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This past May, the USGS New England Water Science Center launched two marked buoy platforms containing water quality instruments at the mouth of Southport Harbor and lower Saugatuck Harbor near Fairfield, Connecticut.

The sensors attached to these buoys are collecting water-quality data at 6-minute intervals and transmitting the information to the USGS National Water Information System (NWIS) over the next two years.

This continuous sampling effort is part of a three-year water-quality data collection project in cooperation with the Connecticut Department of Energy and Environmental Protection (CT DEEP). The investigation will enhance the scientific knowledge of the water quality issues in four coastal Connecticut communities: Mystic, Norwalk, Saugatuck, and the Sasco-Southport complex.

A USGS buoy floating in the water
USGS deployed this buoy platform with connected water-quality equipment in Saugatuck Harbor, Connecticut in May 2022.

Because water depth, flow, and conditions are different at the mouths of rivers and within estuaries, these data will provide a more comprehensive understanding as to when, how, and to what extent nutrient loading impacts Long Island Sound. Knowing these influences will inform the state of Connecticut’s decision-making to improve the environmental health of this economically-, recreationally-, and ecologically-important water body.

USGS scientists are gathering data on water quality and hydrology at these bays from April 2021 through March 2024. Each location will be monitored over a two-year period with both continuous water-quality sampling and discrete water sampling, where scientists collect near surface and near bottom water samples at a specific time and location for analysis. Samples are evaluated for specific characteristics such as alkalinity, temperature, salinity, and clarity as well as for the amount of dissolved oxygen, carbon, nutrients, suspended solids, and chlorophyll, an indication of algal presence.

Intensive sampling occurs during the first summer of monitoring, which was last year for Mystic and Norwalk, and this year for Southport and Saugatuck, followed by less frequent sampling. Measurements of velocity and water surface elevations are also measured at each location during different tidal cycles.

Nutrient models for each bay will be created based on the collected data. These models will augment the current long-term ambient water-quality monitoring network that is currently operated by the USGS and CT DEEP. Estimates of nutrient loading from the tributaries of the Long Island Sound watershed, calculated in another USGS long-term monitoring project, will be used in this project’s nutrient models. This collaboration will support the development of a state-wide watershed hydrology and water-quality model of the nutrient loading into all four of these coastal bays.

Learn more about the project here: Embayment Monitoring to Support Nutrient Management Activities in Connecticut for the Long Island Sound | U.S. Geological Survey (


Four USGS scientists deploy a marked buoy platform.
USGS deployed this buoy platform with connected water-quality equipment in Southport Harbor, Connecticut in May 2022.


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