Panoramic photo of Camp Cady with inset of salt cedar foliage
The invasive salt cedar has high rates of evapotranspiration, which utilize precious groundwater resources

Key Issues

  • Declining groundwater levels have resulted in a loss of critical riparian habitat along the Mojave River
  • Vertical hydraulic connection between shallow and deeper aquifer systems was unknown

Solutions

  • Design and implement a comprehensive field investigation program to characterize hydrogeologic conditions
  • Preserve and restore the riparian habitat by irrigation with groundwater pumped from the deep aquifer system

Field Drilling Program to Support Design of an Engineered Riparian Habitat Restoration

Mojave River Groundwater Basin, San Bernardino County, California

Shallow groundwater, which historically supported important riparian habitat along the Mojave River, has declined over time. Todd Groundwater conducted an extensive field investigation to support design of a restoration plan.

Camp Cady is a 1,870-acre property located 25 miles east of Barstow along a 5-mile stretch of the Mojave River in San Bernardino County. Shallow groundwater at Camp Cady has historically supported dense riparian vegetation, including mesquite, cottonwoods, and willows, which offer critical habitat to migrating birds and other desert wildlife. Since 1979, the California Department of Fish & Wildlife (CDFW) has actively managed Camp Cady as a Wildlife Area. However, over the past 30 years, CFDW has seen increasing groundwater production and invasive species threaten the native riparian vegetation within and along the banks of the river. Todd Groundwater conducted a hydrogeologic investigation to characterize the current groundwater conditions at Camp Cady and evaluate the feasibility of restoring riparian vegetation using an engineered solution.

Photo of drilling rig with core sample inset

To characterize the local hydrostratigraphy and groundwater conditions, a field program was conducted involving the installation of 19 monitoring wells within the main channel and along the banks of the river. Monitoring wells were drilled using hollow-stem auger and sonic drilling methods and ranged in depth from 20 to 200 feet. Formation samples were logged in the field and used to develop a detailed hydrogeologic cross section. Lithologic information obtained from the drilling program indicated that a deep aquifer system (in excess of 150 feet deep) was present beneath Camp Cady and was adequately separated from the shallow water table aquifer by fine-grained deposits associated with the Manix Lake Clay beds.

In coordination with Mojave Water Agency staff, Todd Groundwater also conducted a formal pumping test using three installed monitoring wells as variable-depth observation wells to identify the productivity of and hydraulic connection between the shallow water table and deep aquifer system.

Graph showing aquifer model fit to sampled data
Aquifer Test and Model Analysis
Pumping test data were analyzed by simulating the local groundwater system as a 3-layer model in MODFLOW.

Results of the pumping test confirmed that the deep aquifer was a confined system and the permeability of deeper sand units could be effectively developed to restore lost riparian vegetation along protected river bank areas without dewatering the shallow aquifer system. Results of the field investigation were used to refine the hydrogeologic conceptual model of Camp Cady and used to predict potential water level drawdown in a new production well tapping the deep aquifer system. Key technical components of a habitat restoration program, involving new production well design and well pump specifications (including those for standard electric and solar alternatives) were developed and presented along with supporting field data in a final report that will enable CDFW to realize its goals for riparian restoration at Camp Cady.