Testing the Impact of Management Scenarios on Water Quality Using an Ecosystem Model

Lake Kinneret, the only natural freshwater lake in Israel, provides approximately 30% of the national demand for freshwater and is therefore closely monitored and managed by the Israeli water authorities. Domestic water supply and sustaining the lake’s ecosystem are prime objectives of the water resource's management. The past decade has been characterized by over-pumping from the lake, aggravated by several years of reduced rainfall, changes to the watershed and alterations to the usual algal succession and seasonal dynamics. The changes have led to concerns regarding the stability of the ecosystem. One approach to studying the environmental effects of different management policies is by the application of a model-based decision support system. The system involves the combination of the hydrodynamical model DYRESM, and the biological-chemical model CAEDYM. In addition, a water quality index (WQI) developed at the Kinneret Limnological Laboratory has been integrated into the model output and the graphical interface. The integration provides managers and scientists, alike, with a readily available and easy to use tool for evaluating the impact of management scenarios on the lake ecosystem. In this study, we used the integrated system to examine the following management measures on lake water quality: 1. variations in P loading into the lake and, 2. variations in water retention time due to changes in lake level. These examples are used to illustrate the advantages and constraints of the proposed approach.