Paper No. JAWRA-07-0178-P of the Journal of the American Water Resources Association (JAWRA). Discussions are open until six months from print publication.
AVGWLF-Based Estimation of Nonpoint Source Nitrogen Loads Generated Within Long Island Sound Subwatersheds†
Article first published online: 20 APR 2009
© 2009 American Water Resources Association
JAWRA Journal of the American Water Resources Association
Volume 45, Issue 3, pages 715–733, June 2009
How to Cite
Georgas, N., Rangarajan, S., Farley, K. J. and Jagupilla, S. C. K. (2009), AVGWLF-Based Estimation of Nonpoint Source Nitrogen Loads Generated Within Long Island Sound Subwatersheds. JAWRA Journal of the American Water Resources Association, 45: 715–733. doi: 10.1111/j.1752-1688.2009.00318.x
- Issue published online: 26 MAY 2009
- Article first published online: 20 APR 2009
- Received December 17, 2007; accepted November 24, 2008.
- watershed modeling;
- decision support systems;
- total maximum daily load;
- nonpoint source pollution;
- Long Island Sound;
- generalized watershed loading functions;
- ArcView generalized watershed loading functions
Abstract: 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%).