Huge amounts of water are currently diverted down-stream from the Sea of Galilee (Lake Kinneret) to the rift valley, Israel. Part of the non-utilized water is saline (around 2000 mg/l chlorides) originated in the northern section of Lake Kinneret and separated from the bulk high quality water (between 200 mg/l and 250 mg/l chlorides). The flow rate of the saline water is very much affected by the level of the water in the lake that serves as the prime natural storage reservoir for water supply in Israel. The wasted amount of the diverted water can be shared, after adequate treatment, for use in the Rift Valley primarily for agricultural irrigation in the Kingdom of Jordan and the State of Israel for their mutual benefits. A management model was defined and tested towards optimal treatment of the saline water. The two major purposes of the model are (i) to delineate a methodology for economic assessment towards optimal use of membrane technology, and; (ii) to provide guidelines for optimal membrane selection in regards to the pretreatment stage. The linear model defined takes into account the cost of the feed saline water, the desalination stage, based on the reverse osmosis (RO) process, and the brine disposal. Technological constraints refer primarily to the longevity of the membrane, their performance and time dependent changes in flow-rates, Eight different saline water qualities, subject to various pretreatment options, for a tentative desalination plant for a capacity of 30,500 m(3)/d close to Lake Kinneret were examined, The final treated unit water cost, which is expressed by the objective function, includes investment, operation and maintenance, water intake, pretreatment, RO components, post treatment, brine removal and incentive for permeate low salinity. Analyzing various scenarios allows optimal selection of the membrane and the related pretreatment method. The cost range of the desalinated water according to the model is between $0.39/m(3) and $0.45/m(3).