (RCP4.5 and RCP8.5). Two types of glacier modelling are applied, a constant and dynamic glacier area conceptualisation. Streamflow droughts are identified with the variable threshold level method and their characteristics are compared between two periods, a historical (1975–2004) and future (2071–2100) period. Two existing threshold approaches to define future droughts are employed: (1) the threshold from the historical period; (2) a transient threshold approach, whereby the threshold adapts every year in the future to the changing regimes. Results show that drought characteristics differ among the combinations of glacier area modelling and thresholds. The historical threshold combined with a dynamic glacier area projects extreme increases in drought severity in the future, caused by the regime shift due to a reduction in glacier area. The historical threshold combined with a constant glacier area results in a drastic decrease of the number of droughts. The drought characteristics between future and historical periods are more similar when the transient threshold is used, for both glacier area conceptualisations. With the transient threshold, factors causing future droughts can be analysed. This study revealed the different effects of methodological choices on future streamflow drought projections and it highlights how the options can be used to analyse different aspects of future droughts: the transient threshold for analysing future drought processes, the historical threshold to assess changes between periods, the constant glacier area to analyse the effect of short-term climate variability on droughts and the dynamic glacier area to model more realistic future discharges under climate change.
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Van Loon, A. F., S. W. Ploum, J. Parajka, A. K. Fleig, E. Garnier, G. Laaha, and H. A. J. Van Lanen. "Hydrological drought typology: temperature-related drought types and associated societal impacts." Hydrology and Earth System Sciences Discussions 11, no. 9 (September 19, 2014): 10465–514. http://dx.doi.org/10.5194/hessd-11-10465-2014.
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Abstract. For drought management and prediction, knowledge of causing factors and socio-economic impacts of hydrological droughts is crucial. Propagation of meteorological conditions in the hydrological cycle results in different hydrological drought types that require separate analysis. In addition to the existing hydrological drought typology, we here define two new drought types related to snow and ice. A snowmelt drought is a deficiency in the snowmelt discharge peak in spring in snow-influenced basins and a glaciermelt drought is a deficiency in the glaciermelt discharge peak in summer in glacierised basins. In 21 catchments in Austria and Norway we studied the meteorological conditions in the seasons preceding and at the time of snowmelt and glaciermelt drought events. Snowmelt droughts in Norway were mainly controlled by below-average winter precipitation, while in Austria both temperature and precipitation played a role. For glaciermelt droughts the effect of below-normal summer temperature was dominant, both in Austria and Norway. Subsequently, we investigated the impacts of temperature-related drought types (i.e. snowmelt and glaciermelt drought, but also cold and warm snow season drought and rain-to-snow-season drought). In historical archives and drought databases for the US and Europe many impacts were found that can be attributed to these temperature-related hydrological drought types, mainly in the sectors agriculture and electricity production (hydropower). However, drawing conclusions on the frequency of occurrence of different drought types from reported impacts is difficult, mainly because of reporting biases and the inevitably limited spatial and temporal scales of the information. This study shows that the combination of quantitative analysis of causing factors and qualitative analysis of impacts of temperature-related droughts is a promising approach to identify relevant drought types in other regions, especially if more data on drought impacts become available.
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MacDonald, Mason T., Rajeswari Kannan, and Renuga Jayaseelan. "Ascorbic Acid Preconditioning Effect on Broccoli Seedling Growth and Photosynthesis under Drought Stress." Plants 11, no. 10 (May 17, 2022): 1324. http://dx.doi.org/10.3390/plants11101324.
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Drought is an abiotic stress that decreases crop photosynthesis, growth, and yield. Ascorbic acid has been used as a seed preconditioning agent to help mitigate drought in some species, but not yet in broccoli (Brassica oleracea var. italica). The objective was to investigate the effect of ascorbic acid on growth, photosynthesis, and related parameters in watered and drought-stressed broccoli seedlings. A 2 × 4 factorial experiment was designed where stress (watered or drought) was the first factor and ascorbic acid preconditioning (untreated, 0 ppm, 1 ppm, or 10 ppm) was the second factor. Positioning within the greenhouse was included as a blocking factor and the experiment was replicated three times. All seedlings were watered for 8 weeks and then half had water withheld for 7 days to impose drought while the other half continued to be watered. Ascorbic acid preconditioning increased shoot dry mass, root dry mass, water use efficiency, and photosynthesis in all seedlings while also increasing chlorophyll, relative water content, and leaf area in droughted seedlings. Ascorbic acid preconditioning also decreased membrane injury in droughted seedlings to the point that membrane injury was not significantly different than the watered control. There was strong evidence to support ascorbic acid as a successful seed preconditioning agent in watered and droughted broccoli.
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Heudorfer, B., and K. Stahl. "Comparison of different threshold level methods for drought propagation analysis in Germany." Hydrology Research 48, no. 5 (September 30, 2016): 1311–26. http://dx.doi.org/10.2166/nh.2016.258.
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The Threshold Level Method is an approach that enables comparability across all hydrological levels. This advantage is used especially in studies on drought propagation. There are different calculation procedures for this method. The effect that the choice of a variable versus a constant threshold level method has on drought characteristics and drought propagation patterns has not been fully explored yet. Also, most drought propagation studies have analyzed modelled data, suggesting that applicability to observations be tested. We tested the Constant and the Variable Threshold Level Method for the 10th, 20th and 30th percentile on observed precipitation, streamflow, and groundwater data from Germany, and compared drought characteristics and drought propagation patterns by means of statistical analysis and synoptic assessment. The characteristic effects of choosing a variable versus a constant threshold are: (1) a substantial increase in short droughts, (2) a moderate decrease in intermediate droughts and (3) a minor increase in long droughts. Furthermore, in slow-reacting lowland catchments, theoretical propagation characteristics could mostly be confirmed. In faster-reacting upland catchments, this was not always the case and considerable differences arose. Sources of ambiguity were predominantly groundwater in lowlands and streamflow in the mountainous catchments. In conclusion, there is potential of diverging inference from the same data, depending on the chosen methodology.
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Yaltı, Sedanur, and Hakan Aksu. "Drought Analysis of Iğdır Turkey." Turkish Journal of Agriculture - Food Science and Technology 7, no. 12 (December 16, 2019): 2227. http://dx.doi.org/10.24925/turjaf.v7i12.2227-2232.3004.
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Climate change increases the odds of worsening drought in many parts of the World. Climate projections for the Mediterranean basin in which Turkey is located expresses alarming conclusions about severe droughts. Droughts are expected to prevail in different severities and periods throughout Turkey. Iğdır plain, which lies in eastern part of Turkey is convenient for cultivation of many agricultural products because of its fertile soils and micro-climatic properties. In this study, drought analysis were carried out for Iğdır by using Standardized Precipitation Index (SPI), Reconnaissance Drought Index (RDI) and Streamflow Drought Index (SDI). The data (precipitation and flow) were obtained in monthly intervals from Turkish institutions, namely General Directorate of Meteorology and General Directorate of State Hydraulic Works. Study was aimed to examine the integrated effect of low precipitations and high temperatures on hydrological and meteorological drought. Annual SPI results show that four severe and three moderate drought events whereas RDI detected four severe and four moderate drought events for the study period (47 years, 1971-2018). SPI index detected severe category droughts in the water years of 1980, 1989 and 1997. RDI detected severe category droughts in the mentioned years together with one more event in 2000. SDI identified 2002 as extreme drought year, and identified 1982, 1984, 1986 and 2002 as moderate drought years. The output of the study is aimed to serve for better understanding of droughts in the Igdir Plain.
