Mojave Groundwater Resources


2020 Mojave Region Water-Level Study

REGIONAL WATER TABLE (2020) IN THE MOJAVE RIVER AND MORONGO AREAS, SOUTHWESTERN MOJAVE DESERT, CALIFORNIA by Meghan C. Dick and Whitney Seymour

2020 Groundwater Levels

Data for groundwater-levels measured in 616 wells during water year 2020 (November 2019-June 2020) by the U.S. Geological Survey (USGS), the Mojave Water Agency (MWA), and other local water districts were compiled to construct a regional water-table map which can be viewed as part of an interactive water data map. The regional water-table map shows the elevation of the water table in and around the Mojave River and Morongo areas, in San Bernardino County, California. Due to the dynamic nature of the interactive map, some features referenced in the text may not be visible until zooming in on the map. Previous hydrologic studies (Izbicki and others, 1995; Stamos and Predmore, 1995; Stamos and others, 2001) have modified the boundaries of El Mirage Valley, Upper Mojave River Valley, Middle Mojave River Valley, Lower Mojave River Valley, Harper Valley, Coyote Lake Valley, and Caves Canyon Valley groundwater basins defined by the California Department of Water Resources (California Department of Water Resources, 2016) and herein are collectively referred to as the Mojave River area. Similarly, Trayler and Koczot (1995) modified the boundaries of Lucerne Valley, Johnson Valley, Means Valley, Bessemer Valley, Ames Valley, Deadman Valley, Twentynine Palms, Copper Mountain Valley, Warren Valley, and Joshua Tree groundwater basins (California Department of Water Resources, 2016) and herein are collectively referred to as the Morongo area. Groundwater levels recorded by the USGS and MWA staff were measured and compiled according to the procedures described in the Groundwater Technical Procedures of the USGS (Cunningham and Schalk, 2011). Groundwater levels from other local water districts were measured according to the procedures established by the corresponding agency. Groundwater-level measurements that were furnished by other local water districts but did not meet USGS standards for inclusion in the USGS National Water Information System (U.S. Geological Survey, 2023) are available from the respective well owner upon request. All groundwater-level records compiled for the 2020 study were compared to historical data for quality-assurance purposes.

Groundwater-level contours from the 2018 regional water-table map (Dick and Seymour, 2023) were used as a guide to shape the 2020 groundwater-level contours (Seymour and Dick, 2023). Contours are dashed (approximate) on the regional water-table map where data are sparse. Groundwater-level contours for all study years can be displayed on the interactive map by clicking the desired year under the “Water-level Contours” menu. The 2020 groundwater-level data used to create the contours can be displayed on the interactive map for the Mojave River and Morongo areas by clicking the desired year under the “Groundwater Data” menu. Groundwater-level data for 2020 are accessible through this website's data downloads page by following the Water-level Sites link for 2020 Sites (2020 study).

Groundwater-Level Changes

Groundwater-level data from the USGS National Water Information System database were used to construct 37 groundwater-level hydrographs to show long-term (1930-2020) and short-term (1990-2020) groundwater-level changes in the Mojave River and Morongo areas. Groundwater-level changes between the spring of 2018 and spring of 2020 were calculated by subtracting depth-to-water below land surface measured in the same well during 2018 and 2020. Groundwater-level changes between any of the study years on this website can be displayed on the interactive map by selecting the “Start Year” and “End Year” from the "Water-Level Changes" menu.

Long-Term Groundwater-Level Hydrographs

There are 25 long-term (1930–2020) hydrographs for the Mojave River and the Morongo areas. Three wells were destroyed or were unable to be measured in 2020 (wells 5N/5W-22E6, 11N/4W-29R1, and 11N/4W-30N1), but the historical groundwater levels are included because they are discussed in previous groundwater-level reports.

In some hydrographs, data from more than one well are included to show groundwater-level changes throughout long periods. Data from multiple wells were combined onto a single hydrograph for wells that went dry due to a decline in the groundwater table, or wells that could no longer be measured, and data from a nearby well could be used to continue the record. Data from different wells on the same hydrograph have differently colored data points.

