Effect of land use change on groundwater hydrological process in Yuxi River Basin

Land use change alters water resources allocation and groundwater hydrological processes in arid and semi-arid areas, leading to water and ecological problems such as regional groundwater level decline and land desertification. In these areas, where surface water resources are scarce, groundwater serves as the primary source for domestic and agricultural use. This study focused on the Yuxi River Basin, a primary tributary of Wuding River in the Yellow River Basin. By employing the land use data of four periods in 2005, 2010, 2015, and 2020, and using the improved dynamic attitude of secondary land use as the calibration index, this study analyzed the effects of long time scale land use change on groundwater hydrological elements in small catchment based on the coupled WetSpass-Modflow model. The results show that under the influence of urbanization from 2020 to 2035, the construction land converted from grassland and unused land will increase by 247.02 km², resulting in a decrease of 6.8 mm/a in rainfall infiltration recharge in the study area; the change of groundwater level will be within the range of ±3 m, while the evapotranspiration will basically remain unchanged. Land use change mainly reduces rainfall infiltration by reducing the infiltration performance of underlying surface and the interception ability of vegetation. Analysis of net recharge (rainfall infiltration minus evapotranspiration) reveals the following order: unused land > cultivated land > forest land > grassland > construction land. This indicates that the contribution of cultivated land and unused land to groundwater reserves is greater than that of grassland. The results show that the improved WetSpass-Modflow coupling model can be used to estimate and predict groundwater hydrological variables in small watershed from the perspective of land use change. In the future, more efficient agricultural water-saving schemes should be considered, and the increase of agricultural area should be strictly limited to promote the gradual improvement of the sustainability of regional groundwater resources.