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Science in Support of Aquatic-Ecosystem Conservation and Restoration

September 24, 2021

Human land- and water-management practices have resulted in modifications to natural streamflow conditions and reduced the ecological health of aquatic communities. Working in collaboration with our many partners, the New England Water Science Center provides data and scientific analyses to inform and support aquatic-ecosystem conservation and restoration.

Identifying Stream Reaches with High Rates of Baseflow for Habitat Conservation and Stream Restoration to Support Endangered Atlantic Salmon in Maine

Maine is home to the Gulf of Maine Distinct Population Segment of Atlantic Salmon, the last remnant population of Atlantic Salmon in the United States. The identification and conservation of high-quality habitat, including stream reaches with high rates of groundwater discharge (baseflow) that provide cold water during the summer, is critical to their survival as a species. New England Water Science Center staff working in collaboration with colleagues at NOAA’s National Marine Services and the Maine Department of Marine Resources recently developed a statistical regression model to help resource managers assess relative amounts of baseflow in Maine streams with Atlantic Salmon habitat (Lombard and others, 2021; Lombard and Sturtevant, 2021).

Atlantic Salmon
Atlantic Salmon. (Photograph by National Oceanographic and Atmospheric Administration. Public domain.)
Researchers found that of the more than 80 basin characteristics tested as potential explanatory variables, just two variables—the percentage of the basin underlain by sand and gravel aquifers and mean July precipitation in the basin—were needed to produce a best-fit model to predict baseflow during August, the warmest part of the summer. The model used streamflow data from 31 USGS continuous-record streamflow gages having from 9-31 years of data.

The map below of the Narraguagus watershed in eastern coastal Maine shows stream reaches color-coded by relative amounts of baseflow predicted by the model, as an example of how results of the model can be applied throughout Maine. The map can be used to identify reaches with relatively higher amounts of baseflow during periods of low summer streamflow for habitat conservation and stream restoration.

Predicted relative amounts of baseflow normalized by drainage area
Map of the Narraguagus watershed in eastern coastal Maine showing predicted relative amounts of baseflow normalized by drainage area for each stream reach in the watershed. Values are given in cubic meter per second of baseflow per square kilometer of drainage area (cms/km2). Stream segments over the sand and gravel aquifer in the central portion of the watershed show the highest amounts of estimated mean August baseflow (Lombard and others, 2021). (Public domain.)

Improved Fish Passage and Decreased Flood Inundation in Response to Dam Removals and Culvert Retrofits

A recently completed study by the New England Water Science Center was done to demonstrate the benefits of dam removal and culvert retrofits to restore aquatic connectivity for fish passage (Olson and Simeone, 2021; Simeone and others, 2021). Restoration of natural streamflow conditions also can improve water quality, sediment transport, and aquatic and riparian habitat, and decrease risks to surrounding communities from flood events and aging and inadequate infrastructure. The project was a collaborative effort between the Water Science Center and U.S. Fish and Wildlife Service.

River-hydraulic models were developed to evaluate velocity and depth suitability for fish passage and flood inundation at eight dam-removal sites in Massachusetts, Rhode Island, Connecticut, and New Jersey, and a single culvert-retrofit site in New Jersey. Model scenarios were done at each site for conditions prior to and after dam removal or culvert retrofit. The scenarios showed that fish passage was improved at all sites by removing the dams and retrofitting the undersized culvert.

Survey at a dam-removal and culvert-retrofit site
USGS staff survey the Mill River near the former Hopewell Mills Dam site in Taunton, Massachusetts. Surveys at the dam-removal and culvert-retrofit sites provided topographic and bathymetric data for hydraulic models developed for the study. (Credit: Jeffrey Kinsey, U.S. Geological Survey. Public domain.)

Decreases in water-surface elevations and associated flood-inundation areas also resulted from the dam removals and culvert retrofit. The figure below illustrates inundation areas simulated for pre- and post-dam removal at the Hopewell Mills Dam site on the Mill River in Taunton, Massachusetts. The dam was one of three along the river that were removed between 2012 and 2018. Removal of the dams opened miles of aquatic habitat to migratory fish species and improved flood resiliency and safety in Taunton.

Map showing Inundation areas at the Hopewell Mills Dam study site, Taunton, Massachusetts
Inundation areas of the 1-percent annual exceedance probability discharge at the Hopewell Mills Dam study site, Taunton, Massachusetts. (Public domain.)

Inundation areas at the Hopewell Mills Dam study site, Taunton, Massachusetts, for model simulations at the 1-percent annual exceedance probability discharge (Olson and Simeone, 2021). Removal of the dam decreased the water-surface elevation by 10.4 feet immediately upstream from the dam location at this simulated rate of discharge.


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