The California Water Plan Update B ULLETIN 160-98

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EGIONS 9-6 served by surface water. Future water demands in the Truckee Basin are not expected to exceed theinterstate allocations contained in the Truckee-CarsonPyramid Lake Water Rights Settlement Act (PL 101-618), which limits the basin’s annual use to 32 taf. On the California side of the Lake Tahoe Basin, South Tahoe PUD, Tahoe City PUD, and North Tahoe PUD account for most of the water delivered to urbanusers. Water is supplied from the lake and from groundwater sources. The interstate allocation for California’s Lake Tahoe Basin in PL 101-618 would limit future water use in the basin to 23 taf of gross diversions, which represents the basin’s estimated future water needs at its full development. Future development in the Lake Tahoe Basin is strictly limited by the bistate Tahoe Regional Planning Agency to protect the basin’s environmental quality. In both the Truckee and TahoeBasins, water use for snowmaking at the area’s ski resorts has been addressed in the interstate allocations. Urban development in the Carson and Walker River Basins is minimal and is clustered around thetowns of Markleeville in Alpine County and Bridgeport in Mono County. More than 90 percent of the watershed on the California side is federally owned,primarily under the management of the Toiyabe National Forest. Groundwater is the source of supply for individual users and small community systems located in valley areas. In the upper watershed, communities may lack suitable sites to locate wells and therefore must depend on surface water sources. The Town of Markleeville depends on surface water and experienceda water shortage in 1989 when the stream that supplies the community went dry. Water had to be piped 4 miles from another creek to the town’s treatment plant. In the upper Carson River watershed, water is stored in several very small alpine reservoirs originally constructed to supply irrigation needs. Much of thiswater is still used for irrigation downstream in Nevada. The largest of the alpine reservoirs is Heenan Lake on Monitor Creek, tributary to the East Fork Carson River, with a capacity of nearly 3 taf. TheCarson River supports a popular recreational trout fishery in the upper watershed. DFG has used Heenan Lake for raising Lahontan cutthroat trout to stock at other locations throughout the Sierra. DFG currently manages State-owned lands adjacent to Heenan Lake and has arranged to purchase water on an annual basis to maintain a minimum reservoir pool for fish rearing. Two special-purpose reservoirs were constructedin the upper Carson watershed to receive treated wastewater effluent exported from South Tahoe PUD in the Lake Tahoe Basin. (Disposal of treated wastewaterwithin the Lake Tahoe Basin was banned to help protect the lake’s clarity.) Beginning in the 1960s,wastewater effluent was delivered to Indian Creek Reservoir for subsequent release to agricultural users as a supplemental irrigation supply. In 1989, exports (about 5 taf/yr) were redirected to Harvey Place Reservoir.Indian Creek Reservoir is now used for freshwater recreation. In addition to several small reservoirs in the upper watershed, the Walker River watershed has two largereservoirs—Topaz Reservoir (an offstream storage facility on the West Walker) and Bridgeport Reservoir on the East Walker. Both of the large reservoirs were USBR’s Stampede Reservoir is the second largest reservoir in the Truckee River Basin. Lake Tahoe is the largest reservoir in the basin.

Courtesy of USBRThe California Water Plan Update B ULLETIN 160-98

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EGIONS 9-7built by Walker River Irrigation District to sustain summer irrigation flows in its service area downstream in Nevada. WRID holds California water rights to store 57.6 taf of West Walker water, plus 200 af of local inflow, in Topaz Reservoir. WRID can store up to 39.7 taf in Bridgeport Reservoir. SWRCB has establishedinstream flow and minimum reservoir pool requirements at Bridgeport, in response to fish kills that occurred during the last drought. Both reservoirs are popular local recreational destinations. Part of the East Fork Carson River—approximately10 miles from the town of Markleeville to the California/Nevada state line—has been added to the California wild and scenic river system. On the West Walker River, approximately 37 river miles have also been given State designation. The designated reach is from Tower Lake at the headwaters downstream to the confluence with Rock Creek, and about 1 mile of Leavitt Creek. As occurred in the Truckee River Basin, water right disputes in the Carson and Walker River Basins were settled with federal court decrees. The 1980 AlpineDecree on the Carson River and the 1936 Decree C125 on the Walker River control most river operations.The decrees established surface water rights, including reservoir storage rights, of water users in both California and Nevada. However, the decrees onlyquantify individual water rights of parties to the litigation and did not address rights perfected under state

USBR’s Prosser Creek Reservoir is one of the

Truckee River system reservoirs whose operation would be covered by the TROA. law by others—not all existing water uses are necessarily covered in the decrees. PL 101-618 established aninterstate allocation in the Carson River Basin; the California allocation corresponds to existing water uses.

Local Water Resources Management Issues

Truckee River Operating AgreementNegotiation of a proposed Truckee River Operating Agreement and preparation of its draft EIR/EIS have been the major water management activities in the region. A new operating agreement for the TruckeeRiver is required by PL 101-618. Negotiation of a proposed TROA and preparation of an EIR/EIS for the TROA began in 1991. The draft EIR/EIS was releasedfor public review in 1998 and is expected to be completed in 1999. PL 101-618 settled years of disputes over Truckeeand Carson River waters by making an interstate allocation between California and Nevada. It also settledcertain tribal water right claims and provided for water supplies for specified environmental purposes inNevada. The act allocated 23 taf annually to California in the Lake Tahoe Basin and 32 taf annually in theTruckee River Basin below Lake Tahoe. The act allocated water corresponding to existing Carson River Basin water uses to California. The remainder of theThe California Water Plan Update B ULLETIN 160-98

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EGIONS 9-8 Truckee and Carson River supply was allocated to Nevada. When executed, the TROA would establish river operations procedures to meet water rights on the Truckee River and to enhance spawning flows in the lower Truckee River for cui-ui and Lahontan cutthroat trout. TROA would provide for management of water within the Truckee Basin in California, including instream flow requirements and reservoir storage forfishery and recreation uses, and would include procedures for coordinating releases and exchanges of wateramong the watershed’s reservoirs. TROA would become the exclusive federal regulation governing releases of water stored in Lake Tahoe, Martis Creek, Prosser Creek, Stampede, and Boca Reservoirs. The agreement would provide an accounting procedure for surface and groundwater diversions in California’s part of theTruckee Basin and would establish criteria to minimize short-term reductions in river flow potentially caused by future well construction near the river.In 1993, an agreement was signed by Sierra Pacific Power Company, Washoe County WaterConservation District, and Sierra Valley Water Company settling a dispute about when the water company was required to stop diverting water from the Little Truckee River. This agreement, which resolves disputesthat had often occurred during droughts, is being incorporated into the proposed TROA.

Walker River

Recent activities in the Walker River Basin havefocused on the declining level of Walker Lake in Nevada and the resulting impact on the lake’s fishery.Because Walker Lake is a terminal sink, salts accumulate as the lake water evaporates. Declining lake levelshave resulted in most Great Basin terminal sinks being too saline to support fisheries. Walker Lake is one of three terminal lakes in Nevada that support fish life. The water level at Walker Lake has declined from an elevation of about 4,080 feet in 1882 to 3,944 feet in 1994; salinity has increased during the same period from about 2,500 mg/L TDS to 13,300 mg/L TDS. In most years, Walker River is the primary source of inflow to Walker Lake. Flow in the river comes fromrunoff in the Sierra in California. Upstream agricultural diversions have contributed to reduced inflows, resulting in a declining lake level and increased lake salinity. If the trend continues, the Lahontan cutthroat and the tui chub (an important food source for the trout) may not be able to survive in the lake. To maintain lake salinity at the current level, about 33 taf/yr more inflow is needed. Even with a stable lake level, salinity will slowly increase because Walker Lake has no natural outlet. A solution to Walker Lake problems could affect water users in California and Nevada. Potential tribal water rights claims on the Nevada side of the basin could also affect existing water users.

Lake Tahoe
Lake Tahoe’s clarity has been declining as increasing development around the shoreline increases thesediment load and nutrients reaching the lake. Nutrients, such as nitrogen and phosphorous used in lawn or golf course fertilizers, can enter the lake in the form of storm water runoff. Nutrients promote growth of algae, reducing clarity. Clarity of lakes is measured by the depth to which a Secchi disk, a small plastic disk of specific size, is visible. In the late 1960s, average Secchi disk visibility in Lake Tahoe was about 100 feet. Now the figure is closer to 70 feet. Programs to manage Lake Tahoe water quality by regulating development and preventing pollutants fromreaching the lake are being implemented at the federal, state, and local levels. The Tahoe Regional Planning Agency, a bistate agency created by Congress, sets regional environmental standards, issues land usepermits (including conditions to protect water quality), and takes enforcement actions throughout the basin. TRPA’s regional plan provides for achievementand maintenance of environmental targets by managing growth and development. In addition to itsregulatory activities, TRPA carries out a capital improvement program to repair environmental damage done before its regional plan was adopted. TRPA has identified nearly $500 million in capital improvements needed to achieve environmental targets. Federal, state,and local governments have invested nearly $90 million in erosion control, storm water drainage, stream zone restoration, public transit, and other capital projects. Over 70 percent of the land in the Tahoe Basinis controlled by the USFS’s Lake Tahoe Basin Management Unit. The LTBMU has implemented a watershed restoration program and a land acquisition program to prevent development of sensitive private lands.In recent years, federal and state agencies have increased funding to protect the environment of Lake Tahoe. The State of Nevada approved a $20 millionThe California Water Plan Update B ULLETIN 160-98

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EGIONS 9-9 bond measure to perform erosion control and other measures on the east side of the lake. In California, Proposition 204 provides $10 million in bond fundsfor land acquisition and programs to control soil erosion, restore watersheds, and preserve environmentally sensitive lands.

Leviathan Mine

Leviathan Mine, an abandoned sulfur mine locatedin Alpine County, is one of the most significant abandoned mine sites in the region. From 1863 to 1952, operations at the site involved tunnel mining. Later,the site was converted to an open-pit operation. Under this operation, tailings and overburden materialwere placed in (or washed into) streams, creating water pollution problems with acid mine drainage and metals. The mine was ultimately abandoned, leaving an open pit, waste and spoil areas, and surface water drainage and erosion problems. Neither the owner nor the county had the resources to clean up the site. In 1980, SWRCB approved a pollution abatement project for Leviathan Mine. The remediation projectincluded channeling Leviathan Creek, filling and regrading the mine pit, excavating and regrading thewaste dump, creating onsite evaporation ponds, regrading the spoil areas, and improving drainage. The Stateacquired the site in 1983 and the project was completed in 1985. Although the project reduced theamount of acid mine drainage reaching the creek, contamination problems still occur today from pond overflows, acidic springs, seepage, and erosion. The RWQCB is currently involved in activities to further reduce the pollution.

Sierra Nevada Ecosystem ProjectThe Sierra Nevada Ecosystem Project was an assessment of forests, key watersheds, and significant natural areas on federal lands. In 1996, the University of California released its Sierra Nevada Ecosystem Study

, the result of a three year, congressionally-mandatedstudy of the entire Sierra Nevada, with primary emphasis on gathering and analyzing data to assist Congress in future management of the mountain range. The study stated that “excluding the hard-to-quantify public good value of flood control and reservoir-based recreation, the hydroelectric generating, irrigation, andurban use values of water are far greater than the combined value of all other commodities produced in theSierra Nevada.” The report estimated the value of water at 60 percent of that of all commodities produced in the foothills and mountains of the Sierra Nevada.

January 1997 Flood Event
The January 1997 flood was among the most significant floods on record in the North Lahontan Region. Lake Tahoe recorded its highest level since 1917 at an elevation of 6,229.39 feet. This elevation was the lake’s highest since the 1935 Truckee River Agreement, which limited the operating range of Lake Tahoe’s surface elevation to between 6,223.0 feet (its natural rim) and 6,229.1 feet. Flood damage occurred along the Truckee’s channel immediately downstreamfrom the lake, although the greatest economic damages occurred in the Reno-Sparks area. In California, flooding in downtown Truckee caused the closure of major highways. Downstream from Truckee, the river washed away Floriston Dam, a diversion dam used by Sierra Pacific Power Company to divert water to its run-of-river hydroelectric plant at Farad. Stream flows along the Carson and Walker River systems exceeded previous flood records. Flows along the East Fork Carson River at Markleeville and West Fork Carson River at Woodfords peaked at 21,000 cfs and 8,000 cfs, respectively, considerably above the record peak flows attained in 1963 and in excess of a 100-year flood event for these reaches of the river. The East Walker River near Bridgeport and West Walker River near Coleville peaked at 1,810 cfs and 6,220 cfs, respectively, also above previously record flows. In Mono County, about 8 miles of U.S. Highway 395 were washed out, isolating the communities of Colevilleand Walker. At the lower mouth of the Walker Canyon, homes and properties in the community of Walker were damaged when the West Walker River spilled its banks.

Water Management Options for the North Lahontan Region Table 9-4 shows a list of options for the region, and the results of an initial screening of the options. The retained options were evaluated (Table 9A-1 in Appendix 9A) based on a set of fixed criteria discussedin Chapter 6. Potential options to augment water supplies during drought conditions are water conservation, groundwater pumping, and reservoir construction. Land is idled during droughts if water is not available. In Mono County, cutbacks in surface water deliveriesThe California Water Plan Update B ULLETIN 160-98

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ABLE 9-4 North Lahontan Region List of Water Management Options

Option Retain Reason for Deferral or Defer

Conservation

Urban

Outdoor Water Use to 0.8 ETo Retain

Indoor Water Use Retain Interior CII Water Use Defer No significant depletion reductions attainable. Distribution System Losses Defer No significant depletion reductions attainable. Agricultural

Seasonal Application Efficiency Improvements Defer No significant depletion reductions attainable. Flexible Water Delivery Defer No significant depletion reductions attainable. Canal Lining and Piping Defer No significant depletion reductions attainable. Tailwater Recovery Defer No significant depletion reductions attainable.