Mojave River Area

The Mojave River area is divided into six subareas: Este, Alto, Oeste, Alto Transition zone, Centro, and Baja. The long-term hydrographs (1930-2020) for the Mojave River area indicate that groundwater levels generally:

  • declined about 20 feet (ft) in the Oeste subarea since 1980 (well 6N/7W-10P2),
  • declined more than 50 ft east of the Mojave River in the Alto subarea since the 1930s (well 4N/3W-1M1),
  • declined about 60 ft in the eastern part of the Harper (Dry) Lake region of the Centro subarea since the 1930s (wells 11N/3W-28R1, -28R2),
  • increased more than 19 ft southwest of Harper (Dry) Lake in the Centro subarea from 1998 to 2020 (well 10N/4W-10D1) because of a sustained reduction in groundwater pumping since the early 1990s (Mojave Basin Area Watermaster, 2021), and
  • declined about 115 ft in the Baja subarea since the late 1940s (wells 9N/2E-20Q1, -20K1, and -20G3).

Morongo Area

The Morongo area is divided into 17 subbasins. All the long-term hydrographs for the Morongo area showed declines in groundwater levels of variable magnitude since the wells were first measured. Groundwater levels generally:

  • declined about 43 ft in the central area of the Joshua Tree subbasin since the late 1950s and increased about 5 ft since 2015 (well 1N/7E-32C1) due to imported water deliveries (Mojave Basin Area Watermaster, 2021),
  • declined about 40 ft the Reche subbasin since 1980 (well 2N/6E-18B2),
  • declined about 110 ft near Lucerne Lake in the Lucerne subbasin between the early 1950s and the mid-1990s (well 5N/1W-25G1), but groundwater levels have recovered about 14 ft because of a sustained reduction in groundwater pumping since the mid-1990s,
  • declined about 121 ft in the eastern part of the Surprise Spring subbasin since 1952 (well 2N/7E-2C1), and
  • declined about 32 ft in the western part of the Warren subbasin between 1951 and 2020, and by more than 320 ft between 1951 and the early 1990s, but have increased about 260 ft since 1994 (wells 1N/5E-36K1 and -36K2) in response to recharge with imported water infiltrated from ponds at the Morongo Basin recharge sites (Mojave Water Agency, 2021).

Short-Term Groundwater-Level Hydrographs

Twelve short-term hydrographs were constructed from data collected between 1990 and 2020 in the Mojave River area. Most hydrographs are for wells located along the Mojave River, which display effects of seasonal recharge from streamflow in the Mojave River, managed recharge, and evapotranspiration. Groundwater levels generally:

Groundwater-Level Changes from 2018 to 2020

Groundwater levels were measured at 522 wells in the Mojave River and Morongo areas in both 2018 and 2020. Groundwater-level changes between both years (or any two years) can be viewed by selecting those years on the groundwater-level change map (groundwater-level change maps can be created using the "Water-Level Changes" menu). The groundwater-level data for 2018 and 2020 were collected during years with below average precipitation, however 2019 had above average precipitation (Mount and others, 2021). Some wells had declines or increases in groundwater levels that were opposite of those in wells in the same area; these anomalies are likely a result of fluctuations in local pumping and distance to managed recharge areas. From 2018 to 2020, groundwater levels generally:

  • increased between 15.01 and 45 ft in about 1 percent of the wells (7)
  • increased between 5.01 and 15 ft in about 7 percent of the wells (38)
  • increased between 0.51 and 5 ft in about 22 percent of the wells (113)
  • remained within 0.50 ft of 2018 levels in about 31 percent of the wells (160),
  • declined between 0.51 and 5 ft in about 34 percent of the wells (179),
  • declined between 5.01 and 30 ft in about 5 percent of the wells (24), and
  • declined more than 30 ft in 1 well.

Mojave River Groundwater Basin

Of the 368 wells within the Mojave River area, groundwater levels:

  • increased between 15.01 and 30 ft in about 1 percent of the wells (4),
  • increased between 5.01 and 15 ft in about 7 percent of the wells (26),
  • increased between 0.51 and 5 ft in about 23 percent of the wells (86),
  • remained within 0.50 ft of 2018 levels in about 23 percent of the wells (85),
  • declined between 0.51 and 5 ft in about 39 percent of the wells (143),
  • declined between 5.01 and 15 ft in about 5 percent of the wells (20), and
  • declined more than 15 ft in about 1 percent of the wells (4).

