Presentation on theme: "Torrey Lindbo, Jan Miller, SWRP Clean Water Services"— Presentation transcript:
1 Torrey Lindbo, Jan Miller, SWRP Clean Water Services Water Quality IndexTorrey Lindbo, Jan Miller,SWRP Clean Water Services
2 Role of the Water Quality Index WQI numerically summarizes the information from multiple water quality parameters into a single valueThe single value can be used to compare data from several sitesIt can be used to look at trends over time on a single site
3 Parameters used for WQI UnitsFor a Q value of 90 [Oregon standards]DO % sat.% sat.>82% [>90% unless spawning, then >95%]pHpH units6.9 or 7.9 [6.5 to 8.5]E. coliCFU/100 mL<4 CFU/100 mL [406 CFU/100 mL for grab sample] Temp °C+2.5°C or -4°C [<17.8 deg. C]TurbidityNTU4.0 NTU’sT Phosmg/L P0.05 mg/L P [0.1 mg/L P, Tualatin TMDL]NO3mg/L N0.5 mg/L NBOD5mg/L0.8 mg/LStudent Watershed Research Project (SWRP)
4 Parts of the Water Quality Index Q-Value - indication of water quality relative to 100 of one parameterWeighting Factor - sets the relative importance of the parameter to overall water quality
5 Q ValueThe Q-Value is an indication of how good (or bad) the water quality is relative to one parameter.100 = Very Good1 = Very BadQ = 0Q = 100Q = 25Q = 75Q = 50Very BadVery GoodMedium
11 Adjusting for Missing Data When a parameter is missing, the sum of the weighting factors that have data can be used to adjust the WQISum of the Parametric Index Values is divided by the sum of the weighting factors that have data.