Estimating spatiotemporal variability and sustainability of shallow groundwater in a well-irrigated plain of the Haihe River basin using SWAT model

Abstract

Quantitatively estimating the spatiotemporal variability and sustainability of shallow groundwater with a distributed hydrological model could provide an important basis for proper groundwater management, especially in well-irrigated areas. In this study, the Soil and Water Assessment Tool (SWAT) model was modified and applied to a well-irrigated plain of the Haihe River basin. First, appropriate initial values of the parameters in the groundwater module were determined based on abundant hydrogeological investigations and assessment. Then, the model was satisfactorily calibrated and validated using shallow groundwater table data from 16 national wells monitored monthly from 1993 to 2010 and 148 wells investigated yearly from 2006 to 2012. To further demonstrate the model’s rationality, the multi-objective validation was conducted by comparing the simulated groundwater balance components, actual evapotranspiration, and crop yields to multiple sources data. Finally, the established SWAT was used to estimate both shallow groundwater table fluctuation and shallow aquifer water storage change in time and space. Results showed that the average shallow groundwater table declined at a rate of 0.69–1.56ma−1, which depleted almost 350×108m3 of shallow aquifer water storage in the cropland during the period of 1993–2012. Because of the heterogeneity of the underlying surface and precipitation, these variations were spatiotemporally different. Generally, the shallow groundwater table declined 1.43–1.88mduring the winter wheat (Triticum aestivum L.) growing season, while it recovered 0.28–0.57m during the summer maize (Zea mays L.) growing season except when precipitation was exceptionally scarce. According to the simulated depletion rate, the shallow aquifer in the study area may face a depletion crisis within the next 80years. This study identified the regions where prohibitions or restrictions on shallow groundwater exploitation should be urgently carried out.