Measuring river health

Overall Health Index

The Sudbury-Assabet-Concord River report card compares 20 indicators of river health to scientifically-derived thresholds. These individual indicators were combined to calculate scores for each of the five values identified by stakeholders—Water Quality, Streamflow, Scenery, Habitat, and Recreation—for the upper and lower segments of each river. The scores for these five values were then combined into an Overall Health score for each river segment. The overall grade for the river system is the average of these six river segment scores, weighted by area.

Water Quality

  Dissolved Oxygen | How much oxygen fish need to survive

  Temperature | Temperature suitable for our rivers’ fish

  Suspended Solids | Particles in the water that can damage aquatic life

  Phosphorus | A nutrient that can cause excessive aquatic plant growth

  Nitrates | A nutrient that can cause excessive aquatic plant growth

  Floating Biomass | Aquatic plants at the surface or reaching the surface



  Streamflow Alteration | How much our rivers deviate from natural flows

  Groundwater Level | The depth of the water table

  Channel Flow | Habitat availability in streams 

  Summer Streamflow | A composite of minimum river flows



  Visual Quality | Scenic quality of select views

  Cultural Importance | Historic and cultural qualities, local landmarks, and interpretation



  Impervious Cover | Percent of land covered by impervious material

  Aquatic Connectivity | Disruption by culverts, bridges, and dams

  Habitat Connectivity | Disruption of habitat connections

  Ecological Integrity | Disruption of habitat



  Passability | Dams per river mile and ease of portage around dams

  Access | Public access points per river mile

  Trails | Miles of trail along riverfront

  Fish Edibility | Whether people can safely eat the fish

  Bacteria | Presence of fecal bacteria contamination