Modeling the effects of water diversion projects on surface water and groundwater interactions in the central Yangtze River basin.

Due to the lack of the quantification of surface water (SW) and groundwater (GW) interaction, the chemicals transport and fate and wetland evolution are hard to predict under impact of both the natural condition and water diversion projects. To address this issue, a 3D regional numerical model is proposed in this study to analyze the effects of the South-to-North Water Diversion (SNWD) and Yangtze-Hanjiang Water Diversion (YHWD) projects on groundwater flow regimes and SW-GW interactions of Jianghan Plain in the central Yangtze River basin. The model results show that the Yangtze River and groundwater interactive pattern varied little, whereas the exchange capacity has been significantly affected by the SNWD but little affected by the YHWD. If only implemented SNWD project, the Hanjiang River and groundwater interactive pattern varied and the net exchange rate between the Hanjiang River and groundwater decreased by 69.3% compared to natural condition. Since YHWD was introduced to complement SNWD, the net exchange rate has been reduced by 25.3% compared with that under the only SNWD. SNWD and YHWD projects implementation caused the decrease of the groundwater level along the Yangtze River with the maximum value of 0.19 m but the increase of groundwater level along the Hanjiang River with the maximum rise reaching up to 0.78 m. This study provides the insights for quantification of GW-SW interaction at regional scale, which will benefiting for integrated water resource management and understanding contaminant reactive transport and wetland evolution in the central Yangtze River basin.