Scientific Investigations Report 2007–5005

Scientific Investigations Report 2007–5005

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In March 2003, 16,500 acres of salt evaporation ponds owned by the Cargill Corporation in the San Francisco Estuary were purchased using State, Federal, and private funds. Currently (2006), the California Coastal Conservancy is leading a collaborative planning effort with the U.S. Fish and Wildlife Service (USFWS) and the California Department of Fish and Game to restore the ponds to tidal action while providing for flood management, public access, and recreation.

The ponds presently are being operated and maintained according to the South Bay Salt Ponds Initial Stewardship Plan (ISP). The goals of the ISP are to maintain existing habitat and prevent a build-up of salt in the ponds, in a cost-effective manner, until the long-term restoration plan is in effect (Life Science!, Inc., 2003). The Alviso Salt Pond Complex, located in South San Francisco Bay, (fig. 1) is made up of 8,300 acres of salt ponds. Water is discharged from five of the Alviso ponds (A2W, A3W, A7, A14, and A16) into South San Francisco Bay or adjacent sloughs to prevent the build-up of salt in the ponds, as happened in the Napa salt ponds (Lionberger and others, 2004). This discharge is allowed through a permit issued by the Regional Water Quality Control Board. As a requirement of the permit, the USFWS must estimate the amount of discharge from each of the five ponds for the period May through November of each year.

Purpose and Scope

The purpose of this report is to present a pond discharge calculator (PONDCALC) for the Alviso salt ponds. Relevant theory, pond discharge measurements, discharge relations, tidal predictions, input data, calculator output, and assumptions and limitations are described. PONDCALC is applicable to only the five Alviso ponds (A2W, A3W, A7, A14, and A16) that discharged to South San Francisco Bay or to sloughs connected to South San Francisco Bay in 2005. The USFWS must report discharges that occur during the period May though November to the Regional Water Quality Control Board, so calculations are limited to this period. PONDCALC is available as a Microsoft Excel™ file.


Neil Ganju of the USGS assisted with discharge measurements. Pat Mapelli of Cargill Corporation provided culvert invert elevations and information about the weir structures. Clyde Morris and Eric Mruz of the Don Edwards San Francisco Bay National Wildlife Refuge provided additional information and access to the ponds. Bassam Younis, Jim Orlando, and Charles Parrett provided thoughtful reviews that greatly improved the manuscript. Funding was provided by the U.S. Fish and Wildlife Service and the U.S. Geological Survey Priority Ecosystem Science Program.

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