Precipitation-driven hydrological characteristics of Bei hot spring: Insights from dynamic variations of natural tracers (water discharge, water temperature, and electrical conductivity)

Study region: Bei hot spring in Chongqing, China. Study focus: The primary objectives of this research are to analyze geothermal water characteristics of Bei hot spring, simulate the dynamic process of water discharge (Q), groundwater temperature (Tw), and electrical conductivity (EC) during the precipitation event, and build the hydrogeological genetic model for the Bei hot spring. Results: Water flow of Bei hot spring reaches depths ranging from approximately 2.61 to 5.42 km, with the thermal reservoir temperature varying between about 72.00 and 127.36 °C. The recharge ratios of pore water, fracture water, conduit water, and hot water from the geothermal reservoir were 6.14 %, 8.86 %, and 78.63 %, respectively. The highest recession coefficient in the fracture and the relativley low conduit water ratio indicate that Bei hot spring features a less developed conduit in its upper section, along with a well-connected fracture network. The hydrological pulse model effectively simulates the dynamic variations of Q, Tw, and EC in Bei hot spring, showing a sensitive response to individual precipitation event. The catchment area of Bei hot spring, which spans 67.87 km2, was subsequently calculated. Finally, a hydrogeological genetic model for Bei hot spring was developed, considering the spatial geological structure, water sources, and water circulation. These findings had significant implications for the assessment of water sources in karst hot springs.