Delaware.gov logo

Water Quality Monitoring



Delaware’s bays, ponds, streams, and rivers are monitored on a regular basis to assess the quality of Delaware’s surface waters. Much of the monitoring is done by DNREC, though other groups, including federal agencies, academic institutions, and citizen volunteer monitoring programs, also contribute to these efforts.

Contact Us

Watershed Assessment and Management
302-739-9939

Water Quality Monitoring Plans DNREC Water Quality Data Portal

Delaware’s Surface Water Quality Monitoring Program collects data on the chemical, physical, and biological characteristics of Delaware’s surface waters and consists of seven major components:

  • General Assessment Monitoring
  • Chesapeake Non-tidal Monitoring
  • Continuous Water Quality Monitoring
  • Biological Assessment Monitoring
  • Toxics in Biota Monitoring
  • Toxics in Sediment Monitoring
  • Monitoring under the Watershed Approach to Toxics Assessment and Restoration (WATAR) Plan

DNREC Monitoring

DNREC routinely collects water quality data through the General Assessment Monitoring Network (GAMN). Currently, this network consists of more than 156 monitoring sites across the state. 22 sites are monitored monthly, while the remainder are monitored either six or 12 times a year on a rotating basis. Some of the stations in this network have been active since the 1970s, which provides for long-term status and trends assessments.

All water quality samples are analyzed for up to 30 parameters. General characteristics, like temperature, salinity, water clarity, and dissolved oxygen levels, are measured. In addition, the concentrations of several species of the nutrients nitrogen and phosphorus are quantified, as are the levels of carbon, organic material, and bacteria. Some stations in select watersheds are also monitored for the dissolved forms of key metals like copper, lead, and zinc, in the water column.

Monitoring Data

Data produced from these monitoring efforts is used for several purposes. First, it is compared to Delaware’s Water Quality Standards and used to prepare a Combined Watershed Assessment Report (305(b) Report) and List of Impaired Waters (303(d) List) every even-numbered year.

In addition, data has been used to support Total Maximum Daily Load (TMDL) development, justify the need for pollution reduction strategies, and allow for the evaluation of best management practice (BMP) effectiveness and annual progress towards meeting goals.

Water Quality Monitoring Partners

In addition to the monitoring conducted by DNREC, several partner organizations also collect water quality data.

The US Geological Survey maintains a National Water Information System (NWIS) and has several active stations within Delaware where stream flow, tidal stage, and chemical and physical data are collected.

The University of Delaware coordinates a Citizen Monitoring Program of volunteers who actively collect data on water quality conditions in the Broadkill River and Inland Bays Watersheds.

The Nanticoke Watershed Alliance coordinates the Creekwatcher Citizen Monitoring Program where volunteers collect water quality samples from across the Nanticoke Watershed in both Delaware and Maryland.

The Delaware Nature Society maintains a Technical Monitoring Program that allows volunteers to monitor stations in the Christina River Basin as well as in both the Appoquinimink River and Mispillion River Watersheds.

Learn more about the quality of Delaware’s waters using the DNREC Water Quality Monitoring Network Data Portal. This site allows users to search for monitoring stations throughout the state, see the latest water quality conditions, generate graphs of data, and download data reports.




+