Impacts of Urbanization and Climate Variability on Groundwater Environment in a Basin Scale

Globally, groundwater resources are experiencing decline in hydraulic heads resulting from the dual effect of urbanization and climate change, thereby necessitating the need for integrated and sustainable water resources management. Urban development in cities of Kansai region, western Japan are presenting a significant challenge to sustainable groundwater resources. This study aims to assess the combined influence of urbanization and climate change on the groundwater resources of Nara basin using MODFLOW 6 for two different periods (Pre-Urbanization Period (PreUP): 1980 -1988, Post-Urbanization Pe-riod (PostUP): 2000-2008). Simulated hydraulic heads were assessed based on three different recharge scenarios: uniformly, spatiotemporally and spatially distributed. The uniform recharge scenario both overestimates and underestimates hydraulic heads, emphasizing the need for spatiotemporal variations in recharge input for groundwater flow simulation. Our findings indicate a significant decrease in groundwater heads from the PreUP to PostUP in the unconfined aquifer, attributed to the effects of land use and climate change, while the declines in deep confined aquifers are primarily influenced by climatic variations over several years. These head changes were notably evident in the interactions between surface and groundwater. Effective management of groundwater resources amidst urbanization and climate change necessitates a holistic and integrated approach.