Dynamic volume in karst aquifers: Parameters affecting the accuracy of estimates from recession analysis

Abstract

Reliable estimates of the dynamic volume of karst aquifers, i.e. the drainable volume of groundwater, are important in the context of sustainable management and environmental protection of the karst water resources. Extrapolation of the observed recession of spring hydrographs is commonly used as a basis for the estimation of the dynamic volume. However, our understanding concerning the reliability of this approach is still limited. Therefore, the adequacy of this approach is investigated using flow models of hypothetical karst aquifers to assess the deviation of the extrapolated from the real recession curve and identify parameters controlling the extrapolated recession coefficient. The results show that parameters such as the geometry of the catchment area and point recharge have little effect on the accuracy of the estimated dynamic volume. Low extension of the highly conductive zone and increase in specific yield or catchment area with depth of the aquifer result in the underestimation of the dynamic volume. Groundwater abstraction and decrease of specific yield or catchment area with increasing saturated thickness can lead to an overestimation of the dynamic volume. These findings clarify the potential underestimation or overestimation in dynamic volume estimates on the basis of the observed recession characteristics.