Lake Management Plan

go to PGOLID main pageChapter 1 includes an introduction and abstract
Chapter 2 includes the goals of PGOLID
Chapter 3 history covers geological formation to current district projects
Chapter 4 covers watershed characteristics of most of northwest Minnesota
Chapter 5 covers the main watershed around the Pelican Lakes
Chapter 6 covers the minor watersheds that surround Pelican Lake
Chapter 7 describes the types of data collected and why
Chapter 8 reports the data and water quality of inlets and outlets to Pelican Lake
Chapter 9 reports the water quality data for the Pelican Lakes

Chapter 10
Chapter 11 Safety and Buoys

 

Questions?
PGOLID Water Resource Coordinator
218-846-1465, email

Chapter 8: Impacting Streams and Rivers

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Big Pelican Lake Trophic State Index

Pelican water quality at site 206 has been monitored from 1996 to 2011.

Results show that the overall average TSI for Pelican Lake is 42.6. This TSI is typical for lakes in the area. It corresponds to a Mesotrophic lake with a great sport fishery (walleye, northern pike and muskellunge). For recreation, the lake is very usable. There may be some slight algae blooms in late summer, but otherwise the lake is great for recreation.

A trend analysis showed that there has been no trend in the data over this 15 year period, meaning that the TSI hasn't gotten better or worse, it has just stayed the same.

The resulting numbers from secchi depth, chlorophyll-a, and total phosphorus measurements cover different units and ranges and thus cannot be directly compared to each other or averaged. In order to standardize these three measurements to make them directly comparable, we convert them to a trophic state index using an equation. You can find the equations online at: http://dipin.kent.edu/tsi.htm.

The overall trophic state index (TSI) of a lake is the average of the TSI for phosphorus, the TSI for chlorophyll-a and the TSI for secchi depth; therefore, it can be thought of as the lake condition taking into account phosphorus, chlorophyll-a and secchi depth.

It is important to understand that Trophic States are defined divisions of a continuum in phosphorus and algal concentration. more information on trophic state index



2011 Results

In 2011, all three lake sites were monitored for water transparency, chlorophyll-a and total phosphorus. From these measurements, the Trophic State Index was calculated. The results were similar between all sites. The 15-year average TSI is 42.6; therefore, the average for 2011 was slightly lower than the historical average. For results from each individual site, please see below.

Table 1. 2011 Trophic State Index results.

Site Mean TSI Total Phosphorus TSI Chlorophyll-a TSI Secchi TSI
201 40.9 39.2 43 40.1
206 41.2 39.6 44.7 39.2
205 41.7 40.4 44.9 39.8

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