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1
Mirza, M. Monirul Qader. "The Choice of Stage-Discharge Relationship for the Ganges and Brahmaputra Rivers in Bangladesh." Hydrology Research 34, no. 4 (August 1, 2003): 321–42. http://dx.doi.org/10.2166/nh.2003.0010.
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The Ganges and Brahmaputra are the two largest rivers in Bangladesh. Discharge estimations of these rivers from a stage-discharge relationship or rating curve are crucial for flood warning/control/mitigation and water resources development. So far, logarithmic rating curves have been widely used in Bangladesh. The suitability of semi-logarithmic, polynomial and quadratic rating curves has not been investigated. In this study, all four recognised stage-discharge relationships were examined for the Ganges and Brahmaputra rivers. Unbiased least squares estimators were determined for the segmented logarithmic and semi-logarithmic rating curves. This enhanced their efficiency in inter-and extrapolating discharges from the given river stages. Based on detailed analysis and goodness-of-fit criteria, segmented logarithmic and third order polynomial rating curves were found to be the best for the Ganges and Brahmaputra rivers, respectively.
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Hopson, Thomas M., and Peter J. Webster. "A 1–10-Day Ensemble Forecasting Scheme for the Major River Basins of Bangladesh: Forecasting Severe Floods of 2003–07*." Journal of Hydrometeorology 11, no. 3 (June 1, 2010): 618–41. http://dx.doi.org/10.1175/2009jhm1006.1.
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Abstract This paper describes a fully automated scheme that has provided calibrated 1–10-day ensemble river discharge forecasts and predictions of severe flooding of the Brahmaputra and Ganges Rivers as they flow into Bangladesh; it has been operational since 2003. The Bangladesh forecasting problem poses unique challenges because of the frequent life-threatening flooding of the country and because of the absence of upstream flow data from India means that the Ganges and Brahmaputra basins must be treated as if they are ungauged. The meteorological–hydrological forecast model is a hydrologic multimodel initialized by NASA and NOAA precipitation products, whose states and fluxes are forecasted forward using calibrated European Centre for Medium-Range Weather Forecasts ensemble prediction system products, and conditionally postprocessed to produce calibrated probabilistic forecasts of river discharge at the entrance points of the Ganges and Brahmaputra into Bangladesh. Forecasts with 1–10-day horizons are presented for the summers of 2003–07. Objective verification shows that the forecast system significantly outperforms both a climatological and persistence forecast at all lead times. All severe flooding events were operationally forecast with significant probability at the 10-day horizon, including the extensive flooding of the Brahmaputra in 2004 and 2007, with the latter providing advanced lead-time warnings for the evacuation of vulnerable residents.
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Islam, S. M. N., S. H. Rahman, D. A. Chowdhury, M. M. Rahman, and S. M. Tareq. "Seasonal Variations of Arsenic in the Ganges and Brahmaputra River, Bangladesh." Journal of Scientific Research 4, no. 1 (December 23, 2011): 65. http://dx.doi.org/10.3329/jsr.v4i1.7820.
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Dissolved arsenic concentrations in the Ganges, Brahmaputra Rivers and confluence of these two rivers show important seasonal variations and maximum arsenic concentrations are observed during the monsoon season (July–October). These seasonal variations of dissolved arsenic concentrations were closely related to intense river-water discharge during the monsoon season with high arsenic-rich suspended particulate matter (SPM) loads. These arsenic-rich SPM mainly are primarily originated from erosion of agricultural land in upstream region irrigated with arsenic contaminated shallow groundwater and to some extent weathering of bed rocks. Considerable amount of iron and manganese enriched SPM adsorbs arsenic and increased water temperature in the summer accelerates microbially-mediated reduction of arsenic (V) to more soluble arsenic (III). Additionally, dissolution of solid arsenic-bearing mineral phases also attributes to high arsenic concentrations in water and causes seasonal variations. It is realized that the SPM of these two major rivers primarily controls the arsenic inputs into the Ganges-Brahmaputra-Meghna delta system. The cycling of arsenic in this delta is related to the monsoon seasonal dynamics, land use patterns and biogeochemical processes.Keywords: Arsenic; Ganges; Brahmaputra; Seasonal variation; Bangladesh.© 2012 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved.doi: http://dx.doi.org/10.3329/jsr.v4i1.7820J. Sci. Res. 4 (1), 65-75 (2012)
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Alam, Md Ashraful, Craig Farnham, and Kazuo Emura. "Bayesian inference for extreme value flood frequency analysis in Bangladesh using Hamiltonian Monte Carlo techniques." MATEC Web of Conferences 276 (2019): 04006. http://dx.doi.org/10.1051/matecconf/201927604006.
