THE R DISTRICT. Board of Directors The Metropolitan Water District of Southern California Building. Gentlemen:

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1 THE R DISTRICT RNIA OFFICE OF GENERAL MANAGER AND CHIEF ENGINEER JUL Board of Directors The Metropolitan Water District of Southern California Building Gentlemen: At the meeting held May 24, 1960, the Board instructed the Staff to sumit a report on the amount of water which is availale now arid the amount which will e availale in the future, at appropriate locations from the Upper and Lower feeders, for the purpose of replenishing underground asins. Maximum annual delivery of Colorado River water to the District s constituent municipalities is expected to e on the order of l,l~0,000 acre-feet per year, after deducting possile losses from the District s contract allotment of 1,212,000 acre-feet per year. Consequently, irrespective of the capaility of the distriution system to transport water to points of delivery, the maximum total quantity availale for ground water replenishment in any year will e l,l~0,000 acre-feet less the other demands during such year, comprising demands for direct delivery of water for domestic, municipal, industrial, and agricultural uses. Taulation 1 attached hereto shows, for the period extending to 1974, the estimated demand for Colorado River water for comined domestic, municipal, industrial, and agricultural uses, the remainder availale for ground water replenishment, and a possile division of the latter etween the Orange County Coastal Basin and the Central and West Coastal Basins in Los Angeles County. The taulation represents conditions of average rainfall and is ased on the assumptions that 1,212,000 acre-feet of water can e diverted from the Colorado River each year and that the aqueduct system is capale of delivering l,1~o,o0o acre-feet of this water to the District s constituent and contracting agencies. In the event of a comparatively wet series of years, the demands for water other than for replenishment would e less than shown on Taulation 1 and the quantity of water availale ~or replenishment would e greater. At the same time the use of

2 imported water for replenishment might e less than indicated in the taulation, resulting in prolonging the period of time during which less Colorado River water is used than could e delivered y the aqueduct. Taulation 1 indicates that after 1964 there may e insufficient Colorado River water for replenishment to meet the comined requirements of the Central and West Basin Replenishment District and Orange County Water District unless a series of years of aove average rainfall should occur. Untreated Colorado River water for replenishment of ground water in the Orange County Coastal Basin will e delivered through the 300 cfs capacity East Orange County feeder for percolation in the Crill spreading grounds of Orange County Water District, and also through the Lower feeder spiliway pipe line for percolation in the Santa Ana River channel spreading grounds downstream from the Yora ridge. The Lower feeder has capacity in excess of estimated requirements for other deliveries during the next 5 years to transport 250,000 to 300,000 acre feet of untreated water to the aove-mentioned spreading grounds. This availale capacity is greater than the predicted demand for replenishment in Orange County, and consideraly greater than the quantities indicated in Taulation 1 to e~availa1e for such replenishment. Untreated Colorado River water for replenishment in the Central Coastal Basin will e applied at the San Gariel River and Rio Hondo spreading grounds of the Los Angeles County Flood Control District in the Monteello Foreay area elow Whittier Narrows. Filtered Colorado River water will e applied y injection methods in the fresh water arriers proposed for repulsion of sea water intrusion in the Central and West Coastal Basins across the Los Alamitos Gap in the vicinity of the San Gariel River estuary, across the Dominguez Gap etween the Los Angeles River estuary and the Palos Verdes Hills, and along the coast of Santa Monica Bay for a distance of 11 miles etween Playa del Rey and the Palos Verdes Hills. The last-mentioned arrier represents the proposed extension of the existing experimental injection project of the Los Angeles County Flood Control District at Manhattan Beach and is expected to e completed in aout 3 or 4 years. It may e several years more efore the other two arriers will e in operation. Delivery of untreated Colorado River water to the Monteello Foreay of the Central and West Coastal Basins requires utilization of the La Verne-Garvey portion of the Middle feeder, which has a capacity of 250 cfs for delivery into Garvey Reservoir and a maximum capacity of aout 400 cfs for delivery of water to the San Gariel River arid Alhamra Wash turnouts for the Los A.ngeles County Flood Control District, when no water is eing delivered elsewhere from the feeder. The San Gariel River turnout presently is out of service to accommodate construction of river 2.

