- 1). Determine the dissolved oxygen concentration of the water by reading water quality testing results. Read the dissolved oxygen quality index (Q) value off a graph of Q vs. dissolved oxygen concentration.
- 2). Determine the fecal coliform concentration of the water by reading water quality testing results. Read the fecal coliform index value (Q fecal coliform) off a graph of Q vs. fecal coliform concentration. If the number of fecal coliform colonies is greater than 100,000, the fecal coliform quality index is 2.
- 3). Determine the pH of the water by reading water quality testing results. Read the pH index value (Q pH) off a graph of Q vs. pH.
- 4). Determine the Biochemical Oxygen Demand (BOD) of the water by reading water quality testing results. Read the BOD index value (Q BOD) off a graph of Q vs. BOD.
- 5). Determine the temperature change of the water between the point of interest and a point one mile upstream. Read the temperature index value (Q temperature) off a graph of Q vs. temperature.
- 6). Determine the total phosphate of the water by reading water quality testing results. Read the total phosphate index value (Q total phosphates) off a graph of Q vs. total phosphates.
- 7). Determine the nitrates of the water by reading water quality testing results. Read the nitrates index value (Q nitrates) off a graph of Q vs. nitrates.
- 8). Determine the turbidity of the water by reading water quality testing results. Read the turbidity index value (Q turbidity) off a graph of Q vs. turbidity.
- 9). Determine the total solids of the water by reading water quality testing results. Read the total solids index value (Q total solids) off a graph of Q vs. total solids.
- 10
Calculate the Water Quality Index by weighting the individual water quality indices with the following equation:
WQ Index = (Q dissolved oxygen * 0.17) + (Q fecal coliform * 0.16) + (Q pH * 0.11) + (Q BOD * 0.11) + (Q temperature * 0.11) + (Q total phosphates * 0.10) + (Q nitrates * 0.10) + (Q turbidity * 0.08) + (Q total solids * 0.07).
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