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In Bangladesh, major floods are frequent due to its unique geographic location. About one-fourth to one-third of the country is inundated by overflowing rivers during the monsoon season almost every year. Calculating the risk level of river discharge is important for making plans to protect the ecosystem and increasing crop and fish production. In recent years, several Bayesian Markov chain Monte Carlo (MCMC) methods have been proposed in extreme value analysis (EVA) for assessing the flood risk in a certain location. The Hamiltonian Monte Carlo (HMC) method was employed to obtain the approximations to the posterior marginal distribution of the Generalized Extreme Value (GEV) model by using annual maximum discharges in two major river basins in Bangladesh. The discharge records of the two largest branches of the Ganges-Brahmaputra-Meghna river system in Bangladesh for the past 42 years were analysed. To estimate flood risk, a return level with 95% confidence intervals (CI) has also been calculated. Results show that, the shape parameter of each station was greater than zero, which shows that heavy-tailed Frechet cases. One station, Bahadurabad, at Brahmaputra river basin estimated 141,387 m3s-1 with a 95% CI range of [112,636, 170,138] for 100-year return level and the 1000-year return level was 195,018 m3s-1 with a 95% CI of [122493, 267544]. The other station, Hardinge Bridge, at Ganges basin estimated 124,134 m3 s-1 with a 95% CI of [108,726, 139,543] for 100-year return level and the 1000-year return level was 170,537 m3s-1 with a 95% CI of [133,784, 207,289]. As Bangladesh is a flood prone country, the approach of Bayesian with HMC in EVA can help policy-makers to plan initiatives that could result in preventing damage to both lives and assets.
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Islam, A. K. M. Saiful, Supria Paul, Khaled Mohammed, Mutasim Billah, Md Golam Rabbani Fahad, Md Alfi Hasan, G. M. Tarekul Islam, and Sujit Kumar Bala. "Hydrological response to climate change of the Brahmaputra basin using CMIP5 general circulation model ensemble." Journal of Water and Climate Change 9, no. 3 (October 25, 2017): 434–48. http://dx.doi.org/10.2166/wcc.2017.076.
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Abstract The Ganges–Brahmaputra–Meghna river system carries the world's third-largest fresh water discharge and Brahmaputra alone carries about 67% of the total annual flow of Bangladesh. Climate change will be expected to alter the hydrological cycles and the flow regime of these basins. Assessment of the fresh water availability of the Brahmaputra Basin in the future under climate change condition is crucial for both society and the ecosystem. SWAT, a semi-distributed physically based hydrological model, has been applied to investigate hydrological response of the basin. However, it is a challenging task to calibrate and validate models over this ungauged and poor data basin. A model derived by using gridded rainfall data from the Tropical Rainfall Measuring Mission (TRMM) satellite and temperature data from reanalysis product ERA-Interim provides acceptable calibration and validation. Using the SWAT-CUP with SUFI-2 algorithm, sensitivity analysis of model parameters was examined. A calibrated model was derived using new climate change projection data from the multi-model ensemble CMIP5 Project over the South Asia CORDEX domain. The uncertainty of predicting monsoon flow is less than that of pre-monsoon flow. Most of the regional climate models (RCMs) show an increasing tendency of the discharge of Brahmaputra River at Bahadurabad station during monsoon, when flood usually occurs in Bangladesh.
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Hale, Richard, Rachel Bain, Steven Goodbred Jr., and Jim Best. "Observations and scaling of tidal mass transport across the lower Ganges–Brahmaputra delta plain: implications for delta management and sustainability." Earth Surface Dynamics 7, no. 1 (March 12, 2019): 231–45. http://dx.doi.org/10.5194/esurf-7-231-2019.
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Abstract. The landscape of southwest Bangladesh, a region constructed primarily by fluvial processes associated with the Ganges River and Brahmaputra River, is now maintained almost exclusively by tidal processes as the fluvial system has migrated east and eliminated the most direct fluvial input. In natural areas such as the Sundarbans National Forest, year-round inundation during spring high tides delivers sufficient sediment that enables vertical accretion to keep pace with relative sea-level rise. However, recent human modification of the landscape in the form of embankment construction has terminated this pathway of sediment delivery for much of the region, resulting in a startling elevation imbalance, with inhabited areas often sitting >1 m below mean high water. Restoring this landscape, or preventing land loss in the natural system, requires an understanding of how rates of water and sediment flux vary across timescales ranging from hours to months. In this study, we combine time series observations of water level, salinity, and suspended sediment concentration with ship-based measurements of large tidal-channel hydrodynamics and sediment transport. To capture the greatest possible range of variability, cross-channel transects designed to encompass a 12.4 h tidal cycle were performed in both dry and wet seasons during spring and neap tides. Regional suspended sediment concentration begins to increase in August, coincident with a decrease in local salinity, indicating the arrival of the sediment-laden, freshwater plume of the combined Ganges–Brahmaputra–Meghna rivers. We observe profound seasonality in sediment transport, despite comparatively modest seasonal variability in the magnitude of water discharge. These observations emphasize the importance of seasonal sediment delivery from the main-stem rivers to this remote tidal region. On tidal timescales, spring tides transport an order of magnitude more sediment than neap tides in both the wet and dry seasons. In aggregate, sediment transport is flood oriented, likely as a result of tidal pumping. Finally, we note that rates of sediment and water discharge in the tidal channels are of the same scale as the annually averaged values for the Ganges and Brahmaputra rivers. These observations provide context for examining the relative importance of fluvial and tidal processes in what has been defined as a quintessentially tidally influenced delta in the classification scheme of Galloway (1975). These data also inform critical questions regarding the timing and magnitude of sediment delivery to the region, which are especially important in predicting and preparing for responses of the natural system to ongoing environmental change.
