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What is the WQI?CityofGreensboroNorthCarolina
The Water Quality Index is a single value that represents several combined measurements. The single value can be easily interpreted by managers, elected officials, and citizens.

The calculation for the WQI varies slightly for each monitoring program, as each program uses different measurements. To view real-time water quality data, visit this interactive water quality index map.

Stream Monitoring
The WQI calculation for streams consists of nine measurements including temperature, dissolved oxygen (DO%), fecal coliform, biochemical oxygen demand (BOD), total phosphorus, turbidity, total suspended solids, total dissolved solids, and nitrate nitrogen. Each measurement is assigned a score from 0-100, these nine scores are then averaged to determine the WQI value. The WQI value for each stream site is assigned a score ranging from 0-100.

Good (80-100)
Above Average (60-80)
Average (40-60)
Below Average (20-40)
Poor (0-20)

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Habitat Monitoring
The WQI value for habitat takes into account stream conditions such as bottom substrate, shading, pool and riffle variety, and bank stability. The WQI value is calculated from the habitat assessment form created by the Division of Water Quality of North Carolina Department of Environment and Natural Resources (NCDENR). The WQI value for habitat is assigned a score ranging from 0-100. For more information on the habitat assessment form, visit the Biological Assessment Unit Web page, and refer to the Standard Operating Procedure Manual under the Benthos section.

Good (80-100)
Above Average (60-80)
Average (40-60)
Below Average (20-40)
Poor (0-20)

waterqualityindex

Benthic Macroinvertebrate Monitoring
The qualitative WQI rating for benthic macroinvertebrates is the same as the bioclassification rating, which is based on the type and number of species collected. Different benthic macroinvertebrate species have varying levels of pollution tolerance, which impacts their ability to survive in a particular stream based on the stream's conditions. For more information on bioclassification rating, visit the NCDENR's Biological Assessment Unit Web page, and refer to the Benthos section.

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Fish Community Sampling
The qualitative WQI rating for fish community sampling is the same as the North Carolina Index of Biological Integrity (NCIBI). The NCIBI is based on twelve factors such as the type and number of species found, their age group and whether signs of disease were observed. For more information on the NCIBI, visit the NCDENR's Biological Assessment Unit Web page, and refer to the Fish Community section.

nonnumericWQIscale

Last updated: 6/27/2017 1:42:45 PM