Lake Management Plan
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Big Pelican Lake Total Phosphorus
Phosphorus is the limiting nutrient in lakes, meaning that plants and algae need it to grow, and the amount of plants and algae present in the lake depends on how much phosphorus is available. Generally, the less phosphorus in the lake, the better the water quality for recreation. more information on total phosphorus
Pelican Lake phosphorus concentration at Site 206 has been monitored from 1996 to 2011, and has an average of 15.3 ppb. A trend analysis showed that there is a trend in the data over this 15 year period, meaning that the phosphorus concentration is decreasing.
2011 Results
In 2011, all three lake sites were monitored for total phosphorus. The lowest phosphorus concentration was at Site 206 in the middle of the lake. This makes sense because this site is the furthest from any inlets to the lake, and lake inlets are usually the highest source of phosphorus.
Site 205 had the highest phosphorus concentration, which makes sense because the Pelican River is the largest contributer of phosphorus to Pelican Lake. The Pelican River enters Pelican Lake on the east end.
Table 1. 2011 phosphorus monitoring results.
| Site | Mean Total Phosphorus (ppb) | Min Total Phosphorus (ppb) | Max Total Phosphorus (ppb) |
| 201 | 11.6 | 7 | 16 |
| 206 | 12.4 | 5 | 19 |
| 205 | 13.2 | 6 | 21 |
In Pelican Lake , the total phosphorus concentration starts out low in the spring and gradually increases throughout the summer. This pattern is most likely due to internal loading.
Site 206
Site 206 has been monitored from 1996 to 2011.
Tracking trends in data over several years can indicate improving or declining water quality. Generally, it is best to have 8-10 years of data with 4 or more measurements per year to be confident in an emerging trend. Statistically, the probability that a trend is truly describing the water quality and not just a random trend is important. A probability over 90% is required by the MPCA to really be confident in the observed trend.
There is no evidence of a trend in phosphorus for Pelican Lake.
Site 201
Site 201 was added in 2007 to see if the total phosphorus was different on the west end of the lake due to two inlets. Bob Creek and Spring Creek both flow into Pelican Lake on that end.
Site 205
Site 205 was added in 2007 to see if the total phosphorus was different on the east end of the lake due to the Pelican River inlet flowing through Little Pelican Lake. The average total phosphorus at site 205 was higher than Sites 206 and 201. This is probably due to the fact that the Pelican River contributes 75% of the phosphorus loading to Pelican Lake.