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Tadić, Lidija, Tamara Brleković, Andreja Hajdinger, and Save Španja. "Analysis of the Inhomogeneous Effect of Different Meteorological Trends on Drought: An Example from Continental Croatia." Water 11, no. 12 (December 12, 2019): 2625. http://dx.doi.org/10.3390/w11122625.
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The majority of central Europe has a transitional climate type as a result of interactions between maritime and continental climates. This study focuses on the appearance and severity of drought in continental Croatia, which is part of the transitional climate area. It is situated between 15° E and 19° E. The altitude declines from west (167 m a.s.l) to east (88 m a.s.l.). The time period analysed is 1981–2018. Air temperature and precipitation data series from 13 meteorological stations were analysed. The analysis was done on an annual basis to define the spatio-temporal variability in air temperature and precipitation and their impact on drought episodes using the standardised evapotranspiration precipitation index. Different statistical methods (e.g., the nonparametric Mann–Kendall test and agglomerative hierarchical clustering) were used to examine the trend homogeneity of the analysed region. The analysis indicated inhomogeneity across the study area in terms of what significantly impacted the occurrence and severity of droughts. Drought occurrence is influenced more strongly by increasing trends in air temperature as compared with increasing or decreasing precipitation trends. The probability of severe drought occurrence was estimated using a copula function, and the results demonstrated that areas with higher precipitation could be more exposed to drought. Furthermore, the results demonstrated the impacts of specific regional characteristics on drought occurrence, severity, and duration, which indicates that small-scale research on droughts is more reliable.
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Vidal, J. P., E. Martin, N. Kitova, J. Najac, and J. M. Soubeyroux. "Evolution of spatio-temporal drought characteristics: validation, projections and effect of adaptation scenarios." Hydrology and Earth System Sciences 16, no. 8 (August 23, 2012): 2935–55. http://dx.doi.org/10.5194/hess-16-2935-2012.
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Abstract. Drought events develop in both space and time and they are therefore best described through summary joint spatio-temporal characteristics, such as mean duration, mean affected area and total magnitude. This paper addresses the issue of future projections of such characteristics of drought events over France through three main research questions: (1) Are downscaled climate projections able to simulate spatio-temporal characteristics of meteorological and agricultural droughts in France over a present-day period? (2) How such characteristics will evolve over the 21st century? (3) How to use standardized drought indices to represent theoretical adaptation scenarios? These questions are addressed using the Isba land surface model, downscaled climate projections from the ARPEGE General Circulation Model under three emissions scenarios, as well as results from a previously performed 50-yr multilevel and multiscale drought reanalysis over France. Spatio-temporal characteristics of meteorological and agricultural drought events are computed using the Standardized Precipitation Index and the Standardized Soil Wetness Index, respectively, and for time scales of 3 and 12 months. Results first show that the distributions of joint spatio-temporal characteristics of observed events are well simulated by the downscaled hydroclimate projections over a present-day period. All spatio-temporal characteristics of drought events are then found to dramatically increase over the 21st century, with stronger changes for agricultural droughts. Two theoretical adaptation scenarios are eventually built based on hypotheses of adaptation to evolving climate and hydrological normals, either retrospective or prospective. The perceived spatio-temporal characteristics of drought events derived from these theoretical adaptation scenarios show much reduced changes, but they call for more realistic scenarios at both the catchment and national scale in order to accurately assess the combined effect of local-scale adaptation and global-scale mitigation.
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Gustafson, Eric, Brian Miranda, and Brian Sturtevant. "Can Future CO2 Concentrations Mitigate the Negative Effects of High Temperature and Longer Droughts on Forest Growth?" Forests 9, no. 11 (October 24, 2018): 664. http://dx.doi.org/10.3390/f9110664.
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(1) Background: Climate change may subject forests to climate conditions to which they are not adapted. Elevated temperatures can potentially reduce net photosynthesis by increasing respiration rates and increasingly long droughts dramatically increase morbidity. While CO2 enrichment enhances productivity, it is not clear to what extent CO2 enrichment can offset the negative effects of elevated temperatures and longer droughts; (2) Methods: We used a mechanistic landscape model to conduct controlled simulation experiments manipulating CO2 concentration, temperature, drought length and soil water capacity; (3) Results: We found that elevated CO2 stimulates productivity such that it dwarfs the negative effect caused by elevated temperature. Energy reserves were not as strongly mitigated by elevated CO2, and the mortality of less competitive cohorts increased. Drought length had a surprisingly small effect on productivity measures, but longer droughts increased the risk of mortality; (4) Conclusions: Elevated CO2 compensated for the negative effect of longer droughts in terms of productivity measures, but not survival measures.
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Javadinejad, Safieh, Rebwar Dara, and Forough Jafary. "Evaluation of hydro-meteorological drought indices for characterizing historical and future droughts and their impact on groundwater." Resources Environment and Information Engineering 2, no. 1 (2020): 71–83. http://dx.doi.org/10.25082/reie.2020.01.003.
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The effect of meteorological and hydrological droughts is very important in arid and semi-arid regions. Analyzing these effects on groundwater supplies plays an important role for water management in those regions. This paper aims to characterize droughts in the Isfahan-Borkhar basin, an arid area of Iran. The observed hydro-climatic data (for the period of 1971-2005) were used for hydro-meteorological projections (for the period of 2006-2040). Meteorological and surface hydrological drought evaluated by Standardized Precipitation Index (SPI), Standardized Runoff Index (SRI), and the effect of hydro-meteorological droughts on groundwater was investigated by Groundwater Resources Index (GRI). Results showed that dry and wet conditions would occur in the region in the initial and subsequent decades, based on the three indices. There was a significant association between SPI, SRI, and GRI at the time scale of 12 months. The SPI estimated using only meteorological variables alone and it is useful for estimating meteorological drought forecasts. However, SRI and GRI can represent hydrological drought that computed using catchment discharge, soil moisture and groundwater level. Results showed a considerable alteration in time of drought outlines across the area and association between the variables of predicted precipitation, temperature and the kind of indices. The projection of all three drought indices indicated drier conditions in the future period (2006-2042). The results provide reasonable management strategy for management of water resources in arid coastal plains.
