Conjunctive operation of surface and subsurface dams based on drought severity

As an effective water management method to respond to the increasing severity of drought, this study proposed a conjunctive operation using a surface reservoir and subsurface dams. The proposed methodology predicts the probable rainfall according to the drought severity and the water demand, and uses these as the basis for water allocation. Sokcho City, located in South Korea, was used as the study case. Sokcho is a tourist city that has suffered from water shortages for many years due to its excessive dependence on a single groundwater dam. Considering conjunctive operation, drought frequency, and drought duration, a total of 80 cases under four scenarios were generated and simulated to determine the water supply capability over the entire year. The results indicate that domestic water can be supplied throughout the year with appropriate water allocation, even when a once-in-50-year drought lasts for 120 days. Furthermore, the water supply potential, which is the additionally available capacity in a reservoir, was used to assess the effects of conjunctive operation. It was estimated that, for a once-in-10-year drought, up to 318% of the annual water demand was available in the reservoir. As the proposed methodology is relatively simple, it offers a useful water resource management tool for sites with similar social and environmental conditions.