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Gain, A. K., W. W. Immerzeel, F. C. Sperna Weiland, and M. F. P. Bierkens. "Impact of climate change on the stream flow of the lower Brahmaputra: trends in high and low flows based on discharge-weighted ensemble modelling." Hydrology and Earth System Sciences 15, no. 5 (May 20, 2011): 1537–45. http://dx.doi.org/10.5194/hess-15-1537-2011.
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Abstract. Climate change is likely to have significant effects on the hydrology. The Ganges-Brahmaputra river basin is one of the most vulnerable areas in the world as it is subject to the combined effects of glacier melt, extreme monsoon rainfall and sea level rise. To what extent climate change will impact river flow in the Brahmaputra basin is yet unclear, as climate model studies show ambiguous results. In this study we investigate the effect of climate change on both low and high flows of the lower Brahmaputra. We apply a novel method of discharge-weighted ensemble modeling using model outputs from a global hydrological models forced with 12 different global climate models (GCMs). Our analysis shows that only a limited number of GCMs are required to reconstruct observed discharge. Based on the GCM outputs and long-term records of observed flow at Bahadurabad station, our method results in a multi-model weighted ensemble of transient stream flow for the period 1961–2100. Using the constructed transients, we subsequently project future trends in low and high river flow. The analysis shows that extreme low flow conditions are likely to occur less frequent in the future. However a very strong increase in peak flows is projected, which may, in combination with projected sea level change, have devastating effects for Bangladesh. The methods presented in this study are more widely applicable, in that existing multi-model streamflow simulations from global hydrological models can be weighted against observed streamflow data to assess at first order the effects of climate change for specific river basins.
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Gain, A. K., W. W. Immerzeel, F. C. Sperna-Weiland, and M. F. P. Bierkens. "Impact of climate change on the stream flow of lower Brahmaputra: trends in high and low flows based on discharge- weighted ensemble modelling." Hydrology and Earth System Sciences Discussions 8, no. 1 (January 18, 2011): 365–90. http://dx.doi.org/10.5194/hessd-8-365-2011.
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Abstract. Climate change is likely to have significant effects on the hydrology. The Ganges-Brahmaputra river basin is one of the most vulnerable areas in the world as it is subject to the combined effects of glacier melt, extreme monsoon rainfall and sea level rise. To what extent climate change will impact river flow in the Brahmaputra basin is yet unclear, as climate model studies show ambiguous results. In this study we investigate the effect of climate change on both low and high flows of the lower Brahmaputra. We apply a novel method of discharge-weighted ensemble modeling using model outputs from a global hydrological models forced with 12 different global climate models (GCMs). Based on the GCM outputs and long-term records of observed flow at Bahadurabad station, our method results in a multi-model weighted ensemble of transient stream flow for the period 1961–2100. Using the constructed transients, we subsequently project future trends in low and high river flow. The analysis shows that extreme low flow conditions are likely to occur less frequent in the future. However a very strong increase in peak flows is projected, which may, in combination with projected sea level change, have devastating effects for Bangladesh. The methods presented in this study are more widely applicable, in that existing multi-model streamflow simulations from global hydrological models can be weighted against observed streamflow data to assess at first order the effects of climate change for specific river basins.
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Jian, Jun, Peter J. Webster, and Carlos D. Hoyos. "Large-scale controls on Ganges and Brahmaputra river discharge on intraseasonal and seasonal time-scales." Quarterly Journal of the Royal Meteorological Society 135, no. 639 (January 2009): 353–70. http://dx.doi.org/10.1002/qj.384.
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Gusyev, M. A., Y. Kwak, M. I. Khairul, M. B. Arifuzzaman, J. Magome, H. Sawano, and K. Takeuchi. "Effectiveness of water infrastructure for river flood management – Part 1: Flood hazard assessment using hydrological models in Bangladesh." Proceedings of the International Association of Hydrological Sciences 370 (June 11, 2015): 75–81. http://dx.doi.org/10.5194/piahs-370-75-2015.
