Detecting the leakage source of a reservoir using isotopes

A good monitoring method is vital for understanding the sources of a water reservoir leakage and planning for effective restoring. Here we present a combination of several tracers (222Rn, oxygen and hydrogen isotopes, anions and temperature) for identification of water leakage sources in the Pushihe pumped storage power station which is in the Liaoning province, China. The results show an average 222Rn activity of 6843 Bq/m3 in the leakage water, 3034 Bq/m3 in the reservoir water, and 41,759 Bq/m3 in the groundwater. Considering that 222Rn activity in surface water is typically less than 5000 Bq/m3, the low level average 222Rn activity in the leakage water suggests the reservoir water as the main source of water. Results of the oxygen and hydrogen isotopes show comparable ranges and values in the reservoir and the leakage water samples. However, important contribution of the groundwater (up to 36%) was present in some samples from the bottom and upper parts of the underground powerhouse, while the leakage water from some other parts indicate the reservoir water as the dominant source. The isotopic finding suggests that the reservoir water is the main source of the leakage water which is confirmed by the analysis of anions (nitrate, sulfate, and chloride) in the water samples. The combination of these tracer methods for studying dam water leakage improves the accuracy of identifying the source of leaks and provide a scientific reference for engineering solutions to ensure the dam safety.