Groundwater resources in Kathmandu valley, Nepal is perceiving immense stress due to high rate of abstraction along with climate change. The upshot of over abstracting groundwater results in declining groundwater levels and further leads to social, environmental and economic problems. Climate change might add immense pressure on groundwater by affecting the groundwater recharge rates and change the availability of groundwater. Mapping groundwater resiliency can aid in understanding the dynamic of groundwater system thus, help in developing the strategy for groundwater protection and management and sustainable use. This study emphasis on analyzing the impact of climate change on groundwater resources and mapping the groundwater resiliency under different climate change scenarios.
The climate data forecasted by ACCESS, CNRM and MPI for three future periods; Near Future (2010-2039), Mid Future (2040-2069) and Far Future (2070-2099) and RCP 4.5 and RCP 8.5 scenarios were corrected using the linear downscaling technique. All RCMs predicts that the temperature is continuously increasing in the study area, however, future precipitation is highly complex and uncertain and there was a significant difference among various RCMs and both RCPs scenarios. A hydrological model SWAT developed based on the meteorological data (1992-2005) along with DEM, soil map and land use map of the study area is used to estimate the groundwater recharge and suggest that groundwater will be a decrease in future and the decrease in groundwater recharge ranges from 3.3 mm to 50.7 mm in RCP 4.5 scenario and 19 mm to 100.8 mm in RCP 8.5 scenario. GMS-MODFLOW model was set up to estimate the groundwater level of Kathmandu Valley. Boundary conditions, recharge rates, pumping rates and hydraulic properties are the important input required to run the model. The model developed for 2001 and 2008 using a three-layer conceptual model revealed that the groundwater level will be decreased in future and decrease is up to 133.5 m. Based on the result of GMS-MODFLOW, groundwater resiliency indicator is developed, and this indicator is used to generate the resiliency map of Kathmandu valley. It is found that groundwater will be highly resilient for the rural part of the valley and not resilient in the city area.