AVGWLF-Based Estimation of Nonpoint Source Nitrogen Loads Generated Within Long Island Sound Subwatersheds

The Generalized Watershed Loading Functions (GWLF) model and its ArcView interface (AVGWLF) were used to estimate and examine the components of the total nitrogen (TN) nonpoint source (NPS) load generated within New York and Connecticut (CT) watersheds surrounding Long Island Sound (LIS, the Sound)....

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Bibliographic Details
Published in:Journal of the American Water Resources Association 2009-06, Vol.45 (3), p.715-733
Main Authors: Georgas, Nickitas, Rangarajan, Srinivasan, Jagupilla, Sarath Chandra K
Format: Article
Language:English
Subjects:
agricultural runoff
ArcView generalized watershed loading functions
base flow
best management practices
calibration
decision support systems
Earth sciences
Earth, ocean, space
Engineering and environment geology. Geothermics
environmental models
estimation
Exact sciences and technology
forests
generalized watershed loading functions
groundwater flow
hydrologic models
Hydrology. Hydrogeology
Long Island Sound
methodology
model validation
nitrogen
nonpoint source pollution
nutrients
pollution control
pollution load
Pollution, environment geology
sewage effluent
stream flow
total maximum daily load
urban runoff
water pollution
Water resources
watershed modeling
watersheds
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Summary:The Generalized Watershed Loading Functions (GWLF) model and its ArcView interface (AVGWLF) were used to estimate and examine the components of the total nitrogen (TN) nonpoint source (NPS) load generated within New York and Connecticut (CT) watersheds surrounding Long Island Sound (LIS, the Sound). The majority of data used as model inputs were generally available from online sources, and the work involved an overall calibration to streamflow and TN data in accordance with generic guidelines recommended in the GWLF manual. The GWLF model performance for three calibration and two validation watersheds in CT was compared with results of a detailed model, Hydrological Simulation Program in Fortran, developed in a previous study. The results of the application illustrate the usefulness of the relatively simpler, less parameter-intensive GWLF model in performing exploratory loading analysis in preparation for adaptive nutrient management in the LIS watersheds. The presented methodology is valuable for identification of priority watersheds for NPS pollution reduction and also for planning-level evaluation of best management practices to achieve the desired reductions. It is estimated that ground-water base flow may be the largest pathway for NPS TN to the Sound, contributing about 54% of the total NPS TN load, a finding with significant implications for LIS total maximum daily load reduction scenarios. In addition to ground water, septic systems are estimated to contribute about 17% of the total load, with the remaining TN load being mostly runoff from urban (17%), agricultural (5%), and low impact (e.g., forest) areas (6%).
ISSN:1093-474X
1752-1688
DOI:10.1111/j.1752-1688.2009.00318.x