AQUA TERRA Consultants
Back to Project List

Nutrient Planning and Management For Long Island Sound Water Quality Improvements

Client: HydroQual, Inc., Mahwah, NJ

Nutrient loadings from watersheds within the state of Connecticut have a large impact on the water quality and aquatic health of Long Island Sound (LIS). In this study, funded by EPA and the Connecticut Department of Environmental Protection (CTDEP), a statewide watershed model was developed by AQUA TERRA Consultants using the U.S. EPA Hydrological Simulation Program - FORTRAN (HSPF) and the U.S. Geological Survey's graphical user interface GenScn to quantify all sources of key nutrients to the LIS.

The Connecticut Watershed Model (CWM) was developed to evaluate nutrient sources and loadings within each of six nutrient management zones that lie primarily within the state of Connecticut, and assess their delivery efficiency to LIS. The Connecticut Watershed Model evolved by first performing calibration and verification on three small test basins across the state (Norwalk, Quinnipiac, and Salmon) representing a range of land uses, including urban, forest, and agricultural. The model was then extended to three major river calibration basins (Farmington, Housatonic, and Quinebaug) and subsequently expanded to a statewide model by using the most spatially applicable set of calibrated watershed parameters in non-calibrated areas. Based on urban growth rates predicted to occur by the year 2020, full buildout scenarios and resulting loads to LIS were developed for the six management zones. To evaluate potential impacts of alternative best management practices (BMPs), pollutant removal efficiencies were extracted from the National Pollutant Removal Performance Database for Stormwater Treatment Practices for BMP categories determined to be technically feasible and effective at removing the pollutants of concern. Composite pollutant removal efficiencies were then computed based on an assumed mix of BMPs for both urban and agricultural lands.

Alternative levels of BMP implementation were represented by defining increasing fractions of the subwatershed landuses and areas served by BMPs. Ultimately, three nonpoint source BMP implementation scenarios were developed and simulated, in addition to the full buildout scenario with and without BMPs; and the associated nutrient reductions were evaluated. The user-friendly interface and framework of the CWM was specifically designed to promote continuing use by CTDEP staff to assess additional BMPs, implementation levels, and point source controls for nutrient reductions to LIS.

Back to Project List