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Scientific Investigations Report 2011–5203

Prepared in cooperation with the Onondaga Lake Partnership

Improvement in Precipitation-Runoff Model Simulations by Recalibration With Basin-Specific Data, and Subsequent Model Applications, Onondaga Lake Basin, Onondaga County, New York

By William F. Coon

Thumbnail of and link to report PDF (10.3 MB)Abstract

Water-resource managers in Onondaga County, New York, are faced with the challenge of improving the water quality of Onondaga Lake, which has the distinction of being one of the most contaminated lakes in the United States. To assist in this endeavor, during 2003–07 the U.S. Geological Survey (USGS), in cooperation with the Onondaga Lake Partnership, developed a precipitation-runoff model of the 285-square-mile Onondaga Lake Basin with the computer program Hydrological Simulation Program–Fortran (HSPF). The model was intended to provide a tool whereby the processes responsible for the generation of loads of sediment and nutrients that are transported to Onondaga Lake could be better understood. This objective was only partly attained because data for calibration of the model were available from monitoring sites only at or near the mouths of the major tributaries to Onondaga Lake; no calibration data from headwater subbasins, where the loads originated, were available. To address this limitation and thereby decrease the uncertainty in the simulated results that were associated with headwater processes, the USGS conducted a 3-year (2005–08) basinwide study to assess the quality of surface water in the Onondaga Lake Basin. The study quantified the relative contributions of nonpoint sources associated with the major land uses and land covers in the basin and also monitored known sources and presumed sinks of sediment and nutrient loads, which previously had not been evaluated. The use of the newly acquired data to recalibrate the HSPF model resulted in improvements in the simulation of processes in the headwater subbasins, including suspended-sediment, orthophosphate, and phosphorus generation and transport.

Simulation of streamflows in small subbasins was improved by adjusting model parameter values to match base flows, storm peaks, and storm recessions more precisely than had been done with the original model. Simulated recessional and low flows were either increased or decreased as appropriate for a given stream, and simulated peak flows generally were lowered in the revised model. The use of suspended-sediment concentrations rather than concentrations of the surrogate constituent, total suspended solids, resulted in increases in the simulated low-flow sediment concentrations and, in most cases, decreases in the simulated peak-flow sediment concentrations. Simulated orthophosphate concentrations in base flows generally increased but decreased for peak flows in selected headwater subbasins in the revised model. Compared with the original model, phosphorus concentrations simulated by the revised model were comparable in forested subbasins, generally decreased in developed and wetland-dominated subbasins, and increased in agricultural subbasins. A final revision to the model was made by the addition of the simulation of chloride (salt) concentrations in the Onondaga Creek Basin to help water-resource managers better understand the relative contributions of salt from multiple sources in this particular tributary. The calibrated revised model was used to (1) compute loading rates for the various land types that were simulated in the model, (2) conduct a watershed-management analysis that estimated the portion of the total load that was likely to be transported to Onondaga Lake from each of the modeled subbasins, (3) compute and assess chloride loads to Onondaga Lake from the Onondaga Creek Basin, and (4) simulate precolonization (forested) conditions in the basin to estimate the probable minimum phosphorus loads to the lake.

First posted January 18, 2012

For additional information contact:
Director
U.S. Geological Survey
New York Water Science Center
425 Jordan Road
Troy, NY 12180
(518) 285-5600

http://ny.water.usgs.gov

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Suggested citation:

Coon, W.F., 2011, Improvement in precipitation-runoff model simulations by recalibration with basin-specific data, and subsequent model applications, Onondaga Lake Basin, Onondaga County, New York: U.S. Geological Survey Scientific Investigations Report 2011–5203, 37 p., at http://pubs.usgs.gov/sir/2011/5203/.



Contents

Abstract

Introduction

New Data for Model Recalibration

Model Revisions

Extension of Input Datasets

Structural Changes

New Otisco Lake Tributary Subbasin

Revisions to Land-Use and Land-Cover Acreages

Changes to Hydrologic Response Units

Elimination of Unique Row-Crop PERLND

Creation of New Landslide PERLND

Creation of New PERLNDs in Harbor Brook Basin

Mitigative Effects of the Onondaga Reservoir

Mitigative Effects of Otisco Lake

Changes to Model Parameter Values and Comparison of 2003 and 2008 Simulation Results

Changes to the Hydrologic Components of the Model

Changes to the Sedimentological Components of the Model

Basinwide Particle-Size Analyses

Suspended Sediment and Total Suspended Solids

Changes to the Water-Quality Components of the Model

Orthophosphate Concentrations

Phosphorus Concentrations

Chloride Concentrations in Onondaga Creek

Model Applications

Sediment and Phosphorus Loading Rates

Subbasin Loads of Sediment and Phosphorus

Watershed-Management Analysis

Chloride Loads in Onondaga Creek

Precolonization (Forested) Scenario

Summary

References Cited

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