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Van Loon, A. F., S. W. Ploum, J. Parajka, A. K. Fleig, E. Garnier, G. Laaha, and H. A. J. Van Lanen. "Hydrological drought types in cold climates: quantitative analysis of causing factors and qualitative survey of impacts." Hydrology and Earth System Sciences 19, no. 4 (April 24, 2015): 1993–2016. http://dx.doi.org/10.5194/hess-19-1993-2015.
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Abstract. For drought management and prediction, knowledge of causing factors and socio-economic impacts of hydrological droughts is crucial. Propagation of meteorological conditions in the hydrological cycle results in different hydrological drought types that require separate analysis. In addition to the existing hydrological drought typology, we here define two new drought types related to snow and ice. A snowmelt drought is a deficiency in the snowmelt discharge peak in spring in snow-influenced basins and a glaciermelt drought is a deficiency in the glaciermelt discharge peak in summer in glacierised basins. In 21 catchments in Austria and Norway we studied the meteorological conditions in the seasons preceding and at the time of snowmelt and glaciermelt drought events. Snowmelt droughts in Norway were mainly controlled by below-average winter precipitation, while in Austria both temperature and precipitation played a role. For glaciermelt droughts, the effect of below-average summer air temperature was dominant, both in Austria and Norway. Subsequently, we investigated the impacts of temperature-related drought types (i.e. snowmelt and glaciermelt drought, but also cold and warm snow season drought and rain-to-snow-season drought). In historical archives and drought databases for the US and Europe many impacts were found that can be attributed to these temperature-related hydrological drought types, mainly in the agriculture and electricity production (hydropower) sectors. However, drawing conclusions on the frequency of occurrence of different drought types from reported impacts is difficult, mainly because of reporting biases and the inevitably limited spatial and temporal scales of the information. Finally, this study shows that complete integration of quantitative analysis of causing factors and qualitative analysis of impacts of temperature-related droughts is not yet possible. Analysis of selected events, however, points out that it can be a promising research area if more data on drought impacts become available.
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Dunn, James W., and Piotr Bórawski. "THE EFFECT OF THE 2012 U.S. DROUGHT ON GLOBAL GRAIN MARKETS: A MEASURE OF GLOBALIZATION." sj-economics scientific journal 10 (December 30, 2012): 129–33. http://dx.doi.org/10.58246/sjeconomics.v10i.453.
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The objective of the paper was to present drought’s effects in the USA in 2012 on global grain markets. The problem of drought is very important for farmers, but also for food consumers. The USA is a world leader in grain production and exporters. Lower grain supply had an impact on high prices both grains and nutritious products. The next effect of drought was the increase of fodders for animals and other products.
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van der Graaf, S. C., T. A. J. Janssen, J. W. Erisman, and M. Schaap. "Nitrogen deposition shows no consistent negative nor positive effect on the response of forest productivity to drought across European FLUXNET forest sites." Environmental Research Communications 3, no. 12 (December 1, 2021): 125003. http://dx.doi.org/10.1088/2515-7620/ac2b7d.
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Abstract Atmospheric reactive nitrogen (N) deposition is an important driver of carbon (C) sequestration in forest ecosystems. Previous studies have focused on N-C interactions in various ecosystems; however, relatively little is known about the impact of N deposition on ecosystem C cycling during climate extremes such as droughts. With the occurrence and severity of droughts likely to be exacerbated by climate change, N deposition—drought interactions remain one of the key uncertainties in process-based models to date. This study aims to contribute to the understanding of N deposition-drought dynamics on gross primary production (GPP) in European forest ecosystems. To do so, different soil water availability indicators (Standardized Precipitation Evapotranspiration Index (SPEI), soil volumetric water) and GPP measurements from European FLUXNET forest sites were used to quantify the response of forest GPP to drought. The computed drought responses of the forest GPP to drought were linked to modelled N deposition estimates for varying edaphic, physiological, and climatic conditions. Our result showed a differential response of forest ecosystems to the drought indicators. Although all FLUXNET forest sites showed a coherent dependence of GPP on N deposition, no consistent or significant N deposition effect on the response of forest GPP to drought could be isolated. The mean response of forest GPP to drought could be predicted for forests with Pinus trees as dominant species (R 2 = 0.85, RMSE = 8.1). After extracting the influence of the most prominent parameters (mean annual temperature and precipitation, forest age), however, the variability remained too large to significantly substantiate hypothesized N deposition effects. These results suggest that, while N deposition clearly affects forest productivity, N deposition is not a major nor consistent driver of forest productivity responses to drought in European forest ecosystems.
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Kaňová, D., and E. Kula. "The effect of stress factors on birch Betula pendula Roth." Journal of Forest Science 50, No. 9 (January 11, 2012): 399–404. http://dx.doi.org/10.17221/4636-jfs.
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In a controlled pot trial, plants of birch (Betula pendula Roth) were treated in six variants: acid watering (pH 3), acid watering with spraying, drought, ammonium sulphate fertilisation, ammonium sulphate fertilisation in combination with drought, and control. The response to the treatment with ammonium sulphate in terms of the increment was discordant as it increased the sensitivity of birch to frost. Drought had a negative effect on increments. A combination of ammonium sulphate and drought; drought; ammonium sulphate and sprayed acid watering delayed the shedding of leaves; this was due to a longer vegetation period, significantly higher nitrogen content in these variants, with the exception of drought.
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Zhao, Jingxue, Tongren Xu, Jingfeng Xiao, Shaomin Liu, Kebiao Mao, Lisheng Song, Yunjun Yao, Xinlei He, and Huaize Feng. "Responses of Water Use Efficiency to Drought in Southwest China." Remote Sensing 12, no. 1 (January 6, 2020): 199. http://dx.doi.org/10.3390/rs12010199.
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Water use efficiency (WUE) measures the tradeoff between carbon uptake and water consumption in terrestrial ecosystems. It remains unclear how the responses of WUE to drought vary with drought severity. We assessed the spatio-temporal variations of ecosystem WUE and its responses to drought for terrestrial ecosystems in Southwest China over the period 2000–2017. The annual WUE values varied with vegetation type in the region: Forests (3.25 gC kg−1H2O) > shrublands (2.00 gC kg−1H2O) > croplands (1.76 gC kg−1H2O) > grasslands (1.04 gC kg−1H2O). During the period 2000–2017, frequent droughts occurred in Southwest China, and overall, drought had an enhancement effect on WUE. However, the effects of drought on WUE varied with vegetation type and drought severity. Croplands were the most sensitive to drought, and slight water deficiency led to the decline of cropland WUE. Over grasslands, mild drought increased its WUE while moderate and severe drought reduced its WUE. For forests and shrublands, mild and moderate drought increased their WUE, and only severe drought reduce their WUE, indicating that these ecosystems had stronger resistance to drought. Assessing the patterns and trends of ecosystem WUE and its responses to drought are essential for understanding plant water use strategy and informing ecosystem water management.
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Vandegeer, Rebecca, Rebecca E. Miller, Melissa Bain, Roslyn M. Gleadow, and Timothy R. Cavagnaro. "Drought adversely affects tuber development and nutritional quality of the staple crop cassava (Manihot esculenta Crantz)." Functional Plant Biology 40, no. 2 (2013): 195. http://dx.doi.org/10.1071/fp12179.
