Application of the tracer test in karst hydrogeological prospecting: An example of Heilongtan, Lijiang, Yunnan

The purpose of this work was to investigate the connection between groundwater and the surrounding springs in the recharge area of the Jiuzihai depression, Lijiang, Yunnan Province, and to provide scientific basis for spring water restoration. Using the artificial chemical tracer method a large-scale groundwater tracer test has been conducted with potassium iodide as tracer. Based on the experimental data, the seepage velocity of groundwater was calculated and the characteristics of the groundwater system in Heilongtan springs area were analyzed. The results show that the groundwater in the Jiuzihai depression is significantly connected with Heilongtan and Gucheng springs, while not connected with Qingxi springs and Bailanghua springs. The seepage velocity of groundwater from Jiuzihai to Heilongtan and Gucheng is around 405.86-1,077.84 m· d-1 and 349.96-629.09 m· d-1, respectively. The Jiuzihai depression is the main recharge area of the groundwater system of the Heilongtan springs area, which can also be used as an effective injection site for the restoration of Heilongtan springs. After receiving the recharge, it is mainly transported to area around Heilongtan-Gucheng by deep karst pipelines, of which the Heilongtan springs are the discharge area of the groundwater system.