Ambient Lakes Monitoring

Lakes are valued for the multiple benefits they provide to the public, including recreational boating, fishing, drinking water, and aesthetic enjoyment.  The Division of Water Resources seeks to protect these waters through monitoring, pollution prevention and control, restoration, and public education activities. The Ambient Lakes Monitoring Program (ALMP) originated under EPA's Clean Lakes Program and is designed to identify long-term trends of lakes and reservoirs across North Carolina.  The water quality data collected is used to calculate the state of nutrient enrichment (trophic state) and determine if lakes meet their designated use. 

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 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.



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:


Trophic State
< -2.0
-2 – 0.0
0.0 - 5.0
> 5.0



Basinwide Assessment Reports are created every 5 years on a rotating basis. Reports for a given summer season are typically uploaded the following spring. All reports are uploaded here. Scroll down to Basinwide Assessment Reports and use the accordion to navigate to the basin of interest. 


Staff Contacts:

NC Lakes Monitoring Program Coordinator
(919) 743-8413

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The mission of the Water Sciences Section is to provide the Division with accurate information pertaining to waters of the state. Excellent service along with water quality monitoring and certification programs and analytical laboratory analyses that provide scientifically defensible data are the section’s main avenues for accomplishing this mission. These activities support the management and protection of North Carolina’s water resources for the health and welfare of the citizens of North Carolina and the economic well-being of the state.  

 Water Sciences Section 1621 Mail Service Center Raleigh, NC 27699-1621

919.733.3908 (Chemistry)