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Cassava (Manihot esculenta Crantz) is the staple food source for over 850 million people worldwide. Cassava contains cyanogenic glucosides and can be toxic to humans, causing paralysing diseases such as konzo, and even death if not properly processed. Konzo epidemics are often associated with times of drought. This may be due to a greater reliance on cassava as it is drought tolerant, but it may also be due to an increase in cyanogenic glucosides. Episodic droughts are forecast to become more common in many cassava-growing regions. We therefore sought to quantify the effect of water-stress on both yield and cyanogenic glucoside concentration (CNc) in the developing tubers of cassava. Five-month-old plants were grown in a glasshouse and either well watered or droughted for 28 days. A subset of droughted plants was re-watered half way through the experiment. Droughted plants had 45% fewer leaves and lower tuber yield, by 83%, compared with well-watered plants. CNc was 2.9-fold higher in the young leaves of droughted plants, whereas CNc in tubers from droughted plants was 4-fold greater than in tubers from well-watered plants. Re-watered plants had a similar biomass to control plants, and lower CNc than droughted plants. These findings highlight the important link between food quality and episodic drought.
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Rajee, R., and V. Emayavaramban. "Examining drought behaviour using departure index and rainfall anomaly index in Nambiyar river basin, Tamil nadu." Geo Eye 7, no. 2 (December 15, 2018): 20–24. http://dx.doi.org/10.53989/bu.ge.v7i2.6.
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Drought is one of the complex natural phenomena. In extreme cases, drought causes great damage to the economy and human life. Drought is caused by a lack of long-term rainfall. The humans as well as the environment are greatly affected due to drought. It is not related to particular climate regions but it causes a similar effect in all climatic regions of the world. There are several drought-prone areas in India so the Government of India has developed a Drought Affected Area Plan which is being implemented in drought-prone areas. An attempt has been made in this paper studying two drought indices such as Departure Index (DI) and Rainfall Anomaly Index (RAI) in the Nambiyar River Basin of Tamil Nadu to assess the drought condition. Only 3 classifications (moderate, mild, and no droughts) are observed in the Departure Index. Mild drought years are highly found in the Nambiyar River basin followed by moderate and no droughts. Chidambarapuram, Nainaputhoor station had a maximum drought of 24 years and 6 years of moderate drought is observed in Vallioor station. The frequency of drought years for RAI index are repeatedly noted high during the year 2003, 2016, and Keeriparai station had the highest negative anomaly value of -10.67 in the year 2017. Keywords: Rainfall; RAI; DI; drought; Nambiyar river basin
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Vinothkanna, S., and V. Emayavaramban. "Exploring the drought condition in Namakkal District, Tamilnadu, through standardized precipitation index." Geo Eye 8, no. 2 (December 15, 2019): 46–53. http://dx.doi.org/10.53989/bu.ge.v8i2.7.
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Drought has long been recognized as one of the major causes of human misery and being the natural disaster that annually claims the most victims. Droughts are recurring climatic events, which often hit everywhere, bringing significant water shortages, economic losses and adverse social consequences. Water scarcity can be said as the cause and effect of drought. It is not possible to avoid droughts. But drought preparedness can be developed and drought impacts can be managed. The levels of drought preparedness in countries of the region differ significantly. The success of both depends, amongst the others, on how well the droughts are defined and drought characteristics quantified. Hence, an attempt has been made in this study to identify the drought condition on rainfed namakkal district. Annual normal rainfall of Namakkal is found to vary from 478 to 860 mm with an average of 732 mm. Among the monsoons, Southwest monsoon (SWM) had higher amount of average rainfall followed by Northeast monsoon (NEM) rainfall. During SWM, except the locations Paramathy all other locations have dependable rainfall. During NEM, the locations Namakkal, Rasipuram and Paramathy had CV higher than 50 Per cent that are not dependable. Except this all other locations have dependable rainfall. Most of the locations had witnessed 1 to 6 moderate drought years in both the monsoons. The study based on SPI will be helpful for assessing the drought severity. Keywords: Rainfall; SWM; CV; Drought; Index
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Zhang, Linqi, Yi Liu, Liliang Ren, Adriaan J. Teuling, Ye Zhu, Linyong Wei, Linyan Zhang, et al. "Analysis of flash droughts in China using machine learning." Hydrology and Earth System Sciences 26, no. 12 (June 24, 2022): 3241–61. http://dx.doi.org/10.5194/hess-26-3241-2022.
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Abstract. The term “flash drought” describes a type of drought with rapid onset and strong intensity, which is co-affected by both water-limited and energy-limited conditions. It has aroused widespread attention in related research communities due to its devastating impacts on agricultural production and natural systems. Based on a global reanalysis dataset, we identify flash droughts across China during 1979–2016 by focusing on the depletion rate of weekly soil moisture percentile. The relationship between the rate of intensification (RI) and nine related climate variables is constructed using three machine learning (ML) technologies, namely, multiple linear regression (MLR), long short-term memory (LSTM), and random forest (RF) models. On this basis, the capabilities of these algorithms in estimating RI and detecting droughts (flash droughts and traditional slowly evolving droughts) were analyzed. Results showed that the RF model achieved the highest skill in terms of RI estimation and flash drought identification among the three approaches. Spatially, the RF-based RI performed best in southeastern China, with an average CC of 0.90 and average RMSE of the 2.6 percentile per week, while poor performances were found in the Xinjiang region. For drought detection, all three ML technologies presented a better performance in monitoring flash droughts than in conventional slowly evolving droughts. Particularly, the probability of detection (POD), false alarm ratio (FAR), and critical success index (CSI) of flash drought derived from RF were 0.93, 0.15, and 0.80, respectively, indicating that RF technology is preferable in estimating the RI and monitoring flash droughts by considering multiple meteorological variable anomalies in adjacent weeks to drought onset. In terms of the meteorological driving mechanism of flash drought, the negative precipitation (P) anomalies and positive potential evapotranspiration (PET) anomalies exhibited a stronger synergistic effect on flash droughts compared to slowly developing droughts, along with asymmetrical compound influences in different regions of China. For the Xinjiang region, P deficit played a dominant role in triggering the onset of flash droughts, while in southwestern China, the lack of precipitation and enhanced evaporative demand almost contributed equally to the occurrence of flash drought. This study is valuable to enhance the understanding of flash droughts and highlight the potential of ML technologies in flash drought monitoring.
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Wu, Xiaoping, Rongrong Zhang, Virgílio A. Bento, Song Leng, Junyu Qi, Jingyu Zeng, and Qianfeng Wang. "The Effect of Drought on Vegetation Gross Primary Productivity under Different Vegetation Types across China from 2001 to 2020." Remote Sensing 14, no. 18 (September 18, 2022): 4658. http://dx.doi.org/10.3390/rs14184658.
