The mission of Stream Watch is to increase citizen community engagement in water resource protection and improve our knowledge of stream conditions based on measured stream data.

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What are we monitoring and why?

Bacteria (E. coli & Enterococcus)

People frequently ask if it is safe to swim in White Clay Creek. The answer is complicated. Bacterial samples are collected at multiple sites 5-10 times during the recreational season (May-October) during base flow (48 hours or more of less than .25" of rain preceding the sample grab). This is the time of year when most people use the creek and are likely to be in direct contact with the water. There are 30+ monitoring sites throughout the watershed (DE/PA) where the White Clay Wild and Scenic Program takes samples. This provides a snapshot of the water quality during the recreational season and results often show that the creek does not meet state or federal standards set by the Clean Water Act — sixty-seven stream miles have been added to Pennsylvania's list of impaired streams for exceeding bacteria standards, and preliminary USGS sampling in the White Clay Creek Preserve has shown similarly elevated levels. However, that does not mean people should not get out and enjoy the creek. They must take the proper precautions, like staying out of the creek during a rain event (up to 72 hours after). Rain washes fecal material from pets, wildlife, agriculture, and failing septic systems into the Creek, elevating the levels of harmful bacteria or fecal indicator bacteria (FIB).

Fecal indicator bacteria (FIB) tend to attach themselves to soil particles, so high suspended solids after a rain event lead to increased harmful pathogens. It should be noted that Delaware and Pennsylvania use different standards to measure bacteria that are harmful to human health. The state of Delaware uses Enterococcus, while the state of Pennsylvania uses Escherichia coli (E. coli). In general, the larger tributaries like the main stem and main branches generally have lower bacteria counts due to dilution then smaller headwater streams. While levels are generally above the state water quality standards, swimmers and waders can take the following precautions to recreate to protect themselves from harmful bacteria:

Avoid getting in the water during heavy rainfall and for approximately three days afterward.
Avoid getting in the water if you are sick or have open cuts, scrapes, or wounds.
Shower with soap and warm water after swimming.
Look for signs of poor water quality, such as dead fish, trash, and oil slicks or scum on or near the water, and do not enter water if you see any of the above.
Bring hand sanitizer or soap and clean water for washing your hands after enjoying the creek.

This monitoring effort has been running since 2012, when it began in partnership with the Pennsylvania Department of Environmental Protection; today it continues in partnership with Stroud Water Research Center, Delaware Nature Society, and the University of Delaware. We've also created land-use maps for the drainage area behind each sampling site to help pinpoint likely sources of contamination, and starting in 2016 we added genetic marker testing to identify which specific sources — human, agricultural, wildlife, or pet waste — are present at a given site. Knowing the source lets us target restoration efforts where they'll do the most good, rather than treating every site the same way.

Lab Chemistry (NO₃-N, Ortho-P, Chloride)

Some sites are monitored year-round. At these sites, water samples are collected monthly and analyzed for nitrate (NO3N), orthophosphate (OP), and chlorides (CL). Hand-held water temperature and conductivity measurements are also recorded. Additionally, USGS has several gage locations in the White Clay Creek. This data can be viewed in real time online using the USGS Map Viewer.

Nutrients (NO3-N & Ortho-Phosphate)

The majority of stream miles in the White Clay are listed as impaired for nutrients (nitrates and phosphates) which can enhance algal blooms, deplete oxygen available in the water, and create more expensive treatment costs to water purveyors who depend on the White Clay for drinking water. We are working with our partners to support agricultural and stormwater best management practices (BMPs) on agricultural, municipal, and residential properties throughout the watershed to prevent nutrient and sediment pollution. Agricultural and stormwater BMPs, like manure management, cattle fencing, stream-side tree plantings, vegetated swales, and rain gardens help collect stormwater at the source, slow it down, and allow it to infiltrate and be filtered by plants and soil before it enters the waterway.