Modifying Existing Reservoirs/Operations

— ——
New Reservoirs/Conveyance Facilities Petes Valley Reservoir Defer High costs. Willard Creek Reservoir Defer High costs. Goat Mountain Reservoir Defer High costs. Crazy Harry Gulch Reservoir Defer High costs. Honey Lake Dike and Reservoir Defer Water quality inadequate for agriculture. Very low yields with large estimated capital costs. Long Valley Creek Reservoir Defer Very little firm yield. Hope Valley Reservoir Defer High costs. Leavitt Meadows Reservoir Defer Site is located on the West Walker River, upstream of a reach designated as wild and scenic. Also subject to interstate water issues with Nevada.

Pickle Meadow Reservoir Defer Same concerns as Leavitt Meadows site.

Roolane Reservoir Defer Same concerns as Leavitt Meadows site.

Mountain Lakes Reservoir Defer Same concerns as Leavitt Meadows site.

Groundwater/Conjunctive Use Agricultural Groundwater Development Retain Eastside Warner Mountain Recharge Defer DFG concerns about potential wildlife impacts have diminished local interest in a pilot program and/or reconnaissance level planning study.

Water Marketing

— ——
Water Recycling Water recycling options Defer Water recycling options would not generate new water supply in this region.The California Water Plan Update B ULLETIN 160-98

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EGIONS 9-11during the recent drought resulted in pasture not being irrigated.

Water Conservation

Urban. Urban water demand forecasts for 2020 assume that BMPs are in place; consequently, only those urban conservation efforts which exceed BMPs are considered as options. Urban conservation optionsin this region provide little potential for depletion reductions. Reducing outdoor water use to 0.8 ET

o in new and existing development would only conserve about 1 taf/yr. Likewise, reducing indoor water use to 55 gpcd would conserve about 1 taf/yr. Agricultural. The 2020 agricultural water demand forecasts assume that EWMPs are in place. As withthe urban water management options, only those agricultural conservation efforts which exceed EWMPs are considered as options. The efficiency of border irrigation systems used for alfalfa and pasture can be improved through leveling fields and better managing applications. No significant depletion reductions areexpected in the region, however, since most alfalfa irrigation occurs in Honey Lake Valley where excess applied irrigation water recharges the groundwater basin.

New Reservoirs or Conveyance Facilities In 1992, the Department investigated six potential reservoir sites in Lassen County that could provide up to 20 taf of storage. Sites were located on the Susan River, Willow Creek, and Long Valley Creek. An analysis of project costs indicates that the reservoirs were not economically feasible for agricultural water users in the region.In the late 1950s and early 1960s, the Department examined potential reservoir sites in MonoCounty that could serve agricultural lands in California. USBR, USGS, NRCS, and WRID have studied these and other potential sites in California that couldprovide water for Nevada uses. Projects that serve Nevada only are not included as options. The four potential sites in Mono County located on the West Walker River have similar economic constraints as the sites in Lassen County. They are also subject to interstate water rights concerns.

Groundwater Development or Conjunctive Use Although groundwater is available in the larger valleys used for irrigated agriculture, water needs are usually met from surface water. Groundwater cannotbe economically used to replace surface water uses because of pumping costs. Modoc County Resource Conservation District investigated groundwater recharge on six creeks whichdrain the east slopes of the Warner Mountains in Surprise Valley. This project would recharge the alluvialfans using existing stream channels or constructed recharge facilities. Experimental construction of recharge areas on one or two of the creeks was proposed, but potential environmental impacts and lack of funding prevented implementation. This option was deferred. T

ABLE 9-4 North Lahontan Region List of Water Management Options (continued)

Option Retain Reason for Deferral or Defer
Desalting

Brackish Groundwater

— — —

Seawater

— — —
Other Local Options

— — —
Statewide Options

— — —The California Water Plan Update B ULLETIN 160-98

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ABLE 9-6 Options Most Likely to be Implemented by 2020 (taf) North Lahontan Region

Average Drought Applied Water Shortage a 10 128 Options Likely to be Implemented by 2020

Conservation

— — Modify Existing Reservoirs/Operations

— — New Reservoirs/Conveyance Facilities

— — Groundwater/Conjunctive Use

— — Water Marketing

— — Recycling

— — Desalting

— — Other Local Options

— — Statewide Options

— — Expected Reapplication

— — Remaining Applied Water Shortage 10 128

a Majority of shortages in this region are agricultural. Options Likely to be Implemented in the North Lahontan Region
Water supplies are not available to meet all of the region’s 2020 water demands in average or drought years. Applied water shortages are forecasted to be 10 taf and 128 taf in average and droughtyears, respectively. Ranking of retained water management options for the North Lahontan Region is

T ABLE 9-5 Options Ranking for North Lahontan Region

Option Rank Cost ($/af) Potential Gain (taf) Average Drought

Conservation

Urban

Outdoor Water Use to 0.8 ET

o – New and Existing Development M a 1 1 Indoor Water Use (55 gpcd) M 600 1 1
Groundwater/Conjunctive Use Agricultural Groundwater Development M aaa

a Data not available to quantify. summarized in Table 9-5. Table 9-6 summarizes options that can likely be implemented by 2020 to relieve the shortages. Although groundwater could be developed to help meet drought year water needs, it is not ranked highly due to its cost. During droughts, pasture irrigation will probably continue to be curtailed.The California Water Plan Update B ULLETIN 160-98

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EGIONS 9-13The California Water Plan Update B ULLETIN 160-98

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EGIONS 9-14 F IGURE 9-3 South Lahontan Hydrologic Region

MONO

INYO

SAN BERNARDINO

KERN

LOS ANGELES N E V A D A

M O J A V E D E S E R T Grant Lake

Lake Crowley

Amar

River

Fairmont Reservoir Haiwee Reservoir River Mono Lake

Mo River

Silverwood Lake Owens

jave gosa

Los Angeles Aqueduct

West Branch of California Aqueduct East Branch of California Aqueduct Silver Lake

Soda Lake Tinemaha ReservoirThe California Water Plan Update B ULLETIN 160-98

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EGIONS 9-15 Description of the Area

The South Lahontan Region encompasses the area from the drainage divide between the Walker River and Mono Lake Basin to the divide south of the Mojave River (Figure 9-3). The region is bordered on the east by the Nevada stateline and on the west by the crest ofthe southern Sierra Nevada and San Gabriel Mountains. The region includes all of Inyo County and parts of Mono, San Bernardino, Kern, and Los Angeles Counties. Prominent geographic features of the regionare Owens Valley and Death Valley. The region contains the highest and lowest points in the lower 48 states—Mount Whitney (elevation 14,495 feet) and Death Valley (elevation 282 feet below mean sea level).The region includes several closed drainage basins and many desert valleys containing central playas, or dry lakes. Major waterbodies in the region are, from north to south, Mono Lake, Owens River, and MojaveRiver. The Amargosa River contains water only during rare flash floods. Floodwaters in the Amargosa River would eventually flow south to a sink area at the Silver Lake and Soda Lake Playas. This sink area is also the terminus of the Mojave River, which flows eastward from its headwaters in the San Bernardino Mountains across the Mojave Desert to the playa lakes. Averageannual precipitation for the region’s valleys ranges between 4 and 10 inches. Death Valley receives only 1.9 inches annually. The Sierra Nevada can receive up to 50 inches annually, much of it in the form of snow. In some years, the community of Mammoth Lakes can have snow accumulations of more than 10 feet.

The Joshua Tree, a member of the yucca family, is endemic to the

Mojave Desert. . . . 

# South Lahontan Hydrologic RegionThe California Water Plan Update B ULLETIN 160-98

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EGIONS 9-16 Although sparsely populated, the region containssome rapidly growing urban areas, including the Cities of Lancaster and Palmdale in Antelope Valley (Los Angeles County) and the Cities of Victorville, Hesperia, and Apple Valley in San Bernardino County. Many residents in these areas have chosen a long commuteto the greater Los Angeles area in exchange for affordable housing. Future population growth in the region is expected to be concentrated in communities within commuting distance of the Los Angeles area. Bishop, Ridgecrest, and Barstow are other population centers in the region. The economies of these and other small towns in the eastern part of the region are tied to theregion’s military facilities and other governmental employers, and to providing services for travelers and tourists. Public lands constitute about 75 percent of the region’s area, providing a major recreational resource. Popular destinations in the region include the Mono Lake area, June Lakes and Mammoth Lakes, Inyo National Forest, Death Valley National Monument, and the recently created Mojave National Preserve. Only about 1 percent of the region’s land is used for urban and agricultural purposes. Most of the irrigated acreage, primarily alfalfa and pasture, is in theMono-Owens PSA. (This PSA includes Owens Valley, the Lake Crowley area northwest of Bishop, andHammil and Fish Lake Valleys.) Some deciduous orchard acreage is found in the western part of the region. Table 9-7 shows population and crop acreage for the region. Major perennial waterbodies in the region are Mono Lake and Owens River. Since relatively little surface water is available in the rest of the region, the region’s environmental water use is concentrated in theMono Lake-Owens Valley corridor. The major environmental water use requirements are associated with maintenance of Mono Lake levels and fishery instream flow requirements for the Owens River system. DFG operates four fish hatcheries in the Mono-Owens area: Mt. Whitney, Big Springs, Hot Creek, and Black Rock Hatcheries.The largest surface water development in the region is the Los Angeles Aqueduct and its associated facilities, described in the following section. There arealso a few relatively small, high-elevation dams operated by Southern California Edison for nonconsumptive hydropower purposes. These dams do not provide water supply for the region. SWP’s75 taf Lake Silverwood on the East Branch of the California Aqueduct regulates and stores imported water.

Water Demands and SuppliesThe water budget for the South Lahontan Region is shown in Table 9-8. Increased environmentalwater demands from recently settled court actions involving LADWP’s water diversions from the Owens Valley and Mono Lake are reflected in the base water budget. A pending order issued by an air pollution control district in 1997 could increase environmentalwater demands in the region. This increase is not included in the water budget because final action hasnot yet been taken (see the local water resources management issues section).
Los Angeles Aqueduct The Los Angeles Aqueduct is the region’s major water development feature, although it does not serve water to the region. In 1913, the first pipeline of LAA was completed and began conveying water from Owens Valley to the City of Los Angeles. The aqueduct wasextended north of the Mono Basin and diversions beThe Owens River, with the Sierra Nevada in the background. T ABLE 9-7 Population and Crop Acreage

Population Irrigated Crop Acreage (thousands) (thousands of acres)

1995 713 61
2020 2,019 45The California Water Plan Update B ULLETIN 160-98

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EGIONS 9-17 gan in 1940. A second pipeline was completed in 1970, increasing the aqueduct’s annual delivery capacity to about 550 taf/yr. Both aqueducts terminate at the 10 taf Los Angeles Reservoir in the South Coast Region. The first aqueduct begins at the intake on Lee Vining Creek and the second begins at Haiwee Reservoir. There are eight reservoirs in the LAA system with a combined storage capacity of about 323 taf (Table 9-9). These reservoirs were constructed to store andregulate flows in the aqueduct. The northernmost reservoir is Grant Lake in Mono County. Six of the eight reservoirs are located in the South Lahontan Region. Bouquet and Los Angeles Reservoirs are in the South Coast Region. Water from both aqueducts passes through 12 powerplants on its way to Los Angeles. The annualenergy generated is over 1 billion kWh, enough to supply the needs of 220,000 homes.

State Water ProjectThe East Branch of the California Aqueduct follows the northern edge of the San Gabriel Mountains, bringing imported water to Silverwood Lake. Table 9- 10 shows SWP contractors in the region and their contractual entitlements.Antelope Valley-East Kern Water Agency, the largest SWP contractor in the region, serves 5 major and 16 small municipal agencies, as well as Edwards AFB, Palmdale Air Force Plant 42, and U.S. Borax andChemical Facilities. AVEK was formed to bring imported water into the area.Mojave Water Agency was created in 1960 in response to declining groundwater levels in the area. Communities within MWA’s boundaries have nosource of supply other than groundwater. CommuniT

ABLE 9-8 South Lahontan Region Water Budget (taf) a

1995 2020 Average Drought Average Drought

Water Use

Urban 238 238 619 619 Agricultural 332 332 257 257 Environmental 107 81 107 81 Total 676 651 983 957 Supplies

Surface Water 322 259 437 326 Groundwater 239 273 248 296 Recycled and Desalted 27 27 27 27 Total 587 559 712 649 Shortage 89 92 270 308

a Water use/supply totals and shortages may not sum due to rounding.

