The Impact of Water Diversion on Groundwater Resources in an Inland River Basin

The Heihe River Basin (HRB) is one of the most intensely exploited and ecologically stressed inland river basins in the world. The HRB is characterized by three distinct ecohydrological systems: the mountainous upper reach where most of the water resources for the HRB originate from the rainfall, snow and permafrost; the middle reach with an arid climate and irrigated agriculture; and the lower reach dominated by wide stretches of Gobi desert. The study site, Zhangye Basin, is situated in the middle reach. It contains 92% population of the HRB and consumes about 80% of water resources as a regional agricultural and industrial center. To improve the deteriorating health of the ecosystems in the lower HRB, the Chinese government initiated the Heihe Water Diversion Project (HWDP) in 2000, which stipulated that at least 0.95 billion cubic meters of surface water must be delivered from the middle reach to the lower reach annually. A three-dimensional groundwater flow model has been developed for the Zhangye Basin to understand groundwater-surface water interactions in the Zhangye Basin and assess how the HWDP project has impacted the groundwater availability and water budgets in the region. The flow model has been reasonably calibrated using multiple sources of field data. The output of the groundwater model provided estimates of head differences before and after the HWDP project between 1999 and 2010. The results show that the groundwater level has declined widely, except in the Zhangye urban area where the groundwater level has increased by 0.5 to 7m and a few other localized spots. The calculated water budgets indicate that the spring discharge to the Heihe River has been continuously decreasing, and the total river leakage to the aquifer has been increasing. These results are in reasonable agreement with those from previous studies based on independent water balance calculation. The groundwater model is being integrated with surface water and land use data to provide a decision support system for more sustainable management of the water resources in the in the Zhangye Basin.