Cha et al. (Water Resources Management, 26(18):4183–4201 2012) improved the method used to measure the vulnerability of a reservoir water supply that arises due to water scarcity in a dry season. Water supply vulnerability is expected to increase due to climate change. The authors showed that the Gwangdong Reservoir Drought Management Model (GRDM2), developed in a previous study and based on the adaptation mechanism, is useful to estimate the vulnerability of water supplies. The authors assumed 48 future scenarios, consisting of a combination of 6 future inflow scenarios and 8 future water requirement scenarios, of the Gwangdong reservoir drought management system. They computed damage cost of water scarcity in dry seasons until the 2050s. Simulation results showed that severe damage may take place from the 2020s and damage four times greater than in the 2009 water scarcity event may occur in the 2050s. As a result, GRDM2 was reported to be useful to measure the magnitude of climate change vulnerability, concentrating on damage of water scarcity in a dry season.