LIMNOLOGY OF A WARM HYPERTROPHIC WASTE-WATER RESERVOIR IN ISRAEL .1. THE PHYSICAL-ENVIRONMENT

This paper deals with stratification in a small reservoir (50 000 m3 v olume, 5.5 m depth) receiving wastewater with a BOD of 80 mg/l during the winter in order to irrigate agricultural areas during the dry summ er. The reservoir goes through three partially overlapping annual cycl es: solar radiation, water temperature and reservoir operation. It pre sents both permanent (deep) and ephemeral (shallow) stratification dur ing the summer in spite of the strong breeze, due to both thermal and biogenic chemical gradients. There are stratified and non-stratified w astewater reservoirs in Israel. Stratification in hypertrophic impound ments seems to depend also on parameters derived from the chemical com position of hypertrophic waters. (e.g., turbidity, biogenic gradients, wind/water friction coefficient, viscosity).