Buchanan Lake, Chowchilla River Basin, California
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June 1970 Revised: March 1971 Environmental Statement Buchanan Lake Chowchllla River Basin, California prepared by U. S. Army Engineer District, Sacramento, California SUMMARY , ENVIRONMENTAL STATEMENT BUCHANAN LAKE, CKCWCHILLA RIVER BASE!, CALIFORNIA 1. Coordination With Other Agencies. - Date of Date of Agency Reouest Comments U.S. Bureau of Uport Fisheries and Wildlife 11 Sep 70 3 Nov 70 Federal Water Quality Administration 11 Sep 70 23 Oct 70 (Environmental Protection Agency) National Park Service 11 Sep 70 15 Oct 70 Bureau of Outdoor Recreation 11 Sep 70 27 Oct 70 State of California Resources Agency 11 Sep 70 11+ Jan 71 Board of Supervisors, County of Madera 11 Sep 70 21 Oct 70 2. Environmental Impacts. - The project, consisting of a reservoir and downstream channel improvement, would provide flood control, irrigation and recreation. The reservoir would inundate 1500 acres of oak-digger pine, grassland and would result in the loss of almost all of the remaining vege tation and associated values along 18 miles of the 20 miles total channel improvements. The project will facilitate increased urban, industrial and agricultural developments within the basin. 3 . Adverse Environmental Effects Which Cannot be Avoided. - The loss of riparian vegetation associated with channel improvements is a loss of aesthetic, wildlife, and other natural values of the river. U. Alternatives. - The following alternatives were studied and found to be less desirable than the adopted plan principally for the reasons indicated: a. Channel improvements alone would add to flood problems on the San Joaquin River, would cause greater damage to riparian habitat, and would not provide irrigation supply, fishery resources or recreation opportunities. b. Channel improvements and a single-purpose irrigation supply reser voir would also add to flood problems on the San Joaquin River and cause ■f greater damage to riparian habitat, and would not provide as great a fishery resource or as many recreation opportunities. c. Channel improvements and a single-purpose flood control reservoir would not provide irrigation supply, fishery resources or recreation oppor tunities. d. A multiple-purpose reservoir without channel improvements could avoid the need for extensive damage to riparian channel habitat, but would have to be very large and would be significantly more expensive. e. No development at all would permit continued flood damages and would not provide the irrigation supply, fishery resources or recreation oppor tunities. 5. This is an administrative action, although further Congressional appropriations are required for project completion. The project was authorized by Section 203 of the Flood Control Act of 1962, Public Law 87-87U. Advance planning is essentially complete and real estate acqui sition for the reservoir is 85 percent complete. The initial construction contract for this project would be advertised and awarded in mid-1971 and would consist of relocating Madera County Road 607. ENVIRONMENTAL STATEMENT BUCHANAN LAKE CHOWCHILLA RIVER BASIN, CALIFORNIA 1. Project description. - The Buchanan Lake, Chowchilla River Basin Project was authorized by Section 203 of .the Flood Control Act of 1962, Public Law 87-874, and is now in the advance engineering and design phase. Acquisition of real estate— about 3,380 acres for the dam and reservoir areas are required— is 85 percent complete. The project plan calls for construction of a rockfill dam about 205 feet high creating a reservoir having a capacity of 150,000 acre-feet and a shoreline of 20 miles. An unlined, ungated emergency spillway would be provided. The project purposes include flood control, irrigation, general recreation, and fish and wildlife enhancement. A 10,000 acre-foot minimum pool will be provided for sediment storage, recreation, and other purposes. Downstream channel improvements will consist of increasing to 5,000 c.f.s. (cubic feet per second) the capacity of about 12 miles of Ash Slough from its present controlling capacity of 3,000 c.f.s., and increasing to 2,000 c.f.s. the capacity of about 8 miles of Berenda Slough from its present controlling capacity of 1,000 c.f.s. These improvements, located immediately upstream from the Chowchilla Canal, will include channel enlargement, channel clearing, and levee construction. On Ash Slough 660 acres of stream are involved and 400,000 cubic yards of material will be removed, and on Berenda Slough 310 acres are involved and 250,000 cubic yards will be removed. Bank protection will be placed at sharp bends on Ash Slough. Patrol roads will be constructed on the levee crowns and gravity drainage structures will be constructed through the new levees. The objective of the flood control operation of the reservoir will be to protect the urban and suburban areas of the city of Chowchilla against a flood of about "standard project" magnitude, and the rural agricultural areas along the Chowchilla