Effective Water Management in the Mahaweli Reservoir System: Analyzing the Inflow of the Upmost Reservoir

Abstract

Mahaweli cascaded reservoir system is built contiguous to the Mahaweli river, enhancing the water storage and transferring ability to reinforce the needs of water in accordance with the climatic changes. The foremost requirement of the system is to provide water for irrigation and to produce hydroelectricity to the country that has given rise to conflicting demands of water requirements from the two sectors. Forecasting future water availability is crucial to predict the hydroelectricity generation capacity while maintaining a balance between the provisions of water to both sectors. Therefore, modeling the changes of inflow of the upmost reservoir is substantial to effective water management. Literature has not revealed much evidence for an existence of an accepted statistical model in predicting the inflow, of the system considered. This research is based on the methodologies to test for the seasonality, stochasticity and nonlinearity of the inflow , in advance to fitting a suitable model.

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

“…months of the year ( Figure 10). Dilini et al [26] identified that, starting from March, inflow to Kotmale reservoir steadily increases until July and then shows a slow decrease until October. As discussed in previous paragraphs the amount of rainfall received for the selected stations decreased with time (trend over years: 1985-2010) and due to this reason the inflow to the reservoir also exhibits a decreasing pattern.…”

“…Further eutrophication is also experienced just five years after completion of the Kotmale reservoir, due to eroded soil nutrients from tea plantation in the catchment area [24]. Although the reservoir inflow is higher during June to November compared to other months of the year [25,26] (Figure 2), in the recent decades the reservoir storage reduced down to dead storage level of the reservoir during August and September. Even the ruins of ancient territory which are submerged under the waters of Kotmale reservoir are seen during these recent dry seasons, when the water levels are low [27].…”

Influence of Indian Ocean warming on rainfall of Sri Lanka

“…The major crop cultivation seasons in SL thus relies on seasonal rainfall, where the primary cultivation season of Maha (October–March) begins with the onset of OND rainfall, whearas the secondary cultivation season of Yala (April–September) begins with the onset of AMJ rainfall (Burt & Weerasinghe, 2014; Zubair, 2002). In addition, hydropower, which is one of the major sources contributing to the national power supply in SL (Dilini et al, 2014; Ekanayake et al, 2021), also depends on the amount of seasonal rainfall. However, several studies have revealed the potential impacts of extreme rainfall on agriculture and the economy of SL (Withanachchi et al, 2014).…”

Teleconnection between Cold ENSO Phases and Seasonal Rainfall Over Sri Lanka: Case Study in Kotmale Catchment

“…[24] the degradation of water quality due to sedimentation and eutrophication are causing the reduction of economic use of stored water in Kotmale reservoir [25], [26], [27]. In spite of all, during recent decades, annually, reservoir went down to dead storage and even old sunken monuments were also visible at that period [28], [29].…”