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Abstract. This study introduces a flood hazard assessment part of the global flood risk assessment (Part 2) conducted with a distributed hydrological Block-wise TOP (BTOP) model and a GIS-based Flood Inundation Depth (FID) model. In this study, the 20 km grid BTOP model was developed with globally available data on and applied for the Ganges, Brahmaputra and Meghna (GBM) river basin. The BTOP model was calibrated with observed river discharges in Bangladesh and was applied for climate change impact assessment to produce flood discharges at each BTOP cell under present and future climates. For Bangladesh, the cumulative flood inundation maps were produced using the FID model with the BTOP simulated flood discharges and allowed us to consider levee effectiveness for reduction of flood inundation. For the climate change impacts, the flood hazard increased both in flood discharge and inundation area for the 50- and 100-year floods. From these preliminary results, the proposed methodology can partly overcome the limitation of the data unavailability and produces flood~maps that can be used for the nationwide flood risk assessment, which is presented in Part 2 of this study.
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Ioualalen, M., E. Pelinovsky, J. Asavanant, R. Lipikorn, and A. Deschamps. "On the weak impact of the 26 December Indian Ocean tsunami on the Bangladesh coast." Natural Hazards and Earth System Sciences 7, no. 1 (January 26, 2007): 141–47. http://dx.doi.org/10.5194/nhess-7-141-2007.
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Abstract. The 26 December 2004 Indian Ocean tsunami damaged severely most of the Gulf of Bengal's coastal areas, but the coast of Bangladesh which stands at the edge of an extraordinarily extended continental shelf. This latter feature has been built through huge discharges of river sediments along the Brahmaputra and Ganges rivers. As a result of this enormous discharge, another interesting feature of the area is the deep underwater Canyon, connected with the estuaries, running NE-SW from 25 km off the coast towards the continental slope. We investigate here how these two geological features may have modified/perturbed the Indian ocean tsunami propagation and impact on the Coast of Bangladesh. For that purpose we have realized an ensemble of numerical simulations based on Funwave Boussinesq numerical model and a validated coseismic source. It is found, at first order, that the extended shallow bathymetric profile of the continental shelf plays a key role in flattening the waveform through a defocussing process while the Canyon delays the process. The wave evolution seems to be related at first order to the bathymetric profile rather than to dynamical processes like nonlinearity, dispersion or bottom friction.
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Bhanja, Soumendra N., Abhijit Mukherjee, R. Rangarajan, Bridget R. Scanlon, Pragnaditya Malakar, and Shubha Verma. "Long-term groundwater recharge rates across India by in situ measurements." Hydrology and Earth System Sciences 23, no. 2 (February 7, 2019): 711–22. http://dx.doi.org/10.5194/hess-23-711-2019.
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Abstract. Groundwater recharge sustains groundwater discharge, including natural discharge through springs and the base flow to surface water as well as anthropogenic discharge through pumping wells. Here, for the first time, we compute long-term (1996–2015) groundwater recharge rates using data retrieved from several groundwater-level monitoring locations across India (3.3 million km2 area), the most groundwater-stressed region globally. Spatial variations in groundwater recharge rates (basin-wide mean: 17 to 960 mm yr−1) were estimated in the 22 major river basins across India. The extensive plains of the Indus–Ganges–Brahmaputra (IGB) river basins are subjected to prevalence of comparatively higher recharge. This is mainly attributed to occurrence of coarse sediments, higher rainfall, and intensive irrigation-linked groundwater-abstraction inducing recharge by increasing available groundwater storage and return flows. Lower recharge rates (<200 mm yr−1) in most of the central and southern study areas occur in cratonic, crystalline fractured aquifers. Estimated recharge rates have been compared favorably with field-scale recharge estimates (n=52) based on tracer (tritium) injection tests. Results show that precipitation rates do not significantly influence groundwater recharge in most of the river basins across India, indicating human influence in prevailing recharge rates. The spatial variability in recharge rates could provide critical input for policymakers to develop more sustainable groundwater management in India.
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Moore, Willard S. "High fluxes of radium and barium from the mouth of the Ganges-Brahmaputra River during low river discharge suggest a large groundwater source." Earth and Planetary Science Letters 150, no. 1-2 (July 1997): 141–50. http://dx.doi.org/10.1016/s0012-821x(97)00083-6.
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Dietrich, Matthew, Kelsea B. Best, Jessica L. Raff, and Elli R. Ronay. "A first-order geochemical budget for suspended sediment discharge to the Bay of Bengal from the Ganges-Brahmaputra river system." Science of The Total Environment 726 (July 2020): 138667. http://dx.doi.org/10.1016/j.scitotenv.2020.138667.
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Mohit, Abdul Al, Yoshihiko Ide, Mitsuyoshi Kodama, Masaru Yamashiro, and Noriaki Hashimoto. "CONTRIBUTION OF LARGE RIVER SYSTEM ON WATER LEVEL DUE TO A STORM." Coastal Engineering Proceedings, no. 36 (December 30, 2018): 14. http://dx.doi.org/10.9753/icce.v36.currents.14.
