Identification of Strong Karst Groundwater Runoff Belt by Cross Wavelet Transform

Abstract

Karst aquifers are highly heterogeneous and exhibit hierarchical permeability structures or flow paths. Conduits and fractures typically account for less than 1 percent of the porosity of the aquifer, but more than 95 percent of the permeability. For the purposes of karst groundwater resources management, as well as of protection strategies against potential contamination, identifying the strong karst groundwater runoff belt of an entire aquifer system is generally more important than information about a specific spring. In this project, we introduce cross wavelet transform to analyze the relation between precipitation and spring discharge, and then identify the strong karst groundwater runoff belt. In highly concentrated karst areas, the precipitation signal can penetrate an aquifer relatively easily and will readily affect spring discharge. The precipitation and spring discharge are thus closely related, and the cross wavelet transform coefficients are large. Conversely, in areas of low karst concentration, the cross wavelet transform coefficients are small. We applied the method to Niangziguan Springs Basin in China to detect the strong karst groundwater runoff belt. Results showed that Pingding County and Yangquan City have a high degree of karstification (i.e. the strong karst groundwater runoff belt), Xiyang County and Shouyang County have a moderate degree of karstification, and Yuxian County, Heshun County, and Zuoquan County have a low degree of karstification. The results agree with the geological structure of Niangziguan Springs Basin.