Ground-water reconnaissance in the Fresno Northeast area, Fresno County, California

Abstract

The Fresno northeast area includes about 133 square miles (344 square kilometres) in the central part of California. Four physiographic units occur in the area, the largest of which is the compound alluvial fan of the intermittent streams north of the Kings River. Geologic units consist of consolidated rocks and unconsolidated deposits. The consolidated rocks yield only small quantities of fresh water to wells. The unconsolidated deposits immediately overlie the consolidated rocks and, within their upper part, yield large quantities of water to wells. The dominant structure of the unconsolidated deposits is that of a homocline. Although the deposits are inferred to be faulted, the fault does not have any demonstrated effect on the movement of ground water. Total storage capacity in the area in the upper 200 feet (61metres) is about 1,100,000 acre-feet (1,360 cubic hectometres). The total volume of ground-water underflow moving out of the area was estimated to be about 60,000 to 70,000 acre-feet per year (74 to 86 cubic hectometres per year). Two water-level contour maps indicate that changes in water use over a 12-year period have not greatly affected the direction of ground-water movement. Long-term records show that rises and declines in water level, indifferent parts of the area, often occur during the same period of time. The records also show that most of the storage changes in the reservoir have occurred in the upper 100 feet (30 metres) through a long-term water-level fluctuation of less than 40 feet (12 metres). Short-term trends show that, in general, water levels rise during winter, level off during spring, and decline from summer through autumn.