Flow-Weighted Two-Source Water Blend

The calculation when an operator combines wells or intakes to hold a contaminant (nitrate, fluoride, hardness, TDS, chloride) under its limit. Blend = flow-weighted average (Q1 C1 + Q2 C2)/(Q1 + Q2): 500 gpm at 4 mg/L with 300 gpm at 12 = (2,000 + 3,600)/800 = 7.0 mg/L, under a 10 MCL. To hit a target between the two source values, the lower-source fraction is (Chigh - target)/(Chigh - Clow): reaching 8 mg/L from a 4 and a 12 needs (12-8)/(12-4) = 50% clean flow (equal flows). A target outside both source concentrations can't be blended to -- it needs treatment or a third source. A blending screen; source concentrations vary, the SDWA MCL applies, and the state primacy agency and the operator's monitoring govern compliance.

blended_conc = (flow1_gpm x conc1 + flow2_gpm x conc2) / (flow1_gpm + flow2_gpm); required_low_source_pct = 100 x (Chigh - target_conc) / (Chigh - Clow) when the target lies between the two source concentrations.

Flow-weighted source-water blending mass balance (AWWA / WEF operator-certification math), by name; the source concentrations vary over time, the SDWA maximum contaminant level applies, and the state primacy agency and the operator's monitoring govern compliance.

The flow-weighted blend is a public mass balance; the source flows and concentrations are the system's measured values.

Estimate. AHJ and licensed professional govern.

Field names used by the API: flow1_gpm, conc1, flow2_gpm, conc2, target_conc, blended_conc, required_low_source_pct

• Flow-weighted blend blended = (Q1 C1 + Q2 C2)/(Q1 + Q2); the same mass balance as the pounds formula applied to two streamsAWWA / WEF operator math
• Target split lower-source fraction = (Chigh - target)/(Chigh - Clow) when the target is between the sources; a target outside both can't be blended toblending mass balance