As part of Connecticut’s Second Generation Nitrogen Strategy, the Connecticut Department of Energy and Environmental Protection (CT DEEP) will be modeling:
A watershed model simulates the movement of water, sediment, and pollutants over the landscape and draining to a waterbody. The model first represents the movement of water, starting with precipitation and snow melt. In pervious areas (with natural vegetation) water may evaporate, run off on the surface, or infiltrate and move through the soil or groundwater. In impervious areas (roads, roofs) water does not infiltrate, so only evaporation and surface runoff are considered. The model next simulates the movement of particles, which often carry pollutants. This is done through erosion in the pervious area, and washoff of particulate matter in the impervious area. Finally, the model represents movement of pollutants, in association with either water or particulate matter.
In 2002, CT DEEP developed the Connecticut Watershed Model (CTWM). This statewide watershed model was developed as a tool to evaluate nutrient sources and loadings, including nitrogen, phosphorus, and organic carbon, within each of six nutrient management zones and assess their delivery efficiency to the Sound. The model supported initial efforts to manage watershed nutrient sources, but the final report identified deficiencies that if addressed would improve the accuracy and utility of the model moving forward. Work is now underway to address deficiencies in the 2002 effort by updating the CTWM with the following improvements:
Outcome: The watershed model will be able predict sediment supply to tidal marshes, point and nonpoint source loads, and streamflow and pollutant loads under current and possible future precipitation and land use scenarios. These results will facilitate future implementation of effective management plans. The improvement of the CTWM will also help develop water quality plans for coastal embayments, lakes, and reservoirs. Additionally, the outputs of the model will be used as inputs for other water quality models for the Long Island Sound. For example, the model’s output will be used as an input for Connecticut’s embayment model, which will simulate in-estuarine processes. Furthermore, the output will provide freshwater inputs and nutrient (i.e., nitrogen and phosphorus) and sediment loading information for the Long Island Sound wide eutrophication model.
Information about the watershed modeling work is publicly available on the project web page.
Expected Availability Date: 2022
Groundwater discharge to the north shore coast of Long Island Sound is small relative to discharge from the major rivers but is locally an important nutrient source to coastal embayments. The US Geological Survey (USGS), in cooperation with CT DEEP, is developing a regional groundwater flow model of coastal Connecticut as well as adjacent areas of Rhode Island and New York (excluding Long Island). The model will simulate groundwater budgets, groundwater travel time distributions, and will estimate groundwater loading to receiving waters (rivers or directly to Long Island Sound).
USGS is working to calibrate the groundwater model over two years. In 2020, USGS is refining Niantic River watershed modeling to simulate groundwater nitrogen loading to freshwater receptors (mainly rivers) and the coastal embayment. In 2021, USGS will extend the nitrogen model to the entire model domain. CT DEEP will use the calibrated regional model to better understand groundwater flow systems in coastal areas on the north shore of Long Island Sound, including quantitative information such as groundwater budget components at the watershed- and model-domain scales and travel times to freshwater and coastal receptors.
The work will include:
Outcome: USGS and CT DEEP expect that the outputs from the project will also provide an estimated time context for management scenarios that have an impact on nitrogen in the Sound. USGS could assign travel times from recharge to discharge for different land covers in the present, past, or future to understand the nitrogen discharge input function with time or under future management scenarios. These outputs combined will help CT DEEP prioritize nitrogen reduction actions where groundwater nitrogen discharges are greatest. Additionally, the outputs of this model will complement the current work being conducted for New York’s Solute-Transport Model as the efforts are similar and will cover the entirety of the Long Island Sound shoreline.
The groundwater flow model and supporting data will be publicly available and study results will also be presented on the project web page.
Contact: Janet Barclay, [email protected], USGS
Connecticut continues progress on its Second-Generation Nitrogen Strategy, which prioritizes embayments for further study and the preparation of protection or restoration plans.
In 2017, CT DEEP prioritized the following eight embayment complexes (some complexes include multiple embayments):
CT DEEP has initiated monitoring and modeling efforts in the Pawcatuck River Estuary and Little Narragansett Bay; CT DEEP is also conducting a data synthesis and modeling effort on the Niantic River Estuary. These efforts will serve as a framework for CT DEEP to apply in other priority embayments. In 2020, CT DEEP is initiating monitoring and modeling of Mystic River and Norwalk Harbor. In general, embayment modeling will include:
Outcome: The results of the embayment modeling project will be used to validate upland watershed models and develop and estuarine nutrient process model specific to each embayment. In coordination with CT DEEP’s watershed and groundwater model, the embayment modeling project will help develop embayment specific nutrient targets to manage water quality, specifically to combat eutrophication. The outputs of the three modeling efforts complement each other and will ultimately lead to better management, protection, and restoration efforts to the north shore of the Sound. Additionally, the embayment modeling output will help the development of the Long Island Sound Systemwide Eutrophication Model, in which CT DEEP plans to coordinate with NYCDEP to enterprise on any synergies and avoid redundancies between efforts.
Information about the embayment modeling work is publicly available on the project web page.