NIDWat: A Water Balance Model for the Niger Inland Delta (NID) Floodplain in Mali
Abstract:The Niger river basin is characterized by hydro-climatic changes induced by land use and climate change that have significant impacts on local populations. The Niger Inland Delta (NID) is the single most important wetland conditioning the water availability downstream. A significant fraction of the river flow is lost through evaporation and water use in the NID and the conditions are likely to change with increasing population and changing inflow conditions.
A comprehensive understanding of the NID’s hydro-climatological functioning is therefore crucial for assessing the water resources in the basin under changing conditions in the future.
Despite this significance, the components of the water balance in the NID are poorly quantified.
We use optical and microwave remote sensing data to characterize the temporal flooding, and observations of river flow and spatially explicit information on water abstractions to develop NIDWat, a water balance model for the NID. Simulated evapotranspiration losses varied by ~ 50%, depending on flooded area map or climatic data. The combined effect of irrigation abstraction and climatic data generated a global water losses range of 16 to 33.04 km3 a-1.
The model was validated against observed river discharge and water abstractions and shows a good performance. We then implemented the model as a module in a hydrological model to assess the water balance in the NID and the downstream water availability under changing conditions. We use a multi model approach using regional climate data from the CORDEX initiative. Results suggest, despite increasing runoff an increase in ET losses and changes in the temporal dynamics of flooding that impact water resources availability downstream.