About this Site

This site provides water quality data collected by the Delaware Department of Natural Resources and Environmental Control (DNREC) Surface Water Quality Monitoring Program, DNREC Recreational Water Program, Delaware River Basin Commission Boat Run Program (operated by DNREC), and the University of Delaware’s Citizen Monitoring Program. This site is intended to provide general access to water quality data observed in Delaware’s waterways since 2000. Features of this site include a map interface of all water quality monitoring sites, graphs of water quality data, historical data files, and a water quality conditions search tool.

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. Some stations are also monitored for dissolved metals. The table below provides information on the method and reporting levels of parameters currently available through this site for DNREC water quality monitoring sites:

Water Quality Parameters Visualized in this Site

ParameterMethod Reference (EPA)Reporting Level
Water Column Nutrients
Total PhosphorousEPA365.1 M0.005 mg/l P
Total NSM 4500 NC0.08 mg/l N
Carbon and Organics
Chlorophyll-a (Corr)EPA 445.01 μg/l
Dissolved oxygen – FieldEPA360.10.1 mg/l
Total Suspended SolidsEPA160.22 mg/l
Field pHEPA150.10.2 pH units
SalinitySM20thed-2520B1 ppt
EnterococcusSM20thed-9230C1 cfu/100 ml

University of Delaware Citizen Monitoring Program

Established in 1991, the University of Delaware’s Citizen Monitoring Program collects verifiable water quality data to support public policy decisions and to increase public participation and support for the management and protection of the Inland Bays. Today, the program includes the original Inland Bays Citizen Monitoring Program, the Broadkill River Monitoring Program, the Harmful Algae Monitoring Program, and the Bacteria Monitoring Program.

The program is managed by the University of Delaware Sea Grant Marine Advisory Service at the College of Earth, Ocean, and Environment in Lewes. Support for the program comes from many sources including: Sea Grant; DNREC; the Center for the Inland Bays; U.S. Environmental Protection Agency; the Delaware Estuary Program; the National Fish and Wildlife Foundation and local communities.