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Table 2 Comparison of ROC score DIDI SWSI SPI(3) SPI(6) SPI(9) SPI(12) ROC Score 0.93 0.72 0.60 0.71 0.77 0.76 4. CONCLUSIONS This study developed and evaluated Dam Inflow Drought Index (DIDI) for Chungju Dam in Korea. The DIDI is calculated considering the dam operation. Critical inflows for each month are calculated using the criteria for water supply adjustment. The DIDI can be estimated by dividing the cumulated difference between the observed inflow and critical inflow (CDI) by its standard deviation. Considering the limit of dam storage, the upper limit of CDI has to be determined, and the threshold was estimated by RCO analysis. ROC analysis is implemented using results of the dam operation simulation and DIDI for various thresholds. Optimal threshold of Chungju Dam was calculated as 630 ×106 m3, DIDI applying the threshold expressed the drought at the time of reduction in water supply adequately. And the DIDI also showed much better performance in monitoring dam droughts than SWSI and short- and long-term SPI (3-, 6-, 9-, and 12-months SPI). The DIDI is useful for monitoring and responding the drought of dam inflow, and its application could help to mitigate drought damages. REFERENCES [1] Wilhite, D.A. (2006). Drought monitoring and early warning: Concepts, progress and future challenges. World Meteorological Organization, 24 pp. [2] Sheffield, J., Wood, E.F., and Roderick, M.L. (2012). Little change in global drought over the past 60 years. Nature, 491 (7424), 435-438. [3] Sternberg, T. (2011). Regional drought has a global impact. Nature, 472 (7342), 169-169. [4] Wilhite, D.A., and Glantz, M.H. (1985). Understanding: the drought phenomenon: the role of definitions. Water International, 10 (3), 111-120. [5] McKee, T.B., Doesken, N.J., and Kleist, J. (1993). The relationship of drought frequency and duration to time scales. Proceedings of the 8th Conference on Applied Climatology, Boston, MA, USA, 17 (22), 179-183. [6] Palmer, W.C. (1965). Meteorological drought (Vol. 30). Washington, DC, USA: US Department of Commerce, 58 pp. 578