319 Sediment Modeling

Location: Northwestern Minnesota
Client: Buffalo-Red River Watershed District
Date:7/11/2008

Background:
The most important water quality issues within the Buffalo-Red River Watershed District (BRRWD) and many portions of Minnesota are the sources and amounts of sediment reaching our waterways and waterbodies. Understanding the sediment sources, the magnitude of these sources, and their affect on the rivers and streams, is critical to improving water quality.

A sediment production model was produced by the University of Minnesota Saint Anthony Falls Laboratory (SAFL), under contract to the BRRWD, where the amount of sediment leaving the landscape, actually reaching waterways, and accumulating within a pilot area of the BRRWD (the South Branch of the Buffalo River) was estimated. Application of the model to evaluate the effect of various conservation practices occurred only on a limited basis.

The Project:
The focus of this study is to expand upon the modeling work previously performed. The SWAT computer model will be used to develop sediment water quality goals, and practical measures to achieve these goals, for the BRRWD. The computer model will be used to establish sediment goals, by modeling land use conditions prior to modern agriculture (i.e., pre-modern agricultural circa 1950’s). The estimated sediment concentrations for pre-modern agriculture will in essence establish benchmark sediment conditions within the BRRWD. The computer model will then be used to evaluate 2 to 3 concepts to improve water quality. Current expectations are that these concepts will be consistent with some aspect of the current farm program (or additional practical measures) and include: 1) buffers along legal drainage systems and other waterways; 2) permanent vegetative cover similar to the Conservation Reserve Program; 3) grassed swales; and 4) tillage practices.

Benefits:
The SWAT computer modeling effort will aid in establishing sediment goals, guide focused implementation actions on the landscape, and quantify benefits. Expectations are that the measures identified by modeling will be implemented (as action items) within the District’s Watershed Management Plan, which is currently under revision.