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| 1997-1998 Hydrologic Report |
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WATER CONSERVATION
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Information presented in this section includes amounts of local, imported, and reclaimed water conserved in spreading areas and information on the seawater barrier projects which prevent salt water intrusion into groundwater zones in the coastal areas. Pertinent data is presented regarding the locations and descriptions of the Department's water conservation facilities, as well as facilities owned by others. Additional data not presented in this report or its appendices can be obtained by contacting the custodian of hydrologic records.
In addition to the flood control program, the Department has the equally important mission of conserving as much of the storm and other waters as practicable. The use of water conservation facilities adjacent to river channels and in soft-bottom channels permits water to percolate into groundwater basins for later pumping. These water spreading facilities are located in areas where the underlying soils are composed of permeable formations and in hydraulic connection with the underlying aquifer.
The various types of water conserved, local, imported, and reclaimed are construed to have the following meanings in this section: Local water is primarily runoff due to rainfall on the mountain and valley watersheds, dam releases, and rising water within the County. Imported water is water originating outside the County either from Northern California or from the Colorado River. Reclaimed water is the effluent produced by the Whittier Narrows Water Reclamation Plant, the San Jose Creek Water Reclamation Plant, and the Pomona Water Reclamation Plant, all operated by the Los Angeles County Sanitation District.
The importance of this activity is apparent when it is realized that about 30 to 40 percent of the water used in the County is pumped from groundwater supplies. The growth of the County, combined with periodic droughts, has seriously depleted these supplies on numerous occasions.
The Department's policy is to conserve the maximum possible amount of storm water consistent with runoff quantity and quality, capacities of the spreading facilities, and groundwater conditions.
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During the reporting period, the Department received water imported from the Colorado River and the State Water Project by the Metropolitan Water District (MWD) and spread it in the Coastal Plain at the Department's Rio Hondo and San Gabriel Coastal Spreading Grounds on behalf of the Water Replenishment District of Southern California. MDW water is also spread in the main basin, upper San Gabriel Canyon Basin, and Glendora Basin.
The Department spreads imported water from MWD and the San Gabriel Valley Municipal Water District (SGVMWD) in the San Gabriel Valley on behalf of the San Gabriel Valley Municipal Water District, Upper San Gabriel Valley Municipal Water District, and the Three Valleys Municipal Water District in the following facilities:
- San Gabriel Canyon Spreading Grounds
- Santa Fe Spreading Grounds
- San Gabriel River
- Little Dalton Spreading Grounds
- Forbes Spreading Grounds
- Irwindale Spreading Basin/Manning Pit
- Citrus
- Ben Lomond
- Valley Rubber Dam
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The County Sanitation District's Whittier Narrows Water Reclamation Plant effluent purchased by the Water Replenishment District of Southern California is transported to the Rio Hondo and San Gabriel Coastal Basin Spreading Grounds for groundwater replenishment.
The County Sanitation District's San Jose Creek Water Reclamation Plant made its first delivery of effluent in November 1972. The effluent released into San Jose Creek, San Gabriel River, or directly delivered to San Gabriel Coastal Spreading Ground via pipeline can be purchased by the Water Replenishment District of Southern California.
Water from the Pomona Reclamation Plant is released down the San Jose Creek - San Gabriel River System to the Department's recharge facilities in the Central Basin spreading grounds.
The maximum amount of reclaimed water allowed for spreading in the Montebello Forebay, effective July 1991, is 60,000 acre-feet per year but not to exceed 150,000 acre-feet over a three-year period.
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SEAWATER BARRIER PROJECTS top
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The Department operates three barrier projects to protect the groundwater in the West Coast and Central Basins against seawater intrusion by creating freshwater pressure ridges along the coastline. The pressure ridges are created by injecting freshwater through a series of injection wells. The amounts of water injected by these wells during the reporting period are as follows:
| Facility |
Imported Water
(Acre-Feet) |
Recycled Water
(Acre-Feet) |
Alamitos Barrier Project:
Los Angeles Portion
Orange County Portion* |
3,677
1,503 |
0
0 |
| Dominguez Gap Barrier Project |
3,769 |
0 |
| West Coast Basin Barrier Project |
8,173 |
8,306 |
*Injected on behalf of the Orange County Water District
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SEASONAL DATA AND MAPS top
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During the reporting period, weekly, monthly, and semi-annual measurements of groundwater levels in observation wells located throughout the groundwater basins in Los Angeles County were made and processed.
Locations of the key wells noted herein are shown on the well map in the Water Conservation summary section. Historical key well level data can be downloaded as ASCII file or from the pull down selection in the Water Conservation summary section.