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Climate change has exacerbated the frequency and severity of droughts worldwide. Evaluating the response of gross primary productivity (GPP) to drought is thus beneficial to improving our understanding of the impact of drought on the carbon cycle balance. Although many studies have investigated the relationship between vegetation productivity and dry/wet conditions, the capability of different drought indices of assessing the influence of water deficit is not well understood. Moreover, few studies consider the effects of drought on vegetation with a focus on periods of drought. Here, we investigated the spatial-temporal patterns of GPP, the standardized precipitation evapotranspiration index (SPEI), and the vapor pressure deficit (VPD) in China from 2001 to 2020 and examined the relationship between GPP and water deficit/drought for different vegetation types. The results revealed that SPEI and GPP were positively correlated over approximately 70.7% of the total area, and VPD was negatively correlated with GPP over about 66.2% of the domain. Furthermore, vegetation productivity was more negatively affected by water deficit in summer and autumn. During periods of drought, the greatest negative impact was on deciduous forests and croplands, and woody savannas were the least impacted. This research provides a scientific reference for developing mitigation and adaptation measures to lessen the impact of drought disasters under a changing climate.
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Mens, M. J. P., K. Gilroy, and D. Williams. "Developing system robustness analysis for drought risk management: an application on a water supply reservoir." Natural Hazards and Earth System Sciences 15, no. 8 (August 26, 2015): 1933–40. http://dx.doi.org/10.5194/nhess-15-1933-2015.
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Abstract. Droughts will likely become more frequent, greater in magnitude and longer in duration in the future due to climate change. Already in the present climate, a variety of drought events may occur with different exceedance frequencies. These frequencies are becoming more uncertain due to climate change. Many methods in support of drought risk management focus on providing insight into changing drought frequencies, and use water supply reliability as a key decision criterion. In contrast, robustness analysis focuses on providing insight into the full range of drought events and their impact on a system's functionality. This method has been developed for flood risk systems, but applications on drought risk systems are lacking. This paper aims to develop robustness analysis for drought risk systems, and illustrates the approach through a case study with a water supply reservoir and its users. We explore drought characterization and the assessment of a system's ability to deal with drought events, by quantifying the severity and socio-economic impact of a variety of drought events, both frequent and rare ones. Furthermore, we show the effect of three common drought management strategies (increasing supply, reducing demand and implementing hedging rules) on the robustness of the coupled water supply and socio-economic system. The case is inspired by Oologah Lake, a multipurpose reservoir in Oklahoma, United States. Results demonstrate that although demand reduction and supply increase may have a comparable effect on the supply reliability, demand reduction may be preferred from a robustness perspective. To prepare drought management plans for dealing with current and future droughts, it is thus recommended to test how alternative drought strategies contribute to a system's robustness rather than relying solely on water reliability as the decision criterion.
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Mens, M. J. P., K. Gilroy, and D. Williams. "Developing system robustness analysis for drought risk management: an application on a water supply reservoir." Natural Hazards and Earth System Sciences Discussions 3, no. 1 (January 7, 2015): 203–25. http://dx.doi.org/10.5194/nhessd-3-203-2015.
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Abstract. Droughts will likely become more frequent, of greater magnitude and of longer duration in the future due to climate change. Already in the present climate, a variety of drought events may occur with different exceedance frequencies. These frequencies are becoming more uncertain due to climate change. Many methods in support of drought risk management focus on providing insight into changing drought frequencies, and use water supply reliability as key decision criterion. In contrast, robustness analysis focuses on providing insight into the full range of drought events and their impact on a system's functioning. This method has been developed for flood risk systems, but applications on drought risk systems are lacking. This paper aims to develop robustness analysis for drought risk systems, and illustrates the approach through a case study with a water supply reservoir and its users. We explore drought characterization and the assessment of a system's ability to deal with drought events, by quantifying the severity and socio-economic impact of a variety of drought events, both frequent and rare ones. Furthermore, we show the effect of three common drought management strategies (increasing supply, reducing demand and implementing hedging rules) on the robustness of the coupled water supply and socio-economic system. The case is inspired by Oologah Lake, a multipurpose reservoir in Oklahoma, United States. Results demonstrate that although demand reduction and supply increase may have a comparable effect on the supply reliability, demand reduction may be preferred from a robustness perspective. To prepare drought management plans for dealing with current and future droughts, it is thus recommended to test how alternative drought strategies contribute to a system's robustness rather than relying solely on water reliability as the decision criterion.
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García-Valdecasas Ojeda, Matilde, Emilio Romero-Jiménez, Juan José Rosa-Cánovas, Patricio Yeste, Yolanda Castro-Díez, María Jesús Esteban-Parra, Sergio M. Vicente-Serrano, and Sonia R. Gámiz-Fortis. "Assessing Future Drought Conditions over the Iberian Peninsula: The Impact of Using Different Periods to Compute the SPEI." Atmosphere 12, no. 8 (July 29, 2021): 980. http://dx.doi.org/10.3390/atmos12080980.
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Future drought-hazard assessments using standardized indices depend on the period used to calibrate the probability distributions. This appears to be particularly important in a changing climate with significant trends in drought-related variables. This study explores the effect of using different approaches to project droughts, with a focus on changes in drought characteristics (frequency, duration, time spent in drought, and spatial extent), estimated with a calibration period covering recent past and future conditions (self-calibrated indices), and another one that only applies recent-past records (relative indices). The analysis focused on the Iberian Peninsula (IP), a hot-spot region where climate projections indicate significant changes by the end of this century. To do this, a EURO-CORDEX multi-model ensemble under RCP8.5 was used to calculate the Standardized Precipitation-Evapotranspiration Index (SPEI) at both 3- and 12-month timescales. The results suggest that projections of drought characteristics strongly depend on the period used to calibrate the SPEI, particularly at a 12-month timescale. Overall, differences were larger for the near future when relative indices indicated more severe droughts. For the distant future, changes were more similar, although self-calibrated indices revealed more frequent and longer-lasting droughts and the relative ones a drought worsening associated with extremely prolonged drought events.
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Alemaw, B. F., and J. M. Kileshye-Onema. "Evaluation of drought regimes and impacts in the Limpopo basin." Hydrology and Earth System Sciences Discussions 11, no. 1 (January 7, 2014): 199–222. http://dx.doi.org/10.5194/hessd-11-199-2014.
