Water Quality Monitoring


Tools to track progress towards improving water quality in the Severn River!

The Severn River gets pounded year round by a polluted mix of stormwater runoff that floods the river with nitrogen, phosphorus and sediment contaminants that combine to create algae blooms which then decompose and dilute the river of oxygen.

To track how our river responds to this pollution insult, volunteer citizen scientists have joined our fabled Water Quality Crew to create a river-wide network of monitoring stations.

Our water quality monitoring program is supported by a generous grant from Delaplaine Foundation.

Each week (May-October), our WQ Crew and Boat Captains create profiles of the water column in our river and creeks. They track dissolved oxygen, pH, temperature, salinity and clarity.

We started monitoring 8 stations at the top of the river, from Round Bay to Indian Landing. In 2018, we expanded to our monitoring network to 41 stations to cover the entire river. In 2020, we expanded again to monitor 44 stations (see map below).

In 2021, we expanded again to 51 stations. Our monitoring network now extends from all the creeks, from the creeks of Whitehall Bay and Lake Ogleton at the mouth of the Severn, up through the main stem to the very top of the river at Indian Station.

SRA is a Tier 2 data monitor with our partner, the Chesapeake Monitoring Cooperative (CMC).

In 2021, we started qualifying for Tier 3 status with CMC, the highest level for monitoring.

We follow CMC’s WQ monitoring protocols and share all our data with the scientific and regulatory communities via the CMC’s Chesapeake Data Explorer data sharing platform.

You can view all this data on the Chesapeake Data Explorer. Click here. (Note: You do have to drill down a bit to get to the Severn River monitoring stations).

Thanks to support from Delaplaine Foundation, the Eastport Civic Association and donations from our members and communities, we produced a 10-page State Of The Severn Report for the 2019 season. Click here to read the report.

Severn River Report Cards

SRA now produces Severn River Report Cards in partnership with the University of Maryland Center for Environmental Science.

To download the latest report card, click here.

The grades for the State Of The Severn in 2020 were disappointing.

The river’s grade fell from a B to a C-, and we attribute the decline to excess nutrient pollution flooding into the river with stormwater runoff. This produced an extensive spring algae bloom that lasted for nearly two months and led to creation of widespread dead zones throughout much of the river.

We’re currently working on the 2021 Report Card with our partner, the University of Maryland Center for Environmental Science.

Tracking Dead Zones & Algae Blooms

Every week, from April through October, our WQ Monitoring Crews track and report on very low oxygen levels – the so-called dead zone – in the Severn River, and this phenomenon is echoed inside many creeks.

Good healthy levels of oxygen should normally be 5 mg/L or greater to keep our fish, crabs and oysters happy. But we consistently find oxygen levels well below this 5 mg/L level. Oxygen was falling to less than 2 mg/L in large areas of the river and often times, this dead zone is three to five meters tall on the bottom half of the river and its creeks.

These low levels of oxygen create a dead zone – water with  little to no oxygen content.

This can be fatal to fish, crabs and oysters. Some years, this dead zone area is limited to Round Bay.

SRA tracks this dead zone all season long. It usually extends from the headwaters area (near Ben Oaks and Pointfield Landing Communities) to the foot of the Rt. 50 Bridge. In 2019, it was over 5 square miles, roughly the size of Denton, Md.

You can read SRA’s Mid-Summer Report, Tracking The Severn River’s Dead Zone by clicking here.

The river faces constant challenges from human activities and we’re already feeling the impacts of climate change, rising sea levels, and increased frequency and intensity of storms. Add to this mix:

  • fecal bacteria from pets, septic systems and wildlife,
  • mud floods of sediment from uncontrolled construction sites,
  • overuse of lawn fertilizer, especially springtime applications,
  • air deposition of nitrogen into the Severn River from power plants, car and truck exhaust,
  • rapid development,
  • extensive and expanding impervious surfaces (roads, roofs, driveways, parking lots), and
  • loss of vegetation, buffer areas and tree cover.

Another challenge to the waterway is the overloading of nitrogen and phosphorous pollution, especially in the spring time.

In 2020, SRA’s WQ teams started tracking algae blooms, beginning with a massive bloom, known as a Mahogany Tide, which turned the color of river and creeks from green to shades of red-brown-orange (see picture at right).  SRA now tracks algae bloom activity every week. Sadly, the incidence of these blooms is increasing and they’re lasting throughout the season and into late fall.  SRA reported on the latest Mahogany Tide to appear in early December 2022.

