Special Studies


Campbell Creek Sediment Survey

campbell - sediment 5-12-04.JPG

Campbell Creek is a closely monitored part of the watershed. The creek goes through farm land and is a large contributor of nutrients to lower portions of the watershed at certain times of the year, in particular North Floyd. In 2007 a study was conducted to further evaluate the nutrients and sediments carried by the creek.

2007 Campbell Creek Special Sediment Survey


St. Clair Alum Treatment

A Further Evaluation


In October 1998, the Pelican River Watershed District applied alum (aluminum sulfate) to Lake St. Clair to reduce exports of phosphorus to Ditch 14 and beyond.  This treatment was part of a phased approach intended to cope with unacceptable phosphorus levels in Lake Sallie, (about 3 miles downstream from St. Clair).  26 months after the alum application, in February, 2001, it was reported that total phosphorus concentrations at the outlet of St. Clair were decreased by 58% and export loads were decreased by about 51%.  In addition the water quality in Lake St. Clair exhibited some improvement, and there was some evidence that downstream areas experienced reduced phosphorus conditions.

It is now a little more than 50 months since the treatment; here is a further update of the project.



Prior to the alum treatment, over a period of 6 years, there had been about 300 observations at St. Clair’s outlet, including 207 TP measurements.  In the 4 years since the alum treatment there have been approximately 175 observations including 140 TP and OP samples.  A similar record is available for the Ditch 14 outlet, about 1 mile downstream.  In-lake samples have been taken on a twice-monthly basis during the summer, since the treatment.


While we have few pre-treatment in-lake observations, at this point there is no reason to believe that there have been remarkable changes since the treatment.  Secchi readings vary from time to time, but seasonal averages seem to be fairly stable.  A case can be made that in-lake total phosphorus readings have been climbing, but there have been no readings that approach those which we have immediately before the treatment, and the averages are quite a bit lower.  Also, ortho-phosphorus readings which were in excess of 100 ppb in the summer of 1998, have since been consistently below 25ppb, and in the last three years have been between 10 and 17.



The specific and stated goal of the St. Clair Alum treatment was to reduce down-stream discharges associated with internal loadings of phosphorus from bottom sediments contained in Lake St. Clair.  Evaluation after the first two years concluded that the goal of reducing downstream loadings was achieved.

In the 2001 report, a reduction of 50 percent of total phosphorus, and as much as 75% of orthophosphate was claimed.  Also it was noted that the loading peaks in late winter and late summer had disappeared.

St. Clair Outlet


Discharge mils. cf




































There is little doubt that this pattern has continued through the next two years.  Average 1999-2002 phosphorus loads passing the St. Clair outlet are considerably less than the pre-treatment period.  In 2002 for example, we estimate that only 200 pounds

of phosphorus was discharged from St. Clair, in comparison with an average of 900 pounds in the 1995-1998 period.  While data are not as complete for orthophosphorus (prior to treatment) there is no doubt that it is lower by a factor of one-half to two-thirds.

Flow-weighted mean concentrations of phosphorus, another indicator of St. Clair outlet conditions, also show dramatic reductions.  And it is fairly clear that the bimodal peaks of phosphorus concentrations also have disappeared (see below).

There is one caveat to drawing these conclusions.  Since the alum treatment discharge has dropped significantly, and a case could be made that this is an important factor.  However, discharge levels do not explain the reductions in in-lake phosphorus, especially orthophosphate.  



In the 2001 Evaluation it was noted that the St. Clair alum treatment may also have had some downstream impacts.  Both flow-weighted mean concentrations of phosphorus and phosphorus loadings were significantly lessened at the Ditch 14 outlet to the Pelican River, about 1 ½ mile downstream.

That pattern continued in 2001 and 2002.  Flow weighted mean concentrations of phosphorus prior to treatment were in excess of 100 milligrams per liter, and since treatment they have always been less than 60.  Similarly annual TP loadings, formerly in the 1500 to 2000 pound range, have been consistently around 500 pounds.  Much of this improvement has been as a result of the elimination of the spring peak (see chart).

Of course, it should be remembered that this was a period of lower discharges, and we do not have enough years prior to treatment to adequately assess that influence. -- R. Hecock


Wastewater Treatment and Drinking Water Supply Alternatives Study

February 2008

Lake Sallie and Melissa Chain of Lakes


All Lake Sallie-Lake Melissa Figures Appendix A.pdf Appendix B.pdf Appendix C.pdf
FINAL Report Text Index Map Service Area 1 Service Area 2
Service Area 3 Service Area 4 Service Area 5 Service Area 6
Service Area 7 Service Area 8 Service Area 9 Service Area 10
Service Area 11 Service Area 12 tables.pdf  


Floyd Lake Chain of Lakes

All Floyd-Little Floyd Lake Figures Appendix A.pdf Appendix B.pdf Appendix C.pdf
FINAL Report Text Index Map Service Area 1 Service Area 2
Service Area 3 Service Area 4 Service Area 5 Service Area 6
Service Area 7 Service Area 8 Service Area 9 tables.pdf

Downtown Detroit Lakes Water Quality Treatment Assessment

Wenck Study January 11, 2007

The realignment of US Hwy 10 in Detroit Lakes will allow for new development on a portion of the old highway alignment within the downtown area.  Stormwater management (specifically water quality treatment) within this area is of great importance to the Pelican River Watershed District and the City of Detroit Lakes.  Therefore the PRWD requested Wenck staff to assess the water quality treatment efficiency of the previously constructed PRWD ponds and the proposed TH 10 Phase 3 ponds.  The result of the assessment will indicate whether additional treatment is required for properties that develop within this area.

see full study

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Recent Water Levels
Detroit 1333.9 ft
Last Updated: 10/10/2018
Floyd(s) 1354.6 ft
Last Updated: 10/10/2018

Melissa 1328.2 ft
Last Updated: 10/10/2018
Sallie 1330.2 ft
Last Updated: 9/28/2018

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