Data access

Explore 274 station records in the University of Delaware portal; use DNREC’s 138-station count only for the General Assessment Monitoring Network.

The routine monitoring network

DNREC says its General Assessment Monitoring Network has 138 stations statewide. Twenty-two are sampled monthly; the others are sampled six or twelve times a year on a rotating schedule. Samples can be analyzed for as many as 30 parameters, including temperature, salinity, water clarity, dissolved oxygen, nutrients, carbon, organic material and bacteria. Some stations also monitor selected dissolved metals. Many records extend back decades, making the network useful for assessing long-term trends. It is not a continuous sensor at every waterway.

Source note DNREC Water Quality Monitoring

Why the water portal shows more stations

The University of Delaware’s Water Quality Portal lists 274 station records across multiple program types and regions. That is a broader catalogue than DNREC’s 138-station General Assessment Monitoring Network. The portal includes categories such as beach, general, boat-run, citizen-monitoring and well records. The numbers describe different scopes; they are not contradictory counts of the same network.

Source note Delaware Water Quality Portal · DNREC monitoring network description

How to use the monitoring portal

Open the Delaware Water Quality Portal and filter by station type, basin or watershed. Select a station to review the parameters and dates available, then compare observations from the same location and season when possible. A single reading can reflect recent rainfall, tide, temperature or sampling conditions. A trend requires multiple comparable observations. The portal allows users to explore stations, generate graphs and download reports; consult the data dictionary or agency notes before combining measurements.

Source note University of Delaware CEMA portal

Impaired waters and clean-up plans

Monitoring data are used to compare conditions with Delaware’s Water Quality Standards and to support the state’s biennial assessment and impaired-waters list. A water body listed as impaired may require a Total Maximum Daily Load (TMDL) or another pollution-reduction strategy. A listing does not mean that every part of the water body is unsafe for every use; the designated use, pollutant and location matter. Conversely, the absence of a specific monitoring result is not proof of clean water.

Season, watershed and sampling context

Water quality varies with season, flow, rainfall, tides and land use. Nutrient and bacteria patterns in an Inland Bay tributary can differ from conditions at an ocean beach or an upstream Piedmont stream. When interpreting a chart, note the station location, date range, units, sample type and whether a value is a single result or a statistical summary.