Presenter
Dr. Mingqian Li, School of Ecology and Environment, Institute of Disaster Prevention
Co-author(s)
Dr. He Wang, Jilin University
Sub-theme
1. Water-Human-Economy(Agriculture, Industry, City...)-Ecology Nexus under a Changing Environment
Topic
1-1. Rules and mechanisms of natural hydrological cycling and socio-economic water cycling evolution under climate change
Body
Interactions between groundwater and surface water (GW-SW interactions) play a crucial role in the hydrological cycle; thus, the quantification of GW-SW interactions is essential. However, uncertainty is inherent in the study of GW-SW interactions, which makes it necessary to grasp the basic mode of regional GW-SW interactions in advance when using various methods for research, especially in areas where human activities such as reservoir and irrigation are significant. To solve this problem, a cumulative exchange fluxes method based on mass balance theory is proposed for a stream-aquifer system. This method determines the curve of cumulative fluxes through the water balance term, which can characterize GW-SW interactions, determine the amount of exchange fluxes, and reveal the dynamic process of interactions. This method is used in a reach of the Taizi River Basin, and the GW-SW interactions observed in 2016 are categorized into seven stages and four types (natural controlled, reservoir and irrigation controlled, irrigation controlled, and irrigation hysteresis type). The natural recharge in the study reach is approximately 3.03 × 105 m3·day−1, and the increase caused by irrigation is 7.8–13.87 × 105 m3·day−1. After the irrigation stops, the impact can be sustained for 48 d with an increase of 3.03 × 105 m3·day−1. The water-level change of the typical section further confirms the accuracy of the method for determining the GW-SW interactions. The analysis of error shows that the influence of the evaporation conversion coefficient and flow measurement system is small, the impact of the lag time is small after correction, and the main error comes from the selection of the runoff coefficient. This method is applicable to reaches in plains with flow monitoring data. The hysteresis of streamflow cannot be ignored when the reach is long. Two solutions have been suggested to deal with selection of runoff coefficient and hysteresis. The basic mode and changes of regional GW-SW interactions can be obtained using this method, but it is not possible to accurately determine the exchange fluxes of any particular location in the stream. Although some limitations exist, this method is effective in analyzing the impact of reservoir regulation and irrigation on GW-SW interactions, and the analysis results have significant implications for studies on other GW-SW interactions carried out in this reach.