Impact of Land Use Change on Groundwater Regime and Hydrogeochemistry: A Case Study in the Kongqi River Catchment of Xinjiang

The impact of land use change on groundwater regime and hydrogeochemistry is one of the hottest research topics in the hydrogeological community. This study took the Kongqi river Catchment of Xinjiang as the research area, the spatial and temporal distributions of groundwater regime and hydrogeochemistry were analyzed under the condition of land use change. The results indicated that over the last 50 years, The cultivated land increased rapidly, resulting in a continuous increasement in the amount of groundwater extraction. Additionally, a large amount of surface water was diverted for irrigation, which reduced the amount of groundwater recharge through river channel infiltration in the Kongqi river Catchment. This leads to a significant drop in water table and the formation of groundwater depression zones. The majority of drawdown was 10～40 m, with the biggest value of over 50 m. In the middle and lower reaches of the Kongqi river, the relationship between river and groundwater also changed from gaining steam to loosing stream. Land use change caused variations in hydrogeochemical fields by influencing groundwater circulation conditions and hydrogeochemical processes. The overall decrease in groundwater TDS in the study area was observed, due to a weakened evapotranspiration following water table decline and an enhanced leaching effect by irrigation using low salinity river water. Surface water irrigation also enhanced water chemical mixing in the depression zones, and led to the chemical type changes from Cl·SO₄ to HCO₃·Cl and HCO₃·Cl·SO₄. This study can provide a scientific basis for the rational development, utilization and protection of groundwater in the Kongqi river Catchment and similar areas.