Hydro-Climatic Changes and Corresponding Impacts on Agricultural Water Demand in the Ganges Delta of Bangladesh

The Ganges Delta in Bangladesh, a transboundary rural river basin, is an example of water-related calamities due to natural and human-induced stresses. It is an agriculture-dominated area with the presence of Sundarbans mangrove forest. Recently this area is facing unfavorable conditions due to limitations in quantity, quality, and timing of available freshwater. As a result, floods, droughts, water scarcity, stream depletion, salinity intrusion, excessive sedimentation are becoming common phenomena. These calamities are making this area unsuitable for agriculture and vulnerable to the Sundarbans’ ecosystem. This study aims to provide technical insight into issues related to water scarcity and projected agricultural water demand for 2020-2100 considering the climate change uncertainties. We addressed three critical areas to attain this purpose. As a first task, this study attempted to analyze and understand the observed hydrological changes over the past six decades to fathom the critical reasons for freshwater scarcity. Secondly, interdependency, availability, and accessibility of surface water and groundwater were analyzed to investigate the adequacy of current water demand and supply in agriculture, industrial and domestic sectors. Irrigation demand is much higher than others and occupies 93% of the total water demand. Similarly, irrigation is 96% of total water withdrawal. This high demand in the agriculture sector led to our next objective to estimate agricultural demand for this century. It helps to understand an overall agricultural water consumption scenario for the future. This study provides necessary background information, which is vital for hydro-economically feasible agricultural water management plans

Linkage of Hydro-Climatological Variables to Flood and Drought in the Ganges Delta of Bangladesh

The Ganges Delta of Bangladesh is a good example of two opposite and extreme hydrological conditions, i.e., floods and droughts. This study attempts to determine the changes in hydro-climatological factors and its consequences on floods and droughts. We analyzed four extreme floods (1988, 1998) and droughts (1999, 2006) events. Rainfall, temperature, evapotranspiration, water level, and flow data are used to assess the hydrological changes. The changes in land area corresponding to normal flooding depth over the past 22 years are also considered. River siltation, drainage congestion, backwater effect, land subsidence, synchronization of high flows from major rivers along with the increase of heavy rainfall found to be the key factors for flood events. Dry season of this area is characterized by a negligible amount of rainfall. Upstream water diversion in Ganges River reduces the dry season flow significantly and has made the study area drought prone. Flow duration curves depict a large variation between high flow thresholds (20%) and low flow threshold (70%) in the Bangladesh part of the Ganges River. The statistically significant increase in temperature and evapotranspiration are also contributing to the drought condition. This study highlights the need for an improved management approach of water resources that can minimize droughts and flooding and associated impacts in this deltaic area

Uptake of climate change adaptation research results in South Asia

Climate Resilience and National Resilience programs focus on formulating the Bangladesh National Adaptation Plan (NAP) for long-term adaptation investments and enhancing the national capacity to integrate climate change adaptation (CCA) in planning, budgeting, and financial tracking process. However, these programs and projects need a system-level quantitative tool to assess the requirement for adaptations at different scales and consequently decide on adaptation financing for these programs and projects. The current project is built on the earlier findings of the DECCMA project to address the above issues, with the target to add the necessary refinement through incorporating the equity, accessibility, adequacy, and gender dimensions to be useful at different scales of adaptation for climate change. The Dynamic Adaptation Model (DAM) is a product that has been developed gradually. It can be applied at different scales that can support the different communities and sectorial agencies/departments to guide local and national planning to adaptations while prioritizing in selecting appropriate options in different programs and projects to ensure the efficient use of available resources. DAM is developed based on strong mathematical formulation supported by field evidence. The model is calibrated and validated using field data to quantify the present-day adaptation need and now is being tested for some of the proposed adaptations in the NAP processes to assess its usefulness at the national level. Moreover, it is the home-grown model; therefore, the required customized version for different communities and agencies is possible through updates in the future with its extension for new areal coverage in collaboration with the developers and the alignment of the recent national initiatives. These are the ongoing processes essential to make it worthwhile for the mainstream national adaptation plan that needs further work

Assessing Vulnerability and Risk to Livelihoods in River Deltas Socio-ecological Systems: Alignment of the GDRI With Global Frameworks’ Indicators

