December 2010 Final Indian Creek, Dago Slough, and Prairie Creek LRS/TMDL
105 | P a g e
Table 61 - Prairie Creek; nutrient and sediment load results from vegetation; includes grass areas
not in pasture, forested areas, wetlands, and other vegetation not in production agriculture
Pollutant
Total
Watershe
d
Below
Sample Site
Upstream of Sample
Site Remaining HUC 12
Sediment (ton/yr) 4,905 113 580 4212
% of Watershed
2.30 11.82 85.87
Sediment Delivered
(ton/yr) 3,891 82 492 3,317
Average ton/acre 0.24 0.24 0.2 0.24
% of Watershed
2.12 12.64 85.24
Annual Runoff (ac/ft) 5,374 105 779 4,490
% of Watershed
1.96 14.5 83.54
Nitrogen from Runoff
(lbs/yr) 2,190 43 318 1,830
% of Watershed
1.96 14.5 83.54
Phosphorous Runoff
(lbs/yr) 1,168 23 169 976
% of Watershed
1.96 14.5 83.54
Nitrogen from
Sediment (lbs/yr) 12,454 264 1,574 10,614
% of Watershed
2.11 12.64 85.22
Phosphorous from
Sediment (lbs/yr) 4,825 102 610 4,113
% of Watershed
2.11 12.64 85.24
Annual loadings calculated from stream sample results are lower than those developed
from the pollutant load models in this section. These loading models do not accurately
represent what is delivered to the stream or in the water on an annual basis; they better
represent overall “erosion” or what is lost edge-of-field and not delivery. Table 62
below is a good estimation of what is delivered to the stream each year based on recent
sample data. Comparing both shows that 60-65% of all soil eroded and nutrients lost
from runoff are delivered to Indian Creek and Dago Slough over the course of a year.
In the case of streambank erosion, 100% is delivered. However, any soil eroded or
nutrients lost are stored in the watershed and are ultimately available for delivery to the
stream. As previously noted, Prairie Creek was not fully assessed and therefore
delivery results shown here are actually higher. If Prairie was fully inventoried, results
would likely show a similar ratio as in Indian Creek and Dago Slough.
Table 62 - Annual Loading of Pollutants Delivered to Stream
Watershed
Size (acres)
Avg Annual
Discharge (acre-ft)
TSS Load
(tons/year)
P Load
(tons/year)
Mn Load
(lbs/yr)
Dago Slough 1,303 2,112 2,350 5,450
Indian Creek 5,258 9,828 9,130 14,162
Prairie Creek 7,977 17,900 9,172 24,436 20,8 24