T

ABLE 9-9 Los Angeles Aqueduct System Reservoirs

Reservoir Capacity (taf) County

Grant 47 Mono Crowley 183 Mono Pleasant Valley 3 Inyo Tinemaha 6 Inyo Haiwee 39 Inyo Fairmont 0.5 Los Angeles Bouquet 34 Los Angeles Los Angeles 10 Los Angeles

T ABLE 9-10 SWP Contractors in the South Lahontan Region

Contractor Annual Entitlement (taf) 1995 Deliveries (taf) Antelope Valley-East Kern WA 138.4 47.3 Crestline-Lake Arrowhead WA 5.8 0.4 Littlerock Creek ID 2.3 0.5 Mojave WA 75.8 8.7 Palmdale WD 17.3 7.0The California Water Plan Update B ULLETIN 160-98

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EGIONS 9-18 ties served by MWA include Barstow, Apple Valley,Hesperia, and Victorville. While most of MWA’s service area is within the South Lahontan Region, theservice area extends into the Colorado River Hydrologic Region (the Lucerne and Johnson Valleys and the Morongo Basin). Part of MWA’s SWP entitlement (7.3 taf) is allocated to that area. MWA has taken little of its SWP entitlement to date, due to lack of conveyance facilities. In 1994, MWA completed its Morongo Basin pipeline, a 71- mile pipeline with a capacity of 100 cfs from the SWP’s East Branch to the Mojave River (7 miles) and then20 cfs to Morongo Basin and Johnson Valley. This pipeline allows MWA to bring SWP water into part of its large (almost 5,000 square miles) service area. In 1997, MWA began construction of its 71-mile Mojave River Pipeline (94 cfs capacity) to bring imported water toBarstow and neighboring cities. The El Mirage Aqueduct is the next proposed addition to its distribution system. The aqueduct would deliver approximately 4 taf of imported water annually from the East Branch to the westernmost subarea of the Mojave River Basinnear El Mirage. Imported water would be used to recharge the area’s overdrafted groundwater basin.In 1997, MWA and Berrenda Mesa Water District (a member agency of KCWA) concluded thepermanent transfer of 25 taf of SWP annual entitlement, thereby increasing MWA’s total annual entitlement to 75.8 taf. Local Surface Water SuppliesThe Mammoth Community Water District supplies the town of Mammoth Lakes, located at the northern end of the region. About 70 percent of MCWD’s supply comes from Lake Mary, the largest of a number of small alpine lakes in the Mono Lakes Basin. At present, the remainder of MCWD’s supply comes from groundwater. Although MCWD serves a permanent population of only about 5,000 people, its average daily population is about 13,000, with peak weekends and holiday periods reaching 30,000 people per day. These wide fluctuations in service levels above the base population are typical of the recreational and resort communities in the area. Although the Mojave River appears on maps as a major waterway in the region, it is an ephemeral stream for much of its length. Local communities extract groundwater, which is recharged by river flows, but do not directly divert significant amounts of surface water from the river. There is one dam on the Mojave River at the base of the San Bernardino Mountains— Mojave River Forks Dam, a 90 taf USACE flood control facility. The 3.5 taf capacity Littlerock Reservoir provides water supply to Littlerock Creek Irrigation District and to Palmdale Water District. PWD funded most of a recent seismic rehabilitation of the 1924-vintage dam in exchange for control of the water supply for 50 years. Water from Littlerock Reservoir may be released into a ditch that conveys flows to PWD’s Lake Palmdale, a 4.2 taf storage reservoir.In the San Bernardino Mountains, Lake Arrowhead, owned by the Arrowhead Lake Association, is a 48 taf reservoir providing recreational opportunities and water supply for lakeshore residents.

Groundwater SuppliesHistorically the South Lahontan Region has relied mostly on groundwater, which is the only watersupply available in most parts of the region. Groundwater basin capacities in the Mojave River and Antelope Valley PSAs, for example, total about 70 maf each. (Economically usable storage is significantly less than this amount.) Water quality influences groundwater use. Some areas in the Mono-Owens area have highly mineralized groundwater due to geothermal activity, while saline groundwater is not uncommon in areas near playa lakes. The Mojave River groundwater basin is a large alluvial formation in the Mojave Desert, the only local Littlerock Reservoir is one of the few surface water storage facilities in the Mojave Desert area. The original dam at this site was a multi-arch concrete structure. This photo shows the dam after its seismic rehabilitation.The California Water Plan Update B ULLETIN 160-98

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EGIONS 9-19 water source for residents in the western third of SanBernardino County (part of the basin is in the Colorado River Region). The Mojave River and groundwater basin act as one water source, with theriver recharging the basin and groundwater discharging in several places to provide surface flows in the river. The basin is divided into subareas at hydrogeologic boundaries including the Helendale and Waterman Faults. The operational storage capacity of the basin is about 4.9 maf; currently there is about 3.0 maf of water in storage. The basin has experienced declining groundwater levels due to overextractions (see Mojave River adjudication section). The Antelope Valley groundwater basin underlies the closed drainage in the westernmost part of theMojave Desert in northern Los Angeles and southeastern Kern Counties. It provides most of the local water supplies to users in the high desert from the San Gabriel Mountains to the Sierras, including Edwards Air Force Base. Agricultural pumping from the basin has declined for several decades while urban extraction has increased due to rapid population growth.

Local Water Resources Management Issues

Owens Valley Area In 1972, Inyo County filed suit against the City of Los Angeles, claiming that increased groundwater pumping for the second aqueduct was harming the Owens Valley environment. Inyo County asked that LADWP’s groundwater pumping be analyzed in an Surface water is found in most desert waterways only

after infrequent storms. If local groundwater resources

are not sufficient to supply an area’s needs, water must be imported to augment local supplies. This photo shows

the Mojave River bed at Red Rock Canyon.

Searles Lake

The Mojave Desert has numerous playa lakes, dry or semi-dry lakebeds that occupy topographic low points in closed drainage basins. Playa lakes contain surface water only briefly after the region’s infrequent rains. There may, however, be high groundwater levels immediately beneath an apparently dry lakebed. Groundwater found near these lakebeds is usually too mineralized for most beneficial uses, because salts have been concentrated in lakebed deposits during evaporation of the surface waters. Searles Lake in northwestern San Bernardino County is an example of an extremely mineralized playa lake.

Within geologic time, California’s climate was much wetter than it is today. During the late Quaternary Period, the Owens River flowed into several (now dry) lakes in the Mojave Desert, filling Searles Lake to a depth of over 600 feet. Long-term deposition of evaporates in the lakebed created thick layers of salts and borate minerals. These deposits have been the basis of extensive mining operations at the lake, estimated to have produced more than $1 billion worth of mineral commodities.

Borax mining at the lakebed began as early as 1874. Current mining techniques entail pumping brines from lakebed sediments and processing them at onsite chemical plants to produce commodities such as sodium carbonate, sodium borate, and sodium sulfate. These chemicals are used in the manufacture of drugs, dyes, glass, glazes, paper, soap, detergent, enamel, chemical products, abrasives, gasoline additives, fire retardants, and metal alloys.The California Water Plan Update B ULLETIN 160-98

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EGIONS 9-20 EIR. LADWP prepared an EIR in 1976 and another in 1979, both of which the Third District Court of Appeals found inadequate. In 1983, Inyo County and LADWP decided to work together to develop an EIR and water management plan to settle the litigation. A third EIR was prepared jointly by LADWP andInyo County and released in 1990. In 1991, both parties executed a long-term water management agreement delineating how groundwater pumping and surfacewater diversions would be managed to avoid significant decreases in vegetation, water-dependent recreational uses and wildlife habitat. Several entities challenged the adequacy of the EIR and in 1993 were granted amici curiae status by the Court of Appeals, allowing them to enter in the EIR review process. Anagreement was subsequently executed in 1997, ending 25 years of litigation between Los Angeles and Inyo County. LADWP and Inyo County have begun discussions on how to implement provisions of the agreements and EIR. Timelines for many provisions have already been developed and plans for major activities such as rewatering the Lower Owens River are under review.Surface water diversions for Owens Valley agriculture from the Owens River began in the 1800s. The Los Angeles Aqueduct was completed in 1913. Owens Lake became a dry lakebed by 1929. On windy days, airborne particulates from the dry lakebed violate air quality standards in the southern Owens Valley. In 1997, the Great Basin Unified Air Pollution Control District ordered the City of Los Angeles to implement control measures at Owens Lake to mitigate the dust problems. Under the order, 8,400 acres of lakebed would be permanently flooded with a few inches of water, another 8,700 acres would be planted with grass and irrigated, and 5,300 acres would be covered with a four-inch layer of gravel. This order could reduce the city’s diversions by 51 taf/yr or about 15 percent of its supply. In July 1998, a compromise was reached when LADWP agreed to begin work at Owens Lake by 2001 and to ensure that federal clean air standards would be met by 2006. In turn, the APCD agreed to scale back the improvements sought in its 1997 order.Under this agreement, LADWP’s dust-control strategy may include shallow flooding, vegetation planting, and gravel placement. The implementation schedule requires that 6,400 acres of lakebed be treated by the end of 2001. By the end of 2006, an additional 8,000 acres would be treated, plus any additional lakebed necessary to bring particulate counts into compliance with federal air quality standards. The plan hinges on final approval from the Los Angeles City Council, the APCD’s board, and the State Air Resources Board. Theagreement also requires EPA to grant a 5-year extension of Clean Air Act requirements that direct statesto abate particulate pollution by 2001 or seek an extension until 2006.

Mono Basin
Mono Lake, located east of Yosemite National Park at the base of the eastern Sierra Nevada, is the secondlargest lake completely within California. It is recognized as a valuable environmental resource. The lake is famous for its tufa towers and spires, structures formed by years of mineral deposition by its saline waters. The lake has no outlet. There are two islands in the lake that provide a protected breeding area forlarge colonies of California gulls and a haven for migrating waterfowl. Much of the water flowing into Mono Lake comesfrom snowmelt runoff. Since 1941, LADWP has diverted water from Lee Vining, Walker, Parker, and Rush Creeks into tunnels and pipelines that carry the water to the Owens Valley drainage. There it is conveyed, together with Owens River flows, to Los Angeles via the LAA. Diversions from its tributaries lowered Mono Lake’s water level from elevation 6,417 feet in 1941 to a historic low of 6,372 feet in 1981. With decreasedinflow of fresh water, the lake’s salinity increased dramatically. When water levels drop to 6,375 feet orlower, a land bridge to Negit Island is created, allowing predators to reach gull rookeries; this first happened in 1978 and again during the 1987-92 drought.As a result of these impacts, the lake and its tributaries have been the subject of extensive litigation between the City of Los Angeles and environmental groups since the late 1970s. In 1983, the California Supreme Court ruled that SWRCB has authority toreexamine past water allocation decisions and the responsibility to protect public trust resources where feasible. SWRCB issued a final decision on Mono Lake (Decision 1631) in 1994. The amendments toLADWP’s water right licenses are set forth in the order accompanying the decision. The order sets instream flow requirements for fishin each of the four streams from which LADWP diverts water. The order also establishes water diversion criteria to protect wildlife and other environmental resources in the Mono Basin. These water diversionThe California Water Plan Update B ULLETIN 160-98

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EGIONS 9-21 criteria prohibit export of water from Mono Basin until the lake level reaches 6,377 feet, and restrict Mono Basin water exports to allow the lake level to rise to an elevation of 6,391 feet in about 20 years. Once the water level of 6,391 feet is reached, it is expected thatLADWP will be able to export about 31 taf/yr of water from the basin. The order requires LADWP to prepare restoration plans for the four streams from which it diverts and to restore part of the waterfowl habitat which was lost due to lake level decline. In May1997, parties to the restoration planning process presented a signed settlement on Mono Basin restoration to the SWRCB. If approved, the settlement would guide restoration activities and annual monitoring through 2014. Parties to the settlement include LADWP, the Mono Lake Committee, DFG, State Lands Commission, DPR, California Trout, National Audubon Society, USFS, BLM, and The Trust for Public Land. Key features of stream restoration plan include restoring peak flows to Rush, Lee Vining, Walker, and Parker Creeks; reopening abandoned channels in Rush Creek; and developing a monitoring plan. One of the restoration actions required by SWRCB—bypassingsediment around LADWP diversion dams—was deferred for further analysis. The waterfowl habitatrestoration plan proposes that a Mono Basin waterfowl habitat restoration foundation administer a $3.6million trust established by LADWP. Five of the parties to the agreement would serve as initial members of the foundation. Activities would include annual monitoring, restoring open water habitat adjacent to the lake, and rewatering Mill Creek. LADWP would continue its brine shrimp productivity studies, open several channels on Rush Creek, and make its Mill Creek water rights available for rewatering Mill Creek, based on the recommendations of the foundation. The plans are being considered by SWRCB and a decision is expected at the end of 1998.
Mojave River AdjudicationThe Mojave River groundwater basin has experienced overdraft since the early 1950s, with the largest increase in overdraft occurring in the 1980s. About 80 percent of basin recharge comes from the Mojave River.In 1990, the City of Barstow filed a complaint in Superior Court against the City of Adelanto seeking an average annual guaranteed flow of 30 taf to mitigate reduced runoff and declining groundwater levels in the Barstow area. The complaint also requested a writ of mandate against MWA to compel it to import waterfrom the SWP. MWA filed a cross-complaint requesting a determination of water rights in the basin. In 1991, the court ordered that the litigation beplaced on hold to give parties time to negotiate a settlement and to develop a solution to the overdraft. A Mojave Basin adjudication committee was formed tofacilitate data gathering and to draft a stipulated judgment and physical solution. The court’s final ruling on basin adjudication was issued in January 1996. In its ruling, the court emphasized that the area has been in overdraft for decades and that MWA must alleviateoverdraft through conservation and purchase of supplemental water. MWA was appointed as the basin

watermaster.The adjudication stipulated that any party pumping more than 10 af/yr became a party to the judgment and is bound by it. The judgment stated that each party has a right to its base annual production, which wasits highest usage between 1986 and 1990. The judgment also required MWA to reduce this amount by at least 5 percent each year for four years as one way toachieve a physical solution to the longstanding overdraft. Any party exceeding its annual allotment must purchase replenishment water from MWA or from other parties to the judgment. If there is still overdraft after the end of the first five years of the stipulated judgment, water use in overdrafted subareas will be further reduced. The judgment recognized five basin subareas and required that if an upstream subarea does not meet its obligation to a downstream subarea, the upstream area must pay for supplemental water. Supplemental water for the Mojave River Basin will come from MWA’s SWP entitlement, or from water marketing arrangements, and will be delivered through the California Aqueduct. In March 1997, MWA began constructing its Mojave River pipeline,extending about 71 miles from the California Aqueduct to Newberry Springs, a rural community east of Barstow. MWA also recently purchased the permanent right to 25 taf of additional SWP annual entitlement,nearly a 50 percent increase from the agency’s previous entitlement. The combination of reduced pumping, increased SWP deliveries and other imports,and new delivery facilities are expected to reduce overdraft in the basin.