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Bangladesh is a riverine country in South Asia, which contain about 700 big or small rivers. The major Ganges- Brahmaputra-Meghna river system makes the coast of Bangladesh more complex and disaster vulnerable area. This river system may or may not have its impact on the height of the water level due to a storm. This area is a suitable place for research, but there is no such mention of suitable research conducted in this area. Worth mentioning works done by some scholars are Dube et al. (2004), Agnihotri et al. (2006). All the works are important to the Bay-River interaction for the storm surge simulation, but these studies were also limited by the lack of a representation of proper geometry of the river system. Some of them considered idealized river system with constant water depth and some of them did not consider the proper tidal resume. The present study is a step towards the development of an operational surge forecasting nonlinear Bay-River interaction model that incorporates the major river system with realistic geometry. Both the bay and river model equations are discretized by finite difference method with central in space and forward in time and are solved by a conditionally stable, semi-implicit manner on a staggered Arakawa C-grid system. A stable tidal condition was made by forcing the sea level with the most energetic tidal constituent, M2 , along the southern open boundary of the parent model (Bay model). The developed model was applied to foresee sea-surface elevation associated with the catastrophic cyclone 1991 and a recent cyclone MORA 2017 along the coast of Bangladesh. We also investigated how the river influences the sea surface elevation with and without fresh water discharge. We also intend to investigate the effect of river discharge with sediment. It is observed that the water levels are found to be influenced by the river system.
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Singh, Umesh Kumar, and Balwant Kumar. "Climate change impacts on hydrology and water resources of Indian River basin." Current World Environment 13, no. 1 (April 20, 2018): 32–43. http://dx.doi.org/10.12944/cwe.13.1.04.
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Anthropogenic greenhouse gas emission is altering the global hydrological cycle due to change in rainfall pattern and rising temperature which is responsible for alteration in the physical characteristics of river basin, melting of ice, drought, flood, extreme weather events and alteration in groundwater recharge. In India, water demand for domestic, industrial and agriculture purposes have already increased many folds which are also influencing the water resource system. In addition, climate change has induced the surface temperature of the Indian subcontinent by 0.48 ºC in just last century. However, Ganges–Brahmaputra–Meghna (GBM) river basins have great importance for their exceptional hydro-geological settings and deltaic floodplain wetland ecosystems which support 700 million people in Asia. The climatic variability like alterations in precipitation and temperature over GBM river basins has been observed which signifies the GBM as one of the most vulnerable areas in the world under the potential impact of climate change. Consequently, alteration in river discharge, higher runoff generation, low groundwater recharge and melting of glaciers over GBM river basin could be observed in near future. The consequence of these changes due to climate change over GBM basin may create serious water problem for Indian sub-continents. This paper reviews the literature on the historical climate variations and how climate change affects the hydrological characteristics of different river basins.
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Kibler, Kelly M., Robin K. Biswas, and Andrea M. Juarez Lucas. "Hydrologic data as a human right? Equitable access to information as a resource for disaster risk reduction in transboundary river basins." Water Policy 16, S2 (November 1, 2014): 36–58. http://dx.doi.org/10.2166/wp.2014.307.
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Principles of equitable and reasonable use underpin international water agreements. Despite the potential for hydrologic information to enhance resilience to extreme events, comparable application of just principles to the distribution of hydrometeorological data is poorly established. Within the Ganges–Brahmaputra–Meghna (GBM) river basin, we find that water allocation agreements are codified into treaties or Memorandums of Understanding (MoUs). Analogous decisions regarding hydrometeorological data sharing are often internalized at the level of river basin organizations and are not upheld as MoUs. This institutional structure provides extremely limited data to the most downstream nation of Bangladesh. Available precipitation and discharge stations are well below the minimum densities recommended by the World Meteorological Organization. Forecasters in Bangladesh therefore contend with vast areas of geopolitically ungauged catchment, precluding the application of basin-wide modelling approaches driven by observed data. Thus, capacity for increasing resilience to extreme events within Bangladesh is obstructed, demonstrating the potential for perceived injustice related to distribution of hydrometeorological data. Consensus that water is a human right warrants the application of equity to water allocation. But is security from water-related disasters also a human right? As hydrometeorological data can be a powerful resource with potential to profoundly affect lives and livelihoods, enhanced awareness of justice related to data sharing is needed.
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Tiwari, Manish, Ashutosh K. Singh, and Rengaswamy Ramesh. "High-Resolution Monsoon Records Since Last Glacial Maximum: A Comparison of Marine and Terrestrial Paleoarchives from South Asia." Journal of Geological Research 2011 (August 23, 2011): 1–12. http://dx.doi.org/10.1155/2011/765248.
