Spatial and temporal distribution characteristics of hydrogen and oxygen isotope in typical tributary estuary of Three Gorges Reservoir

Quantitative analysis on the water body composition in the tributary of the Three Gorges Reservoir and the water circulation process are helpful to solving the environmental problems of tributary estuary. The isotopic characteristics of hydrogen and oxygen in water masses were analyzed based on a one-year observation in the Caotang River and adjacent mainstream. Under the interaction of the mainstream and tributary, the source and compositions of the water masses of the tributary estuary were described and the water circulation variation in the tributary estuary after the Three Gorges Reservoir impoundment was discussed. The results show that: δD/δ18O in the Yangtze River mainstream and the tributary estuary were very close to the regional precipitation line, indicating that the main source of water mass is precipitation. The deuterium-surpluses in the Yangtze River and the tributary estuary are obviously different from those before the construction of the reservoir, which indicated that the water body composition of the Yangtze River main stream and the tributary reservoir estuary have changed to some extent after the Three Gorges Reservoir impounded. There are obvious spatiotemporal variations in the mixing ratio of the water body, the proportion of the water mass in the main stream of the Yangtze River ranges from 76.9% to 99%.