Using heat as a tracer to quantify surface water and groundwater interactions in the Baiyangdian wetland

Center for Hydrogeology and Environmental Geology Survey, China Geological Survey, 071051, Baoding, Hebei, China

Abstract

Surface water and groundwater interactions play an important role in hydrological cycle in a wetland ecosystem. Understanding its mechanism and interaction magnitude imposes significant effects in wetland protection and management. In this study, a heat tracer method was taken in the Baiyangdian wetland as a case and temperature time-series data were collected for surface water and wetland sediment of 0.2 m, 0.6 m and 1 m respectively in 3 monitor sites. Then, a one-dimensional vertical steady heat transport model was applied to estimate surface water inflows to groundwater. The results showed that the leakage rates were 0.04-0.29 mm/d and had a spatial and temporal variation. In the same monitor site, the leakage rate was higher in winter than it in summer. A total leakage amount for the Baiyangdian wetland was evaluated as 8.61 million m^3/d. The surface water leakage resulting from the model was subject to several uncertainties including sediments inhomogeneity and the impact of non-ideal conditions. Despite the uncertainties of the model, when correctly applied, heat tracer method is able to provide detailed information on the spatial and temporal distribution of surface water leakage.