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Scientific Investigations Report 2008-5226

Prepared in cooperation with the North Carolina Department of Environment and Natural Resources, Division of Water Resources

Simulation of Water Quality in the Tull Creek and West Neck Creek Watersheds, Currituck Sound Basin, North Carolina and Virginia

By Ana María García

ABSTRACT

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A study of the Currituck Sound was initiated in 2005 to evaluate the water chemistry of the Sound and assess the effectiveness of management strategies. As part of this study, the Soil and Water Assessment Tool (SWAT) model was used to simulate current sediment and nutrient loadings for two distinct watersheds in the Currituck Sound basin and to determine the consequences of different water-quality management scenarios. The watersheds studied were (1) Tull Creek watershed, which has extensive row-crop cultivation and artificial drainage, and (2) West Neck Creek watershed, which drains urban areas in and around Virginia Beach, Virginia.

The model simulated monthly streamflows with Nash-Sutcliffe model efficiency coefficients of 0.83 and 0.76 for Tull Creek and West Neck Creek, respectively. The daily sediment concentration coefficient of determination was 0.19 for Tull Creek and 0.36 for West Neck Creek. The coefficient of determination for total nitrogen was 0.26 for both watersheds and for dissolved phosphorus was 0.4 for Tull Creek and 0.03 for West Neck Creek.

The model was used to estimate current (2006-2007) sediment and nutrient yields for the two watersheds. Total suspended-solids yield was 56 percent lower in the urban watershed than in the agricultural watershed. Total nitrogen export was 45 percent lower, and total phosphorus was 43 percent lower in the urban watershed than in the agricultural watershed. A management scenario with filter strips bordering the main channels was simulated for Tull Creek. The Soil and Water Assessment Tool model estimated a total suspended-solids yield reduction of 54 percent and total nitrogen and total phosphorus reductions of 21 percent and 29 percent, respectively, for the Tull Creek watershed.

First posted January 26, 2009

For additional information contact:
Director
U.S. Geological Survey
3916 Sunset Ridge Road
Raleigh, NC 27607
http://nc.water.usgs.gov/

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Suggested citation:

García, A.M., 2009, Simulation of water quality in the Tull Creek and West Neck Creek watersheds, Currituck Sound basin, North Carolina and Virginia: U.S. Geological Survey Scientific Investigations Report 2008-5226, 22 p. (only online at http://pubs.water.usgs.gov/sir2008-5226).



Contents

Abstract

Introduction

Purpose and Scope

Study Area

Approach

Tull Creek and West Neck Creek Watershed Models

Model Configuration

Model Calibration

Model Application

Summary

References Cited


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