Assessing the impacts of irrigation and soil types on the water balance and groundwater depletion in an irrigation district of the North China Plain based on a coupled SWAT-MODFLOW model
Chunying Wang, Minghuan Liu, Yuping Han, Shuai Chen, Feifei Zhang, Rangjian Qiu, Defeng Wu, Gengchen Zhang, Fuqiang Wang, Junguo Liu
Abstract
Well irrigation can alter water balance and threaten the sustainability of groundwater resources globally. It is a challenge to quantitatively evaluate the effect of complex irrigation water use in different soils on the water balance in the vadose zone and in the phreatic aquifer at a regional scale. An irrigation district in the North China Plain was chosen as the study site, where the soil types were mainly sandy loam and silt loam in well-irrigated areas and silt in surface water irrigation areas. The coupled SWAT-MODFLOW model was robustly verified by the two-year monthly soil water content and groundwater level data. Evaluation of water balance components across the entire study area showed that under the precipitation of 426 mm yr −1 and irrigation of 300 mm yr −1 (5.7 % surface water and 94.3 % groundwater), the actual evapotranspiration (actual ET) was 514 mm yr −1 , soil water recharge to groundwater was 252 mm yr −1 , and the groundwater amount declined 90 mm yr −1 . Irrigation increased the actual ET by 191 mm yr −1 and soil water percolation to groundwater by 134 mm yr −1 compared with the non-irrigation scenario. Groundwater abstraction for irrigation resulted in less soil water percolation (220 mm yr −1 ) and higher groundwater depletion (181 mm yr −1 ) in the sandy loam region than in the silt loam region where soil water percolation was 281 mm yr −1 and groundwater depletion was 161 mm yr −1 . The higher antecedent soil water content resulted in higher soil water percolation in fine-textured soil. Irrigation optimization measures are necessary to mitigate groundwater depletion in coarse-textured soil in the irrigated region of the North China Plain. • SWAT-MODFLOW was verified by two-year monthly soil water and groundwater level data. • Irrigation increased actual ET of 191 mm yr −1 and soil water percolation of 134 mm yr −1 . • Mixed water source irrigation caused groundwater amount declination of 90 mm yr −1 . • Sandy loam with low initial soil water content showed less soil water percolation than silt loam.