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

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 m3/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.