Related Experiment Video
Updated: May 5, 2026

Continuous Instream Monitoring of Nutrients and Sediment in Agricultural Watersheds
Published on: September 26, 2017
Inferences about point source loadings from upstream/downstream river monitoring data
1International Joint Commission, 100 Ouellette Ave., N9A 6T3, Windsor, Ontario, Canada.
Abstract:
Areas of Concern such as the Niagara and Detroit Rivers contain a myriad of point and non-point sources. These are difficult and expensive to monitor and often present unique analytical problems and so are subject to analytical error. The Niagara River Toxics Committee (NRTC) and the Upper Great Lakes Connecting Channels Study Modeling Committee designed programs to indirectly monitor these sources by upstream/downstream sampling at the head and mouth of the rivers. These two studies are compared and the data analysis problems that were encountered are discussed. Upstream/downstream samples were paired to obtain differential loadings wherever possible, but when some results were reported as below the detection limit, a maximum likelihood estimate was used. The resulting differential loading, adjusted for non-point sources, is the total point source load to the river minus any losses due to volatilization, settling or degradation.
Related Concept Videos
Typical Model Studies
Design Example: Analyzing Capacity Contours for Flood Risk Assessment
Distributed Loads
For example, consider a bookshelf filled with books stacked vertically adjacent to each other. The weight of the books is evenly distributed over the length of the shelf. As a result, the pressure at different locations on the surface of the...
Upstream Processing
Eulerian and Lagrangian Flow Descriptions
The Eulerian method focuses on fixed points in space where fluid properties, such as velocity, pressure, and temperature, are observed as the fluid moves between these...

