The Deep Karst Groundwater System in Arid Regions of NorthwesternChina:A Case Study of Karst Fissure Groundwater in Southern Ningxia

Karst fissure groundwater in southeastern Ningxia has been synthetically analyzed by applying the theories of tectonic-controlled groundwater and groundwater geochemistry as well as isotope techniques. The results show that karstis not well developed in the area, the groundwater storage space is mainly madeup of karst fissures, and the distribution of karst groundwater is strictly controlled by the NS-trending faults. Karst groundwater in this region mainly originates from atmospheric precipitation and is mixed with various sorts of primitivewater. Groundwater quality shows zonal characteristics, i.e., good in the southand bad in the north. The water-rock interaction is characterized by dissolution-evapotranspiration and produces salt water in the northern area. In the southern area the water-rock interaction has features of dissolution-mixture and produces fresh water. According to characteristics of hydro-dynamic conditions and water chemistry, the whole karst system has been divided into three subordinate karst groundwater systems. The results have an important scientific significance in the study of the difference between the karst groundwater in western China andthat in eastern China.