Antelope Valley Water Management The Antelope Valley Water Group was formed in1991 to provide coordination among valley water agenThe California Water Plan Update B ULLETIN 160-98

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EGIONS 9-22 cies and other interested entities. AVWG members include the Cities of Palmdale and Lancaster, Edwards AFB, AVEK, Antelope Valley United Water Purveyors Association, Los Angeles County Waterworks Districts, PWD, Rosamond Community Services District, and Los Angeles County. AVWG completed an Antelope Valley water resources study in 1995 to address regional water management issues.The study evaluated the valley’s existing and future water supplies from groundwater, the SWP, Littlerock Reservoir, and recycling, and compared thesesupplies with projected water demands. The study concluded that water supply reliability is low in the study area—full 1998 demands would be met only half the time without overdrafting groundwater resources. The study recommended water conservation, recycling, and conjunctive use measures to reduce expected shortages. The study identified three sites (two on AmargosaCreek and one on Littlerock Creek) with high potential for groundwater recharge through spreading and identified SWP water, recycled water, and local runoffas potential recharge sources. The study also identified several potential groundwater injection sites within existing Los Angeles County Waterworks and PWDmunicipal wellfields. Treated SWP water was identified as a potential recharge source. In 1996, PWD adopted a water facilities master plan for its service area, updating a 1988 plan. PWDrelies on three water sources: Littlerock Reservoir, local groundwater, and SWP water. The plan indicatesthat about 40 percent of PWD supply is from groundwater. Declining groundwater levels have been a local concern in the Palmdale area, although extractions presently appear to be within the basin’s perennial yield.The plan also indicates that existing supplies are insufficient to meet drought demands. Average year shortages are projected to occur by 2005. To meet drought year demands, the plan calls for the construction of up to 12 new production wells. The plan’s draft EIR identified declining groundwater levels as an unavoidable impact of constructing new wells. Mitigation measures recommended includedconservation and drought year demand reduction, conjunctive use programs (as identified in the AntelopeValley water resources study), acquisition of an additional 3.1 taf/yr of SWP entitlement, participation in water transfers, and development of recycled water.

Interstate Groundwater Basins

California and Nevada share three interstate groundwater basins in the South Lahontan Region: Fish Lake Valley, crossed by Highway 168 east of Westgard Pass; Pahrump Valley, located to the east of Death Valley; and Mesquite Valley, just south ofPahrump Valley. Groundwater extraction on the California side of the border supports small-scale agricultural development, largely for alfalfa. Pahrump Valley is the most populated of the three valleys; most of its development is located in Nevada around thecommunity of Pahrump. Pahrump and Mesquite Valleys are within about 35 miles of the rapidly growing Las Vegas metropolitan area. In the early 1990s, theSouthern Nevada Water Authority proposed exporting groundwater from several rural counties in central Nevada to help meet Las Vegas’ rapidly increasing need for water. Opposition by rural Nevada counties to SNWA’s proposal caused SNWA to defer this project. Inyo County residents have historically been concernedabout the proximity of Las Vegas to the interstate basins, although no new interstate issues have come up since SNWA’s proposed project.

Water Management Options for the South Lahontan Region Table 9-11 shows a list of options for the region, and the results of an initial screening of the options. The retained options were evaluated (Table 9A-2 in Appendix 9A) based on a set of fixed criteria discussed in Chapter 6.

Water Conservation

Urban. Urban water demand forecasts for 2020 assume that BMPs are in place; consequently, only those urban conservation efforts which exceed BMPs are considered as options. Reducing outdoor water use to 0.8 ET

o in new development would attain 20 taf/yr of depletion reductions, while extending this measureto include existing development would reduce depletions by 31 taf/yr. Reducing residential indoor wateruse to 60 and 55 gpcd would attain depletion reductions of 7 and 15 taf/yr, respectively. Reducing CIIwater use by an additional 3 and 5 percent would attain 2 and 4 taf/yr of depletion reductions, respectively.Reducing distribution system losses to 7 and 5 percent would save 4 and 12 taf/yr, respectively. Agricultural. The 2020 agricultural water demand forecasts assume that EWMPs are in place. As withthe urban water management options, only those agricultural conservation efforts which exceed EWMPsThe California Water Plan Update B ULLETIN 160-98

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EGIONS 9-23 T

ABLE 9-11 South Lahontan Region List of Water Management Options

Option Retain Reason for Deferral or Defer

Conservation

Urban

Outdoor Water Use to 0.8ET

o Retain Indoor Water Use Retain
Interior CII Water Use Retain Distribution System Losses Retain Agricultural

Seasonal Application Efficiency Improvements Retain Flexible Water Delivery Defer No significant depletion reductions attainable. Canal Lining and Piping Defer No significant depletion reductions attainable. Tailwater Recovery Defer No significant depletion reductions attainable.

Modify Existing Reservoirs/Operations Remove Sediment from Littlerock Reservoir Defer Excessive costs for additional yield.

New Reservoirs/Conveyance Facilities

— ——
Groundwater/Conjunctive Use

— ——
Water Marketing Mojave Water Agency Retain Palmdale Water District Retain

Water Recycling Water recycling options Defer Water recycling options in this region do not generate new water supply.

Desalting

Brackish Groundwater

— —— Seawater

— ——
Other Local Options Line Palmdale Ditch Defer No net increase in supply. Reduce Outflow to Playa Lakes Defer Restrictions on use of flows that provide recharge to overdraft basins. Costs are high and water quality is poor.

Statewide Options — — See Chapter 6.

are considered as options. It is estimated that water savings of 2, 3, and 5 taf/yr could be achieved in this region, by improving SAE to 76, 78, and 80 percent, respectively. Options for flexible water delivery and canal lining and piping are not feasible in this region because most water supply comes from individual wells with minimal conveyance facilities. Modify Existing Reservoirs or Operations

Sediment has accumulated in Littlerock Reservoirand minor additional yield could be realized by removing the sediment. Studies are now under way toevaluate the costs and benefits of this option. Preliminary estimates indicate that the cost of this option is in the order of $2,000/af. Because of the high costs, this option was deferred.The California Water Plan Update B ULLETIN 160-98

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EGIONS 9-24 New Reservoirs or Conveyance Facilities There are no proposed new reservoir developments in this region. The region’s aridity and consequent lackof surface water resources make new reservoirs infeasible. Future local water resources development will be based on groundwater sources.
Water Marketing The California Aqueduct could convey purchased water to MWA’s distribution system to supply some ofthe region’s rapidly urbanizing areas. MWA has entered into a multi-year banking and exchangeagreement with Solano County Water Agency. During wet years, SCWA can bank up to 10 taf of its annualSWP entitlement in MWA’s groundwater basin. During drought years, SCWA can take part of MWA’s SWP entitlement in exchange (up to half the banked amount with a maximum of 10 taf/yr). MWA is also pursuing two demonstration water marketing projects of 2 taf each. PWD is seeking to purchase 3.1 taf/yr of SWP entitlement from Central Valley agricultural water purveyors. Other voluntary marketing arrangementscould be developed through option agreements, storage programs, and purchases of water through the DWB or other spot markets. Capacity has been developed to store additional imported supplies in the Mojave River Basin at MWA’s Rock Springs groundwater recharge facility near Hesperia. Additional recharge facilities in the Barstowarea are in the final planning stages, which would further increase MWA’s ability to take delivery of imported supplies when its Mojave River Aqueduct is completed. Sufficient basin storage is available to store water inwet years when more SWP supplies or purchased supplies might be available.
Water RecyclingWater recycling options are deferred for this region because planned projects would not generate new supply.
Other Local OptionsThe ditch that conveys water from Littlerock Reservoir to Palmdale Lake has an estimated 20 percentconveyance loss, which could be reduced by canal lining. Canal lining would reduce groundwater recharge by approximately 1 taf/yr, resulting in no net increase in water supply. This option was deferred. Some flow of the Mojave River reaches Soda Lake where the flow is lost to evaporation. Annual outflow past Afton Canyon averages 8.4 taf. However, the basin adjudication restricts use of flows that provide recharge to downstream subareas of the basin that arein overdraft. Reducing outflow to Soda Lake was deferred as an option. Likewise, local storm runoff collects in many small playas throughout the basin. These playas generally do not contribute to groundwater recharge, due to the low permeability of playa soils. Water collected in theplayas evaporates, rather than recharging groundwater. Diversion or collection of runoff to playas and recharging it to groundwater basins could increase groundwater supplies by eliminating the evaporation. Six dry lakebeds could potentially store an additional 1.8 taf once every five years. Costs for this option are$1,000 to $3,300/af. Water quality at the playas is generally poor, with high levels of salts and minerals. This option was deferred.

Statewide Options Statewide water supply augmentation options are discussed and quantified in Chapter 6.

Options Likely to be Implemented in the South Lahontan Region Water supplies are not available to meet all of the region’s 2020 water demands in average or drought years. Applied water shortages are forecasted to be 270 taf in average years and 308 taf in drought years. Most of the region’s shortage will be in the Mojave River planning subarea. Water shortages in the AntelopeValley subarea are forecast only in drought years. Ranking of retained water management options for the South Lahontan Region is summarized in Table 9-12.Table 9-13 summarizes options that can likely be implemented by 2020 to relieve the shortages. The options likely to be implemented in this region include SWPsupplies and water transfers conveyed by the California Aqueduct.The California Water Plan Update B ULLETIN 160-98

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EGIONS 9-25 T

ABLE 9-13 Options Most Likely to be Implemented by 2020 (taf) South Lahontan Region

Average Drought Applied Water Shortage 270 308 Options Likely to be Implemented by 2020

Conservation 56 56 Modify Existing Reservoirs/Operations - - New Reservoirs/Conveyance Facilities - - Groundwater/Conjunctive Use - - Water Marketing 7 6 Recycling - - Desalting - - Other Local Options - - Statewide Options 174 204 Expected Reapplication 33 42

Total Potential Gain 270 308 Remaining Applied Water Shortage 0 0 T

ABLE 9-12 Options Ranking for South Lahontan Region

Option a Rank Cost ($/af) Potential Gain (taf) Average Drought

Conservation

Urban

Outdoor Water Use to 0.8 ET

o -New Development M 750 20 20 Outdoor Water Use to 0.8 ET

o -New and Existing Development M b 31 31 Indoor Water Use (60 gpcd) M 400 7 7 Indoor Water Use (55 gpcd) M 600 15 15 Interior CII Water Use (3%) M 500 2 2 Interior CII Water Use (5%) M 750 4 4 Distribution System Losses (7%) M 200 4 4 Distribution System Losses (5%) M 300 12 12 Agricultural

Seasonal Application Efficiency Improvements (76%) H 100 2 2 Seasonal Application Efficiency Improvements (78%) M 250 3 3 Seasonal Application Efficiency Improvements (80%) M 450 5 5

Water Marketing Mojave Water Agency H b 4 4 Palmdale Water District (3.1 taf SWP entitlement) H b 3 2

Statewide Options See Chapter 6.

a All or parts of the amounts shown for highlighted options have been included in Table 9-13.
b Data not available to quantify.The California Water Plan Update B ULLETIN 160-98

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EGIONS 9-26 F IGURE 9-4 Colorado River Hydrologic Region

RIVERSIDE

IMPERIAL SAN BERNARDINO

SAN DIEGO A R I Z O N

A

M E X I C O U T A H

wat River
Coachella

Canal Alamo

er

All American Canal New

River Lake Havasu

Copper Basin Reservoir Gene Wash Reservoir

River Aqueduct

Colorado River Colorado

White er

Salton Sea

Riv Imperial DamThe California Water Plan Update B ULLETIN 160-98

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EGIONS 9-27 Description of the Area

The Colorado River Region encompasses thesoutheastern corner of California. The region’s northern boundary, a drainage divide, begins along the southern edge of the Mojave River watershed in the Victor Valley area of San Bernardino County andextends northeast across the Mojave Desert to the Nevada stateline. The southern boundary is the Mexican border. A drainage divide forms the jagged western boundary through the San Bernardino, San Jacinto, and Santa Rosa Mountains, and the Peninsular Ranges (including the Laguna Mountains). The Nevada stateline and the Colorado River (the boundary withArizona) delineate the region’s eastern boundary (Figure 9-4). Covering over 12 percent of the total land area inthe State, the region is California’s most arid. It includes volcanic mountain ranges and hills; distinctive sand dunes; broad areas of Joshua tree, alkali scrub, and cholla communities; and elevated river terraces. Much of the region’s topography consists of flat plains punctuated by hills and mountain ranges. The San Andreas fault traverses portions of the Coachella and Imperial Valleys. A prominent topographic feature isthe Salton Trough in the south-central part of the region. The climate for most of the region is subtropical desert. Average annual precipitation is much higher inthe western mountains than in the desert areas. Winter snows generally fall above 5,000 feet; snow depthscan reach several feet at the highest levels during winter. Most of the precipitation in the region falls duringthe winter; however, summer thunderstorms can produce rain and local flooding. Despite its dry climate and rugged terrain, the region contains large and productive agricultural areas and popular vacation resorts. Table 9-14 shows the region’s population and crop acreage for 1995 and 2020.

