Map showing well locations in Kern banking model area
The model simulates the influence of a large number of agricultural, municipal and recovery wells

Key Issues

  • Numerous entities involved with importing, recharging, and banking water
  • Potential beneficial and adverse impacts on water levels and/or water quality beyond the boundaries of an individual project
  • Many unknowns, including agricultural pumping well locations and amounts, and aquifer hydraulic parameters.

Solutions

  • Comprehensive data collection from multiple agencies conducted to develop a strong quantitative conceptual model
  • Crop mapping and water use database used to estimate volume, timing, and location of agricultural irrigation and pumping
  • A technically-robust groundwater flow model developed to demonstrate what may have occurred without banking projects
Map showing simulated flows across Kern banking model area
Simulated groundwater flow across the modeled area

MODFLOW Model Development “With and Without Banking” Evaluation

Kern Fan Area, Kern County, California

A conceptual and numerical model, covering over 500 square miles, was used to simulate the Kern Fan Groundwater Basin if no banking had taken place to support groundwater management.
Photo of Kern County banking conveyance canal
Kern County banking conveyance canal

Kern County has become the nexus for innovative groundwater banking projects in California. Favorable hydrogeologic conditions, availability of imported and local water, and cooperation of numerous water agencies and stakeholders have allowed subsurface storage of significant water supplies. Kern County banking projects have substantially improved water supply reliability both locally and throughout the state. However, it is recognized that banking could have both beneficial and adverse impacts on water levels and/or water quality beyond the boundaries of an individual project.

To resolve these questions Todd Groundwater, working with the Kern Fan Monitoring Committee, has developed a numerical model to evaluate potential impacts to groundwater levels and quality “with and without” banking projects. The process involved development of a conceptual hydrogeologic model of the Kern Fan study area, including characterization of:

  • physical boundaries (lateral and vertical);
  • spatial distribution of alluvial aquifer properties;
  • number, areal extent and thickness of layers; and
  • water balance.

The numerical flow model, based on the widely-recognized MODFLOW software, was calibrated over a 25-year period.

Conclusions

The conceptual model and calibrated numerical model indicate that groundwater levels in much of the Kern Fan area are controlled by the combined management of numerous surface water sources and large volumes of agricultural pumping. The “without banking” analysis is ongoing.

Graph of observed and model-simulated groundwater levels
Groundwater level calibration