justified. The problem on Caliente Creek is similar in that the initial 1 X. PLAN OF IMPROVEMENT 61. A determination of the most suitable plan for controlling floods of Kern River must be based on certain controlling factors which are peculiar to this stream. These conditions are recapitulated here for reference. These factors are: (a) Greatest flood damage in the area is caused by late spring (snow melt) floods. Any adequate flood-control plan must therefore be based upon the control of these floods. If sufficient detention storage is provided for this purpose, complete control of winter (rainfall) floods of any probable magnitude will be accomplished. (b) Kern River flows into a closed basin. It therefore follows that flood flows, if detained in a reservoir for later release, must even then be disposed of by irrigation or other means. (c) Regulated discharges must not exceed channel capacities. 62. In determining the reservoir capacity required to provide reasonably adequate flood protection, it is necessary to consider the amount of water and the rate at which it can be usefully absorbed in the area. The mean seasonal run-off of Kern River is 702,000 acrefeet. Damage from late spring floods now occurs in years in which the seasonal run-off exceeds about 1,000,000 acre-feet. Actual canal diversions for the season 1937-38 totaled about 650,000 acre-feet. With adequate flood-control storage the estimated maximum seasonal dispersion of water will increase in the service area and is given in table 24 below. TABLE 24.-Esiimated maximum seasonal dispersion of water in Kern River service area with regulation by reservoirs 63. The run-off of the 45-year period of record was routed through reservoirs of various sizes. A reservoir having a gross storage capacity of 550,000 acre-feet best meets all the requirements for reasonably adequate flood control. 64. The project herein proposed consists of the construction of two dams to form a reservoir on Kern River near the town of Isabella, about 50 miles above Bakersfield. The reservoir would have a gross storage capacity of 400,000 acre-feet to crest of spillway. Crest gates would be provided in the spillway which would afford an additional 150,000 acre-feet of storage for regulation of run-off from Not printed. and ava res fred fee for of pre 6 the inc melting snow during the period from May 15 to October 1. Fifty thousand acre-feet of inactive storage would be provided in the reservoir in accordance with the requirements of the plan of operation of appurtenant works made necessary by reason of the existence of the Borel conduit through the reservoir (see par. 69). The reservoir would have a maximum surface area of 11,000 acres, including portions of the north and south fork valleys, extending approximately 7 miles upstream from the dam. The small villages of Isabella and Kernville fre would be inundated. Construction of a reservoir of the required ri capacity at this site would make necessary: Tak (a) Relocation and construction of approximately 9 miles of State highway, 12 miles of county roads, and 7 miles of farm access road. (b) Construction of three highway bridges. (c) Relocation and construction of 13 miles of transmission line, and several miles of telephone line. 65. Main dam.-The proposed main dam would be a multiple-arch, concrete structure with a maximum height of 165 feet above streambed, and crest length of 1,880 feet. Twenty-three arches would be supported on buttresses spaced 50 feet on centers, with a small concrete gravity section approximately 50 feet long at each end of the dam. A reinforced concrete highway bridge would cross the dam, supported on the buttresses. General details of the proposed structure are shown on enclosures 2-5,1 inclusive. 66. Spillway. The spillway would be located over a ridge at the left abutment of the main dam where topographic features are favorable for construction of a low, concrete gravity ogee section. The waste-way channel would follow the course of a natural ravine. The spillway, with a net length of 360 feet and crest elevation 2,590 feet, would have a discharge capacity of 64,000 cubic feet per second, under a surcharge of 12.5 feet. This capacity is sufficient to discharge a flood of 160,000 cubic feet per second and having a volume of 309,000 acre-feet (50 percent in excess of the estimated maximum historical flood), due allowance being made for detention above the spillway lip and with the added assumptions that 20,000 acre-feet of storage was available at beginning of flood and that the controlled discharge of reservoir outlets was 4,000 cubic feet per second. The minimum freeboard during the passage of such a flood would be 51⁄2 and 10% feet for the multiple-arch and earth-fill dams, respectively. The foregoing spillway design criteria were adopted solely for the safety of the earth-fill dam. The plan of reservoir operation absolutely precludes the possibility of such an occurrence. 