The impact of climate change on the hydrology of the Halda Basin, southeastern Bangladesh

Water security is one of the most challenging issues of the 21st century. Developing countries, including Bangladesh,are particularly vulnerable to climate change due to their low capacity for adaptation and mitigation, high population density and poverty. Climate change has already impacted water security in Bangladesh in many ways, mostly in the form of coastal and inland flooding due to higher monsoon precipitation and runoff, increased salinity and reduced flow during the dry season. Thus, this goal of this thesis is to identify current impacts of climate change on the Halda River Basin, southeastern Bangladesh, and assess potential future consequences of climate and land use change on river discharge. Meteorological records from this region indicate that temperature has increased by 0.4-0.6°C per decade since 1980 and 2013, although there has been no trend in mean or total precipitation. A Soil and Water Assessment Tool (SWAT) was used to simulate the catchment dynamics of a data-poor, monsoon driven, small river basin, and to serve as a baseline for scenario modelling. The model showed good agreement with gauge flow data, except during peak flows. The SWAT model was then used to predict the future impact of climate and land use changes, individually and combined, on streamflow in the Halda Basin. Result indicated a likely net gain in streamflow until at least 2060. Future shifts in temperature and precipitation of the Halda River will have broad ranging consequences. Hence, I also explored seasonal and annual relationships between carp spawn production and key climate and hydrological variables (temperature, precipitation and water discharge), finding that temperature plays the dominant role in determining spawn production over different time scales. However, precipitation and water discharge also influence spawn production on seasonal time-scales. The outcomes of this research could be used in designing management and planning tools to facilitate climate change adaptation.