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Ground-water Resources of the Mojave River Basin, California

Project PhotoProblem: Water supply for the Mojave River basin is derived mainly from ground-water pumpage, and most of the ground-water recharge in the basin is from the Mojave River. A thorough understanding of ground-water and surface- water relations is essential for future management and use of local and imported water and to evaluate management options for artificial recharge along the river. Other areas requiring a thorough understanding include regional ground-water flow, effects of pumping on ground-water levels and land subsidence, and effects of artificial recharge away from the river.

Objective: As the project has evolved from a single study of ground-water and surface-water relations to studies of a number of other ground-water related topics (recharge from ephemeral streams, regional ground-water flow, and land subsidence), the project objectives also have changed with time. The reader is referred to individual discussions of progress and plans for objectives of each of the individual study elements.

Relevance and Benefits: An improved understanding of ground-water and surface- water relations in the Mojave River basin will aid managers in making decisions regarding the best use of local and imported water and evaluating various ground-water management options.

Approach: Historical recharge from the Mojave River will be estimated using discharge records from gaging stations and water-level measurements from wells. Phreatophytes will be mapped using aerial photographs, and ground-water pumpage will be determined from reported values and from water requirements for agricultural and municipal use. Hydraulic conditions controlling exchange of water between the river and river deposits will be quantified by infiltrometer tests, observation-well and gaging-station data, and channel and flood-plain geometry.

Progress and Significant Results in FY 1999:

Water-Level-Contour Map--A report describing 1998 ground-water levels in the Mojave River and Morongo ground-water basins was prepared for colleague review.

Ground-Water Flow Model--A regional ground-water flow model of the Mojave River basin was calibrated, and work was begun on a summary report describing the model results.

Lucerne Valley Ground-Water Model--Work continued on the calibration of the model, which also incorporates simulation of aquifer compaction caused by pumping.

Development of Model Visualization Tools--Work continued on visualization tools to better understand output from regional ground-water flow models.

Lucerne Valley and El Mirage Subsidence--INSAR (Interferometric Synthetic Aperture Radar) images were purchased for the Lucerne Valley and El Mirage area. Preliminary analyses of the INSAR images for October 21, 1993, and May 10, 1996, indicate about 40 millimeters of land subsidence south of El Mirage dry lake.

Ephemeral Stream Recharge--Model simulations were completed and a journal article describing model results was prepared for review. Work also started on a data report for the study and the final interpretive report.

Plans for FY 2000:

Water-Level Contour Map--The report describing 1998 ground-water levels will be revised following review and published. During spring 2000, water levels will be measured ain about 700 wells in the Mojave River and Morongo ground- water basins. Work will begin on a report describing year 2000 water-level conditions (to be published by September 30, 2000).

Ground-Water Flow Model--The final interpretive report describing results of the regional ground-water flow model for the Mojave River basin will be prepared for review and published by September 30, 2000.

Lucerne Valley Ground-Water Model--The final interpretive report describing the geohydrologic framework of Lucerne Valley will be prepared for review and publication by September 30, 2000.

Ephemeral Stream Recharge--The data report and the final interpretive report will be prepared for review and publication. Work will begin on a 2-year extension of this element of the project in order to estimate the rate, spatial distribution, and water quality of ground water recharged through ponds along Oro Grande Wash.

Lucerne Valley and El Mirage Subsidence--An interpretive report will be prepared describing the INSAR methodology and indicating areas of land subsidence.

Age Dating of Water Samples--Since 1995, the USGS has collected water samples from about 600 wells in the Mojave River ground-water basin and adjacent areas. Stable isotopes of hydrogen and oxygen were determined in most of the samples in order to aid identification of the source of recharge water and the time since recharge (age of water). During the coming year, the isotope data will be analyzed in order to determine the source, movement, and age of ground water in a number of areas having important water-management or water-supply issues. Results generated from the analyses of isotopic data will be compared with results of the USGS regional ground-water flow model of the Mojave River basin.

Number: CA497
Location:
Cooperating Agencies: Mojave Water Agency
Project Chief: Peter Martin
Period of Project: Continuing
Team:

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Page Last Modified: Thursday, 05-Jan-2012 15:16:55 EST