2025 Water Quality Across the Chesapeake: What Waterkeepers are Seeing in Their Watersheds

You check the weather before heading out on the water. But there’s another condition worth checking: the water itself.

Across the Chesapeake Bay watershed, Waterkeeper partner organizations ask those questions every year. In 2025, sixteen Waterkeeper organizations monitored rivers, streams, tributaries, and recreational waterways across Maryland, D.C., Pennsylvania, and Virginia, collecting data that help communities understand what’s happening beneath the surface. Eight of those partners produce annual report cards that turn monitoring data into a closer look at the health of local waterways. That’s where we’re focusing our attention.

What we Tracked in 2025

Waterkeepers across the Chesapeake Bay watershed used their monitoring programs to track a range of indicators, including fecal bacteria such as Enterococcus and E. coli, dissolved oxygen, nitrogen, phosphorus, chlorophyll-a, water clarity, turbidity, conductivity, and pH. Some programs also tracked water and air temperatures and considered rainfall and other weather conditions when interpreting results.

For this report, we’re focusing specifically on bacteria because it is closely tied to recreational water quality and because several 2025 monitoring programs documented a connection between rainfall and elevated bacteria levels.

Monitoring frequency and locations varied by watershed. Sampling ranged from biweekly to weekly during the recreational season, while some organizations conducted broader water quality monitoring from spring through fall.

Instead, we looked at what each organization found in its own watershed and asked: Where do we see similar patterns across the Chesapeake?

2025: Dry Conditions, Followed by Rain

Prolonged dry conditions across much of the region played an important role in water quality this season. When extended dry periods are followed by rain, pollutants that have accumulated on the landscape are washed into nearby waterways. Several Waterkeeper monitoring programs saw this pattern in 2025, but the data shows that drought and rainfall were not the only factors affecting bacteria levels.

What We Found: Rain Can Change the Picture Quickly

Across several monitoring programs, rainfall emerged as an important factor in bacteria levels. Sites that had experienced dry conditions could see bacteria increase following rain, highlighting how quickly water quality can change after a storm.

The pattern was especially clear when rain occurred shortly before sampling. Runoff can wash bacteria and other pollutants from streets, fields, shorelines, and other surfaces into nearby waterways.

ShoreRivers saw some of its highest bacteria readings following storms in the Chester, Choptank, Miles-Wye & Bayside, and Sassafras watersheds. Arundel Rivers Federation found that 88% of samples passed when there had been no rain within 48 hours of testing, compared with 70% following minor rain and 25% following severe rain. James River Watch also reported lower recreational water pass rates during a year marked by high precipitation and a particularly stormy July.

The pattern is clear across several programs: rain can quickly change water quality. But that isn’t the whole story.

When High Bacteria Levels Persist in Dry Weather

For several monitoring programs, some sites continued to show elevated bacteria levels despite little or no recent rain. These results suggest that persistent or localized pollution sources may be contributing to poor water quality even in the absence of rainfall.

In the Anacostia watershed, Hickey Run and Watts Branch consistently failed recreational water quality standards, while other sites showed elevated bacteria under both wet and dry conditions.

ShoreRivers found similar patterns on the Eastern Shore. In the Chester watershed, Millington Waterfront Park passed just 13% of sampling events and experienced repeated dry-weather failures. In the Sassafras, Fox Hole Landing passed 20% of the time and experienced six failures following at least 40 hours without rain. Potential sources identified across these sites included septic systems, wastewater infrastructure, stormwater, and boating-related pollution.

These dry weather failures matter because they show that rainfall and runoff alone cannot explain poor water quality at these sites. Rain may trigger bacteria spikes or increase pollution from existing sources, but elevated levels during dry conditions point toward persistent sources that may need to be identified and addressed.

One Watershed, Many Stories

Regional water quality trends can tell us a lot, but they do not tell the whole story. Even within the same watershed, individual sites can experience very different conditions. Some consistently meet the water quality standards, while others are highly variable or regularly struggle.

The Anacostia River provides a clear example. Mainstem sites passed recreational water quality standards 75.8% of the time in 2025, compared with the 13.3% for tributary sites. Smaller tributaries can be more immediately affected by stormwater runoff and nearby pollution sources, while larger mainstem waterways have greater water volume.

And bacteria was only part of the story. Across the Chesapeake, Waterkeepers also documented changes in nutrients, algae, dissolved oxygen, and water clarity, sometimes improving in one part of the watershed and declining in another.

The result is not one Chesapeake-wide story, but a collection of local stories connected by common pressures.

Why Monitoring Matters

Water quality monitoring tells us whether a site passed or failed on a given day, but it also does more than that. Over time, these data points help Waterkeepers identify patterns, investigate potential pollution sources, track changes in local waterways, and give communities information about recreational conditions.

The 2025 data show why that long-term perspective matters. Recurring dry weather problems can point to sources that require a different response, while rainfall can quickly change conditions. Continued monitoring and support from volunteers and communities within those watersheds will help the Waterkeepers distinguish between those patterns and allow them to inform their communities and identify where further action or investigation may be needed.

Explore the 2025 Water Quality Reports

Together, these reports provide a window into both the shared challenges facing the Chesapeake region and the localized conditions affecting individual waterways.

Explore the individual 2025 reports to see what the Waterkeepers found in their local watershed. Make sure to locate your nearest Waterkeeper to stay up to date on water quality monitoring and ways to get involved.