Value of ENSO Information in Reservoir Operations in Korea

The phenomenon known as El Nino/Southern Oscillation (ENSO) has been identified as the single most prominent signal of interannual climate variability. A number of independent efforts have been made to investigate the relationships between ENSO and hydrologic variations. Especially interesting are some statistically significant relationships of ENSO with streamflows in Australia, South America, the Western United States and elsewhere. In such cases, the ENSO could be used as an indicator for long-term streamflow forecasting which would be invaluable to water resources planners and managers. Few studies, however, have addressed this water management issue associated with the ENSO. The primary objective of this paper is to incorporate the ENSO information into a reservoir operation model formulated with stochastic dynamic programming (SDP). In Korea, nobody has as yet investigated the potential ENSO impact on Korean streamflows although previous studies reported that statistical relationships between ENSO and precipitation exist in some basins in Korea. Therefore, the present paper first analyzes a streamflow pattern at a Korean gauging station, Chung-Ju dam, in relation to ENSO, using a statistical technique called composite analysis. This result is then used for deriving an optimal monthly operation rule for Chung-Ju reservoir to illustrate the benefit of employing ENSO information.