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Abstract. Drought is a common phenomenon in the Limpopo River basin. In essence, droughts are long–term hydro-meteorological events affecting vast regions and causing significant non-structural damages. In the interest of riparian states' joint integrated water resources development and management of the Limpopo basin, inter regional drought severity and its impacts should be understood. The study focussed on case studies in the basin which is subdivided into four homogeneous regions owing to topographic and climate variations based on the previous work of the same authors. Using the medium range time series of the Standardized Precipitation Index (SPI) as an indicator of drought, for each homogeneous region monthly and annual Severity-Area-Frequency (SAF) curves and maps of probability of drought occurrence were constructed. The results indicated localized severe droughts in higher frequencies, while only moderate to severe low frequency droughts may spread over wider areas in the basin. The region-level Drought-Severity Indices can be used as indicators for planning localized interventions and drought mitigation efforts in the basin. The approach can also be used to develop improved drought indicators, to assess the relationship between drought hazard and vulnerability and to enhance the performance of methods currently used for drought forecasting. Results on the meteorological drought linkage with hydrological and vegetation or agricultural drought indices are presented as means of validation of the specific drought regimes and their localized impact in each homogeneous region. In general, this preliminary investigation reveals that the western part of the basin will face a higher risk of drought when compared to other regions of the Limpopo basin in terms of the medium-term drought. The Limpopo basin is water stressed and livelihood challenges remain at large, thus impacts of droughts and related resilience options should be taken into account in the formulation of regional sustainable water resources development strategies. This study is exciting in the manner that the variations in the sub-basin drought severities are revealed and are used to suggest the corresponding drought monitoring and management strategies. This will have an overall effect in developing a basin-wide framework for integrated drought management as well as water resources development and management, which requires cooperative efforts among the riparian countries of the Limpopo basin.
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Yuan, Xing, Miao Zhang, Linying Wang, and Tian Zhou. "Understanding and seasonal forecasting of hydrological drought in the Anthropocene." Hydrology and Earth System Sciences 21, no. 11 (November 7, 2017): 5477–92. http://dx.doi.org/10.5194/hess-21-5477-2017.
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Abstract. Hydrological drought is not only caused by natural hydroclimate variability but can also be directly altered by human interventions including reservoir operation, irrigation, groundwater exploitation, etc. Understanding and forecasting of hydrological drought in the Anthropocene are grand challenges due to complicated interactions among climate, hydrology and humans. In this paper, five decades (1961–2010) of naturalized and observed streamflow datasets are used to investigate hydrological drought characteristics in a heavily managed river basin, the Yellow River basin in north China. Human interventions decrease the correlation between hydrological and meteorological droughts, and make the hydrological drought respond to longer timescales of meteorological drought. Due to large water consumptions in the middle and lower reaches, there are 118–262 % increases in the hydrological drought frequency, up to 8-fold increases in the drought severity, 21–99 % increases in the drought duration and the drought onset is earlier. The non-stationarity due to anthropogenic climate change and human water use basically decreases the correlation between meteorological and hydrological droughts and reduces the effect of human interventions on hydrological drought frequency while increasing the effect on drought duration and severity. A set of 29-year (1982–2010) hindcasts from an established seasonal hydrological forecasting system are used to assess the forecast skill of hydrological drought. In the naturalized condition, the climate-model-based approach outperforms the climatology method in predicting the 2001 severe hydrological drought event. Based on the 29-year hindcasts, the former method has a Brier skill score of 11–26 % against the latter for the probabilistic hydrological drought forecasting. In the Anthropocene, the skill for both approaches increases due to the dominant influence of human interventions that have been implicitly incorporated by the hydrological post-processing, while the difference between the two predictions decreases. This suggests that human interventions can outweigh the climate variability for the hydrological drought forecasting in the Anthropocene, and the predictability for human interventions needs more attention.
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Planchon, O., V. Dubreuil, V. Bernard, and S. Blain. "Contribution of tree-ring analysis to the study of droughts in northwestern France (XIX–XXth century)." Climate of the Past Discussions 4, no. 1 (February 25, 2008): 249–70. http://dx.doi.org/10.5194/cpd-4-249-2008.
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Abstract. A tree-ring analysis based on oak samples in the North-West of France showed the effects of droughts periods on the growth index, during the late XIXth and XXth century. Four types of droughts were identified using the results of the tree-ring analysis and the available climate data. The "type 1" was subjected to a continuous and intense drought during all the vegetative period (spring and summer), the "type 2" was subjected to a summer drought succeeding no precipitation deficit in spring, the "type 3" was subjected to a remarkable winter drought and during the years of the "type 4", precipitation deficits were recorded for several but not successive months, over an heterogeneous spatial distribution. The long, intense and countinuous droughts clearly showed a spatial structuring effect on the growth index, especially when the two successive vegetative seasons (spring and summer) recorded strong precipitation deficits combined with shrivellings. These extreme cases involved the lowest growth index over most of the studied area, with some variations due to the altitude and exposure effects on the local-scale spatial distribution of the hydrological stress. The hydrological balance for the station of Rennes (Brittany) confirmed these results in accordance with the intensity and/or duration of drought periods: the most intense droughts of the "type 1" were especially pointed out. A climatic interpretation of growth index data and maps could so be possible over northwestern France with an application to the medieval times and perhaps to other periods, but the cause of the different drought patterns must be more precisely studied during the contemporary period (late XIXth century and all the XXth century).
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Cooper, Matthew, Austin Sandler, Sveva Vitellozzi, Yeyoung Lee, Greg Seymour, Beliyou Haile, and Carlo Azzari. "Re-examining the effects of drought on intimate-partner violence." PLOS ONE 16, no. 7 (July 20, 2021): e0254346. http://dx.doi.org/10.1371/journal.pone.0254346.
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Droughts are associated with several societal ills, especially in developing economies that rely on rainfed agriculture. Recently, researchers have begun to examine the effect of droughts on the risk of Intimate-Partner Violence (IPV), but so far this work has led to inconclusive results. For example, two large recent studies analyzed comparable data from multiple sub-Saharan African countries and drew opposite conclusions. We attempt to resolve this apparent paradox by replicating previous analyses with the largest data set yet assembled to study drought and IPV. Integrating the methods of previous studies and taking particular care to control for spatial autocorrelation, we find little association between drought and most forms of IPV, although we do find evidence of associations between drought and women’s partners exhibiting controlling behaviors. Moreover, we do not find significant heterogeneous effects based on wealth, employment, household drinking water sources, or urban-rural locality.
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Bloomfield, John P., Benjamin P. Marchant, and Andrew A. McKenzie. "Changes in groundwater drought associated with anthropogenic warming." Hydrology and Earth System Sciences 23, no. 3 (March 11, 2019): 1393–408. http://dx.doi.org/10.5194/hess-23-1393-2019.
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Abstract. Here we present the first empirical evidence for changes in groundwater drought associated with anthropogenic warming in the absence of long-term changes in precipitation. Analysing standardised indices of monthly groundwater levels, precipitation and temperature, using two unique groundwater level data sets from the Chalk aquifer, UK, for the period 1891 to 2015, we show that precipitation deficits are the main control on groundwater drought formation and propagation. However, long-term changes in groundwater drought are shown to be associated with anthropogenic warming over the study period. These include increases in the frequency and intensity of individual groundwater drought months, and increases in the frequency, magnitude and intensity of episodes of groundwater drought, as well as an increasing tendency for both longer episodes of groundwater drought and for an increase in droughts of less than 1 year in duration. We also identify a transition from a coincidence of episodes of groundwater drought with precipitation droughts at the end of the 19th century, to an increasing coincidence with both precipitation droughts and with hot periods in the early 21st century. In the absence of long-term changes in precipitation deficits, we infer that the changing nature of groundwater droughts is due to changes in evapotranspiration (ET) associated with anthropogenic warming. We note that although the water tables are relatively deep at the two study sites, a thick capillary fringe of at least 30 m in the Chalk means that ET should not be limited by precipitation at either site. ET may be supported by groundwater through major episodes of groundwater drought and, hence, long-term changes in ET associated with anthropogenic warming may drive long-term changes in groundwater drought phenomena in the Chalk aquifer. Given the extent of shallow groundwater globally, anthropogenic warming may widely effect changes to groundwater drought characteristics in temperate environments.
