Drilling rig and sample of excavated soil

Key Issues

  • Need to map key aquifers and evaluate groundwater quality in a complex hydrogeologic setting
  • Need for additional supplies and multiple strategies to meet projected demands
  • Potential salt loading problems
  • Need for ongoing monitoring and management

Solutions

  • AB3030 Groundwater Management Planning and subsequent SGMA planning
  • Hydrogeologic characterization and field exploration for well and recharge sites
  • Water balance analysis
  • Development and application of numerical groundwater flow model
  • Groundwater quality modeling
  • Groundwater monitoring program and protocols

Groundwater Management Plan

City of Corona,
Riverside County, California

The City of Corona actively manages its groundwater resources for high quality and sustainable supply in the face of increasing demands.

The City of Corona relies on local groundwater for about one-half of its total water supply. In order to more actively manage this limited resource, the City retained Todd Groundwater to prepare a Groundwater Management Plan (GWMP). The plan follows guidelines set forth in Assembly Bill (AB) 3030 (as amended by SB 1938), which allows the City to address issues of groundwater recharge and storage, critical components for effective management of the local subbasins and the City's water supply.

For the GWMP, Todd conducted a basin-wide hydrogeologic investigation that mapped key aquifers, evaluated groundwater quality, and developed a water balance. The assessment indicated that future projections of groundwater pumping could not be sustained without enhanced groundwater recharge.

Approximately 25 groundwater management strategies including enhanced recharge were developed to accomplish the GWMP basin management objectives. Enhanced recharge strategies evaluated numerous water sources including stormwater, recycled water, and imported water. Management strategies were evaluated with a numerical groundwater flow model, constructed by Todd for the project. The evaluation identified changing components of the water balance associated with management strategies and indicated that no one strategy would accomplish management objectives. As such, a comprehensive program was recommended that incorporated a combination of strategies to be implemented over the next seven years. Todd also reviewed the City's monitoring program, developed monitoring protocols, and provided recommendations for improvement.

The City adopted the plan in 2008. Since that time, Todd has been working with the City on various components of development and management. Recent work for the City has included a recharge feasibility study and an exploration program to better delineate the City's most prolific aquifer system in order to optimize well location and pumping. To evaluate potential water quality impacts of recharge projects, Todd constructed a basin-wide “salt balance” model linked to the MODFLOW flow model and applied it to simulations of future imported water recharge projects.

Currently Todd Groundwater is assisting the City with Sustainable Groundwater Management Act (SGMA) planning for the Temescal Groundwater Basin, which underlies the City and has a medium-priority ranking as defined by the Department of Water Resources (DWR). This assistance has included initial review of jurisdictions and existing groundwater management activities in light of DWR-defined groundwater basin boundaries.

A specific effort was successful development of an application to DWR to modify the boundaries of the Temescal Basin and adjoining Elsinore Basin. This was a collaborative application by the City, Elsinore Valley Municipal Water District, and Temescal Valley Water District. The modification involved the creation of a new Bedford-Coldwater Basin and improved alignment of basin boundaries with alluvium. Justification of the boundary changes was based on scientific evidence and explanation by the three local agencies of how the modifications would enhance groundwater management. Todd Groundwater organized and synthesized substantial information on local hydrogeologic conditions and management practices, and assisted the three agencies with compilation and submittal of the application, which was approved by DWR.