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Agricultural production and the availability of fresh water in Indian subcontinent critically depend on the monsoon rains. Therefore it is vital to understand the causal mechanisms underlying the observed changes in the Indian monsoon in the past. Paleomonsoon reconstructions show that the water discharge from the Ganges-Brahmaputra River system to the Bay of Bengal was maximum in the early to mid-Holocene; data from the Western Arabian Sea and Omanian speleothems indicate declining monsoon winds during the Holocene, whereas records from the South West Monsoon (SWM) precipitation dominated eastern Arabian Sea show higher runoff from the Western Ghats indicating gradually increasing monsoon precipitation during the Holocene. Thus there exists considerable spatial variability in the monsoon in addition to the temporal variability that needs to be assessed systematically. Here we discuss the available high resolution marine and terrestrial paleomonsoon records such as speleothems and pollen records of the SWM from important climatic regimes such as Western Arabian Sea, Eastern Arabian Sea, Bay of Bengal to assess what we have learnt from the past and what can be said about the future of water resources of the subcontinent in the context of the observed changes.
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Hasson, S., V. Lucarini, and S. Pascale. "Hydrological cycle over south and southeast Asian river basins as simulated by PCMDI/CMIP3 experiments." Earth System Dynamics Discussions 4, no. 1 (January 22, 2013): 109–77. http://dx.doi.org/10.5194/esdd-4-109-2013.
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Abstract. We investigate how CMIP3 climate models describe the hydrological cycle over four major South and Southeast Asian river basins (Indus, Ganges, Brahmaputra and Mekong) for the XX, XXI, and XXII centuries. For the XX century, models' simulated water balance and total runoff quantities are neither consistent with the observed mean river discharges nor among the models. Most of the models underestimate the water balance for the Ganges, Brahmaputra and Mekong basin and overestimate it for the Indus basin. The only modest inter-model agreement is found for the Indus basin in terms of precipitation, evaporation and the strength of the hydrological cycle and for the Brahmaputra basin in terms of evaporation. While some models show inconsistencies for the Indus and the Ganges basins, most of the models seem to conserve water at the river basin scale up to a good degree of approximation. Models agree on a negative change of the water balance for Indus and a positive change in the strength of the hydrological cycle, whereas for Brahmaputra, Mekong and Ganges, most of the models project a positive change in both quantities. Most of the models foresee an increase in the inter-annual variability of the water balance for the Ganges and Mekong basins which is consistent with the projected changes in the Monsoon precipitation. No considerable future change in the inter-annual variability of water balance is found for the Indus basin, characterized by a more complex meteorology, because its precipitation regime is determined not only by the summer monsoon but also by the winter mid-latitude disturbances.
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Berube, Michelle, Katrina Jewell, Kimberly D. Myers, Peter S. K. Knappett, Pin Shuai, Abrar Hossain, Mehtaz Lipsi, et al. "The fate of arsenic in groundwater discharged to the Meghna River, Bangladesh." Environmental Chemistry 15, no. 2 (2018): 29. http://dx.doi.org/10.1071/en17104.
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Environmental contextArsenic contamination of groundwater is a major environmental problem in many areas of the world. In south-east Asia, iron-rich reducing groundwater mixes with oxidising river water in hyporheic zones, precipitating iron oxides. These oxides can act as a natural reactive barrier capable of accumulating elevated solid-phase concentrations of arsenic. AbstractShallow, anoxic aquifers within the Ganges–Brahmaputra–Meghna Delta (GBMD) commonly contain elevated concentrations of arsenic (As), iron (Fe) and manganese (Mn). Highly enriched solid-phase concentrations of these elements have been observed within sediments lining the banks of the Meghna River. This zone has been described as a Natural Reactive Barrier (NRB). The impact of hydrological processes on NRB formation, such as transient river levels, which drive mixing between rivers and aquifers, is poorly understood. We evaluated the impact of groundwater flow dynamics on hydrobiogeochemical processes that led to the formation of an Fe- and Mn-rich NRB containing enriched As, within a riverbank aquifer along the Meghna River. The NRB dimensions were mapped using four complementary elemental analysis methods on sediment cores: X-ray fluorescence (XRF), aqua regia bulk extraction, and HCl and sodium phosphate leaching. It extended from 1.2 to 2.4 m in depth up to 15 m from the river’s edge. The accumulated As was advected to the NRB from offsite and released locally in response to mixing with aged river water. Nearly all of the As was subsequently deposited within the NRB before discharging to the Meghna. Significant FeII release to the aqueous phase was observed within the NRB. This indicates the NRB is a dynamic zone defined by the interplay between oxidative and reductive processes, causing the NRB to grow and recede in response to rapid and seasonal hydrologic processes. This implies that natural and artificially induced changes in river stages and groundwater-tables will impact where As accumulates and is released to aquifers.