River, Ash Slough and Berenda Slough against at least the 50-year frequency flood. The flood control operation will also aid in decreasing flooding along the lower San Joaquin River. Irrigation operation of the project is expected to furnish an annual yield of about 24,000 acre-feet of new water. Operations studies indicate that the average reservoir pool during the recreation season will have a surface area of approximately 1,100 acres. There will be an average drawdown of about seven vertical feet per month during the recreation season. Initial development of recrea tional features will include a day-use facility with 50 picnic units and a camping facility with 50 camping units. Facilities to be developed at eacli recreation site will include water supply and distribution systems, sanitary facilities, access and circulation roads, parking facilities and boat-launching facilities. In addition, approximately 1,500 acres of undeveloped project lands along the northwest, north and northeast shores of the reservoir will be used for a wildlife management area. Plate II indicates the location of the recreation and wildlife management-areas. About 5.5 miles of Madera County Road No. 607 will be improved to permit access for construction and operation. This will be the first construction contract and is scheduled for initiation in 1971. The overall project will have a benefit-to-cost ratio of 1.9 to 1. 2. Environmental setting without the project. - The Chowchilla River drainage basin is located in the San Joaquin Valley of California, and extends from the Eastside Bypass on the valley floor generally northeast to the western slopes of the Sierra Nevada. The basin, including the valley floor portion, has a length of about 60 miles and an average width of about 10 miles. The watershed above the authorized Buchanan Dam site has an area of about 235 square miles with a normal annual precipitation of about 29.8 inches. Elevations in the basin range from about 6,800 feet in the Sierra Nevada to about 100 feet above sea level on the valley floor. The drainage system above the damsite consists of two major tributaries, the East and West Forks, which flow in relatively deep canyons and join about 15 miles above the Buchanan Dam site to form the Chowchilla River. About 10 miles above the city of Chowchilla, the Chowchilla River system has been diverted into three channels. The Chowchilla River becomes a rather insignificant channel below this point and Ash and Berenda Sloughs become the main channels for the stream system. Local people have constructed control works to divert flows among Chowchilla River, Ash Slough and Berenda Slough. Most of the stream channels have been significantly modified from their natural condition as a result of agricultural activities in the area. Modifications consist of construction of irrigation facilities, realign ment of channels, removal of sand and vegetation from the channels, and construction of intermittent low levees. A map of the basin is shown on plate I. The vegetation in the basin varies from coniferous forest in the upper elevations to oak-grassland and chaparral in the foothills where the reservoir site is located. The lower portion of the basin below the foothills is mostly under cultivation with very little native vegetation remaining except the riparian vegetation which grows along the water courses. Although limited, the sloughs support cottonwoods, willows, blackberries and other vegetation that provides food cover, resting and rearing areas for birds and small game. In the reaches of Ash and Berenda Sloughs where channel work is to be done, there are about 18 miles of channel with "good" riparian habitat (a subjective evaluation indicating the presence of significant riparian vegetative growth, wildlife and scenic and 'aesthetic qualities in comparison with other remaining natural habitat in the vicinity). There are approximately 106 miles of stream channels from the Buchanan Dam site to the San Joaquin River. The principal land uses in the foothills and mountain areas are grazing and lumbering. The alluvial fan and valley floor of the basin downstream from the reservoir site are devoted primarily to agriculture. The land use includes unirrigated pasture, irrigated pasture, field crops, orchards and vineyards. Other related industries include feed lots, grain and milling companies, creamery, concrete pipe plant, lumber mill, and cotton oil mill. The city of Chowchilla is also located in the basin. Land uses have changed the original natural character of the lower portion of the basin; the flood plain includes about 110,000 acres with large areas of highly developed agricultural land and many homes and improvements. The current estimate of value of lands, within the Chowchilla River flood plain is estimated to be in excess of $150,000,000. Lands retaining their natural character are located in the stream floodways and at the lower end of the flood plain, where flood hazard tends to restrict development. Based on information provided by the U.