OCWD Management Area
620
610
2018 Ambient Water Quality
600
Projected Ambient Water Quality
590
TDS (mg/L)
580
Water Quality Objective
570
560
550
2018
2023
2028
2033
2038
2043
2048
Year
Figure 11-1: Estimated TDS Concentration in Base Case for 30-year Period
With regards to nitrate, the approach used to estimate future nitrate concentrations was similar to the approached used for TDS projections. The nitrate (as nitrogen, N) concentration for each inflow component was estimated using available data. Table 11-2 summarizes the inflow terms and their nitrate-N concentrations for the Baseline Scenario. The flow-weighted average nitrate (as N) concentration for all inflows to the management zone is 2.3 mg/L. The initial concentration was set at 2.95 mg/L (based on the current ambient concentration for the most recent 20-year period). Since the inflow concentration is less than the initial concentration, the estimated future nitrate (as N) concentration gradually decreases. For the Baseline Scenario, the ambient nitrate (as N) concentration is projected to decrease from 2.95 mg/L to 2.8 mg/L over the course of 30 years. Again, as with TDS, the impact of recharging large volumes of high quality GWRS water lowers nitrate concentrations in basin groundwater over time.
BASIN 8-1 ALTERNATIVE 2022 UPDATE
Sustainable Management: Water Quality 11-2
Appendix F - 166
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