Water quality assessment

Abstract

Water quality in Lake Kinneret was quantified using a system of indices for which water quality parameters and their permissible ranges were identified and defined through a modified Delphi expert panel process. We calculated an aggregate index of water quality (Composite Water Quality Index, CWQI) as a weighted average of rating values for the entire set of water quality indices, in which variable weights for a given index were inversely proportional to the rating value of that index. Since 1991, annual average CWQI showed a trend of deteriorating lake water quality, due mostly to increases in chloride concentration and relative cyanobacteria biomass. Annual variability in CWQI was explained mostly by water level fluctuations, and less so by external nutrient loading. The Lake Kinneret water quality system has demonstrated its effectiveness as a common language for communication between multiple partners in water resource management, as a tool and target for lake management, and as an output of ecological modeling.