Thursday, August 28, 2008

The Sacramento Valley: California's Great Exception?

The Sacramento River Watershed Program has released a fascinating online report on suburban sprawl and the demise of agriculture in the Sacramento Valley. It appears to be a work in progress, and the "best management practices" identified for governments to cope with sprawl are nothing new. But there is plenty of interesting information and analysis packed into the presentation. The GIS layer maps that accompany the text are especially noteworthy.

One of the more interesting observations related to the suburbanization and exurbanization of the Sacramento Valley concerns the availability of water. In most of the state, the availability of water is one of the principal checks on unrestrained sprawl. Not so in the Sacramento Valley, according to the authors:

Below the Delta and the federal and state pumping plants, water is the principal limiting factor for exurban sprawl. This is not the case for the Sacramento Valley and much of the Sierra foothills in the Sacramento Watershed. The groundwater basin in the Sacramento Valley recharges readily from the normally abundant rainfall in Northern California. In only a few areas has groundwater depletion become problematic, like in eastern Sacramento County where urban and medium density suburbs were allowed to develop solely reliant on groundwater pumping. Very likely, all the areas zoned for low density rural residential development have sufficient groundwater supplies.

Abundant groundwater resources are the exception in California, where most development has depended on guarantees of imported water. Thus, when making predictions about the build-out of the Sacramento Watershed, it is not prudent to look at the patterns from Southern California where local water supplies were the limiting factor, or the Bay Area, where confined geography have restricted exurban rural residential growth. Other areas of the nation may provide more accurate models for the potential of exurban build-out in the Sacramento Watershed.

Groundwater-fed development will also differ from development in regions that rely on surface water (including state or federal project water) in another important aspect. While surface water diversions are highly regulated and governed by a complex system of water rights and contractual obligations, comprehensive regulation of groundwater use in California is much less developed. Where the state plays an active role in overseeing the use of the state's rivers, streams, and reservoirs, the regulation of groundwater extraction is mostly a local matter. The jurisdictions charged with regulating groundwater uses are also those most directly embroiled in local disputes about land use and development. The state has little direct power to ensure the sustainable use of groundwater resources.

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