Modeling Issues of the Delta Salinity Jamie Anderson Ph.D., P.E. CWEMF Workshop February 6, 2007 Modeling Support Branch Bay Delta Office

Delta Salinity Modeling Issues Choice of parameter (Jamie Anderson) Cross sectional variation in salinity (Pete Smith) –Vertical stratification –Lateral variations

Salinity Parameters for Calibration Electrical Conductivity (EC) –A measure of the ability of water to conduct an electric current between electrodes (uS/cm), indirect measurement Total Dissolved Solids (TDS) –A quantitative measure of the residual minerals dissolved in water that remain after evaporation of a solution (mg/l) Practical Salinity Units (PSU) –Unitless scale used in oceanography defined by the ratio –Corrections for field conditions Values range from 2-42 Ocean water  35 psu

Salinity Parameters (cont.) Additional salinity parameters –Chloride – taste, industrial process –Bromide – DBP (THMs, bromate) precursor –Sodium – health –Hardness – M&I uses and –Nitrates and sulfates – Ag uses Water quality standards –Current WQ Control Plan uses EC and chlorides –Bromide may be added for Safe Drinking Water Act

Salinity Parameters for Calibration ECTDSPSU PRO *Widely measured in field data *15-minute measurements Conservative *Conservative *Calculated based on field EC CON *Not conservative *Underestimates salinity at high concentrations *Not widely available *Grab samples *Corrections needed for low EC *Doesn’t reflect land based salts Calibration Issues EC derived dispersion coeffs in bays may be too high for truly conserv. constituent Need to convert field EC to TDS for boundary conditions and internal sites Intended for high salinity, corrections needed for Delta Suits, 2002 Annual Report CH6 Calibrating DSM2-QUAL Dispersion Factors to Practical Salinity

DSM2 Salinity Simulations EC –Simulated directly –Calibrated TDS, Chlorides, Bromides, etc. –Typically not simulated directly –Converted from simulated EC using regression equations that vary by Location Hydrologic year type Season

EC vs TDS Figure D-1. Simultaneous measurements of total dissolved solids concentration and electrical conductivity. c. In Old River near Highway 4 Crossing between March 1989 and February 1998

EC vs Chlorides Figure D-2. Simultaneous measurements of chloride concentration and electrical conductivity. c. In Old River near the Los Vaqueros intake between March 1989 and January 1998