Flow Recession Equations for Karst Systems

Abstract

The proper management and exploitation of karst water resources require first and foremost an accurate characterization of the karst aquifer. Analysis of the recession curve of a spring hydrograph is one efficient approach of determining the hydraulic characteristics of a karst system. In the present work, six flow recession equations for various flow conditions are presented that highlight the dichotomy of the dual flow characteristics between the fissured matrix and the conduit system. They are defined in terms of lumped physical parameters that characterize the dominant flow processes occurring in a karst aquifer. The processes consist either of a pressure-driven flow or a gravity-driven flow in a conduit that is interacting laterally with the groundwater flow in the surrounding matrix. The recession equations are composed of two distinct functions that represent separately the flood flow component and the base flow component. They allow the separate evaluation of the conduit and matrix drainage processes and capture the strongly varying recession in the early stages as well as the slow decline in the latter stages of the spring recession hydrograph. Approximate equations for large times are also developed that allow the direct estimation of the model parameters of the karst system using simple algebraic formulas. The flow recession equations were applied to three real karst systems and proved to be effective in simulating the observed recession hydrographs and estimating its hydraulic properties. ©2020. American Geophysical Union. All Rights Reserved.