Water Quality Index

WQI Tests:

	Dissolved Oxygen
	Fecal Coliform-bacteria primarily found in the intestines of humans and animals
	pH-measure of acidity of basicity in the water
	Biological Oxygen Demand (BOD)
	Temperature
	Total phosphate
	Nitrates
	Turbidity
	Total Solids-amount of sediment in the water

Sample WQI Curve Chart

For example, a dissolved oxygen curve chart is shown above. If the raw data number found was found. First, find 40 on the x-axis and then move straight up to the curve chart line and then read the Q-value which is plotted on the y-axis. In this case, the Q-value would be a 30. Then the Q value is placed on the WQI form shown below. The Q-value is then multiplied by the weighing factor in the next column giving a total. All of the totals are added together giving an Overall Water Quality Rating.

Test	Test Results	Q-value	Weighing Factor	Total
Dissolved Oxygen	% sat.		0.17
Fecal Coliform	col./100 mL		0.16
pH	units		0.11
BOD	mg/L		0.11
Temperature	Change in °C		0.1
Total Phosphates	mg/L		0.1
Nitrates	mg/L		0.1
Turbidity	JTUs		0.08
Total Solids	mg/L		0.07

Overall Water Quality Index ________

For more information about the Water Quality Index System, click here. The link will take you to the WQI's home page.