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​​​​​​Stream Use-Support Index (SUSI)

Charlotte-Mecklenburg Storm Water Services developed the Stream Use-Support Index (SUSI)  to transform large quantities of water quality data into single numbers, or small sets of numbers, that can be reported in non-technical and comprehensive terms. SUSI water quality data can be easily mapped and it allows comparison of water quality in a body of water over space and time. 

SUSI Scores

SUSI scores for monitoring sites range from 0-100, with a score of 100 indicating superior water quality.  The lower the SUSI score, the lower the quality of water at a given monitoring site.

90-100 = fully supporting  [Green]​
70-89 = partially supporting  [Yellow]
50-69 = impaired  [Orange]
0-49 = degraded  [Red]


 See the water quality​ in the stream nearest your property.


SUSI is constructed around 5 categories of water quality data that represent the most important pollutants and indicators of environmental health in Charlotte-Mecklenburg.  The categories of data included in the index are:

  • Bacteriological
  • Metals
  • Nutrients
  • Physical
  • Biological

Water samples that generate SUSI data are collected once per month at 24 locations throughout Charlotte-Mecklenburg.  Monthly, water samples are analyzed for fecal Coliform bacteria, turbidity, dissolved oxygen, pH, temperature, total phosphorus, copper, chromium, lead, and zinc.  Annually, each monitoring site is surveyed for aquatic macroinvertebrates and in-stream habitat conditions. 

How we test water quality in our streams and lakes 

SUSI was also designed to integrate continuous automated monitoring data for the physical parameters at each monitoring site. View continuous monitoring data.  

Request Water Quality Data