The Peripheral Canal and the Future for Water in California

The Peripheral Canal and the Future for Water in California Donald F. Anthrop* Californias average annual runoff of approximately 71 million acre-feet would seem to constitute an abundant water supply (Calif. Bull. 160-74, p. 5). There is, however, a serious problem of distribution. More than 72 percent of this runoff occurs north of the Sacramento-San Joaquin delta. In contrast, approximately 75 percent of the present water use requirement is found south of the delta (Calif. Bull. 160-70, p. 63; Seckler, p. 71). Average delta inflow is about 19.8 million acre-feet (maf), and the Sacramento River is the major contributor to the delta's total net inflow (Table 1) . The Sacramento, the San Joaquin, and several of the eastside streams are regulated, and in some cases there are upstream diversions. The data in Table 1 are based upon an assumed 1970 level of development rather than on unimpaired flows. The central location of the delta, combined with a net annual inflow of nearly 20 maf, makes the delta the focal point of efforts to redistribute California's surface water supplies. Before examining the implications of current California water legislation and the Senate Bill 200 (SB 200) referendum, it will be helpful to trace the historical development of water transfers across the delta and the impacts of those transfers. *Dr. Anthrop is a professor in the Environmental Studies Department, San Jose State University. 109 110ASSOCIATION OF PACIFIC COAST GEOGRAPHERS Table 1. Annual delta inflow (1,000 acre-feet) Annual Inflow groupaverage*MinimumMaximum Sacramento Valley16,7314,908 (1923-24)39,873(1937-38) San Joaquin Valley2,311416 (1976-77)10,861(1937-38) Eastside streams752113 (1960-61)2,865(1951-52) Tidal (during 12 hours)0 -100± (ebbtide)100 ± (flood tide) SOURCE: Draft Environmental Statement on the Reauthorization of the CVP, DES 80-47, Water and Power Resources Service, U.S. Department of Interior, July 29, 1980, p. C-Il. *For 33-year study period, 1922-1954 inclusive, assuming a 1970 level of development. The delta area (Figure 1) consists of about 690,000 acres of land and 50,000 acres of water. Prior to its alteration by man, the delta consisted of swamp and overflow lands that were inundated by ordinary high tides. The relatively flat lands were covered with a dense growth of tules, willows, and cottonwood trees that provided exceptional habitat for waterfowl and wildlife. After more than a century of human activity, the delta landscape has changed noticeably. Artificial levees have been constructed along the natural waterways to divide the delta into about 50 separate parcels. These have been dewatered and drained, and are now islands separated by about 700 miles of meandering waterways. The delta now exists as a rich agricultural area and delta waterways serve as a major repository of aquatic life, including such game fish as salmon and striped bass (DES 80-47, p. C-9). Suisun Marsh, which is located just west of the delta and north of Suisun Bay (Fig. 1) , provides a transitional zone between the saltwater of San Francisco Bay and the freshwater of the SacramentoSan Joaquin River system. This marsh, consisting of approximately 57,000 acres of marshland and 29,500 acres of bays and waterways, comprises about 10 percent of the remaining wetlands in the state. It provides important winter habitat for waterfowl in the Pacific Flyway. Between 100,000 and 700,000 birds use the marsh at any given time. The major source of freshwater to the marsh is the Sacramento-San Joaquin River system. This freshwater repels the intrusion of seawater from San Francisco Bay, and the volume of YEARBOOK · VOLUME 44 · 1982 111 SACRAMENTO 3è Figure 1. Sacramento-San Joaquin delta. 112ASSOCIATION OF PACIFIC COAST GEOGRAPHERS freshwater mixing with seawater during tidal ebb and flow determines the salinity in the marsh. Upstream diversions and large exports of freshwater from the delta have significantly altered both the extent and the duration of salinity intrusion in the marsh. Delta outflow in a "normal" year has been reduced nearly 50 percent by these diversions and exports from what it was at the turn of the century . As a result, water salinities have increased over...