Monitoring Water Resources over the Kotmale Reservoir in Sri Lanka Using ENSO Phases

Abstract

In this study, the El Nino Southern Oscillation (ENSO) phase index is used for water management over the Kotmale reservoir in Sri Lanka. Daily rainfall data of 9 stations over the Kotmale catchment during 1960-2005 June-September (JJAS) season is investigated over the Kotmale catchment. The ENSO phases are identified based on the 0.5 ∘ C sea surface temperature (SST) anomaly over Nino 3 region. The study has brought out few stations showing increasing and a few decreasing seasonal rainfall trends for JJAS season, while there is no change in the annual rainfall for the catchment. Monthly and seasonal rainfall of all the selected stations showed negative correlation with the sea surface temperature (SST) over the Nino-3 region index during JJAS season with varying magnitudes. During the warm phase of ENSO, below average rainfall is prominent for JJAS season over many stations. The rainfall especially during early September showed a significant below average rainfall during the warm ENSO phase. The seasonal rainfall during neutral and cold ENSO phases does not experience similar significant changes as seen during warm ENSO phase. Inflow of the Kotmale reservoir shows decreasing trend for the period of 1960-2005 in the observation from all stations collectively.

Spatio-temporal variability of droughts over the Mullaitivu District in Sri Lanka from 1980 to 2020

“…This shows that there is a significantly positive connection between IOD and droughts in the Mullaitivu district. The finding is consistent with previous studies (Suppaiah, 1996;Chandrasekara et al, 2017;Jayawardene et al, 2015;Zubair, 2002), which showed positive correlations between the rainfall variability and the IOD in Sri Lanka.…”

“…This is similar to El Nino Southern Oscillation (ENSO), which influences countries' air and sea temperature conditions (Shelton & Lin, 2019). Recent findings revealed that the IOD is the leading cause of the extreme dry spell conditions in Sri Lanka (Chandrasekara et al, 2017). Anomalies of the atmospheric temperature and the increases in surface temperature induce dry situations in Northwestern, Northern, Eastern, Southeastern, and North Central provinces of Sri Lanka (Peries, 2006).…”

Five Decadal Trends in Averages and Extremes of Rainfall and Temperature in Sri Lanka

“…Often, climate change first appears as an increase of intensity and frequency of extreme weather events [4], and therefore, it is essential for historical trend assessments to include extreme events. Sri Lanka is affected by both floods and severe droughts, and the impacts of both have intensified in recent years [5][6][7][8].…”

Projection of Future Hydropower Generation in Samanalawewa Power Plant, Sri Lanka

“…e study in [30] studied ways to increase power generation in hydropower plants by controlling soil erosion, reservoir siltation in Uma Oya basin, which is regarded to be one of the most important catchments in Sri Lanka. e study in [31] studied inflows in the Kotmale reservoir using El Nino Southern Oscillation (ENSO) phase index for the period of 1960 to 2005 and found that the inflows to the reservoir have decreased, altering hydropower production and irrigation plan. e study in [32] using GCMs based studies (mainly rainfall) projected that the future production capacity of the hydropower plants in the Mahaweli basin would increase as a result of an increase in consecutive wet days, decrease in consecutive dry days, and increase in annual total precipitation.…”