Water-Resources Investigations Report 00-4156

A Revised Load Estimation Procedure for the Susquehanna, Potomac, Patuxent, and Choptank Rivers

By Steven E. Yochum


This report is available as a pdf.



The U.S. Geological Survey's Chesapeake Bay River Input Program has updated the nutrient and suspended-sediment load data base for the Susquehanna, Potomac, Patuxent, and Choptank Rivers using a multiple-window, center-estimate regression methodology. The revised method optimizes the seven-parameter regression approach that has been used historically by the program. The revised method estimates load using the fifth or center year of a sliding 9-year window. Each year a new model is run for each site and constituent, the most recent year is added, and the previous 4 years of estimates are updated. The fifth year in the 9-year window is considered the best estimate and is kept in the data base. The last year of estimation shows the most change from the previous year's estimate and this change approaches a minimum at the fifth year. Differences between loads computed using this revised methodology and the loads populating the historical data base have been noted but the load estimates do not typically change drastically. The data base resulting from the application of this revised methodology is populated by annual and monthly load estimates that are known with greater certainty than in the previous load data base.





Purpose and scope

Description of study area


Methods of load estimation

Monitoring record

Regression model

Historical load estimates

Revised procedure for load estimate


Description of revised methods

Comparison of historical and revised load estimates

Summary and conclusions

References cited


A. Annual load estimates for the River Input monitoring stations on the

Susquehanna, Potomac, Patuxent, and Choptank Rivers

B. Percent differences between historical and revised load estimates

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Last modified: Thursday, September 01 2005, 02:20:43 PM
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