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Liu, Yinge, Yanjun Wen, Yaqian Zhao, and Haonan Hu. "Analysis of Drought and Flood Variations on a 200-Year Scale Based on Historical Environmental Information in Western China." International Journal of Environmental Research and Public Health 19, no. 5 (February 27, 2022): 2771. http://dx.doi.org/10.3390/ijerph19052771.
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Historical environmental evidence has been characterized by time accuracy, high spatial resolution and rich information, which may be widely used in the reconstruction of historical data series. Taking the upper reaches of the Weihe River as an example in Western China, the grades and index sequences of the drought and flood disasters from 1800 to 2016 were reconstructed based on various historical environmental information and standardized precipitation indicator (SPI). Moreover, the characteristics of droughts and floods were analyzed using statistical diagnostic methods, and the mechanisms affecting centennial-scale droughts and floods were discussed. The validity of reconstruction sequence of droughts/floods was verified, which showed that the reconstruction sequence may reasonably indicate the status of drought and flood. The reconstruction indicated the following periods of drought/flood: a period of extreme and big droughts in 1835s–1893s, 1924s–1943s and 1984s–2008s, a period of extreme and big floods in 1903s–1923s, and a period of extreme and big droughts/floods in 1944s–1983s. Moreover, the droughts were more serious in the western part of this region and the floods were relatively severe in the east of this region, while the droughts and floods have long-term period of about 100 years and mutation. The influence mechanism of external environmental forcing factors driving floods/droughts were revealed. The results showed that the cycle of El Niño Southern Oscillation (ENSO) and sunspot activities were closely related to the variations of drought/flood, meanwhile, ENSO has a significant lag time scale cumulative influence on droughts and floods, especially the 15-year sliding effect was the most obvious. In the peak year of sunspots, the probability of heavy drought/extreme floods was large, and the 102-year sunspot cycle has a more significant effect on drought and flood disasters. The mutation of droughts and floods occurred in the context of the drastic changes in the ground environment, and transformation of precipitation and land use structure. These results will enhance the understandings of historical environmental climate characteristics and mechanisms over the hundred years, and be useful for the future regional water resources and assessment, and ecological environment management.
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Zhou, Junju, Qiaoqiao Li, Lanying Wang, Li Lei, Meihua Huang, Juan Xiang, Wei Feng, et al. "Impact of Climate Change and Land-Use on the Propagation from Meteorological Drought to Hydrological Drought in the Eastern Qilian Mountains." Water 11, no. 8 (August 2, 2019): 1602. http://dx.doi.org/10.3390/w11081602.
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As one of the most destructive and costly natural disasters, drought has far-reaching negative effects on agriculture, water resources, the environment, and human life. Scientific understanding of propagation from meteorological to hydrological drought is of great significance for accurate forecasting of hydrological drought and preventing and mitigating drought disasters. The objective of this study is to analyze the spatio-temporal variational characteristics of propagation from meteorological drought to hydrological drought and the associated driving mechanisms in the eastern Qilian Mountains using the standard precipitation index (SPI), standardized runoff index (SRI), and drought propagation intensity index (DPI). The results show that there has been meteorological humidification and hydrological aridification in the upper reaches of the Shiyang River Basin over the last 56 years; especially in the 2000s, the intensity of hydrological drought was the strongest and the intensity of meteorological drought was the weakest, indicating the propagation intensity of meteorological drought to hydrological drought was extremely strong during this period. The changes of meteorological and hydrological dry–wet are different, both on seasonal and monthly scales. The meteorological dry–wet is shown to have had a significant effect both on the current and month-ahead hydrological dry–wet, where the one-month lag effect was most obvious. The relationship between meteorological and hydrological droughts also vary in space: Hydrological aridification in the Huangyang River, and the rivers east of it, was greater than that in the western tributaries. The drought propagation intensities from west to east showed a decreasing trend, excluding the Huangyang River. Climate and land-use changes are the main factors affecting the propagation from meteorological drought to hydrological drought. When the natural vegetation area accounted for between 76.3–78%, the cultivated land area between 0.55–3.6% and the construction area between 0.08–0.22% were a peer-to-peer propagation process from meteorological drought to hydrological drought in the upper reaches of the Shiyang River.
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Wendt, Doris E., John P. Bloomfield, Anne F. Van Loon, Margaret Garcia, Benedikt Heudorfer, Joshua Larsen, and David M. Hannah. "Evaluating integrated water management strategies to inform hydrological drought mitigation." Natural Hazards and Earth System Sciences 21, no. 10 (October 18, 2021): 3113–39. http://dx.doi.org/10.5194/nhess-21-3113-2021.
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Abstract. Managing water–human systems during water shortages or droughts is key to avoid the overexploitation of water resources and, in particular, groundwater. Groundwater is a crucial water resource during droughts as it sustains both environmental and anthropogenic water demand. Drought management is often guided by drought policies, to avoid crisis management, and actively introduced management strategies. However, the impact of drought management strategies on hydrological droughts is rarely assessed. In this study, we present a newly developed socio-hydrological model, simulating the relation between water availability and managed water use over 3 decades. Thereby, we aim to assess the impact of drought policies on both baseflow and groundwater droughts. We tested this model in an idealised virtual catchment based on climate data, water resource management practices and drought policies in England. The model includes surface water storage (reservoir), groundwater storage for a range of hydrogeological conditions and optional imported surface water or groundwater. These modelled water sources can all be used to satisfy anthropogenic and environmental water demand. We tested the following four aspects of drought management strategies: (1) increased water supply, (2) restricted water demand, (3) conjunctive water use and (4) maintained environmental flow requirements by restricting groundwater abstractions. These four strategies were evaluated in separate and combined scenarios. Results show mitigated droughts for both baseflow and groundwater droughts in scenarios applying conjunctive use, particularly in systems with small groundwater storage. In systems with large groundwater storage, maintaining environmental flows reduces hydrological droughts most. Scenarios increasing water supply or restricting water demand have an opposing effect on hydrological droughts, although these scenarios are in balance when combined at the same time. Most combined scenarios reduce the severity and occurrence of hydrological droughts, given an incremental dependency on imported water that satisfies up to a third of the total anthropogenic water demand. The necessity for importing water shows the considerable pressure on water resources, and the delicate balance of water–human systems during droughts calls for short-term and long-term sustainability targets within drought policies.
