Ambient Lakes Monitoring

ISB samples approximately 160 lakes on 5-year rotating basin schedule.  Lake stations are located statewide.

Lake Sampling Locations (click on site for more information)

List of Location Descriptions 
 

Monitoring:

• Monitoring is performed monthly during the summer (May through September).
• Lakes have 1-12 stations depending on the size and the characteristics.
• Database includes chemical and physical results dating back to 1981

Criteria for lakes in the Ambient Lakes Program include:

• Lake must be >10 acres,
• Lake must be accessible to the public,
• Lakes that are a water supply,
• Lake that has significant recreation,
• Lakes as requested depending on its characteristics or water quality concerns.

Methods:

Detailed Quality Assurance Program (QAPP) which includes methodology can be found to the left of this page.  Physical data such as temperature, dissolved oxygen, pH and specific conductivity are collected from the surface to bottom. Chemical data are collected in the photic zone (zone of light penetration).  Common chemical parameters include total residue, total suspended residue, turbidity, chlorophyll a, phytoplankton and nutrients.  Hardness is collected at the surface.

NC Trophic State Index:

North Carolina Trophic State Index (NCTSI) is calculated by using chemical and physical parameters to determine the productivity of a lake.  The NCTSI formula for this calculation is as follows:

• NCTSI = TONScore+ TPScore+ SDScore+ CHLScore
• CHL = Chlorophyll a (μg/l)
• TON = Total Organic Nitrogen (mg/l)
• TP = Total Phosphorus (mg/l)
• SD = Secchi Depth (inches)

  NCTSI- North Carolina Trophic State Index Scale:

Staff Contacts

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