Ma'ale Kishon, one of the largest reservoirs storing wastewater for irrigation in Israel, has surface area of 1.3 km2, depth of 9 m and volume of 12 million m3. Secondary effluent enters the northern basin and after a mean retention period of 6 weeks, flows into the southern one. Due to this two basins structure, changes taking place during the water storage can be detected. The differences between the two basins were quantitatively studied by an interdisciplinary team.
The sanitary, physico-chemical and biological variables indicated an improvement in water quality, leading to an increased ecosystem stability and a safer environmental performance. These results suggest that deep reservoirs of the type here described serving for wastewater disposal and reuse may have a wide application also in other countries having warm, subtropical climates.