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Pool, Joshua R., Jason J. Griffin, Cheryl R. Boyer, and Stuart L. Warren. "Short-term Recurring Drought Affects Growth and Photosynthetic Capacity of Four Conifer Species." Journal of Environmental Horticulture 31, no. 1 (March 1, 2013): 39–42. http://dx.doi.org/10.24266/0738-2898.31.1.39.
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The Midwest and southern Great Plains are known for historic and severe droughts. More common, however, are short-term recurring drought events that can limit tree survival. The pressure of environmental stress combined with numerous diseases and pests are decimating existing Pinus L. spp. (pine) plantings and driving the effort to identify alternative species. Four species of conifer were subjected to recurring moderate or severe drought to observe the effects on growth and photosynthesis. Species evaluated were: Abies nordmanniana (Nordmann fir), Cupressus arizonica (Arizona cypress), Picea engelmannii (Engelmann spruce), and Thuja × ‘Green Giant’ (‘Green Giant’ arborvitae). Recurring drought reduced height and growth index of T. × ‘Green Giant’. However, photosynthesis and root growth were unaffected by drought treatments. In contrast, reduced Pnet was the only detectable effect of recurring drought in P. engelmannii. Growth of A. nordmanniana was not affected by drought. When subjected to drought, C. arizonica reduced shoot dry weight, while maintaining photosynthesis and root growth. Overall, C. arizonica was able to maintain growth of roots and shoots as well as maintain photosynthesis which may be an advantage in the harsh climate of the Midwest and southern Great Plains.
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Klovenski, Elizabeth, Yuxuan Wang, Susanne E. Bauer, Kostas Tsigaridis, Greg Faluvegi, Igor Aleinov, Nancy Y. Kiang, et al. "Interactive biogenic emissions and drought stress effects on atmospheric composition in NASA GISS ModelE." Atmospheric Chemistry and Physics 22, no. 20 (October 17, 2022): 13303–23. http://dx.doi.org/10.5194/acp-22-13303-2022.
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Abstract. Drought is a hydroclimatic extreme that causes perturbations to the terrestrial biosphere and acts as a stressor on vegetation, affecting emissions patterns. During severe drought, isoprene emissions are reduced. In this paper, we focus on capturing this reduction signal by implementing a new percentile isoprene drought stress (yd) algorithm in NASA GISS ModelE based on the MEGAN3 (Model of Emissions of Gases and Aerosols from Nature Version 3) approach as a function of a photosynthetic parameter (Vc,max) and water stress (β). Four global transient simulations from 2003–2013 are used to demonstrate the effect without yd (Default_ModelE) and with online yd (DroughtStress_ModelE). DroughtStress_ModelE is evaluated against the observed isoprene measurements at the Missouri Ozarks AmeriFlux (MOFLUX) site during the 2012 severe drought where improvements in the correlation coefficient indicate it is a suitable drought stress parameterization to capture the reduction signal during severe drought. The application of yd globally leads to a decadal average reduction of ∼2.7 %, which is equivalent to ∼14.6 Tg yr−1 of isoprene. The changes have larger impacts in regions such as the southeastern US. DroughtStress_ModelE is validated using the satellite ΩHCHO column from the Ozone Monitoring Instrument (OMI) and surface O3 observations across regions of the US to examine the effect of drought on atmospheric composition. It was found that the inclusion of isoprene drought stress reduced the overestimation of ΩHCHO in Default_ModelE during the 2007 and 2011 southeastern US droughts and led to improvements in simulated O3 during drought periods. We conclude that isoprene drought stress should be tuned on a model-by-model basis because the variables used in the parameterization responses are relative to the land surface model hydrology scheme (LSM) and the effects of yd application could be larger than seen here due to ModelE not having large biases of isoprene during severe drought.
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Qi, Peng, Y. Jun Xu, and Guodong Wang. "Quantifying the Individual Contributions of Climate Change, Dam Construction, and Land Use/Land Cover Change to Hydrological Drought in a Marshy River." Sustainability 12, no. 9 (May 6, 2020): 3777. http://dx.doi.org/10.3390/su12093777.
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Hydrological drought for marshy rivers is poorly characterized and understood. Our inability to quantify hydrological drought in marshy river environments stems from the lack of understanding how wetland loss in a river basin could potentially change watershed structure, attenuation, storage, and flow characteristics. In this study, hydrological drought in a marshy river in far Northeast China at a higher latitude was assessed with a streamflow drought index (SDI). A deterministic, lumped, and conceptual Rainfall–Runoff model, the NAM (Nedbor Afstromnings Model), was used to quantify the individual contributions of climate change, land use/land cover (LULC) change, and river engineering to hydrological drought. We found that in the last five decades, the frequency of hydrological droughts has been 55% without considering LULC change and reservoir construction in this wetland-abundant area. The frequency of hydrological drought increased by 8% due to land use change and by 19% when considering both the impacts of LULC change and a reservoir construction (the Longtouqiao Reservoir). In addition to the more frequent occurrence of hydrological droughts, human activities have also increased drought intensity. These findings suggest that LULC and precipitation changes play a key role in hydrological drought, and that the effect can be significantly modified by a river dam construction.
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Zeng, Dingwen, Xing Yuan, and Joshua K. Roundy. "Effect of Teleconnected Land–Atmosphere Coupling on Northeast China Persistent Drought in Spring–Summer of 2017." Journal of Climate 32, no. 21 (November 2019): 7403–20. http://dx.doi.org/10.1175/jcli-d-19-0175.1.
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Northeast China (NEC) suffered a severe drought that persisted from March to July of 2017 with profound impacts on agriculture and society, raising an urgent need to understand the mechanism for persistent droughts over midlatitudes. Previous drought mechanism studies focused on either large-scale teleconnections or local land–atmosphere coupling, while less attention was paid to their synergistic effects on drought persistence. Here we show that the 2017 NEC drought was triggered by a strong positive phase of the Arctic Oscillation in March, and maintained by the anticyclone over the area south to Lake Baikal (ASLB) through a quasi-stationary Rossby wave in April–July, accompanied by sinking motion and north wind anomaly. By using a land–atmosphere coupling index based on the persistence of positive feedbacks between the boundary layer and land surface, we find that the coupling states over NEC and ASLB shifted from a wet coupling in March to a persistently strengthened dry coupling in April–July. Over ASLB, the dry coupling and sinking motion increased surface sensible heat, decreased cloud cover, and weakened longwave absorption, resulting in a diabatic heating anomaly in the lower atmosphere and a diabatic cooling anomaly in the upper atmosphere. This anomalous vertical heating profile led to a negative anomaly of potential vorticity at low levels, indicating that the land–atmosphere coupling had a phase-lock effect on the Rossby wave train originating from upstream areas, and therefore maintained the NEC drought over downstream regions. Our study suggests that an upstream quasi-stationary wave pattern strengthened by land–atmosphere coupling should be considered in diagnosing persistent droughts, especially over northern midlatitudes.