About this Project

This site presents water quality data collected by Delaware Department of Natural Resources and Environmental Control (DNREC) Surface Water Quality Monitoring Program. As part of its Surface Monitoring Program, DNREC maintains a General Assessment Monitoring Network (GAMN) of about 140 stations. GAMN stations are considered long term stations whose data is used to:

  • Describe general water quality conditions of the State’s surface waters;
  • Identify long term trends in water quality;
  • Determine the suitability of Delaware waters for water supply, recreation, fish and aquatic life, and other uses;
  • Calculate annual nutrient loads and track progress toward achieving Total Maximum Daily Loads (TMDLs) targets; and
  • Evaluate the overall success of Delaware's water quality management efforts.

Monitoring frequency at GAMN stations follows a 5-year rotating basin schedule in which every station is monitored monthly for 2 years and monitored every other month for the remaining 3 years. Each station is monitored for conventional parameters such as nutrients, bacteria, dissolved oxygen, pH, alkalinity, and hardness (see Table below for a complete list of parameters). Some stations are also monitored for dissolved metals.

In addition to the GAMN stations, DNREC maintains a limited number of sites where water quality data are collected continuously by YSI datasondes or high frequency sampling is conducted using equipment such as Aqualab Water Quality Analyzer. Data collected at continuous monitoring sites and high frequency sites are posted on this site on a near real-time basis.

Water Quality Parameters analyzed at DNREC GAMN Stations

* Denotes variables reported within this site.
ParameterMethod Reference (EPA)Reporting Level
Water Column Nutrients
Total Phosphorous*EPA365.1 M0.005 mg/l P
Soluble Ortho-phosphorus EPA365.10.005 mg/l P
Ammonia Nitrogen EPA350.10.005 mg/l N
Nitrite+Nitrate N EPA353.30.005 mg/l N
Total N*SM 4500 NC0.08 mg/l N
Carbon and Organics
Total Organic CarbonEPA415.11 mg/l
Dissolved Organic CarbonEPA415.11 mg/l
Chlorophyll-a (Corr)EPA 445.01 μ/l
Biochemical Oxygen Demand
BOD5, N-Inhib (CBOD)SM20thed-5210B2.4 mg/l
BOD20, N-Inhib (CBOD)SM20thed-5210B2.4 mg/l
Dissolved oxygen – WinklerEPA360.20.25 mg/l
Dissolved oxygen – Field*EPA360.10.1 mg/l
Total Suspended Solids*EPA160.22 mg/l
AlkalinityEPA310.11 mg/l
HardnessEPA310.25 mg/l
Field pH*EPA150.10.2 pH units
Conductivity - FieldEPA120.11 μS/cm
Salinity*SM20thed-2520B1 ppt
Secchi DepthEPA/620/R-01/003meters
Light AttenuationEPA/620/R-01/003%
TurbidityEPA180.11 NTU
ChlorideEPA325.21 mg/l
Enterococcus*SM20thed-9230C1 cfu/100 ml