Ground Water

Ground-water is an important resource in the Santa Ana Basin, providing approximately two thirds of the water supply. Water-quality samples were collected from 207 wells in the Santa Ana Basin to assess the occurrence and distribution of dissolved constituents in ground water. These wells were sampled during eight studies from 1999 to 2001 that were designed to sample the used water resource at different scales: 

1. Three subunit surveys (SUS) characterized water quality at a regional scale.  
2. Two flow-path studies (FPS) focused on spatial and temporal variations in water quality along a flow path.
3. One urban land-use study (LUS) focused on evaluation of water quality in shallow ground water.
4. Two California Aquifer Susceptibility studies (CAS) assessed aquifer susceptibility to contamination. 

Ground water samples were analyzed for major ions, nutrients, pesticides, volatile organic compounds, and trace elements.   

The Santa Ana Basin was broken up into three subunit surveys.

• Coastal Subunit Survey
• Inland Subunit Survey
• San Jacinto Subunit Survey