Ground Water in the Central Valley, California: A Summary Report. Regional Aquifer-System Analysis, Central Valley, California

摘要

The agricultural productivity of the Central Valley depends on irrigation. Half of the 22 million acre-feet of irrigation water applied annually is ground water. Nearly all the fresh ground water is contained in the continental rocks and deposits younger than Eocene age. Streamflow, an important factor in recharging the aquifer system, is influenced by precipitation in the mountains surrounding the valley. The majority of recharge from infiltration of streamflow occurs on the east side of the valley. Ground-water pumpage, which greatly exceeds the natural recharge rate, has dramatically altered the ground-water flow in the Central Valley. During the 1960's and 1970's, the recharge rate was more than five times that of the predevelopment period and was largely derived from percolation of imported surface water or recirculated pumped ground water rather than precipitation and recharge from streams. The total fresh ground water presently (1986) in storage in the upper 1,000 feet of the aquifer system is about 800 million acre-feet.