Salt inflows and outflows overlaid on a map of the area surrounding Corona

Key Issue

  • Managed aquifer recharge is necessary to sustain projected future pumping levels

Solutions

  • Conduct a comprehensive basin-wide hydrogeologic investigation to characterize the subbasins including perennial yield and groundwater quality
  • Develop management strategies to address long-term groundwater demand and quality
  • Construct and apply mathematical and analytical models to quantify impacts of water management strategies

Numerical and Analytical Modeling to Support Groundwater Management

City of Corona, California

Numerical and analytical groundwater modeling was conducted to assess impacts of managed aquifer recharge alternatives on groundwater sustainability and quality
Photograph of the outskirts of the City of Corona
	     and surrounding hills

The City of Corona relies on local groundwater for almost one-half of its water supply. In order to more actively manage this limited resource, the City retained Todd Engineers (now Todd Groundwater) to prepare a Groundwater Management Plan. Todd conducted an extensive basin-wide hydrogeologic investigation that mapped key aquifers, evaluated groundwater quality, and developed a water balance of inflows, outflows, and change in storage. The assessment indicated that future projections of groundwater pumping could not be sustained without enhanced groundwater recharge.

Twenty-five groundwater management strategies were identified and evaluated. Many strategies supported the enhanced recharge of various water sources including stormwater, recycled water, and excess imported water.

Management strategies were evaluated with a numerical groundwater flow model (MODFLOW), constructed by Todd. The evaluation indicated that no single strategy would accomplish management objectives. As such, a comprehensive program was recommended that incorporated a combination of strategies.

Graph of simulated annual TDS inflows and outflows

To evaluate potential water quality impacts associated with recharge projects, a basin-wide salt-balance model was constructed to predict future groundwater concentrations of total dissolved solids (TDS) and nitrate. Groundwater volumetric inflows and outflows were linked to TDS and nitrate concentrations for all key sources and sinks, and impacts were estimated for a future 20-year period. The analysis was linked to the MODFLOW flow model.

Simulations of future imported water recharge projects indicate that the addition of relatively higher-quality Colorado River or State Water Project water will help to at least maintain — and more likely improve — overall TDS and nitrate concentrations in the future.