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Macroinvertebrate Survey

Macroinvertebrate Survey and Water Quality Rating

 

D 

Sensitivity 

Macroinvertebrate 

Sensitivity
Rating 

Abundance 

Weight Factor 

A x C 

Very Sensitive 

Stonefly nymph 

10 

 

 

 

Mayfly nymph 

 

 

 

Sensitive 

Alderfly larva 

 

 

 

Caddisfly larva 

 

 

 

Water mite 

 

 

 

Tolerant 

Dragonfly nymph 

 

 

 

Waterstrider 

 

 

 

Whirligig beetle & larva 

 

 

 

Damselfly nymph 

 

 

 

Freshwater shrimp  

 

 

 

Very Tolerant 

Diving beetle 

 

 

 

Freshwater worm 

 

 

 

Waterboatman  

 

 

 

Backswimmer 

 

 

 

Bloodworm  

 

 

 

 

TOTAL 

 

 

 

 


Calculating Water Quality  


1. Refer to the weight table and enter the weight factor for each macroinvertebrate in Column C. 

2. Multiply the sensitivity rating (Column A) by the weight factor (Column C) for each macroinvertebrate and enter in Column D.
 

3. Total Column C (weight factors). 

4. Total Column D (sensitivity rating x weight factor). 

5. Calculate the Stream Pollution Index (SPI) value.  

6. Use the Stream Pollution Index value to find the Water Quality Rating.  


Stream Pollution Index = Total Column D / Total Column C =

Water Quality Rating =