Integrated management of surface water and groundwater for climate change adaptation using hydrological modeling

Conjunctive use of water has an increasingly important role in dealing with climate change impacts in several regions. Water resources are holistically managed by harvesting surplus surface water into aquifers during wet season and extracting it for supply in dry season. This study aims to apply integrated hydrological modeling to evaluate groundwater recharge approaches for conjunctive use of water under future climates. The study area is Yom and Nan River basins, northern Thailand, which always suffers climatic extreme events. Surface water-groundwater regime is simulated by using SWAT-MODFLOW model under minimum and maximum greenhouse gas emission scenarios as the Representative Concentration Pathways (RCPs) 2.6 and 8.5, respectively. Managed aquifer recharge (MAR) method is applied in simulation to represent the conjunctive use of water. Results demonstrate that about 14%, mainly plains, of watershed area have high suitability for managing aquifer recharge. Almost 2000 recharge wells constructed in high suitable areas near existing groundwater pumping wells provide that, by recharging groundwater at 550-700 m3/day in the upper and 820-900 m3/day in the lower watershed areas during 2021-2030 under RCPs 2.6 and 8.5, annual groundwater storage is more added 22 x 106 m3 including 530 x 106-570 x 106 m3 decrease in surface water. During 2031-2040 under RCP 2.6 (8.5), a recharge rate at 1200-1400 (1000-1150) m3/day in the upper area and 1650-1800 (1400-1500) m3/day in the lower area can increase a 48 x 106 m3 of groundwater storage and reduce a 940 x 106-1120 x 106 m3 of surface water. Outputs can enhance information for holistic water management responding to climate change adaptation.