Laboratory Analog Analysis of Spring Recession Curve in a Karst Aquifer with Fracture and Conduit Domains

Abstract

Karst aquifers differ from other types of hydrogeological systems because of their complex behavior, which originates from strong heterogeneity. A karst spring carries an imprint of hydrologic information for the karst aquifer. The shape of the outflow hydrograph recorded at a spring is a unique reflection of the aquifer’s response. A karstic aquifer consisting of a fracture network and a conduit was proposed, and the spring recession curves generated from the designed karst aquifer were analyzed in this study. The purpose of the study was to discuss the influence of the main spring conduit diameter and the saturated thickness of the aquifer on spring recession curves. A combination of 7 groups of outlet pipes with different diameters and 7 initial water levels were used to simulate changes in diameter and saturated thickness, respectively. Thus, a total of 49 experimental tests were carried out in the laboratory karst aquifer. The results indicate that spring recession curves can be separated into two flow segments, and that the main spring conduit diameter has a remarkable influence on the initial flow of recession, recession duration, and recession coefficient. The results also show that the saturated thickness of the aquifer has a great effect on the initial flow of the recession and recession duration, but that its effect on the recession coefficient and the shape of the recession curve is slight.