ENSO Influences on Rainfall and Streamflow: Implications for Water Resource Management of Sri Lanka (PPT)

摘要

Seasonal to annual forecasts of precipitation patterns are very important for water infrastructure management. In particular, such forecasts can be used to inform decisions about the operation of multipurpose reservoir systems in the face of changing climate conditions. Success in making useful forecasts often is achieved by considering climate teleconnections such as the El-Nino-Southern Oscillation (ENSO), Indian Ocean Dipole (IOD) as related to sea surface temperature variations. We present an analysis to explore the utility of using rainfall relationships in Sri Lanka with ENSO and IOD to predict inflows to cascade reservoir systems associated with the two main rivers in the country, Mahaweli and Kelani. The Mahaweli multipurpose system supplies 60% of the hydropower and 20% of the irrigation of the country. The Laxapana (Kelani) reservoir cascade supplies 25% of the hydropower and also comprises the main potable water supply infrastructure. It is especially critical for the country to plan for hydropower deficits so alternate energy sources are available to meet demands. Sixty-five years of precipitation data and inflow data for the reservoirs are analyzed considering El-Nino, normal, and La-Nina conditions and IOD positive and negative conditions. The reservoir inflows of two cascades are related to the ENSO signal to derive a forecast suitable for reservoir operation. The results are used to analyze options for the adaptation of water use of reservoirs to climate conditions.