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2004 Basin Plan Update

2004 Basin Plan Update. Redefining Sub-Basin Boundaries and Ground Water Quality Objectives in the Santa Ana River Watershed. Presenters: Jerry Thibeault, Santa Ana Regional Water Quality Control Board Mark Wildermuth and Andy Malone, Wildermuth Environmental November 15, 2005.

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2004 Basin Plan Update

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  1. 2004 Basin Plan Update Redefining Sub-Basin Boundaries and Ground Water Quality Objectives in the Santa Ana River Watershed Presenters: Jerry Thibeault, Santa Ana Regional Water Quality Control Board Mark Wildermuth and Andy Malone, Wildermuth Environmental November 15, 2005

  2. Develop procedures to calculate groundwater quality objectives • WHY? • Basin Plan Objectives: • TDS: About 200 wells; Two years of data • Nitrate objectives not scientifically calculated • TIN/TDS Study: • TDS/Nitrate: About 1,800 wells; 20 years of data • Nitrate and TDS objectives rigorously calculated

  3. Develop procedures to calculate groundwater quality objectives • Develop volume-weighted management zone estimates of TDS and nitrate concentrations • ConcentrationMZ = MassMZ/GWVolumeMZ • historical ambient conditions (1954 – 1973) • Objective setting period • current ambient conditions (1978 – 1997) • Measure of compliance

  4. Data Collection • Massive data collection effort • Well info, water quality, water level • Procedures: Task 1: Meet with Agencies/Develop Protocols Task 2: Collect Historical Data (1954 to 1997) Task 3: Process, Check, and Upload Historical Data • Data provided in various formats • RDBMS (e.g. OCWD) • Ad hoc storage (e.g. spreadsheets, hard copy)

  5. Develop Queries to Extract Data • QA/QC Checks • Develop TDS and NO3-N time histories • Appropriate statistical tests for normality and outliers • Shapiro-Wilk test • Standard methods tests • Anion-cation balance • Measured TDS vs. calculated TDS • Measured EC and ion sums • TDS to EC ratios • Reject data if any test failed

  6. Develop WQ Point Statistics at Each Well • Each well must have at least three data points in separate years during the analysis period. • TDS and Nitrate-nitrogen • Computed statistics account for variability resulting from: • sampling error • analytical error • hydrological/climatic events • non-homogeneous hydrogeologic properties

  7. Estimate Regional Water Quality • Procedures: • Plot point statistics on maps • TDS and NO3-N • Total maps = 22 • Develop and digitize contours of water quality, accounting for: • Management zone boundaries • Mean values

  8. View Sample Map

  9. Compute Ambient Water Quality for Management Zones • Create 3-D GIS layers of: • Water quality (TDS and Nitrate) • Groundwater elevations • Specific yield • Bottom of the aquifer • Aquifer geometry (layering) where appropriate • 3rd dimension is value of layer

  10. Compute Ambient Water Quality for Management Zones • Create 400x400m grid across all MZs • Populate each grid cell with: • Water quality (TDS and Nitrate) • Groundwater elevations • Specific yield • Bottom of the aquifer • Aquifer geometry (layering) where appropriate

  11. Compute Ambient Water Quality for Management Zones • Post-process GIS grid in Excel • Ambient TDS and NO3 in each MZ • Historical (1954-1973) – Objective • Current (1978-1997) – Compliance • Recomputation (1984-2003) – Compliance • Every three years

  12. Implications of the TIN/TDS Study • Management Zones with Assimilative Capacity • Other Management Zones lack assimilative capacity, and therefore discharges to these basins must have TDS and N03 concentrations at or below the proposed objectives. • Effects: • Planned recycled water recharge projects • Potentially direct recycled water re-use • Surface discharge in reaches that have GWR beneficial uses

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