Abstract
Management of reservoir water quality is a global challenge due to the natural process of eutrophication and anthropogenic aggravation. In Sri Lanka, irrigation reservoirs support several secondary uses such as fish production, livestock farming, and many communal uses including drinking water supply. In the present study, basic limnological parameters of ten irrigation reservoirs of Sri Lanka were investigated from June 2013 to February 2016, with a view to identifying influence of hydrological regimes on reservoir water quality. Spatio-temporal similarities of water quality parameters were studied employing the self-organizing map (SOM) routine of the artificial neural network application. The sample vectors, classified on the SOM lattice, indicated 6 clusters at 50% similarity level. When reservoir that were categorized according to hydraulic retention time (HRT) and relative reservoir level fluctuation (RRWL; defined as the ratio of the mean reservoir level amplitude to mean depth), were compared with dominant water quality parameters in SOM lattice, it was evident that some productivity-related water quality parameters were influenced HRT and RRWL. The results of the study revealed that HRT and RRWL can essentially be controlled through management of hydrological regimes in irrigation reservoirs, thus, close dialogue between irrigation authorities and other users of reservoir water resources are needed to ensure desired water quality of the reservoirs.
Highlights
Sri Lanka is endowed with rich reservoir resources and the cumulative extent of reservoirs is about 206,000 ha (Jayasinghe and Amarasinghe 2018)
Approaches pertaining to water quality indices (WQI) in which the aspects of multipleattributes of water quality can be resolved into a single score sometimes does not provide sufficient information for decision makers (Abbasi and Abbasi 2012)
Many WQIs are potentially useful in the planning of water resource protection, improvement, and utilization, whereas some WQIs have been developed to aid in environmental planning and decision making
Summary
Sri Lanka is endowed with rich reservoir resources and the cumulative extent of reservoirs is about 206,000 ha (Jayasinghe and Amarasinghe 2018). The total extent of reservoirs in the country consists of ancient reservoirs constructed irrigating agricultural lands and, recently constructed upland reservoirs are used for hydroelectricity generation several other purposes. Apart from these primary uses, reservoir resources support several secondary uses such as fish production, livestock farming, and communal uses such as bathing, drinking water supply etc. Eutrophication in aquatic ecosystems is one of the major widespread problems worldwide This natural process is often aggravated due to anthropogenic activities due to accelerated runoff of materials from the land surface to water bodies (Rast and Holland 1988). Monitoring and managing lakes and reservoirs would be important to have desired water quality in lakes and reservoirs and to prevent or limit eutrophication (Wagner and Erickson 2017)
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