the allocated water should proceed; (2) point pollution sources along the river course should be removed, and at the same time nonpoint pollution sources should be identified and controlled; (3) measures for secondary treatment of sewage sources should be taken; and (4) tertiary treatment should be applied, and facilities for pooling wastewater to control the flow of the river should be constructed and operated.
The 28 km of the Yarkon River meander through Israel's most densely populated area. The discharge of the source of Yarkon river, Ein Afek springs, was 220 to 200 million m3/yr of water prior to the transportation of most of it to irrigate the Negev in 1955. The river died out, and to rehabilitate it, 65 million m3/yr of water were allocated in 1992. The effect on the river was most dramatically expressed in the return of its fish fauna. But later this amount was reduced, from the pressures of other users, and the state of the river deteriorated. The master plan for rehabilitating the river (Rahamimov, 1996), commissioned by the Yarkon River Authority, which was established in 1988, paves the way for full rehabilitation of the river. The master plan follows the guidelines for river rehabilitation in Israel and is based on the premise that only 9 million m3/yr of freshwater could be allocated, with the rest replaced by treated wastewater, 12 million m3/yr of which is already allocated. The allocation to be released from the impounded Ein Afek springs, together with the allocation of treated wastewater, is to guarantee 10 percent of the original flow—2,500 m3/hr. The water will be sold to users along the river course, that is to authorities who will operate parts of the riparian areas as recreational areas. Finally, prior to reaching the last, saline section of the river, the water will be impounded for conventional use. Thus, except for the little water lost by evaporation, there will be no losses to the national water budget. Percolated water will recharge the aquifer, and the rest will be sold twice. This arrangement should fully compensate for the cost of impounding the water downstream rather than upstream near the source (i.e., will cover the cost of uplifting the water for users above the point of impoundment). Hundreds of tons of garbage have been removed from the river to restore its original depth, the river's banks have been cleaned up, reinforced, and raised, sewage treatment plants in some cities discharging wastewater to the river have been inaugurated, and mosquito larvae are controlled by introduced predatory fish (Gambusia) and by seasonal application of Baillus thuringiensis israelensis (BTI), a mosquito larvae—specific pathogen, inert to all other forms of life. The last approach is a demonstration of the potential use of local biodiversity—this