T

ABLE 9-14 Population and Crop Acreage

Population Irrigated Crop Acreage (thousands) (thousands of acres)

1995 533 749 2020 1,096 750

Coachella Valley date palms. The Colorado River Region is the main location in California where dates are grown for commercial production. . . . 

# Colorado River Hydrologic RegionThe California Water Plan Update B ULLETIN 160-98

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EGIONS 9-28 Most of the population is concentrated in the Coachella and Imperial Valleys. Major cities in the Coachella Valley include Palm Springs, Indio, and PalmDesert. Other urban centers in the region are the Cities of El Centro, Brawley, and Calexico in Imperial Valley; the Cities of Beaumont and Banning in the San Gorgonio Pass area; and the Cities of Needles and Blythe along the Colorado River. Agriculture is an important source of income forthe region. Almost 90 percent of the developed private land is used for agriculture, most of which is in the Imperial, Coachella, and Palo Verde Valleys. The primary crops are alfalfa, winter vegetables, spring melons, table grapes, dates, Sudan grass, and wheat. Recreation and tourism are another important source of income for the region. In Coachella Valley, the PalmSprings area and adjoining communities are an important resort and winter golf destination. Recreational opportunities provided by the more than 100 golf courses in the Coachella Valley, water-based recreation on the Colorado River and Salton Sea, and desert camping all contribute to the area’s economy.

Water Demands and SuppliesTable 9-15 shows the water budget for the Colorado River Region. Agricultural water demand makes up the majority of the water use in the region. There are two major areas where water is used for wildlife habitat in the region, the Salton Sea National Wildlife Refuge and the Imperial Wildlife Area. There are also several private wetlands. About 90 percent of the region’s water supply is from surface deliveries from the Colorado River (through the All American and Coachella Canals, local diversions, and the Colorado River Aqueduct by means of an exchange for SWP water). Other supplies are from groundwater, SWP water, local surface water,and recycled water. Bulletin 160-98 base year groundwater overdraft in the region was estimated to be about 70 taf and occurs in the Coachella Valley. Major water agencies in the region are the Palo Verde Irrigation District, Imperial Irrigation District, Coachella Valley Water District, Bard Water District, Mojave Water Agency, Desert Water Agency, and San Gorgonio Pass Water Agency.The region’s primary shortages with existing supplies are expected to occur in the Coachella planningsubarea because of groundwater overdraft. (In the future, reduction in California’s Colorado River wateruse to the State’s basic apportionment creates an average year shortage of as much as 0.9 maf in the South Coast Region. This 2020 shortage is shown in the South Coast water budget.)

Supplies from the Colorado River Most of the water supply in the region comes from the Colorado River, an interstate (and international)river whose use is apportioned among the seven Colorado River Basin states by a complex body of statutes, decrees, and court decisions known collectively as the law of the river. Table 9-16 summarizes key elements of the law of the river. USBR acts as the watermaster for the Colorado River, and all users of Colorado Riverwater must contract with USBR for their supplies. Figure 9-4 shows the locations of key Colorado River storage and conveyance facilities.

T

ABLE 9-15 Colorado River Region Water Budget (taf) a

1995 2020 Average Drought Average Drought

Water Use

Urban 418 418 740 740 Agricultural 4,118 4,118 3,583 3,583 Environmental 39 38 44 43 Total 4,575 4,574 4,367 4,366 Supplies

Surface Water 4,154 4,128 3,920 3,909 Groundwater 337 337 285 284 Recycled and Desalted 15 15 15 15 Total 4,506 4,479 4,221 4,208 Shortage 69 95 147 158

a Water use/supply totals and shortages may not sum due to rounding.The California Water Plan Update B ULLETIN 160-98

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EGIONS 9-29 T

ABLE 9-16 Key Elements of the Law of the River

Document Date Main Purpose
Colorado River Compact 1922 Equitable apportionment of the water from the Colorado River system between the two basins. The Upper Basin and the Lower Basin are each provided a basic apportionment of 7.5 maf annually of consumptive use. The Lower Basin is given the right to increase its consumptive use an additional 1 maf annually.

Boulder Canyon Project Act 1928 Authorized USBR to construct Boulder (Hoover) Dam and the All American Canal (including the Coachella Canal), and gave congressional consent to the Colorado River Compact. Also provided that all users of Colorado River water must enter into a contract with USBR for use of the

water.

California Limitation Act 1929 Limited California’s share of the 7.5 maf annually apportioned to the Lower Basin to 4.4 maf annually, plus no more than half of any surplus

waters.

Seven Party Agreement 1931 An agreement among PVID, IID, CVWD, MWDSC, City of Los Angeles, City of San Diego, and County of San Diego to recommend to the Secretary of Interior how to divide use of California’s apportionment among the California water users. Details are shown in Table 9-17.

U.S. - Mexican Treaty 1944 Guarantees Mexico a supply of 1.5 maf annually of Colorado River water.

U.S. Supreme Court Decree in 1964 Apportions water from the mainstream of the Colorado River among the
A rizona v. California, et al. Lower Division states. When the Secretary determines that 7.5 maf of mainstream water is available, it is apportioned 2.8 maf to Arizona, 4.4 maf to California, and 0.3 maf to Nevada. Also quantifies tribal water rights for specified tribes, including 131,400 af for diversion in California.

Colorado River Basin Project Act 1968 Requires Secretary of the Interior to prepare long-range operating criteria for major Colorado River reservoirs.

U.S. Supreme Court Decree in 1979 Quantifies Colorado River mainstream present perfected rights in the Arizona v. California, et al. Lower Basin states. Hoover Dam and Lake Mead. Lake Mead and Lake Powell are the largest of the Colorado River system
reservoirs.

Courtesy of USBRThe California Water Plan Update B ULLETIN 160-98

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EGIONS 9-30 Within California, local agencies’ apportionments of Colorado River water were established under the Seven Party Agreement (Table 9-17), which has been incorporated into water delivery contracts which the Secretary of the Interior has executed with California water users. Uses occurring within a state are charged to that state’s allocation. Thus, federal water uses or uses associated with federal reserved rights (e.g., tribal water rights) must also be accommodated within California’s basic apportionment of 4.4 maf/yr plus one-half of any available surplus water.The major local agencies in California using Colorado River water in the Colorado River Region are T

ABLE 9-17 Annual Apportionment of Use of Colorado River Water (all amounts represent consumptive use)

Interstate/International

Upper Basin States 7.5 maf (Wyoming, Utah, Colorado, New Mexico, small portion of Arizona)

Lower Basin States 7.5 maf (Arizona, Nevada, California)
Arizona 2.8 maf Nevada 0.3 maf California 4.4 maf

Republic of Mexico a 1.5 maf

a Plus 200 taf of surplus water, when available. Water delivered to Mexico must meet specified salinity requirements.

Intrastate (Seven Party Agreement) b

Priority 1 Palo Verde Irrigation District (based on area of 104,500 acres). Priority 2 Lands in California within USBR’s Yuma Project (not to exceed 25,000 acres). Priority 3 Imperial Irrigation District and lands served from the All American Canal in Imperial and Coachella Valleys, and Palo Verde Irrigation District for use on 16,000 acres in the Lower Palo Verde Mesa.

Priorities 1 through 3 collectively are not to exceed 3.85 maf/yr. There is no specified division of that amount among the three priorities.

Priority 4 MWDSC for coastal plain of Southern California-550,000 af/yr. Priority 5 An additional 550,000 af/yr to MWDSC, and 112,000 af/yr for the City and County of San Diego c

. Priority 6 Imperial Irrigation District and lands served from the All American Canal in Imperial and Coachella Valleys, and Palo Verde Irrigation District for use on 16,000 acres in the Lower Palo Verde Mesa, for a total not to exceed 300,000 af/yr.

Total of Priorities 1 through 6 is 5.362 maf/yr.

Priority 7 All remaining water available for use in California, for agricultural use in California’s Colorado River Basin.

b Indian tribes and miscellaneous present perfected right holders that are not identified in California’s Seven Party Agreement have the right to divert up to approximately 85 taf /yr (equating to about 50 taf/yr of consumptive use) within California’s 4.4 maf basic apportionment. T hese users are presently consumptively using approximately 32 taf/yr (assuming about 25 taf/yr of unmeasured return flow).

cSubsequent to execution of the Seven Party Agreement, San Diego executed a separate agreement transferring its apportionment to MWDSC.

PVID, BWD, IID, and CVWD. The Reservation Division of USBR’s Yuma Project provides water toColorado River Indian tribes in California. The remainder of California’s Colorado River water use occurs in the South Coast Region (Chapter 7). Figure 9-5 is a plot of Lower Basin states’ apportionments compared with historical Colorado River water use. As shown in the figure, California’s use has historically exceeded itsbasic apportionment, because California has been allowed to divert Arizona’s and Nevada’s unused apportionments, and to divert surplus water. With completion of the Central Arizona Project and the 1996 enactment of a state groundwater banking act,The California Water Plan Update B ULLETIN 160-98

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EGIONS 9-31 Arizona used more than its basic apportionment in 1997. Reduction of California’s Colorado River use from current levels to 4.4 maf annually (when surpluswater is not available) has significant water management implications for the South Coast Region. In calendar year 1996, actual consumptive use of theLower Basin states (without considering USBR’s unmeasured return flow credit of 239 taf) was: Nevada 241 taf
Arizona 2,813 taf California 5,256 taf Total Lower Basin 8,310 taf Within the Colorado River Region, IID, BWD, and PVID receive virtually all of their supplies from the Colorado River. IID and CVWD’s Colorado River supplies are diverted into USBR’s All American Canal at Imperial Dam; CVWD is served from the Coachella Branch of the AAC. PVID diverts via the Palo Verde Canal from the Colorado River near Blythe. BWD receives its supplies from facilities of USBR’s YumaProject, which serves lands in both California and Arizona. The interstate allocations provided in the 1922 Compact were made after a period of relatively wet hydrology on the Colorado River. Some have suggestedthat the allocations overstate the river’s normally availT ABLE 9-18
Estimated Colorado River Flow and Uses a
maf Average Flow (1906-95)

Upper Basin 15.1 Lower Basin 1.4 Total 16.5

Current Uses

Upper Basin 3.8 Lower Basin (mainstem) b 7.5 Mexico 1.5 Mainstem Evaporation and Losses 1.9 Total 14.7 Average Flow into Reservoir Storage (16.5 - 14.7) 1.8

a Prepared by the CRB.

b Reflects restriction on MWDSC’s diversion as Central Arizona Project and Southern Nevada Water System increase diversions to Arizona’s and Nevada’s basic apportionments.able water supply, even without consideration of subsequent calls on that water supply for tribal water rights and endangered species fishery water needs. Table 9- 18 provides an overview of average river hydrology. While consumptive use from the mainstem in the Lower Basin is assumed to be its basic apportionmentof 7.5 maf, Upper Basin use is still well below its Colorado River Compact apportionment. Current Basic Apportionment and Consumptive Use of Mainstem Colorado River in Lower Basin F IGURE 9-5V o l u m e i n m a f California Use

Arizona Use

Nevada Use California Basic Apportionment

Arizona Basic Apportionment

Nevada Basic Apportionment

1970 0 1 2 3 4 5 6

1975 1980 1985 1990 1995The California Water Plan Update B ULLETIN 160-98

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EGIONS 9-32 USBR’s Imperial Dam on the Colorado River. The structures in the foreground are a series of desilting basins used to reduce the sediment load of river water before it enters the All American Canal.

Courtesy of USBR

T

ABLE 9-19 SWP Contractors in the Colorado River Region

Maximum Annual Agency Contract Entitlement (taf) SWP Deliveries in 1995 (taf) Coachella Valley WD 23.1 23.1 Desert Water Agency 38.1 38.1 Mojave Water Agencya 75.8 8.7 San Gorgonio Pass Water Agency 17.3 0

a Contract entitlement covers both South Lahontan and Colorado River Regions; 7.3 taf of this amount is allocated to Colorado River Region. projections are that the Upper Basin will not reach its full Compact apportionment until after 2060.

Supplies from Other Sources Local agencies contracting with the SWP for part of their supplies are shown in Table 9-19. Neither CVWD nor DWA have facilities to take direct delivery of SWP water. Instead, both agencies have entered into exchange agreements with MWDSC, whereby MWDSC releases water from its Colorado River Aqueduct into the Whitewater River for storage in the upper Coachella Valley groundwater basin. In turn, MWDSC takes delivery of an equal amount of the agencies’ SWP water. San Gorgonio Pass Water Agency, which serves the Banning/Beaumont area, also lacks the facilities to take delivery of SWP water, and to date has received no actual supply from the SWP.SGPWA will receive SWP supply when the Department completes its extension of the East Branch of the California Aqueduct in 2000.Groundwater, local surface water, and water recycling provide the remaining supplies for this region.CVWD, working with DWA, has an active groundwater recharge program for the upper end of the Coachella Valley (generally, the urbanized part of the valley). CVWD recharges groundwater with imported Colorado River supplies and with Whitewater River flows using percolation ponds constructed in the Windy Point area. CVWD and DWA levy extraction fees on larger groundwater users in the upper CoachellaThe California Water Plan Update B ULLETIN 160-98

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EGIONS 9-33 Valley. Imperial Valley, the largest water-using area in the region, does not have significant supplies of usable groundwater.

