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Regional Watershed Plan
Ventura County's Approach for Calleguas Creek
© 1997, 1998 Streamline Publications
As government and society place
an ever greater emphasis on eliminating destructive and dangerous stormwater
runoff, cities and counties must look toward improving water infiltration and
detention. Far from being a burden, efforts to conserve free water from the sky
are good business and insurance against drought. |
 So, you say you're in creekbed erosion control... Funny, you don't look riparian |
Such a program, centered in Ventura
County's agriculturally-verdant Oxnard Plain, collects water in infiltration
basins where it percolates into aquifers. Not only are the aquifers giant
freshwater reservoirs for alleviation of eventual drought conditions, they are a
frontline defense against seawater intrusion from the nearby coastline that
could prove devastating to farming. But the three-cornered challenge of
managing water, land and human habitation, particularly in this semiarid region,
is far more complicated than simply banking water for later. Too much water in
the wrong place is an equally vexing problem.
Silt to the Sea
The Calleguas Creek watershed drains
nearly 350 square miles of Ventura County with its outflow into Mugu Lagoon. The
lagoon, which is under U. S. Navy jurisdiction, is one of the largest, mostly
undisturbed, salt marshes in southern California. Mugu Lagoon is habitat for
nearly 40 threatened and endangered species and serves the nursery needs for a
wide variety of marine mammals and fish. Endangered species at the site include
the American peregrine falcon, California least tern and California brown
pelican among others. It has been identified as one of the final refuges in
southern California for harbor seals to birth their young. Without question,
Mugu Lagoon is a valuable resource for wildlife but the lagoon, itself, is
threatened by sediment carried to it by Calleguas Creek which could eventually
fill the wetland, eliminating the habitat. Before population began developing in
the region, waterflow in the creek was limited to periods of rain. Sediment
reached the lagoon only during these wet periods. By the 1950's channelization
of the streambed had altered, in some way, 50 percent of its length. Vegetation
was stripped away in favor of more efficient water flow and conversion of
estuarine lands to other uses. The pressure of city growth and development
changed the creekflow from rainy season only to year-round. Calleguas Creek now carries wastewater
treatment plant outflows and runoff from imported water for domestic and
agricultural use. The cumulative effect is not only an increased amount of
sediment-laden water reaching the lagoon, but a dramatic increase in the rate
at which it travels. Sediments are entrained longer and move farther as this
greater volume of water moves at higher speeds. The result: rapid deposition of
soils in the lagoon.
Sedimentation is not the only problem.
The runoff carries pollutants from agriculture, industry and residences.
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