On the base flow recession at the Panola Mountain Research Watershed, Georgia, United States

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Abstract

[1] There are two types of nonlinearity for recession slope curves: (1) the data cloud of observed ln(–dQ/dt) versus ln(Q) along a straight line where the slope is not equal to 1, and (2) the data cloud of observed ln(–dQ/dt) versus ln(Q) is concave or convex. From the 0.1 ha hillslope, the 10 ha headwater subwatershed, and the 41 ha watershed at the Panola Mountain Research Watershed (PMRW), the observed ln(–dQ/dt) versus ln(Q) changes from convex to concave. This has been explained by the spatial heterogeneity of recession properties and nonlinearity of hillslope hydraulics. Hillslope bedrock leakage and return flow to the perennial riparian zone aquifer are important factors affecting the ln(–dQ/dt) versus ln(Q) relations, and an assessment of this mechanism for explaining the observed base flow recessions at the PMRW is the sole focus of this research. As a result, the lower envelope and the upper envelope should be used to estimate the recession parameters for the 0.1 ha hillslope and the 41 ha watershed, respectively, and the recession at the 10 ha watershed is a mixture of them. Based on the recession analysis, the leakage to the bedrock on the hillslope and return flow to the perennial stream riparian groundwater can be estimated, and the estimation can be verified by other studies.

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