67. The flood outlets would consist of four 96-inch diameter steellined conduits embedded in mass concrete between the buttresses of the multiple-arch dam. Each conduit would be controlled by a 96inch oil cylinder operated butterfly valve with provision for manual operation. Emergency control would consist of caterpillar-type gates at the upstream face of the dam. A single 48-inch steel-line conduit at elevation 2,460 would be provided for release of impounded water below the flood outlets during extreme drought years. Discharge capacities of outlet valves are shown on er closure 3.1 68. Auxiliary dam.-The auxiliary dam across Hot Spring Valley would be a rolled-earth structure with a maximum height of 73 feet. Crest elevation would be at 2,613 feet or 5 feet above that of the 1 Not printed. multiple-arch dam. This would provide a freeboard of 8 feet above 69. Provisions for water supply to existing Borel conduit.-Because the proposed dam would be constructed across Borel conduit of the Southern California Edison Co., provision must be made to maintain flow through this conduit to the Borel power plant. The proposed plan would consist of the following units: (a) 15-foot diameter steel-lined conduit leading to a powerhouse in the dam. (c) Two hydroelectric generating and pumping units. (d) Tunnel 2,500 feet long. (e) Regulating or surge basin. (f) 1,500 foot concrete-lined canal. The plant would discharge water by gravity into Borel conduit when the reservoir stage would be above elevation 2,550. Below that stage, flow to Borel conduit would be maintained by pumping from the reservoir. Power to operate the pumps would be supplied either by the turbines or by the generators operating as synchronous motors. 70. Cost estimates for the proposed improvement included the above provision for supplying flow to Borel conduit. An alternate method, which should receive detailed study should the project be authorized, would be to provide a tunnel under the dam as an outlet to Borel conduit. Many flume sections of the conduit inside the reservoir area would, however, require modification to prevent flotation during the period when the reservoir would be filling. Also, new outlet works, sand traps, and automatic filling valves would be required. A considerable number of slopes in cuts would require flattening, and riprap on canal banks would become necessary in many places. The estimated cost of this alternate plan is about $600,000. 71. Maintenance of dam and reservoir.-Items of maintenance directly connected with the dam and reservoir would be: (a) Maintenance and painting of spillway gates and operating machinery. (c) Maintenance of both stream-gaging stations. (d) Maintenance of dams. (e) Maintenance of works for water supply to existing Borel conduit. The cost of maintenance of the above items cannot be foretold with any assurance at this time. However, since the design and construction of the project is a responsibility of the United States the maintenance thereof, which is of vital importance to the safety of the dam, should also be borne by the United States. In order that there shall be no division of responsibility for the safety of the project works and lives and property downstream, the Federal Government should undertake all items of maintenance listed above except item (c), which should be a responsibility of local interests or the power company. South woul Kern Not 72. Reservoir operation.-The proposed method of reservoir operation was developed from a study of run-off records of the 45-year la period 1893-1938 and is presented in detail in appendix II.' Drawings B and C of appendix II' show the effect the plan of operation of a reservoir of 400,000 acre-feet gross capacity would have had upon Kern River run-off during the period of record. Drawings D and E of appendix II' are similar studies for the same reservoir but having crest gates (gross capacity 550,000 acre-feet) for the flood years in Galan which detention in the reservoir would have exceeded 400,000 acrefeet. The plan contemplates entering the rainy season on December 1 with not less than 100,000 acre-feet of empty storage space available below spillway crest for the control of winter floods. This space would be kept unimpeded for control of winter floods until March 1, unless continued high flows and an early heavy snow pack indicate the probability of a large run-off. In such a case, 250,000 acre-feet of vacant storage space below spillway crest would be made available by March 1, by release of water at rates within downstream channel capacities. If snow survey reports, the first of which is available about March 1, indicate a late spring run-off of flood proportions, the necessary flood-control storage space up to the maximum of 350,000 acre-feet below spillway crest would be made available in time to control the late spring flood. After all danger of peak flows has passed as indicated by subsequent snow surveys, the reservoir might be allowed to fill to capacity. During summer and fall, the reservoir would be gradually drawn down under normal releases. Under this plan, the 1916 late spring flood (largest of record and 355 percent of the normal seasonal run-off) would have been controlled to safe channel capacities, but 630,000 acre-feet would have reached the lake areas. As an aid to reservoir operation two gaging stations, equipped with radio-reporting devices, would be installed, one on either fork of Kern River upstream from the reservoir. 