Evaluating Surface Water-groundwater Interactions in Consequence of Changes in Climate and Groundwater Extraction

This study explores spatio-temporal patterns of surface water-groundwater interactions in the Yom and Nan River basins, a vulnerable and essential agricultural region in northern Thailand, under various future climate conditions. The SWAT-MODFLOW model performs the coupled simulation of surface/subsurface hydrological processes in the watershed, with projected climate conditions from the three Global Climate Models (MIROC5, CNRM-CM5, and MPI-ESM-MR) under the minimum and maximum Green House Gas emission scenarios, represented as the RCPs 2.6 and 8.5. The results demonstrate that, in the near future (2026-2045) under the two scenarios, a raised air temperature at 0.5-1.0 degrees C with a 2-16% increment of annual rainfall cause a 7-20% decrease in groundwater recharge from surface water percolation, followed by a 11-21% depletion of groundwater flow to river, while aquifer recharge from the river change negligibly. In the intermediate future (2051-2070) and far future (2076-2095), changes in surface water-groundwater interactions under RCP 2.6 are rather similar to the near future because of insignificant differentiation in climate conditions. Whereas, under RCP 8.5, annual rainfall increases by 26% and produces 4-14% increments of groundwater recharging and groundwater discharge to streamflow, while river seepage increases by 1-18%. These provide key insights into northern Thailand watershed systems to deal with future impacts of climate change on water supply.