Abstract: Situated at Ganjiang River Terrace, the left reservoir bank of Xingan Navigation and Power Junction Project is a typical double-layer hydrogeological structure. Depicting the dynamic process of groundwater immersion in the double-layer structural reservoir bank after impoundment is a prerequisite for assessing reservoir immersion reasonably. In this study we established analytical solutions for the transient groundwater flow in upper unconfined and lower confined aquifers between two lateral watercourses and a three-dimensional numerical model of transient groundwater flow for comparative study. Furthermore, we evaluated the influencing range of groundwater immersion based on the judging criteria of reservoir immersion in Ganjiang section. The comparison results indicate that in early stage of assessment both the analytical and numerical methods could describe the dynamic process of groundwater immersion after impoundment. However, in the middle and late stages of evaluation, the result of numerical method is more reasonable as the effect of rainfall infiltration on groundwater immersion gradually becomes more prominent. Meanwhile, the immersion range will increase to 10.91 km² at the end of the third year predicted by the numerical modeling. The research findings provide scientific basis for the design of immersion controlling.

Key words: reservoir immersion, dual-structural reservoir bank, analytical solution, numerical modeling, immersion area