Process-Based Flow Model for a Karst Aquifer System

Abstract:

Karst aquifers are characterized as a dual-flow system comprised of a highly conductive conduit network embedded in a low porosity matrix. The conduits are hydraulically connected to the matrix and behave either as a drain or a source depending on the recharge conditions. Simulation of flow in such systems using distributed karst models faces several challenges primarily due to the high data requirements to achieve robust prediction. A simplified process-based model is herein employed to simulate the spring outflow from a karstic aquifer using a one-dimensional conduit system embedded in a two-dimensional matrix domain. The flow system is driven by the diffuse aquifer recharge that interacts with the conduit along its length as well as by a concentrated recharge at the conduit entrance. The flow is described by a coupled system of partial differential equations: the kinematic wave equation for the open-channel flow in the conduit and the Boussinesq equation for the groundwater flow in the matrix. The analytical model simulates the typical shape of a spring hydrograph using physical parameters rather than empirical ones, and requires less data than two- and three-dimensional dual-hydraulic models. An application of the model to a real karst aquifer system demonstrates its effectiveness in simulating the observed spring hydrograph using physically meaningful parameters.