Local Water Resources Management Issues

Management of California’s Colorado River Water
The major water management issue in this region is California’s use of Colorado River water in excess of its basic annual apportionment of 4.4 maf. In the past, Arizona and Nevada were not using the full amount of their basic apportionments, and in accordance with the law of the river, California was able to use the amount apportioned to, but not used by, Nevada and Arizona. Discussions among the seven basin states andten Colorado River Indian Tribes over changes to Colorado River operating criteria and ways for California to reduce its Colorado River water use began as early as 1991. The drought in Northern California prompted California to request that USBR make surplus wateravailable, so that maximum use could be made of Colorado River water in Southern California. These discussions over changes to reservoir operations and howsurplus or shortage conditions could be established continued for a time in a forum known as the “7/10 process.” More recently, the California local agencies, working through the Colorado River Board of California, have been developing a proposal for discussion withthe other basin states to illustrate how, over time, California would reduce its use to the basic apportionment of 4.4 maf/yr. Drafts of the proposal, known as the Colorado River Board draft 4.4 Plan, have been shared with the other states. Efforts are being made to reach intrastate consensus on the plan in 1998. As Bulletin 160-98 goes to press, the most current version of thedraft plan is the December 1997 version. The following text is based on that version. As currently formulated, the draft plan would be implemented in two phases. The first phase (betweenthe present and 2010 or 2015) would entail implementing already identified measures (such as waterconservation and transfers) to reduce California’s Colorado River water use to about 4.6 to 4.7 maf/yr. The second phase would implement additional measures to reduce California’s use to its basic annual 4.4 maf apportionment in those years when neither surplus water nor other states’ unused apportionments was available. One of the fundamental assumptions madein the plan is that MWDSC’s Colorado River Aqueduct will be kept full, by making water transfers fromagricultural users in the Colorado River Region to urban water users in the South Coast Region. (The Colorado River Aqueduct’s capacity is a maximum of

Imperial Irrigation District,

formed in 1911, acquired conveyance facilities constructed by a bankrupt privately owned irrigation company. In 1918, IID constructed Rockwood Heading (shown here) on the original canal system. Keeping the canal system from being choked by the Colorado River’s high sediment loading was difficult; note the dredge shown in the background. These early facilities were subsequently replaced by the All American Canal.

Courtesy of Imperial Irrigation District.The California Water Plan Update B ULLETIN 160-98

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EGIONS 9-34 1.3 maf/yr. However, as shown in Table 9-17, MWDSC has a fourth priority right to only 550 taf annually—the remaining capacity of the aqueduct has historically been filled with unused apportionment water of other entities or with water from hydrologic surpluses.) In the December 1997 draft plan, specific actions were included in the first phase: core water transfers (every year water transfers) such as the existing IID/ MWDSC agreement and the proposed IID/SDCWA transfer; seepage recovery from unlined sections of theAll American and Coachella Canals; drought year water transfers similar to the PVID/MWDSC pilotproject; groundwater banking in Arizona; and conjunctive use of groundwater in areas such as the Coachella Valley. The actions are described in more detail below. The draft plan recognizes that transfers of conserved water must be evaluated in the context of preserving the Salton Sea’s environmental resources, and also that plan elements must address environmental impacts on the lower Colorado River and its listed species. Other actions to occur as part of the first phase would include implementation of the San Luis Rey Indian water rights settlement authorized in PL 100- 675 and implementation of measures to administer agricultural water entitlements within the first three priorities of the Seven Party Agreement. Examples of such measures include quantifying amounts of water conserved or transferred, and annually reconciling water use with water allocations (e.g., overrun accounting). An important element of the CRB draft 4.4 plan is the concept that existing reservoir operating criteria be changed by USBR to make optimum use of theriver’s runoff and available basin storage capacity. California agencies developed new proposed operating criteria that are included in the draft plan. The draft plan contemplates that changes in operating criteria would be part of both the first and second phases. The other basin states have been cautious in their reaction to California’s proposals for reservoir reoperation, and have suggested, for example, that new criteria should not be implemented until California has prepared the environmental documents and executed the agreements that would be needed to begin implementation of the plan. (In its 1995 five-year review of Colorado River operating criteria, USBR had announced that it planned no changes to existing criteria.) The second phase of the CRB draft 4.4 plan wouldinclude additional average year and drought year water transfers. Specifics on these transfers would bedeveloped during the first phase of plan implementation. One suggested component is construction ofdesalting facilities on rivers tributary to the sea, to divert and treat agricultural drainage water that would otherwise enter the sea. The treated water could beconveyed to urban water users in the South Coast Region via the Colorado River Aqueduct. As with any alternative that would reduce the amount of relativelyfresh water reaching the sea, the environmental impacts of this approach would require careful evaluation. Other components of the second phase would include further transfers of conserved agricultural water to the

USBR’s Parker Dam on the Colorado River impounds Lake Havasu. At this location, the Colorado River forms the stateline between California and Arizona. MWDSC’s Colorado River Aqueduct and the Central Arizona Project divert from Lake Havasu. New Parker Dam photoThe California Water Plan Update B ULLETIN 160-98

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EGIONS 9-35 South Coast and further work on reservoir operating criteria. Implementation of some elements of phase two of the plan may extend beyond the Bulletin 160- 98 planning horizon.

Tribal Water Rights

Colorado River Indian Tribes. As a result of the1964 U.S. Supreme Court decree in Arizona v. California, California’s basic apportionment of Colorado River water was quantified and five lower Colorado River Indian Tribes were awarded 905 taf of annualdiversions, 131 taf of which were allocated for diversion in and chargeable to California pursuant to a later supplemental decree. In 1978, the tribes asked the court to grant them additional water rights, alleging that the U.S. failed to claim a sufficient amount of irrigable acreage, called omitted lands, in the earlier litigation. The tribes also raised claims called boundary land claims for more water based on allegedly larger reservation boundaries than had been assumed by the court in its initial award. In 1982, the special master appointed by the SupremeCourt to hear these claims recommended that additional water rights be granted to the Indian tribes. In 1983, however, the Supreme Court rejected the claims for omitted lands from further consideration and ruledthat the claims for boundary lands could not be resolved until disputed boundaries were finally determined. Three of the five tribes—Fort Mojave Indian Tribe, Quechan Indian Tribe, and Colorado River Indian Tribe—are pursuing additional waterrights related to the boundary lands claims. A settlement has been reached on the Fort Mojave claim andmay soon be reached on the CRIT claim. Both settlements would then be presented to the special master. The Quechan claim has been rejected by the special master on the grounds that any such claim was necessarily disposed of as part of a Court of Claims settlement entered into by the tribe in a related matter in the mid-1980s. As with all claims to water from themainstem of the Colorado River and any determination by the special master, only the U.S. Supreme Court itself can make the final ruling. If both the Fort Mojave and CRIT settlements were approved, the tribes would receive water rights in addition to the amounts granted them in the 1964 decree. San Luis Rey Indian Water Rights Settlement
Act

. The San Luis Rey Indian Water Rights Settlement Act (Public Law No. 100-675; 102 Stat. 4000 [1988]) is to provide for the settlement of the reserved water rights claims of the La Jolla, Rincon, San Pasqual, Pauma, and Pala Bands of Mission Indians. Litigation (affecting the interests of the United States, the City of Escondido, the Escondido Mutual Water Company,the Vista Irrigation District, and the Bands) and proceedings before the Federal Energy Regulatory Commission involved tribal water rights claims to the waters of the San Luis Rey River and questions about the validity of rights-of-way granted by the U.S. acrosstribal and allotted lands. The act authorizes and directs the Secretary of the Interior to arrange for a 16 taf/ yr supplemental supply of water to benefit the Bandsand the local communities. This supply can be obtained either from water development from public lands in California outside the service area of the CVP, from water salvaged as the result of lining part of the AAC or Coachella Canal, or through a contract withMWDSC. Title II of PL 100-675 authorized the Secretary of the Interior to line parts of the canals, and permitted the Secretary to enter into an agreement or agreements with PVID, IID, CVWD, and/or MWDSC for the construction or funding. The act did not authorize appropriation of federal funds for canal lining.

Water Conservation ProgramsThere have been several large-scale water conservation actions involving Colorado River water users, as shown in Table 9-20.

Salton Sea The present day Salton Sea was formed in 1905, when Colorado River water flowed through a break ina canal that had been constructed along the U.S./Mexican border to divert the river’s flow to agricultural lands Colorado River Board of California

The Colorado River Board of California is the State agency responsible for administering California’s Colorado River water allocation, and for dealing with the other basin states on river management issues. The Board is composed of six members representing the California agencies who were signatories to the 1931 Seven-Party Agreement, two public members, and two ex-officio members (the directors of the Department and DFG). The six local agencies represented on the CRB are CVWD, IID, LADWP, MWDSC, PVID, and SDCWA. CRB’s office and staff are located in Glendale.The California Water Plan Update B ULLETIN 160-98

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EGIONS 9-36 in the Imperial Valley. Until that break was repaired in 1907, the full flow of the river was diverted into the Salton Sink, a structural trough whose lowest point is about 278 feet below sea level. Within geologic time, the Colorado River’s course has altered several times. At times, the river discharged to the Gulf of California as it does today. At other times it flowed into the SaltonSink. Lake Cahuilla, the most recent of several prehistoric lakes to have occupied the Salton Sink, dried up some 300 years ago. Over the long term, the sea’s elevation has gradually increased, going from a low on the order of -250 feet in the 1920s to its present level of about -226 feet. The sea’s maximum elevation in recent years was -225.6 in 1995. Since some shoreline areas are relatively flat, a small change in elevation can result in a large difference in the extent of shoreline submerged. Levees have been constructed to protect adjacent farmland andstructures at some sites along the shoreline; the remaining managed acreage of the Salton Sea National Wildlife Refuge is also protected from the sea by levees. The Salton Sea is the largest lake located entirely within California, with a volume of about 7.5 maf at its present elevation of -226 feet. The sea occupies a closed drainage basin—if there were no inflows to maintain lake levels, its waters would evaporate as did those of prehistoric Lake Cahuilla. The area’s average annual precipitation is 3 inches or less, while averageannual evaporation is in excess of 5 feet. The sea receives over 1 maf of inflow annually, primarily from T

ABLE 9-20 Existing Colorado River Region Water Conservation Actions

Year Action Participants Comments/Status Estimated Savings

1980 Line 49 miles of USBR, Project completed. 132 taf/yr Coachella Branch CVWD, of All American MWDSC Canal

1988 IID distribution IID, MWDSC Multi-year agreement, extends 107 taf/yr in 1998 system into 2033. Projects MWDSC has improvements funded include canal lining, and on-farm regulatory reservoir and spill water interceptor canal construction,management tailwater return systems, nonactions leak gates, 12-hour delivery of water, drip irrigation systems, linear-move irrigation systems, and system automation. MWDSC has funded over $150 million for conservation program costs through 1997.

1992 Groundwater MWDSC, Test program to bank up to MWDSC and SNWA have banking in CAWCD, 300 taf. stored 139 taf in Arizona Arizona SNWA groundwater basins.

1992 PVID land PVID, Project completed. Two-year Total of 186 taf was fallowing MWDSC land fallowing test program. made available from the Covered 20,215 acres in PVID. program, although the water MWDSC paid $25 million to was subsequently released farmers over a two-year period. from Lake Mead when flood control releases were made from the reservoir.

1995 Partnership USBR, Provides, among other things, N/A agreement CVWD for studies to optimize reasonable beneficial use of water in the district.The California Water Plan Update B ULLETIN 160-98

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EGIONS 9-37 agricultural drainage. The largest sources of inflow (about 80 percent of the total) are the New and Alamo Rivers which drain agricultural lands in the Mexicali and Imperial Valleys and flow into the sea’s southernend. The New River also receives untreated and minimally treated wastewater flows from the Mexicali area;monitoring results generally indicate that pollution associated with wastewater discharges does not reach the sea because of its distance from the Mexican border. In 1924, President Coolidge issued an executive order withdrawing seabed lands lying below elevation-244 feet for the purpose of receiving agricultural drainage water. That order was expanded in 1928 to lands below elevation -220 feet. The sea supports water-based recreational activities, and has had a popular corvina fishery. During the 1950s, the highest per capita sport fishing catches in California were from the Salton Sea. Over the years, concerns about the sea’s salinity havebeen voiced in the context of maintaining the recreational fishery that was established with introduced species able to tolerate high salinities. The sea also provides important wintering habitat for many species of migratory waterfowl and shorebirds, including some species whose diets are based exclusively on the fish in the sea. Wetlands near the sea and adjoining cultivated agricultural lands offer theavian population a mix of habitat types and food sources. An area at the sea’s south end was established as a national wildlife refuge in 1930, although most of that area is now under water as a result of the sea’s rising elevation. Some of the 380 bird species wintering inthe area include pelicans, herons, egrets, cranes, cormorants, ibises, ducks, grebes, falcons, plovers, avocets, sandpipers, and gulls. The Salton Sea is considered to be a major stopover point for birds migrating on the Pacific Flyway, and has one of the highest levels of bird diversity of refuges in the federal system. Historically, salinity has been the water quality constituent of most concern at the sea. Present levels are about 44,000 mg/L TDS (seawater is about 35,000 mg/L TDS). This high level of salinity reflects long- term evaporation and concentration of salts found in its inflow. Selenium has been a more recent constituent of interest, due to its implications for A false-color infrared satellite photo of the Salton Sea (January 1998 Landsat 5). The irrigated areas in Imperial Valley are clearly visible to the south of the sea,

as are the Algodones Dunes

to the southeast. The City of Mexicali and irrigated

acreage in the Mexicali Valley can also be seen.The California Water Plan Update B ULLETIN 160-98

