Turbidity as an Indicator of Contamination in Karst Springs: A Short Review

Abstract

Karst aquifers are known to be prone to a variety of different types of contamination from a range of different sources. Due to the rapid recharge and high transport velocities associated with karst aquifers, karst springs usually show high discharge dynamics, and water quality often deteriorates very quickly following storm events due to the presence of contaminants such as pathogens, heavy metals, or pesticides. Turbidity has frequently been reported to vary in proportion to the concentration of contaminants in karst spring water, and its use has therefore been proposed to detect periods of contamination. A systematic relationship between such an easily measured parameter and contaminants would be useful for sustainable management of raw water resources in karst aquifers, especially in countries where water is scarce and event water cannot be easily discarded. In this study, we critically review a number of karst spring investigations in which turbidity has been shown to be an effective indicator for contamination. We conclude by identifying the conditions under which turbidity might be valid used to indicate contamination of karst spring water, and those under which this approach appears to be less effective. Our main findings are that the usefulness of turbidity as an indicator of contamination varies from one karst catchment to another and that a critical evaluation of contaminant and turbidity input and transport modes is required for each individual karst system before turbidity can be successfully used as an indicator of contamination. A conceptual model that combines different input and transport modes of turbidity and contaminants is presented.