Abstract
Depletion of groundwater is expected due to climate change. This study describes a catchment-scale study on projected groundwater recharge and storage in the Upper Chao Phraya River basin under changing climate scenarios. The period from 2026 to 2040 was assessed using climate projection results from global climate models (GCMs). Three GCMs, namely MIROC-ESM-CHEM (MIROC), HadGEM2-ES (HadGEM), and GFDL-ESM2M (GFDL), were used along with four greenhouse gas emission scenarios, namely RCP2.6, RCP4.5, RCP6.0, and RCP8.5, as the climate change conditions. The projected changes in groundwater recharge and storage were quantified as percent differences from the simulated recharge and storage for the reference period (1986–2000). A significant trend of decreasing mean monthly rainfall from April to June was detected for the HadGEM and the GFDL models. This change in rainfall pattern was projected to reduce the mean annual groundwater recharge (storage) by −12.9% (−1.46 km3), −9.7% (−1.35 km3), −13.9% (−1.49 km3), and −10.7% (−1.38 km3) for the RCP 2.6, 4.5, 6.0, and 8.5 scenarios, respectively. Based on the results of the relative change in groundwater storage, we expect that groundwater resources will be affected by climate change and that both groundwater recharge and storage will be reduced.