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Abstract

Water quality in reservoirs used for fish culture and field irrigation results from the combined action of management procedures related to the fish culture and water use, and meteorological, biological, and physical processes. The different wind regimes that occur in Israel throughout the year and the weather differences between geographic areas produce different stratification patterns in the water bodies, hence have different effects on water quality. The effects of wind on stratification of reservoirs of different depths located in several regions of Israel were examined. The regular summer breeze affects daily stratification differently as it moves away from the sea. The coastal wind starts blowing soon after the sun rises, so stable stratification has not developed and is prevented from developing in shallow reservoirs. In the mountains of the Harod Valley, the breeze only reaches the area after the sun has been shining for several hours and the water is strongly stratified. However, the wind is so strong that most of the water column mixes. The end of seasonal stratification in lakes and reservoirs occurs in autumn when gradual cooling of the epilimnion makes it isothermic with the hypolimnion. Pumping rate and outlet depth also affect the stratification in reservoirs. (Rochester-PTT)