Baseflow Recession Curve of Small Mountain River and Its Physical Significances

Abstract

The baseflow recession characteristics of a small mountain river are investigated using a two-dimensional sand model. The results indicate that the baseflow recession curve is affected by the characteristics of groundwater recharge from the unsaturated zone and the diffusive flow in the aquifer. An unconfined ground water model with a recharge from the unsaturated zone is developed for the baseflow model of a small mountain river. The recession curve of this model is Q=Q₁ exp (-δ₁t)+Q₂ (Δh) exp (-Δ₂t), where the first and second terms on the right side are the flow components from the unsaturated zone and the aquifer, respectively, and Δh is the initial difference between the groundwater level at the river and groundwater divide. The baseflow recession characteristics depend on δ₁, δ₂ and the Q₁/Q₂ (Δh) ratio. The equation agrees well with the baseflow recession curves of the study rivers.