About 45 percent of the wells in the Mojave River area had groundwater-level declines greater than 0.5 ft and about 23 percent remained within 0.5 ft of 2018 groundwater levels. About half of groundwater levels in wells in the Alto subarea increased. The groundwater-level increases were concentrated along the river and in Victorville and Hesperia, west of the Mojave River. The greatest groundwater-level increases were downstream of the Deep Creek recharge site, which regularly receives water deliveries from the State Water Project (Christy Huiner, Mojave Water Agency, written comm., 2022). Imported water was not applied to the Amethyst Basin recharge site between 2018 and 2020; therefore, increased groundwater levels in those areas are likely the result of reduced pumping volume. Most groundwater levels along the Mojave River in the Alto Transition Zone and the Centro subbasin from Oro Grande to Hodge increased by less than 5 ft. These increases are due to infiltration from the treated wastewater discharged by the Victor Valley Wastewater Reclamation Authority and infiltration of surface-water flow along the Mojave River at the Lower Narrows (10261500; Mojave Basin Area Watermaster, 2021). The majority (61 percent) of wells along the Mojave River in both the Centro and Baja subareas continued to show declines in groundwater levels. A large region of decline between 5 and 15 ft occurred near the Mojave River near the towns of Lenwood and Hinkley Valley. Groundwater-levels continue to decline in this area due to sustained pumping for agricultural and domestic uses (Mojave Basin Area Watermaster, 2021). Southeast of Harper (Dry) Lake, groundwater levels fluctuated about 1 ft from groundwater levels recorded in 2018. In the Baja subarea, wells south of the Mojave River had groundwater-level declines between 0.02 and 4 ft, except for the wells closest to the Newberry Springs managed recharge site. The declines in groundwater levels south of the Mojave River in the Baja subarea were likely due to continued pumping of groundwater for agricultural use (Mojave Basin Area Watermaster, 2021). Most wells north of the Mojave River near Coyote (Dry) Lake had less than 0.5 ft of groundwater-level change.

Morongo Groundwater Basin

Of the 156 wells within the Morongo groundwater basin, groundwater levels:

  • increased between 40 and 45 ft in about 1 percent of the wells (2),
  • increased 20 ft in 1 of the wells,
  • increased between 5.01 and 15 ft in about 10 percent of the wells (15),
  • increased between 0.51 and 5 ft in about 15 percent of the wells (24),
  • remained within 0.50 ft of 2018 levels in about 49 percent of the wells (76),
  • declined between 0.51 and 5 ft in about 24 percent of the wells (37), and
  • declined more than 27 ft in 1 of the wells.

About 24 percent of wells had groundwater-level declines exceeding 0.5 ft since 2018. In the Lucerne subbasin, groundwater levels in wells perforated in the regional aquifer around Lucerne Lake increased by less than 2 ft. Groundwater levels in wells perforated in the perched aquifer changed by less than 5 ft; perched groundwater data are visible on the interactive map under “Additional Data”, “Perched Groundwater (Approx. area)/ Perched-water Wells.” Groundwater-level changes of more than 5 ft did not occur in any wells likely because of reductions in groundwater pumping for agricultural use in the region. Groundwater levels in the Fry, Johnson, Upper Johnson, and Giant Rock subbasins had groundwater-level changes within 0.5 ft of 2018 levels. Groundwater levels in the Deadman, Emerson, and Mainside subbasins were mostly unchanged (within 0.5 ft of 2018 levels), except for one well in each subbasin with groundwater-level increases or declines of 1.1 ft from the 2018 groundwater-level measurement. Most of the wells in the Surprise Spring subbasin had groundwater-level declines less than 5 ft. One well had a groundwater-level increase of 11 ft which can be attributed to a reduction in pumping. In the Reche subbasin, groundwater levels in 4 wells downgradient from the Ames-Reche recharge site increased between 0.9 and 4 ft, while one well south of the site increased 9.3 ft. Groundwater levels in the rest of the subbasin declined slightly (less than 2 ft). The increased groundwater levels are likely due to imported water deliveries to the Ames-Reche managed recharge site (Christy Huiner, Mojave Water Agency, written comm., 2022) and the slight declines are likely due to changes in local pumping. Groundwater levels in the Means subbasin declined less than 3 ft, with the exception of municipal production well 2N/5E-22J1 which increased almost 5 ft. The greatest groundwater-level increases continued to be observed in the Warren subbasin, where managed-recharge operations in Yucca Valley have caused groundwater levels to increase more than 250 ft (well 1N/5E-36K2) since 1994 (Mojave Water Agency, 2021). Well 1N/5E-33J1, in the northern part of the Warren subbasin, had the greatest groundwater-level decline (about 27 ft).