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Yoshimura, Toshihiro, Shigeyuki Wakaki, Hodaka Kawahata, H. M. Zakir Hossain, Takuya Manaka, Atsushi Suzuki, Tsuyoshi Ishikawa, and Naohiko Ohkouchi. "Stable Strontium Isotopic Compositions of River Water, Groundwater and Sediments From the Ganges–Brahmaputra–Meghna River System in Bangladesh." Frontiers in Earth Science 9 (February 26, 2021). http://dx.doi.org/10.3389/feart.2021.592062.
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The Sr isotopic composition of rivers and groundwaters in the Bengal Plain is a major contributor to the global oceanic Sr inventory. The stable strontium isotope ratios (δ88Sr) provide a new tool to identify chemical weathering reactions in terrestrial water. In this study, we investigated the spatiotemporal variations of δ88Sr in samples of river water, bedload sediment, and groundwater collected from the Ganges–Brahmaputra–Meghna drainage basin in Bangladesh, which is known to strongly influence the 87Sr/86Sr ratio in seawater. The average δ88Sr values of waters of the Ganges, Brahmaputra, and Meghna rivers were 0.269, 0.316, and 0.278‰, respectively. Our data showed little difference between seasons of high and low discharge. The δ88Sr values measured in sequential leaching fractions of sediments varied from –0.258 to 0.516‰ and were highest in the silicate fraction, followed in turn by the carbonate fraction and the exchangeable fraction. Both 87Sr/86Sr and δ88Sr of these waters are primarily controlled by the inputs of Sr in weathering products from the Bengal Plain and Sr from the Himalayan rivers (Ganges and Brahmaputra). Values of δ88Sr and Sr/Ca were higher in the Brahmaputra River than in the Ganges River, a difference we attribute to greater input from silicate weathering. The variations of δ88Sr and 87Sr/86Sr were greater in groundwater than in river waters. Mineral sorting effects and dissolution kinetics can account for the large scatter in 87Sr/86Sr and δ88Sr values. The depth profile of δ88Sr showed wide variation at shallow depths and convergence to a narrow range of about 0.31‰ at depths greater than 70 m, which reflects more complete equilibration of chemical interactions between groundwater and ambient sediments owing to the longer residence time of deeper groundwater. We found that δ88Sr values in the groundwater of Bangladesh were almost identical to those of river water from the lower Meghna River downstream of its confluence with the Ganges–Brahmaputra river system, thus confirming that the δ88Sr composition of the groundwater discharge to the Bay of Bengal is very similar to that of the river discharge.
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Yoshimura, Toshihiro, Daisuke Araoka, Hodaka Kawahata, H. M. Zakir Hossain, and Naohiko Ohkouchi. "The Influence of Weathering, Water Sources, and Hydrological Cycles on Lithium Isotopic Compositions in River Water and Groundwater of the Ganges–Brahmaputra–Meghna River System in Bangladesh." Frontiers in Earth Science 9 (July 23, 2021). http://dx.doi.org/10.3389/feart.2021.668757.
Full textAbstract:
The silicate weathering of continental rocks plays a vital role in determining ocean chemistry and global climate. Spatiotemporal variations in the Li isotope ratio (δ7Li) of terrestrial waters can be used to identify regimes of current and past weathering processes. Here we examine: 1) monthly dissolved δ7Li variation in the Ganges River’s lower reaches; and 2) the spatiotemporal variation of river water of the Brahmaputra, Meghna rivers, and groundwater in Bangladesh. From the beginning to maximum flood discharges of the rainy season (i.e., from June to September), Li concentrations and δ7Li in the Ganges River show remarkable changes, with a large influence from Himalayan sources. However, most Li discharge across the rainy season is at steady-state and strongly influenced by the secondary mineral formation in the low-altitude floodplain. Secondary mineral formation strongly influences the Meghna River’s Li isotopic composition along with fractionation lines similar to the Ganges River. A geothermal input is an additional Li source for the Brahmaputra River. For groundwater samples shallower than ∼60 m depth, both δ7Li and Li/Na are highly scattered regardless of the sampling region, suggesting the variable extent of fractionation. For deep groundwater (70–310 m) with a longer residence time (3,000 to 20,000 years), the lower δ7Li values indicate more congruent weathering. These results suggest that Li isotope fractionation in rivers and groundwater depends on the timescale of water-mineral interaction, which plays an essential role in determining the isotopic signature of terrestrial Li inputs to the ocean.
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Elahi, M. W. E., I. Jalón‐Rojas, X. H. Wang, and E. A. Ritchie. "Influence of Seasonal River Discharge on Tidal Propagation in the Ganges‐Brahmaputra‐Meghna Delta, Bangladesh." Journal of Geophysical Research: Oceans 125, no. 11 (October 27, 2020). http://dx.doi.org/10.1029/2020jc016417.
