Abstract:

To scientifically evaluate the response of groundwater system to ecological water conveyance projects in the Xiliaohe plain, this study employed FEFLOW to construct a groundwater flow numerical model. The model simulated the dynamic changes in the unconfined aquifer under three water delivery scenarios with annual operation durations of 70, 80, and 90 days. Considering the uncertainties in specific yield, hydraulic conductivity, and river infiltration recharge intensity of the unconfined aquifer, a Gaussian process regression (GPR) surrogate model combined with the Monte Carlo method was employed to quantify the influence of parameter uncertainty on groundwater storage variations. The results indicate that ecological water conveyance significantly raised the groundwater levels in the Xar Moron-Laoha River confluence zone and the distribution area of confined aquifer, with increases of 0-3 m and 3-5 m, respectively, and the influence range of up to 5 500 m on both sides of the river. The estimated groundwater storage variations under the three scenarios were 3.04×108-5.83×108，3.48×108-6.55×108，and 3.87×108-7.22×108 m3, respectively, with exceedance probabilities of 46.1%, 44.1%, and 45.0%, all below 50%, suggesting that deterministic approaches overestimate actual recharge quantity.

Key words: ecological water conveyance, groundwater level, numerical simulation of groundwater, uncertainty analysis, surrogate model, Monte Carlo, Xiliaohe plain