Disasters have significant impacts on the progress towards achieving the Sustainable Development Goals (SDGs). However, the interlinkage between sustainable development and disaster risk reduction is not considered enough in risk assessment tools. A greater alignment with global frameworks would ease the monitoring while increasing the capacity to address data availability issues for indicator-based assessments. To bridge this gap, we use the Global Delta Risk Index (GDRI), which is composed of multiple components to assess risks to livelihoods: hazards, vulnerability, and exposure of social-ecological systems. The modular library of indicators of the GDRI has been further aligned with the Sustainable Development Goals (SDG) and the Sendai Framework for Disaster and Risk Reduction (SFDRR). To improve the accuracy of the risk assessment, the list of indicators has been weighted and scored through consultation with stakeholders. This research presents the initial results of a multi-hazard risk assessment that encompasses SDG and SFDRR indicators in three Asian river deltas: Ganges-Brahmaputra-Meghna, Mekong and Red River. This work aims at better informing risk management and supporting delta-level interventions to influence progress towards sustainability and resilience of river deltas

Aligning the Global Delta Risk Index with SDG and SFDRR global frameworks to assess risk to socio-ecological systems in river deltas

River deltas globally are highly exposed and vulnerable to natural hazards and are often over-exploited landforms. The Global Delta Risk Index (GDRI) was developed to assess multi-hazard risk in river deltas and support decision-making in risk reduction interventions in delta regions. Disasters have significant impacts on the progress towards the Sustainable Development Goals (SDGs). However, despite the strong interlinkage between disaster risk reduction and sustainable development, global frameworks are still developed in isolation and actions to address them are delegated to different institutions. Greater alignment between frameworks would both simplify monitoring progress towards disaster risk reduction and sustainable development and increase capacity to address data gaps in relation to indicator-based assessments for both processes. This research aims at aligning the GDRI indicators with the SDGs and the Sendai Framework for Disaster and Risk Reduction (SFDRR). While the GDRI has a modular indicator library, the most relevant indicators for this research were selected through a delta-specific impact chain designed in consultation with experts, communities and stakeholders in three delta regions: the Red River and Mekong deltas in Vietnam and the Ganges–Brahmaputra–Meghna (GBM) delta in Bangladesh and India. We analyse how effectively the 143 indicators for the GDRI match (or not) the SDG and SFDRR global frameworks. We demonstrate the interconnections of the different drivers of risk to better inform risk management and in turn support delta-level interventions towards improved sustainability and resilience of these Asian mega-deltas

Evapotranspiration Under Climate Change in the Ganges Delta of Bangladesh

Evapotranspiration (ET) is an essential indicator of water loss, and its measurement is necessary for water resources management. This study attempts to quantify the variability of ET for the Ganges Delta of Bangladesh, an agro-based region with a high inter-annual variation of freshwater availability. We estimated actual ET by incorporating the Normalized Difference Vegetation Index (NDVI) into the complementary relationship model and adjusted it with the correction factors using Latent Heat Flux from Asia flux site. Also, crop ET is calculated to understand the variability in irrigation water requirement. We used observed climate data from the Bangladesh Meteorological Department and NDVI data from MODIS land products subsets. We projected the ET variability for the 2020-2100 period using three regional climate models, i.e., RCA 4, REMO2009 and RegCM 4-4 of two emission scenarios (RCP 4.5 and RCP 8.5). Climate data are used in the random forest algorithm to predict future NDVI. The multi-model analyses show higher crop ET for both the RCP scenarios, leading to higher water requirement in the irrigation sector. Understanding the ET loss will be helpful to develop the hydro-economically viable water management strategies for this region

Instream Water Availability in the Sundarbans Mangrove Ecosystem of Bangladesh

Instream water flow is crucial for the sustenance of an ecosystem. This study attempts to quantify the seasonal variability of instream flows of Sundarbans of Bangladesh which is the part of world’s largest Mangrove ecosystem. It is located at the interface of the Bay of Bengal and is grown on swamps of fresh and saline water. Unfortunately freshwater is depleting at an alarming rate due to diversions of upstream flows in the Ganges River together with low rainfall during dry season and irrigation and industrial water uses. The complimentary relationship method was used to calculate ET using meteorological data from 11 weather stations. Evapotranspiration and off-stream water use (irrigation, industrial and domestic) were used to calculate instream water flow. Flow duration curves (FDC) were used to assess the change of incoming upstream flow. Two treaties were in place to receive upstream water flow to Bangladesh through the Farakka Barrage. Flow data of the recent treaty period (1997-2015) for five major discharge stations were used as flows into the study area. Also 1 km resolution MODIS data of annual maximum green vegetation fraction (MGVF) cover were used to assess the spatial extent of Sundarbans’ mangrove region which is dependent on Ganges Flow. A large variation of around 83% is observed for instream water flow between wet and dry seasons. The flow analysis on Gorai river (1997-2015),the only major spill channel of the Ganges towards Sundarbans, shows 51% and 32% decrease in low and high flow threshold values, respectively from the pre-barrage period (before 1975). Dense vegetation fraction cover (\u3e60%) is decreasing but not statistically significant. These background analyses will help to develop a comprehensive water management plan that can minimize environmental degradation and support ecosystem services of Sundarbans