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Potential effects of increased ground-water pumpage on Barka Slough, San Antonio Creek Valley, Santa Barbara County, California

Water-Resources Investigations Report 80-95

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Abstract

Ground-water use in San Antonio Creek valley is expected to increase significantly as a result of planned extensive agricultural development in the basin. The effects of this additional stress on the ground-water system, particularly on the environmentally sensitive Barka, Slough, are of concern in the basin.

Expectations of the developer are that about 6,640 acre-feet per year of additional consumptive ground-water use will be required to irrigate an agricultural development of 2,500 acres of vineyards and 1,200 acres of truck-farmed vegetables. This represents an increase in net basin pumpage of about 60 percent. The developer plans to obtain this water from 12 large-diameter irrigation wells in the Harris Canyon area.

Analysis of the potential drawdowns in the vicinity of Barka Slough, by using the Theis nonequilibrium formula, indicates that drawdowns would average 6 feet after 10 years of pumping and would eventually exceed 10 feet. Because the artesian head in the aquifer that supplies the slough is generally less than 3 feet above land surface, these declines would probably mean that the wetlands of Barka Slough would disappear.

An empirical relation, based on historical records of base flow in San Antonio Creek and net pumpage in the basin, also indicates that the additional irrigation withdrawals would cause base flow in San Antonio Creek to cease.

Both of these analyses consider the effects of only this particular agricultural development, which would be in addition to any decline caused by other increases in pumpage in the basin.

Additional publication details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Potential effects of increased ground-water pumpage on Barka Slough, San Antonio Creek Valley, Santa Barbara County, California
Series title:
Water-Resources Investigations Report
Series number:
80-95
Year Published:
1980
Language:
English
Publisher:
U.S. Geological Survey
Description:
iv, 16 p.
Country:
United States
State:
California
County:
Santa Barbara County
Other Geospatial:
Barka Slough, San Antonio Creek valley