12 73. Coordination with State water plan.-The State of California has developed a comprehensive plan entitled "The State Water Plan," for full utilization of the available water resources of California. Under this plan, the Friant-Kern Canal from Friant Dam on the San Joaquin River to a point southeast of Bakersfield in Kern County, would follow the southern San Joaquin Valley along the edge of the eastern foothills. This canal would deliver San Joaquin River water to various irrigation units between the San Joaquin and Kern Rivers, and would pass through an area now served by Kern River water. In order to secure water for the Edison-Arvin area southeasterly of Bakersfield, which is too high in elevation to be served by the proposed Friant-Kern Canal, it has been proposed that this canal distribute water to a portion of the Kern River service area and, in exchange, Kern River water belonging to that area be diverted at a higher elevation to supply the Edison-Arvin area. The delivery of Kern River water to the Edison-Arvin area would necessitate the construction of a canal of about 1,500 cubic feet per second capacity, which would divert from the river at Kern Canyon and proceed southerly along the foothills. A distribution system for this canal would also be required. Complete coordination of water use in the Kern area would permit the use of this canal and distribution system 1 Not printed. for the spreading of excess flood flows of the Kern River. A system of this type, operated in coordination with the project proposed in this report, would provide practically complete flood control of Kem River. At the same time, it would insure beneficial use of water which would otherwise flow into Tulare Lake basin with damaging effect. Although consideration was given to this matter, the indefinite status of the location and other features of the Friant-Kern Canal made it impracticable to undertake detailed studies of the proposal at this time. Adequate consideration of this matter should be undertaken at a later date, coincident with the development of final plans for the FriantKern Canal. XI. POWER DEVELOPMENT 74. Coordination of power development with flood control.-In connection with this report, a comprehensive survey was made of poten tial reservoir sites on Kern River with a view to determining the pos sibility of their use in a multiple-purpose project. These surveys, described in detail in appendix IX, disclosed the fact that because of topographic and/or hydrologic conditions, the Isabella site is the only one possessing satisfactory characteristics for adequate flood-detention storage which, in addition, could be applied economically to the gener ation of electric power. In connection with these surveys, an anlaysis was made to determine the existing power demand in the area and probable future trends thereof. Summarizing the conclusions of these surveys and studies, it appears probable that future development of hydroelectric power on the Kern River, while feasible from an engineering standpoint, would have little or no direct effect on floodcontrol matters. 75. Effect of proposed improvement on existing power installations.— As stated in paragraph 34, existing power installations on Kern River utilized natural stream flow. Three of these installations are below the proposed improvement, and would be benefited by the regulation of flow afforded by a dam at Isabella. Studies included in appendix IX' show that an additional output of approximately 16,000,000 kilowatt-hours per annum would result from the regulatory effect of the proposed improvement for the plants below Isabella Dam. XII. BENEFITS FROM IMPROVEMENT 76. Flood-control benefits.-The direct flood-control benefits which would result from the construction of the proposed project would be: (a) Elimination of damages due to winter floods. (b) Control of late spring floods to the extent economically justifiable for the agricultural districts in the lake areas. (c) Control of a late spring flood equal to the maximum of record to within safe channel capacities. The present estimated average annual flood damage of $878,900 would be reduced to $146,200 with regulation by means of the 550,000 acre-feet reservoir. The resultant average annual benefit would be $732,700. The residual average annual damage is that anticipated from late spring floods of great volume and infrequent occurrence. This damage would be confined to the lake areas. The direct aver age annual flood-control benefit for the proposed project (both with and without crest gates) is summarized in table 25 below. 1 Not printed. TA Kern Ri Goose L Buena Buena V Wasco Tulare To 77. the pi (a) As a contro elimin |