Heterogeneous reservoir seepage characterized by geophysical, hydrochemical and hydrological methods

Seepage characterization from reservoirs is challenging for various environmental and water resource applications. Non-intrusive geophysical methods can achieve excellent detection results, but they cannot provide a quantitative description of the amount of seepage. Integrating geophysical methods with traditional hydrochemical and hydrological methods enables simultaneous localization and quantitative analysis of heterogeneous reservoir seepage. Ground and waterborne ERT were employed to scan a reservoir under a typical cut-off wall anti-seepage system, and the measurements revealed the northern preferential infiltration area. The hydrochemical results revealed that the seepage bypass of the cut-off wall has led to evident ion concentration variations in groundwater near the dam. Based on the geological stratum information, the typical cut-off wall anti-seepage system was divided into three scenarios for numerical simulation to calculate the seepage. The total seepage of the reservoir over 15 months was about 7.15×10 6 m 3 , which is consistent with traditional water budget methods. However, in the northern part of the reservoir, only 27% of the whole dam, contributes 77% of the total seepage. All methods have confirmed that the heterogeneous seepage is caused by the absence of an anti-seepage seal in the northern region, which should be a primary focus for future monitoring and operational efforts. With the geophysical results undergoing extensive cross-validation, the results from the above methods are comprehensively leveraged, effectively lowering uncertainties and overcoming the limitations of geophysical methods in quantitatively characterizing seepage.