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EGIONS 9-38 aquatic species. Although selenium levels in the water column in the sea are less than the federal criterion of 5 u g/L, this concentration can be exceeded in seabed sediment and in influent agricultural drainage water. Agricultural drain flows also contribute significant nutrient loading to the sea, which supports large algal blooms at some times of the year. These algal blooms have contributed to odor problems and low dissolved oxygen levels in some areas of the sea. Over the years, USBR and others have consideredpotential solutions to stabilize the sea’s salinity and elevation. Most recently, the Salton Sea Authority (a joint powers authority consisting of Riverside and Imperial Counties, IID, and CVWD) and others have been performing appraisal level evaluations of some of thefrequently suggested alternatives. Categories of alternatives considered include: • Diking off part(s) of the sea to create evaporation pond(s) adjoining the primary water body. This approach would divert part of the sea’s water into managed impoundments, where the water would be concentrated into a brine and the salts would eventually be removed. The facilities would be sized to maintain a primary waterbody at some desired salinity concentration and elevation. The desired salinity concentration would probably be near that of ocean water (or slightly greater) to maintain the recreational fishery. • Pumping Salton Sea water and exporting it to some other location. Possible discharge locations include nearby dry desert lakebeds (to create evaporation ponds), evaporation ponds to be constructed near the sea, the Gulf of California, or the Laguna Salada in Mexico. • Building treatment facilities (such as a desalting plant) to remove salts from inflows to the sea.• Importing fresh water to the sea. The most apparent source would be the Colorado River, but only in years when flood control releases were being made in excess of U.S. needs. Maintaining a viable Salton Sea has several water management implications. First will be the actions needed to stabilize the sea’s salinity in the near-term, such as the Authority’s diking proposal. Eventually, a long-term solution will need to be developed. A widerange of costs has been mentioned for a long-term solution, including amounts in the billion-dollar range. Some of the possible long-term solutions suggestedwould entail constructing facilities in Mexico, bringing a greater level of complexity to their implementation. Other water management programs in the region, such as proposals to transfer conserved agricultural water supplies, will have to be evaluated in terms of their impacts on the sea. Recent proposals to desalt water in the Alamo or New Rivers and to transport that water in the Colorado River Aqueduct to the South Coast for urban water supply have raised concerns about maintaining the sea’s environmental productivity. Such proposals might be implemented as part of the second phase of CRB’s draft 4.4 Plan. (In 1997, CVWD filed an application with the SWRCB for water rights to storm water flows and drainage flows in the Whitewater River at the sea’snorthern end. MWDSC made a similar filing for agricultural drainage flowing into the sea’s southern end.) Congressional legislation introduced in 1998 would authorize expenditure of federal funds for a multi-year study of the sea’s resources and potential solutions for managing its salinity.

Coachella Valley Groundwater Overdraft Most PSAs within the Colorado River Region have sufficient water to meet future water needs, with the exception of Coachella Valley. Groundwater overdraftis occurring in the upper (urbanized) part of the valley; DWA and CVWD have been managing extractions in that basin to minimize future overdraft. Importedsurface water at the upper end of the valley has provided a source of recharge water. Groundwater overdraft is also occurring in the Roadrunners are one of the bird species found year-round in the Salton Sea area.The California Water Plan Update B ULLETIN 160-98

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EGIONS 9-39 lower (agricultural) portion of the valley, an area thatroughly coincides with CVWD’s Improvement District No.1. CVWD estimates that actual 1995 water use within the district was about 520 taf, part of which was supplied by overdrafting the groundwater basin. (Irrigators in the lower valley are supplied by surface water from the Coachella Canal and by groundwater.)The district is in the process of preparing a groundwater management plan for the lower valley, and has considered alternatives including basin adjudication, water conservation, water recycling, and direct or in lieu recharge with water imported from the ColoradoRiver or from the SWP. CVWD estimates that overdraft in the lower valley is about 170 taf/yr. Overdraft calculated from Bulletin 160-98 water budgets is 70 taf/yr for the upper and lower valley combined.

Lower Colorado River Environmental Water IssuesListed fish species on the mainstem of the Colorado River include the Colorado squawfish, razorbacksucker, humpback chub, and bonytail chub. Restoration actions to protect these fish may affect reservoiroperation and streamflow in the mainstem and tributaries. Other species of concern in the basin include the bald eagle, Yuma clapper rail, belted kingfisher, southwestern willow flycatcher, and Kanab ambersnail.In 1993, USFWS published a draft recovery implementation plan for endangered fish in the upperColorado River Basin. The draft plan included protecting instream flows, restoring habitat, reducing impacts of introduced fish and sportsfish management, conserving genetic integrity, monitoring habitat and populations, and increasing public awareness of the role and importance of native fish.Problems facing native fish in the mainstem Colorado River and its tributaries will not be easily resolved.For example, two fish species in most danger of extinction, the bonytail chub and razorback sucker, are not expected to survive in the wild. Although therewas a commercial razorback fishery until 1950, in recent years most stream and reservoir fisheries in the basin have been managed for non-native fish. Thesemanagement practices have harmed residual populations of natives. Many native fish are readily propagatedin hatcheries, and thus recovery programs include captive broodstock programs to maintain the species. Reestablishing wild populations from hatchery stocks will have to be managed in concert with programs tomanage river habitat. For example, although 15 million juvenile razorback suckers were planted in Arizona streams from 1981-90, the majority of these planted fish were likely eaten by introduced predators. In 1994, the states of Colorado, Wyoming, and Utah reached an agreement with USFWS on protocols for stockingnon-native fish in the Upper Basin—stocking protocols consistent with native fish recovery efforts. In a program which began in 1989, USBR and other state and federal agencies have cooperated to capture, rear, and successfully reintroduce about 15,000 razorback sucker larvae in Lake Mojave.Instream flows in the mainstem and key tributaries are being evaluated as components of native fishrecovery efforts. State and federal agencies are conducting studies to estimate base flow and flushing flow needs for listed and sensitive species in various river Groundwater recharge ponds

at Windy Point, to the east of San Gorgonio Pass in Riverside County. Water from the Whitewater River,

along with Colorado River Aqueduct supplies exchanged for SWP deliveries of CVWD and DWA, provides recharge in the upper Coachella Valley area.The California Water Plan Update B ULLETIN 160-98

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EGIONS 9-40reaches. An example of flushing flow evaluation occurred in the spring of 1996 when releases from GlenCanyon Dam were increased for several days to attempt to redistribute sediment and create shallow water habitat in the mainstem below the dam.In a 1997 court action involving the southwestern willow flycatcher, an environmental group filed a lawsuit against USBR and USFWS under the ESA’s citizen suit provisions. The group alleged that USBR’s operation of Lake Mead was endangering the flycatcher’s habitat at the upper end of Lake Mead. The federal district court for Arizona ruled in favor ofUSBR, but the environmental group appealed the district court’s decision to the Ninth Circuit Court of Appeals. The appellate court subsequently declined to hear the case, letting the district court’s decision stand.

Lower Colorado River Multi-Species Conservation Program

In 1995, DOI executed partnership agreements with California, Nevada, and Arizona to develop amulti-species conservation program for ESA-listed species and many non-listed, but sensitive, species within the 100-year floodplain of the lower Colorado River, from Glen Canyon Dam downstream to the Mexican border. In 1996, a joint participation agreement was executed to provide funding for the program. USFWS has designated the LCRMSCP steering committee asan ecosystem conservation and recovery implementation team pursuant to ESA. The steering committee is composed of representatives from the three states, DOI,Indian tribes, water agencies, power agencies, environmental organizations, and others.The conservation program will work toward recovery of listed and sensitive species while providing for current and future use of Colorado River water and power resources, and includes USBR’s Colorado River operations and maintenance actions for the lowerriver. Over 100 species will be considered in the program, including the southwestern willow flycatcher,Yuma clapper rail, and the four listed fish species mentioned above. Developing the program is estimated to take three years. Costs of program development andimplementation of selected interim conservation measures, estimated at $4.5 million, are to be equally split between DOI and the nonfederal partners. USBR initiated a formal Section 7 consultationprocess with USFWS, who issued a five-year biological opinion on USBR operation and maintenance activities from Lake Mead to the southerly international boundary with Mexico in 1997. USBR has estimated that the cost of implementing the biologicalopinion’s reasonable and prudent alternatives and measures could be as high as $26 million. The steering committee is currently participating in funding several interim conservation measures. These include a razorback sucker recovery program at Lake Mojave, restoration of Deer Island near Parker,Arizona, and a “Bring Back the Natives” program sponsored by the National Fish and Wildlife Foundation.

Water Management Options for the Colorado River RegionThe only forecasted shortages within the Colorado River region are those resulting from groundwater overdraft in Coachella Valley. Implementing the draftCRB 4.4 Plan entails developing options in the Colorado River Region to keep MWDSC’s Colorado River Aqueduct flowing at its full capacity, as described earlier. The reduction in California’s use of ColoradoRiver water to the basic 4.4 maf apportionment reduces the supply available to California by as much as 0.9 maf/yr. Table 9-21 shows a list of options for the region, and the results of an initial screening of the options. The retained options were evaluated (Table 9A-3 in Appendix 9A) based on a set of fixed criteria discussedin Chapter 6. These options could be used for implementing the draft CRB 4.4 Plan and for reducing the Colorado River Region’s groundwater overdraft.

Water Conservation
Urban. Urban water demand forecasts for 2020 assume that BMPs are in place; consequently, only those urban conservation efforts which exceed BMPsare considered as options. All urban conservation options were retained. Reducing outdoor water use to 0.8 ET

oin new development would attain 9 taf/yr of depletion reductions, while extending this measure to include existing development would reduce depletions by 18 taf/yr. Reducing indoor water use to 60 gpcd and 55 gpcd would reduce depletions by 2 and 3 taf/ yr, respectively. Reducing commercial, institutional, and industrial water use by 3 percent and 5 percentwould save 1 and 2 taf/yr, respectively. Reducing distribution system losses to 7 and 5 percent would result in 9 and 13 taf/yr of depletion reductions, respectively. Agricultural. The 2020 agricultural water demand forecasts assume that EWMPs are in place. As withThe California Water Plan Update B ULLETIN 160-98

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ABLE 9-21 Colorado River Region List of Water Management Options

Option Retain Reason for Deferral or Defer

Conservation

Urban

Outdoor Water Use to 0.8ET

o Retain

Indoor Water Use Retain

Interior CII Water Use Retain Distribution System Losses Retain Agricultural

Seasonal Application Efficiency Improvements Retain Flexible Water Delivery Retain Canal Lining and Piping Retain Tailwater Recovery Retain

Modify Existing Reservoirs/Operations Reoperating Colorado River System Reservoirs Defer Concurrence of USBR and other basin states not yet obtained.

New Reservoirs/Conveyance Facilities Additional Conveyance Capacity for Colorado Defer California’s current excess use of Colorado River
River Water water.

Groundwater/Conjunctive Use Groundwater Recharge Project at East Mesa Defer Scoped as one-time program.

Water Marketing Interstate banking Retain Intrastate banking and transfers Retain Land fallowing program Retain

Water Recycling Water recycling options Defer Water recycling options would not generate new water supply.

Desalting

Brackish Groundwater

— —— Seawater

— ——
Other Local Options Desalting local drainage water Defer To be evaluated in phase 2 of draft CRB 4.4 Plan. Lining All American Canal Retain Additional Lining of Coachella Canal Retain Weather Modification Defer Complicated by interstate management issues.

Statewide Options — — See Chapter 6.The California Water Plan Update B ULLETIN 160-98

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EGIONS 9-42the urban water management options, only those agricultural conservation efforts which exceed EWMPsare considered as options. Improving seasonal application efficiency to 80 percent from the base of73 percent could reduce depletions by 50 taf/yr. Improving flexible water delivery, canal lining (on-farmand distribution system), and tailwater recovery systems could together realize 140 taf/yr in depletionreductions. However, the ability to implement conservation options that would reduce the amount of fresh water inflow to the Salton Sea must be evaluated on a project-specific basis. Goals for preservation of the sea’s environmental resources may limit the extent of feasible conservation measures. Land Fallowing. Programs such as the Palo Verde test land fallowing program could be implemented to provide water for transfer to urban areas in the South Coast Region during drought periods. In 1992, MWDSC conducted a two-year land fallowing test program with PVID. Under this program, growers in PVID fallowed about 20,000 acres of land. The saved water, about 93 taf/yr, was stored in Lower Colorado River reservoirs for future use by MWDSC (the water was later released when Colorado River flood control releases were made from Lake Mead). MWDSC paid each grower $1,240 per fallowed acre, making the costof the water to MWDSC about $135/af. Similar programs could be implemented in the future to provide about 100 taf/yr during drought years. Future landfallowing agreements would need to consider the availability of storage for the transferred water.

Potential Sources of Water for Intrastate Marketing The ability to market conserved water has already been demonstrated in the region. Table 9-22 summarizes some potential sources of water for intrastate transfers. Such transfers could make up some of the shortages in the South Coast Region resulting fromCalifornia reducing its use to California’s basic apportionment of 4.4 maf. Construction of additional conveyance capacity from the Colorado River Region to the South CoastRegion has been a recent subject of discussion. Proposition 204 provides funding for a feasibility study of a new conveyance facility from the Colorado River tothe South Coast Region. Conveyance facilities mentioned include a new aqueduct from the Imperial Valley area to San Diego (on the United States side of theborder), as well as San Diego’s participation in enlarging the existing aqueduct serving Tijuana, Mexico. Tijuana’s situation is similar to San Diego’s, in thatTijuana is seeking to expand its urban supplies by negotiating transfer of agricultural water from theMexicali Valley. Figure 9-6 is a map of the U.S. - Mexican border area, showing the area’s larger water facilities. A preliminary engineering study of constructing a new canal from Imperial Valley to SDCWA’s service areahas been prepared for SDCWA. Additional work, including geotechnical exploration and environmentalstudies, would be needed to evaluate the project’s feasibility. The preliminary study highlighted the need to evaluate desalting the water that the aqueduct would supply, to enable San Diego’s continued reliance on ahigh level of water recycling. New conveyance facilities from the Colorado River Region to the South CoastRegion have been deferred from evaluation in Bulletin 160-98 because it does not appear that they would be constructed within the Bulletin’s planning horizon, given the other basin states’ concerns about California’s T

ABLE 9-22 Potential Colorado River Water Conservation Programs

Program Participants Comments/Status Estimated Savings

Lining of All USBR, IID Authorized by PL 100-675. Final EIS/EIR Not implemented yet. American Canal CVWD, MWDSC published. Preferred alternative is constructing Potential of 67.7 taf/yr a new, lined parallel canal. savings.

Agreement for a IID, SDCWA SCDWA and IID executed an agreement in Not implemented yet - long-term transfer 1998. Initial agreement negotiated for wheeling up to 200 taf/yr savings. of up to 200 taf/yr water in MWDSC’s Colorado Aqueduct. EIR/EIS not yet prepared.

Additional lining USBR, others Authorized by PL 100-675. Draft EIR/EIS Not implemented yet. of Coachella Canal issued. Potential of 25.68 taf/yr savings.The California Water Plan Update B ULLETIN 160-98

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EGIONS 9-43 F IGURE 9-6 U.S.-Mexican Border Region

All American Colorado

River

Imperial

Beach El Centro Alamo

River New

River Canal

Calexico Coachella

River Imperial

Dam Laguna Dam Colorado

River San Luis Rey River San Diego

San Vicente Reservoir Aqueducts

Lower Otay Reservoir San Diego Gila Salton

Sea

Senator Wash Dam AR IZONA ORN IA CAL IF

CAL IFORN IA

P
a
c i f

i c O

c

e

a

n Gulf of California Rodriguez Reservoir Tecate

Rio de las Palmas

Ensenada

Rio San Carlos

Rio Santo Tomas

Rio San Antonio San Luis Mexicali Morelos Dam

Yuma

Tijuana Canal Alamo

Laguna Salada River El Carrizo Reservoir Rio Colorado - Tijuana Aqueduct

Cienega de Santa Clara River Tiju MEX ICO MEX ICO AR IZONA A q u e d u c t

C a n a l

ana

C o l o r a d

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EGIONS 9-44use of Colorado River water and the international complexities associated with a joint project with Mexican agencies.SDCWA and IID have been negotiating a potential transfer of water saved due to extraordinaryconservation measures within IID. The agencies initially executed a 1995 MOU concerning negotiation of a transfer agreement, followed by 1998 executionof an agreement specifying the transfer’s terms and conditions. The agreement has a minimum 45-year term, and can be extended for an additional 30 years. An initial transfer of 20 taf would begin in 1999, with the annual quantity of transferred water increasing to a maximum of 200 taf. In order to transfer the acquired water, SDCWA (a member agency of MWDSC) has negotiated an initial wheeling agreement with MWDSC for use of capacity in MWDSC’s Colorado River Aqueduct. Environmental documentation for the transfer is pending.Past conservation projects in the region have included land fallowing, canal lining, distribution system reservoir and spill interceptor canal construction, and irrigation distribution system improvements. Some proposed projects to recover canal seepage include:

• Lining part of the All American Canal. PublicLaw 100-675 authorized the Secretary of the Interior to line the canal or to otherwise recover canal seepage, using construction funds from PVID,IID, CVWD, or MWDSC. USBR’s environmental documentation evaluated a parallel canal alternative, several in-place lining alternatives, anda well field alternative, and concluded that the preferred alternative was the construction of aconcrete-lined canal parallel to 23 miles of the existing canal. The parallel canal alternative has thepotential to conserve an estimated 67.7 taf annually of Colorado River water. Recently, the well field alternative has been reevaluated and found to be infeasible. The well field alternative, although less expensive than canal lining, has been set asidebecause of international concerns about groundwater extraction near the border.

• Lining the Remaining Section of the Coachella Canal. This project would involve lining the remaining 33.4 miles of the Coachella Canal, which loses about 32.4 taf/yr through seepage. Four alternatives that have been identified are conventional lining, underwater lining, parallel canal, and no action. It is estimated that the preferred alternative, conventional lining, would conserve 25.7 taf/yr. Intrastate Groundwater Recharge or Banking

IID has proposed a groundwater recharge projectat East Mesa in the Imperial Valley. The proposed recharge project would divert a portion of flood controlreleases from Lake Mead to a recharge site or sites located along the alignment of the old, unlined CoachellaCanal. (The old canal was abandoned when an adjacent lined canal was constructed.) IID estimates that up to 20 taf could be recharged in 1998. IID prepareda mitigated negative declaration for a one-time program in 1998, when flood control releases are occurring. Since Colorado River flood control releases have historically been infrequent, future water supply for such a recharge program would be available only occasionally. This option was scoped as a one-time project and is not considered as a 2020-level option in Bulletin 160-98.MWDSC has executed agreements with three entities to study the potential of groundwater bankingarrangements that would involve storing surplus Colorado River water, when available, in groundwater basins near its Colorado River Aqueduct. The water would be withdrawn for use in the South Coast in droughtyears. An agreement with Cadiz Land Company covered a potential project that would entail constructinga 35-mile pipeline from the Cadiz Valley/Fenner Valley area, and diverting up to 100 taf/yr of surplus Colorado River water to storage. Estimated available groundwater storage capacity is 500 taf, with droughtyear withdrawal capability of 100 taf. This arrangement could additionally have a marketing component; perhaps 20 to 30 taf/yr of recharge in Cadiz and Fenner Valleys could be blended with Colorado River waterand delivered to the South Coast Region. An agreement with Catellus Development Company covered a potential groundwater storage site in the Mojave Desert with an estimated capacity of 600 taf. The withdrawal capability of this site is estimated at about 150 taf/yr.A third agreement was with CVWD. CVWD is presently performing pilot studies to estimate recharge and withdrawal capabilities in the lower valley. (MWDSC and CVWD have already been evaluating increased recharge at the upper end of the valley, in the Whitewater River drainage basin.) Technical studies of the feasibility of these projectsremain to be completed, and environmental documentation has not yet been prepared. It appears likely that at least 100 taf/yr of drought year supplies could be provided through this group of potential storage sites.The California Water Plan Update B ULLETIN 160-98

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EGIONS 9-45 Interstate Banking/Conservation Under an existing agreement between MWDSC and the Central Arizona Water Conservation District, MWDSC can store a limited amount of Colorado River water in Arizona for future use. The Southern Nevada Water Authority is also participating in the program. The agreement stipulates that MWDSC and SNWA can store up to 300 taf in central Arizona through the year 2000. As of 1997, MWDSC has placed 89 taf in storage and SNWA has placed 50 taf in storage, for a total of 139 taf. About 90 percent of the stored water can be recovered, contingent upon the declaration of a surplus. When MWDSC is able to draw on this source, it can divert up to a maximum of 15 taf in any one month. The stored water would be made available by Arizona foregoing the use of part of its normal supply from Central Arizona Project. MWDSC plans to recover the stored water at times inthe future when its Colorado River Aqueduct diversions may be limited. Like the East Mesa project described in the preceding section, this interstate project was a one-time action, and is not considered as a 2020-level option in Bulletin 160-98.In its 1996 session, the Arizona Legislature enacted legislation establishing the Arizona WaterBanking Authority. The Authority is authorized to purchase unused Colorado River water and to store it in groundwater basins to meet future needs. Conveyance to storage areas is provided by the Central ArizonaProject. The legislation further provided that the Authority may enter into agreements with California and Nevada agencies to bank water in Arizona basins, with the following limitations: • Regulations governing interstate banking would need to be promulgated by the Secretary of the
Interior. • The Arizona Department of Water Resources finds that DOI’s regulations adequately protect Arizona’s rights to Colorado River water.• The ability to bank interstate water would be subordinate to banking of water to supply Arizona needs. • Interstate banking would be precluded in years when Arizona is using its full apportionment of2.8 maf (including water being delivered to Arizona for banking by Arizona agencies), unlesssurplus conditions were declared for the river system. • Interstate withdrawals from the bank are limitedto 100 taf/yr, although there is no statutory limitation on annual deposits. Under this legislation, future interstate banking in Arizona would have a maximum annual yield of100 taf. However, Arizona may effectively limit withdrawals in drought years by declining to decrease its diversions of surface water to allow recovery of thebanked water. USBR released draft rules and regulations for the interstate banking program for publiccomment in December 1997, and is presently reviewing the public comments.

Reoperating Colorado River System Reservoirs Member agencies represented by the CRB have discussed proposing reservoir operating criteria to the Secretary of the Interior that would benefit Californiawhile protecting the apportionments of the other basin states and satisfying Mexican treaty obligations. Such criteria would also constitute part of the package of actions for California to transition its use of river water from current levels to 4.4 maf/yr. Operations studies have evaluated specific shortage and surpluscriteria for the river system, including selection of desired probabilities for water supply reliability and reservoir operating elevations. Results of the operations studies performed byCRB and by USBR suggest that there could be minimal hydrologic risk to using reservoir reoperation—particularly as a limited-term measure to help California reduce its Colorado River use—as a water management option for this region. As described in Chapter 3, the Colorado River has a highratio of storage capacity to average annual runoff. Projections of consumptive use for the upper basin states suggest that those states will not attain full use of their compact apportionments until after year 2060. USBR’s surplus declarations to date have not adverselyimpacted the other states’ use of their apportionments—for example, flood control releases were made both in 1997 and 1998, and are expected in 1999. The more significant impediment to implementing reoperation would be concerns of the other basin states about impacts of an extended period of reoperation on future shortages, considering the river’s variable year to year runoff. For Bulletin 160-98, reservoir reoperation is notevaluated as a water management option and no numerical evaluation is made, since consensus of USBR and the basin states has not yet been obtained.

Weather Modification A fundamental management issue associated withThe California Water Plan Update B ULLETIN 160-98

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EGIONS 9-46Colorado River water supplies is the apparent overstatement of the Compact apportionment relative tothe river’s historical hydrology. There have been proposals over the years to augment the river’s base flow to provide additional supplies. For example, USBR haddeveloped a proposed pilot program in 1993 to evaluate cloud seeding potential in the Upper Basin. The State of Colorado did not favor moving ahead with this program. Weather modification has recently been raised again as part of a possible menu of options to resolveCalifornia’s use in excess of the 4.4 maf basic apportionment, although no specific proposals have beenmade. In concept, this option would entail cloud seeding in the Upper Basin to increase runoff, and might yield a 5 percent increase in base flow from the area seeded. Large-scale weather modification projects are typically difficult to implement due to institutional and third-party concerns, and can require several yearsof study and testing prior to being placed in operational status. Weather modification on the Colorado River is also complicated by interstate management issues. This option has been deferred for these reasons.

Options for Coachella Valley
As discussed earlier, MWDSC has executed an agreement with CVWD to study banking of surplus Colorado River water, when available, in the lower Coachella Valley. Banking programs typically entail putting more water into the groundwater basin than is extracted, to address losses and to avoid potential localized impacts to existing basin pumpers. Over the long term this extra recharge would help stabilize groundwater basin levels. CVWD is presently in the planning stages of expanding its existing pilot recharge/ extraction site in the lower valley. CVWD also plans to form a groundwater replenishment district to help manage overdraft.MWDSC and CVWD are evaluating additional recharge possibilities in the Whitewater River drainage at the north end of the valley. Water recharged in this areacould come from surplus Colorado River flows, from yearto-year purchases of SWP water or purchase of SWP entitlement, or from other water marketing arrangements that could take advantage of SWP/CRA conveyance. For example, CVWD purchased about 39 taf of water from other SWP contractors in 1996, on a one-time basis.Additional recharge possibilities in the Whitewater drainage have not yet been quantified, and are not evaluated further in Bulletin 160-98. CVWD could, as other SWP urban water contractors are doing, participate in the permanent transfer of agricultural entitlement water provided for in the Monterey Agreement contract amendments. CVWD could also purchase water from other sources, by way of exchange with MWDSC, subject to negotiation of conveyance in the SWP and CRA. Since no specific proposals are currently pending, this option is not quantified in the Bulletin.

Statewide Options Statewide water supply augmentation options are discussed and quantified in Chapter 6.

Options Likely to be Implemented in the Colorado River Region Applied water shortages are forecasted to be 147taf in average years and 158 taf in drought years. Ranking of retained water management options for the Colorado River Region is summarized in Table 9-23.Table 9-24 summarizes options that can likely be implemented by 2020 to relieve the shortages. Options identified for this region will likely be used for reducing Coachella Valley overdraft and for managing water to benefit the South Coast Region, as called for in CRB’s draft 4.4 Plan. An evaluation of these options is shown in Table 9A-3 in Appendix 9A. Bulletin 160-98 assumes that water made available byoption implementation is first allocated to reduce overdraft within the region, and that remaining water is then available for use in the South Coast Region. For readers interested in comparing Bulletin 160- 98 options with the draft CRB 4.4 Plan, Table 9-25 summarizes the Bulletin’s findings in a format similar to that used in the draft CRB 4.4 Plan. There is an important differences between the two documents— Bulletin 160-98 assumes that water conservation dueto EWMP implementation occurs as part of base demand forecasts and not as an optional measure. Actions that may be implemented as part of phase two of the draft CRB 4.4 Plan are not shown in the table, because they have not yet been formulated and quantified.