Israel Water Context

10.  Small Basins

In addition to the main basins in Israel there are several smaller basins that are reviewed here from north to south. These basins are exploited through boreholes or drafting spring flows and are connected to the national water system (with the exclusion of the Negev-Arava basin). See "Kinneret Basin" regarding the aquifers draining to the Kinneret.

The Western Galilee Basin

The western Galilee basin drains the western Galilee mountains to the Mediterranean Sea. The basin extends from the seacoast in the west to the water divide in the east, and from the Yizre'el (Jezreel) Valley in the south to the Israel-Lebanon border in the north. Included in the realm of the basin are two aquifer units: limestone and dolomite rocks of Cenomanian-Turonian age, which are exposed on the mountains in the eastern basin; and sandstone and kurkar rocks of Pleistocene age, which are exposed in the west of the basin. The two aquifer units are joined at their westernmost parts.

The replenishment to the western Galilee basin is estimated to be, on average, ~150 million m³/yr. The chief natural outlets of the basin are the Kabri and Na'aman springs, whose historical discharge was ~70 million m³/yr, in addition to their seepage to the Mediterranean Sea. Today the entire flow is drafted and the basin is exploited through many boreholes. In the last ten years ~90 million m³/yr was pumped from the basin and the total discharge of the springs diminished, on average, to ~40 million m³/yr, ranging between ~20 and ~-55 million m³/yr. As a result of this, the amount of water naturally flowing to the sea also decreased.

The quality of the water in the basin is very good in its mountainous part, and suffices in the coastal part. In this area trends of rising concentrations of chloride and nitrate were observed in the last decades. It should be noted that, just like the coastal aquifer, the coastal section of the western Galilee basin is sensitive to contaminants originating on the surface and also to salinization from the Mediterranean Sea. The high concentration of settlements, fish ponds, industrial plants, barns, and the like, above the coastal belt obligates ongoing monitoring to prevent deterioration of the quality of the water in the basin.

The Karmel (Carmel) Basin

The Karmel ridge extends south of Haifa Bay. It is around 30 km long and it widens from around 5 km in the north to more than 20 km in the south. The Karmel rises to around 500 m above sea level, and slopes steeply to the Mediterranean Sea in the west and to the Yizre'el Valley in the east. In the subsurface, a water divide separates the eastward drainage to the Yizre'el Valley and the westward drainage to the Mediterranean Sea.

The replenishment to the aquifer is estimated at ~44 million m³/yr, of which 20 million m³/yr infiltrate in the eastern part, and the rest, in the western part. Two aquiferial units are included in the Karmel: limestone and dolomite rocks of Cenomanian-Turonian age that are exposed on the mountain in the eastern basin; and sandstone and kurkar rocks of Pleistocene age that are exposed in the western basin. As in the western Galilee, the two aquiferial units are connected in the westernmost part, and water from the limestone aquifer drains to the sandy one and from there to the Mediterranean Sea. In the westernmost area, the Karmel coast, the quality of the water is not high and is characterized by large amounts of chloride that reach a level exceeding 900 mg/Cl/l, and therefore various desalination installations have been set up in the last years in Maagan Mikhael, Atlit, and in Maayan Zevi, which treat more than 12 million m³/yr and efficiently exploit this water. In the eastern basin the water quality is good and the water is exploited without any treatment.

The Negev-Arava Basin

The Negev-Arava basin extends from the Ashqelon-Mezada line southward. Despite its large area, the replenishment to the basin is estimated to be only ~30 million m³/yr; this is because of the low amount of precipitation and because most of the rain waters in the Negev flow as surface runoff in strong floods. Three aquiferial units are included in the basin: sandstone of Early Cretaceous age (exposed in very small outcrops) in the Negev; limestone and dolomite rocks of Cenomanian-Turonian age (exposed in the Negev); and clastic rocks (sand and conglomerate) of Neogene age exposed in the Arava (the "Arava Fill" aquifer). The flow of water in every one of the aquifers in the Negev is in the direction of the Arava Fill aquifer. The larger part of the Arava is drained to the Dead Sea and the southern pat is drained to the Gulf of Elat (Aqaba). In the last years ~90 million m³/yr (of them ~60 million m³/yr of saline water) was produced from the aquifer at the expense of the one-time store. Around 60% of the exploitation is from the Arava Fill aquifer. Half of the water produced is highly saline, around 600 mg/Cl/l, and is supplied to the heavy industry plants or for desalination in Elat. The rest of the water is supplied to the Arava settlements for drinking and for agriculture.