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Mondal, Md Sanaul H., and Md Serajul Islam. "Chronological trends in maximum and minimum water flows of the Teesta River, Bangladesh, and its implications." Jàmbá: Journal of Disaster Risk Studies 9, no. 1 (March 30, 2017). http://dx.doi.org/10.4102/jamba.v9i1.373.
Full textAbstract:
Bangladesh shares a common border with India in the west, north and east and with Myanmar in the southeast. These borders cut across 57 rivers that discharge through Bangladesh into the Bay of Bengal in the south. The upstream courses of these rivers traverse India, China, Nepal and Bhutan. Transboundary flows are the important sources of water resources in Bangladesh. Among the 57 transboundary rivers, the Teesta is the fourth major river in Bangladesh after the Ganges, the Brahmaputra and the Meghna and Bangladesh occupies about 2071 km2 . The Teesta River floodplain in Bangladesh accounts for 14% of the total cropped area and 9.15 million people of the country. The objective of this study was to investigate trends in both maximum and minimum water flow at Kaunia and Dalia stations for the Teesta River and the coping strategies developed by the communities to adjust with uncertain flood situations. The flow characteristics of the Teesta were analysed by calculating monthly maximum and minimum water levels and discharges from 1985 to 2006. Discharge of the Teesta over the last 22 years has been decreasing. Extreme low-flow conditions were likely to occur more frequently after the implementation of the Gozoldoba Barrage by India. However, a very sharp decrease in peak flows was also observed albeit unexpected high discharge in 1988, 1989, 1991, 1997, 1999 and 2004 with some in between April and October. Onrush of water causes frequent flash floods, whereas decreasing flow leaves the areas dependent on the Teesta vulnerable to droughts. Both these extreme situations had a negative impact on the lives and livelihoods of people dependent on the Teesta. Over the years, people have developed several risk mitigation strategies to adjust with both natural and anthropogenic flood situations. This article proposed the concept of ‘MAXIN (maximum and minimum) flows’ for river water justice for riparian land.
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"El-Nino/Southern Oscillation (ENSO): Recent Evolution and Possibilities for Long Range Flow Forecasting in the Brahmaputra-Jamuna River." Issue 3 8, no. 3 (April 29, 2013): 179–85. http://dx.doi.org/10.30955/gnj.000377.
Full textAbstract:
The El Nino-Southern Oscillation is the dominant pattern of short-term climate variation, and
is therefore of great importance in climate studies. Some recent studies showed the
teleconnection between stream flow and the El-Nino Southern Oscillation (ENSO) of the
equatorial Pacific Ocean. This paper presents an overview of the relationship between ENSO
and stream flow in the Brahmaputra-Jamuna and the potential for wet season flow
forecasting. This seasonal forecast of stream flow is very invaluable to the management of
land and water resources, particularly in Bangladesh to improve the predictability of severe
flooding. Over the years, large investments have been made to build physical infrastructure
for flood protection, but it has been proved that it is not feasible, both economically and
technically, to adopt solely structural mitigation approach. The choice of non-structural
measures in this country focused mainly on flood forecasting because many of the nonstructural
measures including flood plain zoning, compulsory acquisition of flood prone land,
relocation etc have also been proved inappropriate for Bangladesh.
The aim of this research is to find out an effective and long-lead flow forecasting method with
lead time greater than hydrological time scale, using El Nino-Southern Oscillation index.
Some studies indicate that SST can be predicted one to two years in advance using several
ocean/ coupled ocean atmosphere models, therefore the ability to predict flow patterns in
rivers will be highly enhanced if a strong relationship between river discharge and ENSO
exists, and is quantified. With this view, to assess the strength of teleconnection between river
flow and ENSO, at first correlation analyses between ENSO indices of any year and wet
season flow of that year have been done. Here sea surface temperature (SST) has been
used as ENSO index. This correlation analysis demonstrates a noteworthy relationship
between natural variability of average flow of the months July-August-September (JAS) of the
Brahmaputra-Jamuna River with SST of the corresponding months. Then discriminant
prediction approach, also known as “Categoric Prediction” has been used here for the
assessment of long range flood forecasting possibilities. This approach will be able to forecast
the category of flow (high, average or low) using the category of predictor (predicted SST) at
a sufficient lead time. In order to judge the forecast skill, a synoptic parameter “Forecasting
Index” has also been used. This discriminant approach will improve the forecasting lead-time
while the hydrologic forecast through rainfall-runoff modeling could provide a lead time on the
order of the basin response time, which is several days or so. As the Ganges–Brahmaputra
river basin is one of the most populous river basins of the world and is occupied by some
developing countries of the world like Bangladesh, any reduction in the uncertainty about the
flood in the Brahmaputra-Jamuna River would contribute a lot to the improvement in flow
forecasting as well as to the economic development of the country.