Abstract: Based on the experimental ecological water replenishment in the plain section of Hutuo River in 2018, we analyzed the water replenishment effect from three aspects: water level fluctuation, influence range, and groundwater storage variable. The influencing factors of groundwater depth change in Hutuo River plain were quantitatively analyzed by correlation analysis and principal component regression analysis to establish the corresponding mathematical model. The results showed that water replenishment had a significant effect on water level rise near Zhengding County, and that the area with water level rise accounted for 33.2% of the total area of the study region. The closer to the river, the faster the groundwater response and the greater the water level rise. Water replenishment effect in the middle and lower reaches were not significant. The results of principal component analysis showed that rainfall infiltration coefficient had the greatest influence on the change of groundwater depth, with a contribution rate of 24%. The contribution rates of upstream cumulative inflow and groundwater exploitation intensity to the change of groundwater depth were 20.26% and -19.72%, respectively, which were less important than the rainfall infiltration coefficient. The multivariate linear regression model established in the lower reaches of the Hutuo River had higher prediction accuracy. Taking the water supplement data of river section 1 as a reference, when the upstream water volume of river section 2 and river section 3 reached 4.78×10⁸ and 5.22×10⁸ m³ respectively, the downward trend of groundwater level in the corresponding river section could be reversed, while water replenishment of river section 4 was difficult and groundwater exploitation should be restricted. This study is of great significance for reasonable regulation of water diversion and sustainable development of regional water resources.

Key words: groundwater regime, principal component regression, river infiltration recharge, groundwater depth, water level fluctuation, contribute rate