Drainage-return, surface-water withdrawal, and land-use data for the Sacramento-San Joaquin Delta, with emphasis on Twitchell Island, California

Abstract

Partial data on drainage returns and surfacewater withdrawals are presented for areas of the Sacramento-San Joaquin Delta, California, for March 1994 through February 1996. These areas cover most of the delta. Data are also presented for all drainage returns and some surface-water withdrawals for Twitchell Island, which is in the western part of the delta. Changes in land use between 1968 and 1991 are also presented for the delta. Measurements of monthly drainage returns and surface-water withdrawals were made using flowmeters installed in siphons and drain pipes on Twitchell Island. Estimates of monthly returns throughout the delta were made using electric power-consumption data with pump-efficiencytest data. For Twitchell Island, monthly measured drainage returns for the 1995 calendar year totaled about 11,200 acre-feet, whereas drainage returns estimated from power-consumption data totaled 5 percent less at about 10,600 acre-feet. Monthly surface-water withdrawals onto Twitchell Island through 12 of the 21 siphons totaled about 2,400 acre-feet for 1995. For most of the delta, the monthly estimated drainage returns for 1995 totaled about 430,000 acre-feet. The area consisting of Bouldin, Brannan, Staten, Tyler, and Venice Islands had the largest estimated drainage returns for calendar year 1995. Between 1968 and 1991, native vegetation in the delta decreased by 25 percent (about 40,000 acres), and grain and hay crops increased by 340 percent (about 71,000 acres). For Twitchell Island, native vegetation decreased about 77 percent (about 850 acres), while field crop acreage increased by about 44 percent (about 780 acres).

SPARROW Modeling of Nitrogen Sources and Transport in Rivers and Streams of California and Adjacent States, U.S.

“…The Bay‐Delta system is the largest estuary on the west coast of North America consisting of about 4,160 km 2 of which the Delta makes up about 2,984 km 2 . The Delta is also a point of transfer of significant amounts of freshwater to cities and agricultural regions from two pumping facilities (Templin and Cherry, ). Both the Sacramento and San Joaquin Rivers deliver freshwater to the Delta with about 84% coming from the Sacramento River, 13% coming from the San Joaquin River, and 3% from other smaller rivers (Jassby and Cloern, ).…”

Guidelines for preparation of State water-use estimates for 2005

“…A commonly used method to estimate irrigation withdrawals involves calculating consumptive use for irrigated crops using crop water-consumption coefficients for several crops and system types (see Allen and others, 1998;U.S. Department of Agriculture, 1970, 1976, 1997, 2002. The amount of water consumed by crops, plus additional water used in conveyance or needed for other irrigation uses, is the total withdrawal.…”

Dissolved organic carbon concentrations and compositions, and trihalomethane formation potentials in waters from agricultural peat soils, Sacramento-San Joaquin Delta, California; implications for drinking-water quality

“…By the mid-1800's, settlers began farming the rich organic soils of the Delta, and, by 1869, extensive levee systems were built around Sher man and Twitchell Islands (California Department of Water Resources, 1993) to allow for the expansion of agriculture. Reclamation of Delta islands for agricul tural purposes continued into the 1920's, and agricul ture accounts for about 70 percent of the current landuse in the Delta (Templin and Cherry, 1997).…”