High concentrations of nitrate and TDS occur infrequently in the study area but moderate concentrations are relatively widespread. Six percent (6%) of the wells analyzed for trends had current nitrate concentrations that were high (> 10 mg/L as N), 37% had moderate nitrate concentrations (> 5 ≤ 10), and 57% had low nitrate concentrations (≤ 5) (Table 2). Current TDS concentrations were high (> 500 mg/L) in 5% of the wells, moderate (> 250 ≤ 500) in 67%, and low (≤ 250) in 28% (Table 2). The frequency of wells having high, moderate, and low concentrations in this study, is similar to the results of Kent and Belitz (2012) for the present study area within an assessment of the entire Inland Santa Ana Basin when the lower benchmark for TDS used in the present study is taken into account.