Watershed Achievements Report

Minnesota Watershed Red River Basin River Achievements Basin Report 2008
Watershed Achievements Report Statewide
2015
Bois de Sioux Watershed
Bois de Sioux Watershed Nutrient Load
Assessment
Bois de Sioux Watershed with North Ottawa Drainage Basin
The main purpose of this project is to monitor
phosphorous nutrient loading at the North Ottawa
Impoundment site in the Bois de Sioux Watershed and to
assess the potential for the capture, removal and reuse
of phosphorus from the watershed through aquatic plant
management (primarily cattails) growing within Pool C
of the impoundment. MPCA completed a pollutant load
monitoring process between 2007 and 2009 to look at
Minnesota watersheds and their contributions of TP and
TSS. The Bois de Sioux Watershed is listed among the
moderately high watersheds in the state with P yields
ranging between .153- .377 lbs. /ac TP yield and 51-100
lbs. /ac TSS yield.
Historically, the International Water
Institute (IWI) has been monitoring
at sites upstream and downstream of
the North Ottawa site to measure any
positive effects that this site has on water
quality. This project reviewed historical
monitoring results as a reference to
support loading and removal potential.
The project timeline, May-September
2014, allowed for summer sampling at
targeted sites including the inlet, outlets
and within the main retention pool
(Pool C) in an attempt to gather baseline
information as a reference for longer
term monitoring. The project also included soil sampling
and analysis work to collect baseline nutrient analysis
within the three pools (A, B, C). Pools B and C within the
impoundment are farmed unless there is a need to hold
water beyond the capacity of Pool C.
There is a need to understand watershed nutrient
pathways and processes to help define a statistical range
of input/output P and N for off channel flood storage
sites. This information will lead and support best practices
for managing existing sites and for planning and design
across the watershed and where future impoundments
will be constructed.
Goals
• Gather and review existing water quality data for
project site.
• Targeted monitoring of North Ottawa impoundment to
measure nutrient loading.
• Establish potential nutrient (phosphorus) removal
potential through vegetation harvesting and removal.
Results that count
• Targeted monitoring at inlet and outlet of the
impoundment from this project have yielded
significantly different results when compared to
historical data collected to measure water quality
conditions and North Ottawa impoundment effects on
water quality improvement.
• Targeted monitoring of impoundment at inlet
and outlets reflects the following reductions after
treatment through the impoundment: P 38%, N 70%,
TSS 84%.
Pool C of the North Ottawa impoundment for the Bois de Sioux Watershed
Minnesota Pollution Control Agency www.pca.state.mn.us 95