Impacts of El Nino/Southern Oscillation (ENSO) on streamflows in Nepal

This thesis investigates the impact of the El Niño/Southern Oscillation (ENSO) on mean monthly streamflows in Nepal using the Mann Whitney U test, harmonic analysis and correlation analysis. El Niño causes below-normal streamflows between July to December in western Nepal and between June and December in eastern Nepal in the El Niño years. La Niña causes above-normal streamflows in western Nepal between June and January. The multivariate ENSO index (MEI) can be used for streamflow prediction with lags of 1–2 months.; El Niño has a stronger impact on streamflows than La Niña. A stronger ENSO impact in western Nepal than in eastern Nepal suggests an inverse relationship between El Niño impact and monsoon strength and a direct relationship between La Niña impact and monsoon strength. This study is the first step in understanding the ENSO-streamflow relationship in Nepal and provides important information on streamflow variability during ENSO events.