资源环境科技发展态势分析平台

Recession flow analysis is usually conducted to infer hydraulic parameters of hillslope aquifers. Various Boussinesq equation-based models, both linear and nonlinear, have been used to analyze the recession curves for sloping aquifers, with a focus on the long-time recession behavior. Based on a modified Boussinesq equation with capillarity incorporated, we demonstrate the significant effect of unsaturated flow on the recession curve, which result in three (instead of two) power law regimes with two transition points (instead of one) corresponding to the formation of a fully unsaturated zone at the adjacent area of the upslope boundary and across the whole domain, respectively. The results show that the power of the second and third recession regime is variable, depending on the slope angles, soil types, and hillslope geometries. The unsaturated flow effects also lead to the absence of drastic drop of -dQ/dt at the transition between the first and second regime, which was predicted by previous numerical models but has not been observed in the field or laboratory experiments. These findings have important implications for recession flow analysis in studies of hillslope aquifers.