ASABE Technical Library - Abstract
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Long Prairie River Watershed TMDL Project – Lessons Learned from Phase I
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org
Citation: Pp. 141-147 in Total Maximum Daily Load (TMDL) Environmental Regulations: Proceedings of the March 11-13, 2002 Conference, (Fort Worth, Texas, USA) 701P0102.(doi:10.13031/2013.7540)Authors: Hafiz M. Munir, Bashar Sinokrot, Dennis E. Ford
Keywords: TMDL, Long Prairie, SWAT, model, monitoring, DO, Minnesota
Long Prairie River drains a predominantly agricultural 883-square mile watershed in central Minnesota.
Designated uses of the River are aquatic life, recreation, industrial consumption, agriculture, wildlife,
aesthetic enjoyment, and navigation. Monitoring in recent years has shown dissolved oxygen (DO)
concentrations in portions of the river and at Motley intermittently below the state water quality
standard of 5 mg/L. As a result, Minnesota Pollution Control Agency (MCPA) placed four lower-river
reach segments on the agencys 1998 303(d) list.
The objectives of the study are to define the extent, persistence, and severity of the DO depletion
problem, and develop a TMDL for the watershed. The project has three phases. Phase I is an
analysis of existing data to determine what additional data will be needed to complete the project
objectives and what technical issues will need to be addressed within the scope of the project.
Additional data will be collected, analyzed, and reported in Phase II. Modeling and TMDL
development will be conducted in Phase III. The project is anticipated to complete by December
2002.
Review of the existing water quality data for the Long Prairie River indicates substantial seasonal
and inter-annual variability but no significant long-term trends. Longitudinal total phosphorus
profiles show a consistent pattern of gradual increase from the headwaters to Long Prairie, followed
by a steep increase downstream from City of Long Prairie. Longitudinal nitrogen series profiles
indirectly suggest significant nitrification in the reach between the cities of Long Prairie and
Browerville. Diurnal DO variations in the vicinity of City of Long Prairie indicate substantial
primary productivity. Based on the review and preliminary analysis of existing data, a modeling
strategy has been outlined, and data gaps and additional monitoring needs have been defined.