The recent United Nations Climate Change Conference COP24 held in Katowice, Poland once more demonstrated the world’s climate change concerns. In the Indus, Ganges, and Brahmaputra river basins, a global climate change hotspot and home for about 900 million people, these concerns are pressing, since the river systems provide water resources for the important agricultural, domestic, and industrial sectors that serve these people. Melt water from glaciers and snow feed the headwaters of these rivers and are strongly influenced by rising temperatures. In addition, the monsoon and its dynamics, which determine the regional hydrology, are expected to change. Moreover, strong socio-economic developments and a rapid and continuous population growth will result in tremendous increases in water demand and cause pressure on water resources. It is therefore very likely that a water gap will develop in the future.
A new study published (open access) in Hydrology and Earth System Sciences led by René assesses the combined impacts of climate change and socio-economic developments on the future “blue” water gap in the Indus, Ganges, and Brahmaputra river basins until the end of the 21st century. In this joint effort by FutureWater, Utrecht University, Wageningen Environmental Research and ICIMOD a hydrological model that simulates future changes in the upstream water reserves (SPHY) is coupled with a hydrology and crop production model that simulates future changes in the downstream water balance (LPJmL). The models were forced with the latest climate change projections and socio-economic scenarios.
The findings of this study indicate that the surface water availability will increase, which can mainly be attributed to increases in monsoon precipitation. Besides the increases in surface water availability, water consumption by irrigation will most likely decline due to shorter growing seasons that emerge from temperature increases, and a shift from blue water irrigation to green water/rainfed irrigation due to increases in precipitation. However, this increase in water availability cannot outweigh the strong increases in water demand that are associated with the strong socio-economic development, and will thus likely lead to a substantial increase in the water gap with 7% and 14% in the Indus and Ganges river basins, respectively, during the 21st century. This implies the importance of robust adaptation strategies to cope with future water shortages in the region.
Maps showing the annual groundwater depletion for the reference period (a) and the projected changes in groundwater depletion for RCP4.5 (b), RCP8.5 (c), RCP4.5 – SSP1 (d), and RCP8.5 – SSP3 (e). The projected changes are given for the end of the 21st century. Green indicates less depletion and red indicate more depletion.
