Land use change in California,USA: Nonpoint source water quality impacts |
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Authors: | Robert Charbonneau G M Kondolf |
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Institution: | (1) Office of the President Office of Legislative Analysis and Environmental Policy, University of California, 300 Lakeside Dr. 7th floor, 94612-3550 Oakland, California, USA;(2) Department of Landscape Architecture, University of California, 94720 Berkeley, California, USA |
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Abstract: | California’s population increased 25% between 1980 and 1990, resulting in rapid and extensive urbanization. Of a total 123,000
ha urbanized in 42 of the state’s 58 counties between 1984 and 1990, an estimated 13% occurred on irrigated prime farmland,
and 48% on wildlands or fallow marginal farmlands. Sixty-six percent of all new irrigated farmland put into production between
1984 and 1990 was of lesser quality than the prime farmland taken out of production by urbanization. Factors dictating the
agricultural development of marginal farmlands include the availability and price of water and land, agricultural commodity
prices, and technical innovations such as drip irrigation systems that impact the feasibility and costs of production. The
increasing amount of marginal farmland being put into production could have significant water quality consequences because
marginal lands are generally steeper, have more erodible soils, poorer drainage, and require more fertilizer than prime farmlands.
Although no data exist to test our hypothesis, and numerous variables preclude definitive predictions, the evidence suggests
that new irrigated marginal lands can increase nonpoint source (NPS) pollution for a given size area by an order of magnitude
in some cases. |
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Keywords: | Nonpoint source pollution Water quality Erosion Prime farmland Watershed management Urbanization Land use conversion Best management practices |
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