This explosion of algae is caused by an overabundance of nutrient-rich stormwater runoff, much of it caused by fertilizing lawns during the spring. Since most of this fertilizer washes off during spring rains, it fuels these algae blooms.

This year’s Mahogany Tide was particularly intense. It last nearly eight weeks and blotted out sunlight that is crucial to the return of our summertime underwater grasses.

The video at the left shows how an intense algae bloom severely reduces clarity in the river.

When we lowered the Secchi Disc into Back Creek, it disappeared right away, barely registering 12 cm reading (about 5 inches) where normally we could expect to see a 50 cm visibility reading.

As rural areas turned suburban and then urban, the Severn lost its ability to bound back from these challenges. Instead, the river suffers from algae blooms, bacterial infestations, sediment and nutrient overloading during every rain event.

Another major challenge to the river is sediment runoff. The picture at right is of silt plume in Luce Creek just after a heavy rain the night before.

Culprit: A dirt-bike recreational area that lacks any best management practices to control stormwater runoff.

This is a problem because the sediment not only silts in the river and creeks, but it carries nitrogen and phosphorus nutrients with it that fuel algae blooms, which cloud the waters, block sunlight from underwater grasses and ultimately cause the dead zone conditions in the river.

Algae die off is a key cause of low-oxygen and dead zone conditions because when algae decompose, that process depletes oxygen.

These factors that have created permanent, oxygen-depleted conditions in our river. Without oxygen, the fishery dies. Fish and crabs swim and sidle away and leave our river. Oysters can’t swim away, so without oxygen, they suffocate in these conditions.

Result: The Environmental Protection Agency declared the Severn River an “impaired” waterway and imposed a “pollution diet” to reduce the flood of pollutants, primarily nitrogen, phosphorous and sediment.

How do we track progress? With a team of volunteer citizen scientists who help monitor 44 stations throughout the entire Severn River watershed. We visit these stations every week from May through October.


Track real data of actual conditions in the Severn River.

Computer modeling can only get to a best-guess of what conditions are like in a waterway.

The only way to really know whether we’re making any progress towards improving water quality – especially reducing the scale of the dead zones – is to collect water quality monitoring data from the river itself.

This is why the Severn River Association collects weekly data readings to paint a portrait of the water column at 44 locations along the 14-mile Severn River and its 39 creeks and coves.

The SRA water quality program was first created under the guidance of Prof. Andrew Muller in 2018. Prof. Muller, an Associate Professor of Oceanography at the U. S. Naval Academy, provided the initial training to a small team of citizen scientist volunteers who collected data from 8 stations in the top of the river.

Since then, SRA’s volunteers, dubbed the WQ Crew, greatly expanded the initial program. They now visit 51 stations every week.

The program collects basic water profile information: dissolved oxygen levels, salinity, pH, temperature and clarity.

Above is WQ Crew Team leader, Mackenzie, recording the data collected at our Marylanders Grow Oysters restoration reef at the foot of the Rt. 50 Bridge.

The photo at left is one of our volunteers, Steve, using a Secchi disk to measure clarity in Lake Ogleton.

A key source of the pollution problems in the Severn River is stormwater runoff from impervious surfaces. SRA advocates for a no net-gain of impervious surface policy. Instead of cutting down trees for development, SRA urges Anne Arundel County to focus on redevelopment of already concreted surfaces, such as underused shopping malls. The no net-gain policy is detailed here.


Severn River Association, Delaplaine Foundation, Chesapeake Monitoring Cooperative, Operation Clearwater, Spa Creek Conservancy, Anne Arundel Community College, Chesapeake Conservation Corps, Chesapeake Bay Trust and our volunteer boat captains and water quality crew.


Program Goal

Collect water quality monitoring data that tracks actual conditions in the Severn River water column

Program Outcomes

  • Collect high-quality data that reveals actual conditions in the Severn River water column
  • Raise public awareness about the condition of water quality in the river
  • Use data to support regulatory, policy and legal decisions designed to reduce pollution levels in the river and improve water quality
  • Support enforcement actions based on collection of top-quality water quality data
  • Create long-term record of water conditions
  • Produce annual report cards on the State Of The Severn River as a means of educating the public about progress towards restoring the river to fishable and swimmable goals of the Clean Water Act.

It’s easy to get involved with the water quality monitoring project. Volunteers are needed from May through October for weekly tours of the river.

For more information, email: