and releaching has been disturbed by human activity. Unlike precipitation, which contains very low concentrations of salts, irrigation with surface and ground water adds considerable salts to the soil zone. Even more salts are added when the source of irrigation water is recycled agricultural and municipal wastewater.

To recycle as much water as possible, drainage from agricultural lands is often recaptured and reused for irrigation. The use of this water, enriched in salts, can lead to serious problems of soil salination, as has occurred in the J'esreel Valley in Israel after about 20 years of such practice. Reuse of municipal wastewater is another serious source of salinity. Through water softening, food processing, use of detergents, and physiological sources, urban wastewater is enriched with salts. For example, an excess of 100 to 200 milligrams per litter (mg/l) of chloride is contained in wastewater in Israel when compared to the source water. Most treated wastewater in the study area has a dissolved solids content of more than 1,000 mg/l. The use of such water for irrigation has led to crop damage and reduced yields and may eventually lead to irreparable soil salination.

Both percolation of saline irrigation water and the leaching of salt by natural recharge lead to increases in dissolved solids in underlying ground water. These trends have occurred along the Mediterranean coast in Israel and the Gaza Strip, in the Jordan Valley and the Dhuleil area east of Amman, and elsewhere. The withdrawal of this enriched water for irrigation or domestic use (with ensuing treatment and reuse for irrigation) creates a cycle of increasing salination of both soil and ground water. Furthermore, the almost total elimination of natural ground water and surface water discharge effectively blocks the natural discharge of salts, so that the study area is now importing salts but not exporting them. The salts leached by winter rains from irrigated soils above the coastal aquifer accumulate in ground water at a rate of 2 mg/l chloride per year. While chloride concentration in ground water was 110 mg/l in 1963, it was 170 mg/l in 1993. Similar increases in chlorine contamination have been seen elsewhere in the study area.

One lesson from the area's history of soil and ground water salination is that total utilization of water, when coupled with significant internal recycling of water through reuse, is not sustainable because of progressive salt accumulation. A sustainable water management system should include salt removal, by natural leaching, removal of salty drainage water, or desalination.

In the context of sustainability, the simplest definition of ''available" water is the average quantity of water available on a renewable basis. The

Front Matter (R1-R16)

Executive Summary (1-9)

1 Introduction and Background (10-23)

2 The Study Area and Patterns of Water Use (24-53)

3 Factors Affecting Patterns of Water Use (54-65)

4 Water and the Environment (66-99)

5 Options for the Future: Balancing Water Demand and Water Resources (100-168)

Appendix A: Excerpts from the Treaty of Peace Between the State of Israel and the Hashemite Kingdom of Jordan (169-181)

Appendix B: Excerpts from the Israeli-Palestinian Interim Agreement on the West Bank and Gaza Strip (182-194)

Appendix C: Effects of Water Use on Biodiversity in the Study Area (195-202)

Appendix D: Guidelines for Rehabilitation of Rivers (203-210)

Appendix E: Bibliography (211-219)

Appendix F: List of Meeting Places and Dates (220-220)

Appendix G: Committee on Sustainable Water Supplies for the Middle east Biographical Sketches (221-226)