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Little Rock Lake-Sartell Pool Drawdown Project Information

Little Rock Lake-Sartell Pool Drawdown Project Information

A proposal to consider a summer drawdown at Sartell Dam 2018

Two public information meetings scheduled:

Friday, August 11, 7:00-9:00 PM Watab Town Hall

Wednesday, September 27, 7:00-9:00 PM Watab Town Hall

These are informational sessions to receive information and comments on the propoosed drawdown. 

We would like to see your thoughts and hear your questions or comments you can fill out the online entry form here: https://goo.gl/forms/bIwV3ks3TOekVHTq2

 

 

Feasibility study that explains much of the history and projects related to the potential drawdown. 

Recent meetings with Eagle Creek Energy suggested we may need to consider some alternatives to a system-wide longer term drawdown. Maintenance requirements, loss of significant revenue and complexities with FERC licensing made it worthwhile looking at other options. One of which may be operation of the dam at a lower level (IE 2ft below full pool instead of 3ft). Another potential option may be a temporary coffer that would isolate the lake using water inflatable tube dam. Several manufacturers make the products. A potential option may include the use of a temporary dam and pumping after a short (4-5 day) drawdown for a longer term drawdown, within Little Rock Lake and the channel area. In either case, options are available and funding can be acquired to make the project happen. We will be working closely with Little Rock Lake Association and Benton SWCD to put a grant proposal in for the project timeline of Summer 2018. 

Letter and Fact sheet sent to area residents

 Common questions about the drawdown

Detailed maps below!

Water quality is an issue on Little Rock Lake. A TMDL was established for the lake in 2011 for excessive nutrients. Water clarity at times is less than a few inches due to pervasive algal blooms. 

 

 Close up of algae bloom on Little Rock Lake.A picture of Little Rock Lake looking west at a peak algae bloom in summer.

Many efforts have been made in the watershed to try and address the source of excess nutrients including: alternative farming, irrigation, manure management and septic system upgrades. Despite these improvements there are still water quality issues on the lake. Something more large-scale needs to be done to address the problem. 

The 2012 TMDL report suggests a large portion of the higher phosphorous loading has come in during spring runoff events and then remains resident in the lake basin (Internal Loading). None of the suggested alternatives have attempted to address internal phosphorous loading. 

Benton County Little Rock Lake TMDL Page

Drawdowns have been shown as effective methods to process nutrients in the soils, stabilize shorelines, increase water clarity/quality and provide valuable fish/wildlife habitat. The proposal would be for six weeks, likely starting around the second week of July through the end of August 2018.  It will affect recreation to some extent in both the Mississippi River up to the Rice Bridge (County Road 2), Little Rock Lake itself and will likely make navigation through the Harris Channel extremely limited.

Pictures from the Mississippi River Pool 8 Drawdown, 2001 and 2002.

Drawdowns have been used throughout the country and in Minnesota as a management tool to improve fish/wildlife habitat, improve water quality and manage nuisance vegetation or fish. Typically, a frequency of summer drawdowns every 7-10 years has been proven effective at maintaining water quality and habitat standards. However, each reservoir complex is different.

The Sartell pool and Little Rock Lake have an artificially maintained stable water level that has not changed since 1908, when the dam at Sartell was installed.  Natural systems have a natural rise and fall which builds stability in the sediments and plant growth. Little Rock Lake and the Sartell Pool are still adjusting to this day. 

 

Some potential submerged vegetation growth may occur in areas that may not have been visible in the past. There are provisions within the DNR Aquatic Plant Management Program (APM) to control certain areas and types of plants without a permit. Please see APM Permit Information

Little Rock Channel and 15 miles of the Mississippi River (Two Rivers Campground- Sartell Dam) were mapped late April-early May 2016 and maps were created with the help of Biobase. Little Rock Lake was also mapped in May.  The information was used to calculate more accurately how much area will be exposed if or when a drawdown does occur. The information is available on the Insight Genesis website in a downloadable format for Lowrance units. it is available as a "Social Map" on the Insight Genesis website.

River and Lake Contour Maps in PDF format from Two Rivers Campground to Sartell Dam in order from upstream to downstream 1:5000 view. Each map shows the areas that would be exposed if there was a three foot drawdown. Also shown are single foot contours of the river and Little Rock Lake.
River Map 1 River Map 9 River Map 17 River Map 25
River Map 2 River Map 10 River Map 18 River Map 26
River Map 3 River Map 11 River Map 19 Lake Map - Upper 
River Map 4 River Map 12 River Map 20 Lake Map - Middle 
River Map 5 River Map 13 River Map 21 Lake Map - Lower
River Map 6 River Map 14 River Map 22 Lower Basin - North 
River Map 7 River Map 15 River Map 23 Lower Basin - South
River Map 8 River Map 16 River Map 24 Harris Channel

 

Where is the process now - August 2017?