Chlorides

The year-round stations improve our understanding of the persistance of salt pollution in streams and rivers (see Freshwater Sources Less “Fresh” from Greater Salt Use, Scientists Say). Salt and brine spread on roads during winter coats roads and parking lots throughout the region. During thaws and rain events, this salt is carried into streams where it can have chronic and sometimes acute effects on biological communities. According to the U.S. Environmental Protection Agency (USEPA), freshwater aquatic organisms should not be affected unacceptably if:

1. Chronic exposure—Four-day average concentration of dissolved chloride, when associated with sodium, does not exceed 230 mg/L more than once every three years.

2. Acute exposure—One-hour average concentration does not exceed 860 mg/L more than once every three years on average.

During snow melts preliminary data from our sensors and grab samples show Conductivity levels in the thousands for prolonged periods. Conductivity is a measure of the ability of water to conduct an electrical current and is directly related to the amount of material (ions) dissolved in the water, meaning that conductivity rises as salt enters the water. Wintertime increases in conductivity in streams throughout the Delaware River Basin have been recorded by the sensor stations and, as expected, have been most pronounced in urban areas with prevalent paved surfaces that are treated with road salt. Below is an example of what we are seeing at Mill Creek during periods of snowmelt.

Starting in 2025, White Clay Wild & Scenic runs a Salt Snapshot survey, a focused sampling effort layered on top of our year-round monitoring network. During the height of road-salting season (typically January–February), volunteers and staff collect chloride and conductivity readings at additional locations beyond our regular monitoring sites, to see how far and how intensely road salt runoff is reaching the stream network during snow and ice events. Road salt (chlorides) applied to streets and parking lots washes into streams during thaws and rain, and unlike many pollutants — chloride doesn’t break down or settle out, once it’s in the water or groundwater, it can persist for months or years. Elevated chloride is toxic to many freshwater organisms: it interferes with the ability of fish, amphibians, and aquatic insects to regulate the salt and water balance in their bodies, and chronic exposure can reduce survival and reproduction long before levels are high enough to cause a visible fish kill. Salt Snapshot data helps us pinpoint where salt loading is most severe across the watershed, informing conversations with municipalities and road departments about smarter winter maintenance practices.

In-Stream Measurements (Water Temperature & Conductivity)

Water temperature is one of the most fundamental factors shaping which species can live in a stream. Warmer water holds less dissolved oxygen, so as temperatures climb, less oxygen is available for fish, macroinvertebrates, and other aquatic organisms, right when their metabolic demand for it is highest. Coldwater species like native brook trout, and many pollution-sensitive macroinvertebrates (mayflies, stoneflies, caddisflies), are especially vulnerable: sustained temperatures above their thermal tolerance can cause stress, reduced growth and reproduction, or die-offs, and can shift a stream’s community toward more pollution-tolerant, warm-adapted species over time. Elevated stream temperatures are often driven by the loss of shading streamside vegetation, stormwater runoff crossing hot pavement, and impoundments that slow and warm water before it re-enters the stream. That’s why we track in-stream temperature at all of our sites and compare readings against state-designated thermal standards, Cold Water Fishery, Trout Stocked Fishery, and Warm Water Fishery, that vary by stream reach and by month.

Conductivity is measured alongside temperature at every site — see the Chlorides section above for why sudden conductivity spikes matter as an early-warning sign of road salt and other pollutant inputs.

Macroinvertebrates

Macroinvertebrates (small aquatic organisms) are excellent indicators of water quality. During 1991-2008, The White Clay Watershed Association gathered baseline data on stream health, and in 2004 partnered with Stroud Water Research Center to conduct a more robust macroinvertebrate study of all 19 Stream Watch sites. The results indicated that only one out of nineteen sites was considered good, ten were fair, and the remaining eight were considered poor based on what was found living there.

Click here to download a brochure of the 1991-2008 Stream Watch project.

Click here to read the full 1991-2008 Stream Watch Report.

State Water Quality Report Submissions

The Clean Water Act (CWA) requires states to identify waters that do not or are not expected to meet applicable water quality standards with current pollution control technologies alone. The White Clay Watershed Association submits our data to both state agencies for consideration in their Integrated Water Report. The data submissions can be accessed below.