Free-Aquifer Ground-Water Depletion Hydrographs

by Stanley S. Butler,

Serial Information: Journal of the Irrigation and Drainage Division, 1967, Vol. 93, Issue 1, Pg. 65-82

Document Type: Journal Paper


The relationship of free-aquifer base flow or ground-water depletion (GWD) discharge to aquifer characteristics is analyzed, leading to semi-rational equations for the GWD hydrograph. For a shallow isotropic aquifer, the GWD discharge per foot of channel is q = 1/[K(t + C)2], in which t = time in days. For a deep isotropic aquifer, q = K1/10t/K2. The constants K, C, K1 and K2 are shown to be functions of permeability, specific yield, and aquifer geometry. The derivations use the Darcy and hydrologic equations, with the Dupuit and other simplifying assumptions. Laboratory and field evidence indicates that the equations may be of fairly wide applicability. Although derived for GWD, the equations may be applied also to base flow. In a field test, the base flow or GWD hydrograph for a single long dry spell should be used in preference to a composite hydrograph derived by combining short segments, as a composite hydrograph may have too little curvature.

Subject Headings: Base flow | Aquifers | Hydrographs | Groundwater flow | Isotropy | Composite materials | Groundwater depletion | Water discharge

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