Water Quality and Streamflow

Water Quality Parameters

Water quality is monitored at 25 different sites throughout the watershed. The following parameters are tested: dissolved oxygen, phosphorus (total and dissolved), nitrogen (nitrates and ammonia), suspended solids, conductivity, pH, and water temperature.

Streamflow levels

OARS maintains staff gauges at nine tributary stream sites in the SuAsCo watershed to measure streamflow; streamflow is recorded for these sites with every water quality sampling. Streamflow data is also recorded from USGS for their five continuous flow gauges in the watershed:

Groundwater levels are recorded from the USGS monitoring well in Acton.

Physical Habitat

Fish rely on specific features within a stream to find food, reproduce, avoid predators, and escape from warm water temperatures. Fish rely on specific features within a stream to find food, reproduce, avoid predators, and escape from warm water temperatures. These features, known as habitat measures, include:

The availability of cover for fish, such as woody debris, overhanging vegetation, and undercut banks
Stream bed composition
The variety of current velocities
The mixture of riffles, runs, and pools in the stream
Alterations to the bank and near-stream land areas

Most of these parameters change with the change in streamflow. Therefore, estimating the amount of the streambed covered with water can provide an indication of the changes in habitat availability. As flows decrease, the water pulls away from the riverbanks and their protective overhanging vegetation, banks, and debris. (Channel Flow Status—the amount of streambed exposed—is estimated at a riffle near the staff gauge by the volunteer gauge reader.)

Water Quality and Stremflow-Physical Habitat-Covered streambed along the Elizabeth Brook

Streambed completely covered
Channel Flow Status = 20

Water Quality and Stremflow-Physical Habitat-Elizabeth Brook largely dry riffle

Same riffle largely dry
Channel Flow Status = 1

Water Quality and Stremflow-Physical Habitat-Riffle along the Elizabeth Brook.2

Riffle along Elizabeth Brook, Stow

Riffles are generally the fast, shallow sections of a stream where the water flows over partially submerged rocks and gravel and the surface is broken into small standing waves
Runs have a variety of streambed substrates including sand and gravel

Water Quality and Stremflow-Physical Habitat-Run or glide along the Elizabeth Brook

A run of glide along Elizabeth Brook, Stow

Runs or glides are deeper sections with moderate flow velocities where the flow is still visible, but the water’s surface is smooth and unbroken
Glides tend to have slower flow velocities and fine-grained substrates—sand, silt, organic debris