Static groundwater elevation contour maps for the three major groundwater regions in Los Angeles County are available from the local basin water agencies:
| Groundwater Basin |
Contact |
Upper Los Angeles River Area
(San Fernando Valley) |
Upper Los Angeles River Watermaster
P.O. Box 111, Room 1455
Los Angeles, CA 90051
(213) 367-1020
(213) 367-1131 (FAX) |
| San Gabriel Valley |
Main San Gabriel Basin Watermaster
729 North Azusa Avenue
Azusa, CA 91702
(626) 815-1300
(626) 815-1303 (FAX) |
| Coastal Plain |
Water Replenishment District of Southern California
12621 East 166th Street
Cerritos, CA 90703
(562) 921-5521
(562) 921-6101 (FAX) |
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GROUNDWATER BASINS AND GROUNDWATER RECHARGE
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Groundwater in Los Angeles County is stored in basins underlying five major geographic areas. These groundwater basins are separated by geologic features which impede groundwater movement or by political boundaries. A map of these groundwater basins and the Department's spreading grounds is available upon request from the Department. General spreading grounds facility information is included in the summary section. Monthly water conservation data for the reporting period at the Department's facilities and other pertinent facilities are included in the Water Conservation Summary section of this report. The monthly imported and recycled water deliveries for the reporting period are also included in the Water Conservation summary section. The following is a background summary of the Department's groundwater recharge activities within each of these major areas:
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The Department operates 2,436 acres of spreading grounds and soft-bottom channel spreading areas for replenishment of local groundwater supplies. The Department also assisted in the operation and maintenance of 269 acres of spreading grounds owned by others. An additional 656 acres of spreading grounds are controlled maintained and operated by other agencies. The total gross acreage of spreading grounds in Los Angeles County is 3,361 acres.
Groundwater replenishment consists of storm runoff, imported water, and recycled water. County-wide, the Department spread the following amounts during the reporting period:
County Rainfall Index
(% of Normal) |
211 |
Storm Runoff
(acre-feet) |
365,567 |
Imported Water
(acre-feet) |
40,530 |
Recycled Water
(acre-feet) |
37,510 |
The Department is continuing its efforts to improve its water spreading facilities in order to maximize the amounts of water conserved and to simplify the spreading operations.
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The Department operates 20 spreading facilities in the San Gabriel Valley that receive direct valley runoff and flows from the San Gabriel Mountains. Some of these facilities can also receive imported water. Valley-wide, the Department spread the following amounts during the reporting period:
Storm Runoff
(acre-feet) |
199,709 |
Imported Water
(acre-feet) |
39,363 |
Diversions to Grounds Owned by Others
(acre-feet) |
8,648 |
The Department's spreading grounds replenished the Valley's several groundwater basins as follows:
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Storm Water
(acre-feet) |
Imported Water
(acre-feet) |
Key Wells |
| Main San Gabriel Basin |
130,972 |
10,840 |
3030F, 2965C |
| Upper San Gabriel Canyon Basin |
5,601 |
11,499 |
4284A |
| Lower San Gabriel Canyon Basin |
1,735 |
0 |
4285 |
| Wayhill Basin |
410 |
765 |
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| Foothill Basin |
3,732 |
0 |
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| Glendora Basin |
2,777 |
0 |
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| Claremont Heights Basin |
0 |
0 |
4508A, 4508B |
| Live Oak Basin |
0 |
0 |
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| Chino Basin |
0 |
0 |
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| San Dimas Basin |
62 |
0 |
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| Pomona Basin |
0 |
0 |
3251E, 3261P, 4469A |
| Puente and Spadra Basins |
0 |
0 |
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| Raymond Basin |
8,250 |
0 |
4057H |
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The groundwater basins underlying the Coastal Plain are divided by geological features into the Central (includes the Montebello and Los Angeles Forebays), West Coast, Santa Monica, and Hollywood Basins. Most of the water is spread in the Montebello Forebay. The Department spread the following amounts in the Coastal Plain during the reporting period:
Storm Runoff
(acre-feet) |
96,706 |
Imported Water
(acre-feet) |
953 |
Recycled Water
(acre-feet) |
37,510 |
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The Central Basin has the most storage capacity of the basins in the Coastal Plain. In addition to the water recharged in the Department's spreading facilities, water injected in the Alamitos Barrier Project also contributes to the replenishment of the pressure aquifers underlying the Central Basin. The basin contains Key Well Nos.460K, 1601T, and 906D.
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The West Coast basin is the second largest basin underlying the Coastal Plain and is separated by the Newport-Inglewood Fault zone. Groundwater is primarily recharged by Central Basin subsurface flows and by water injected by the Department in the West Coast Basin and Dominguez Gap Barrier Projects. Groundwater elevations in the West Coast basin are below sea level except in the area of the West Coast Basin Barrier injection mound. The basin contains Key Well Nos. 1346D and 760C.
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Santa Monica and Hollywood Basins
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The Department has no spreading facilities in either of these basins.
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The San Fernando Valley is also known as the Upper Los Angeles River Area (ULARA). Most of the runoff from the surrounding mountains flows to the Valley. The Valley comprises of four basins:
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The basin is the largest basin underlying the San Fernando Valley. The basin contains Key Well Nos. 3872H and 4709. The Department spread the following during the reporting period:
Storm Runoff
(acre-feet) |
61,901 |
Imported Water
(acre-feet) |
141 |
Recycled Water
(acre-feet) |
0 |
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Sylmar, Verdugo, and Eagle Rock Basins
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The Department has no spreading facilities in these much smaller basins.
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The Department has no spreading facilities in the area. Much of the Valley is open space, permitting substantial natural percolation.
The Upper Santa Clarita subunit comprises five basins.
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There are several groundwater subbasins underlying the Antelope Valley. Five of them are located within Los Angeles County.
The Department operates no spreading facilities in the Antelope Valley.
Key Well Nos. 9974 and 8825 are located in the Lancaster and Little Rock subbasins, respectively.
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