Groundwater Basin Summaries
Western Mountain Basin

Typical well construction in the Western Mountain Basin is illustrated by well 15314002 in the west-central part of the basin. The 170-m deep well withdraws water from the Turronian-Cenomanian aquifer between depths of 130 and 170 m, with a water level of about 20 m, and an average yield of about 150 L/s.

Water levels in well 15-19/039 in the northern part of the basin, and well 7813901 in the southern part generally have declined over the years. In the northern part of the basin, declines were accompanied by a gradual decline in flow of the Taninim Spring and a complete cessation of the flow from Rosh-Haayin Spring. High precipitation during the winter of 1991-92 resulted in a full water-level recovery and increased springflow. In the northern part of the basin, chloride concentrations in well 15-19/039 have decreased since the late 1960's but nitrate concentrations have increased. In the southern part of the basin, chloride concentrations in well 7813901 fluctuate annually, showing a slight increase since the 1970's. Changes in chloride and nitrate concentration in the north are related to surface sources of pollution, primarily urban sewage; whereas, in the south, chloride concentrations are related to subsurface influx of water from saline groundwater bodies.

• The Turronian-Cenomanian aquifer, the most productive aquifer in the basin, consisting of limestone and dolomitic limestone of geologic unit Kj; and
• The Albian aquifer, of secondary importance, consisting of sandstone and dolomite of geologic unit Kk.

Groundwater levels are influenced primarily by precipitation and pumpage, and generally fluctuate about 1.5 to 2.5 m/yr. Larger fluctuations are observed in areas influenced by local pumping. Groundwater is generally of good quality, with concentrations of chloride from 50 to 250 mg/L, and nitrate from 16 to 28 mg/L. Chloride concentrations generally increased during the last 30 years, with more pronounced changes in the southern part of the basin.