3 channel improvements. Upon completion of the channel work late in 1960 the turnout will e restored to service with a delivery capacity of 200 cfs. The Alhainra Wash turnout has a capacity of 225 cfs. Hence it would e possile to deliver a maximum of aout 400 cfs of untreated water to the Flood Control District for use at the San GaD~el and Rio Hondo coastal spreading grounds, during periods when the La Verne-Garvey feeder is not needed for delivery of softened water and when a diversion of that magnitude from the Upper feeder at La Verne can e accommodated without conflict with other required service. However, ecause of other demands on the Upper feeder the quantity of untreated water availale for delivery at these turnouts, even during off-peak seasons, cannot e expected to exceed aout 350 cf a for the greater part of the time. Until the Lower feeder treatment plant near Yora Linda shall have een completed, scheduled early in 1963, the La Verne-.Garvey feeder will e needed during a period of aout 5 months of high demand each year for transportation of softened water from La Verne to Garvey Reservoir. Under these conditions the quantity of water that can e delivered to the Monteello Foreay for spreading during the next succeeding two fiscal years may e limited to aout 150,000 acre feet per year. After completion of the first development (200 mgd) of the Lower feeder treatment plant, delivery of filtered water through the Lower feeder to service areas in Orange and Los Angeles Counties will enale the La Verne Garvey portion of the Middle feeder to e utilized to a greater extent for transportation of untreated water for replenishment purposes. However, expected increases in demand for domestic, municipal, and industrial uses in the higher service areas which can e served only through the Upper feeder will diminish the excess capacity therein availale for transportation of water for spreading and detailed routing studies for supplying predicted monthly demands indicate that it will e prolematical whether more than aout 200,000 acre-feet of water for spreading can e delivered to the Monteello Foreay during any succeeding year through the District s distriution system as 4t will e constituted after completion of projects now authorized. order to utilize the availale distriution facilities m.ost L1n advantageously, it will e necessary to augment deliveries for spreading at the Monteello Foreay y release of treated water for this purpose when availale during periods when treated water is eing transported through the La Verne-Garvey feeder, assuming that the question of price differential can e resolved sati sfactorilyj~ Delivery of filtered water to the three proposed fresh water arriers will present a lesser prolem after 1962 than delivery to Monteello Foreay ecause the arriers can e served through the Lower feeder, which has a greater reserve of capacity than the Upper feeder. 3.

4 Further amplification of the feeder system for increased deliveries to the Central and West Basin Replenishment District would require construction of an intermediate feeder taking out from the Lower feeder at a point upstream from the treatment plant and extending to the Monteello Foreay of the Central Basin. Such an intermediate feeder with a capacity of 250 cfs would cost aout *12,000,000. However, there is a possiility that the feeder system as now authorized will suffice for delivery of all the water otherwise availale from the Colorado River supply for replenishment in the Central and West Basins in Los Angeles County during the years succeeding the eginning, of operation of the Lower feeder treatment plant in Consequently, it appears to e inadvisale to consider amplifying the feeder system for purposes of transporting water for replenishment in Los Angeles County pending further oservation of the progress made y the Los Angeles County Flood Control District and other agencies concerned in providing works for utilization of the water and of the capaility of the present feeder system in supplying the requirements; provided, however., that the feeder to the Long Beach area for transporting filtered water from the West Coast feeder for use y means of injection to repel salt water intrusion in the Dominguez Gap and Alaxnitos Gap should e constructed as now authorized. In the Annual Survey Report on Ground Water Replenishment, prepared for the Central and West Basin Replenishment District y its consulting engineers under date of March ~, 1960, it is recommended that the Replenishment District purchase 70,000 acre-feet of untreated Colorado River water and 5,000 acre-feet of softened water for replenishment of ground water supplies during the ensuing water year Octoer 1, 1960 through Septemer 30, 1961, it eing assumed that the 70,000 acre-feet of untreated water all will e purchased after January 1, In addition, it is expected that ao,000 acre-feet of untreated Colorado River water will e purchased for replenishment purposes Basin y the Los Angeles County Flood Control District utilizing funds derived, from ad valorum assessment in Zone I of the Flood Control District. in the Central The San Gariel Coastal spreading grounds and the Rio Hondo Coastal spreading grounds in the Monteello Foreay of the Central Basin have a comined percolation capacity estimated at 4~5 cfs, with an additional 70 cfs availale in the ed of the San Gariel River. Annual overdraft in the Central and West Basins for is estimated to e 258,400 acre feet and for is estimated to e 249,100 acre-feet. These estimated overdrafts are indicated to e proaly less than actual, as recent impairments in supply due to increased use of water upstream in the San Gariel 4.

5 Valley were not accounted for in the estimates. The accumulated overdraft in these two asins is estimated to e presently 700,000 acre feet. Considering these circumstances and the quantities of Colorado River water indicated in the attached Taulation 1 to e availale for replenishment in the Central and West Basins it appears that to accomplish a sustantial reduction in the accumulated overdraft represents a formidale task unless a period of aundant rainfall commences in the very near future. Very truly yours, A. Skinner Assistant Chief Engineer End (Taulation 1)

6 I Taulation 1 Water Year Estimated Use of Colorado River Water Exclusive of Ground Water Repleni shment Acre-feet Colorado River Water Estimated to e availale for Ground Water Replenishment Central and West Orange Coastal Basins in County Los Angeles Coastal Total County Basin Acre-feet Acre-feet Acre-feet l967-6~ l96~ Cc) 567, , , ,000 7~O,OOO ~25,OOO ~7O,OOO 915, ,000 1,000,000 1,040,000 l,0~0,0oo 1,120,000 1,l~O,00O 2~9,00O 307, , , , , , , ,000 l~o,0oo 140, ,000 60,000 - a a a. ) ) ) 154, , , , , , , , , ,000 g5,ooo 60,000 35, , , , , , , , ,000 ~5,OOO 70,000 55,000 40,000 25,000 ) ( (c) Quantities estimated y replenishment agencies. Quantities availale for replenishment if aqueduct is operated at full capacity throughout the year. Lower feeder treatment plant in operation early in /l~/60