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Back to the Future
Back before high dams and long levees imprisoned and straitjacketed the rush of water from the mountains to the ocean, the Estuary functioned in an entirely different way. A soon-to-be released analysis of pre- and post-development conditions explores how the estuarine and watershed ecosystem has changed since the 1850s, and more specifically what its key natural characteristics were before humans put their stamp on the scene.
"Learning how the system functioned historically can help tell us what's necessary to restore, what we may only be able to rehabilitate, and what's been irretrievably lost," says Gary Bobker of the Bay Institute, which undertook the analysis with the Environmental Defense Fund. Their purpose was to provide CALFED with an ecosystem-based framework for prioritizing, integrating and evaluating its massive, multi-million dollar restoration plan (see cover). "This is nothing new, in terms of information on historical changes. What's new is that instead of looking at each cause and effect, we've tried to construct an integrated history, and discover how changes over time may have limited the ability of the system to sustain itself."
The biggest changes to the system took the form of "a one-two-punch," says Institute hydrologist Peter Vorster. The first punch wiped out a big chunk of fish and wildlife habitat. It occurred in the late 19th and early 20th century, when farmers and settlers drained ("reclaimed") Delta wetlands and river floodplains in order to put down roots - dramatically reducing the watery reach of the ecosystem and binding natural flows between unnatural levees. The second punch not only further confined the great rivers but also exported large amounts of water out of the system. Indeed since the 1920s, huge flood control projects, water diversions and long distance aqueducts have cut off the rivers from their flood plains and rearranged the whole flow pattern of the ecosystem.
"The first punch occurred because the valley had too much water, and the second because there wasn't enough water elsewhere in California where the cities and farms developed," says Vorster. "The dams had the biggest impact in terms of alteration of the hydrograph because they dramatically reduced spring flows and increased some summer flows. Water now shoots down into the Bay much faster than it would have naturally. Some rivers now totally dry up at some times of the year. At the landscape scale, much of the underlying connectivity and geophysical support for essential structural characteristics and ecosystem processes has been disrupted."
The analysis goes on to link these changes to various responses in the ecosystem. For example, alteration of flooding, levee construction and land use changes almost totally eliminated the Delta's once dominant tule marshes. Similarly, the big dams cut off more than 90% of the historical spawning habitat of the system's once abundant salmon runs.
The analysis-due for release later this year- is just one piece in a three step effort to provide a firmer theoretical foundation for restoration planning, says Bobker. The first step was development of a set of indicators of ecosystem health-now being refined- the second, the historical analysis, and the third, a series of recommendations as to what extent key functions of the system can and should be restored.
The enviros would like to see a more intense focus on restoring the system's underlying physical processes and natural flow patterns. "We need to find the flows and the land for the rivers to flex their muscle," says Vorster.
They'd also like to see a series of habitat reserves throughout the ecosystem that are large enough to have diverse benefits and are carefully connected to other reserves so there are no "choke points" in the system, says Bobker, and so the "fish fry don't fry" on their way from one reserve to another, says Vorster.
"CALFED's current restoration targets are based on protecting the status quo," says the Defense Fund's Rod Fujita, "and many of the targets are disproportionately small compared to the extent of habitat degradation that occurred according to our analysis."
Contact: Rod Fujita (510)658-8008
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