Water Quality Projects 2009

Cross Lake Water Quality–Background and Proposed Projects

There has been important and extensive top-to-bottom data collection and analysis of water samples of Cross Lake at various specific sites for several years.  Incoming streams have been tested for E-coli bacteria and nutrients.  The information gained is telling us much more of the details of what is going on in the lake.  We have been looking for both trends and causes of problems.

We are all aware of the problems of Curleyleaf Pondweed and algae bloom.  The joint Pokegama and Cross Lake water quality committee has been searching for answers for over a year, listening to experts and asking lots of questions.  We have been studying the chemistry of lakes including research that has been done. There is valuable information and expertise available from commercial companies dealing with aeration systems, useful non-hazardous muck-eating aerobic bacteria, and other natural biological material, iron filings, barley straw, etc.  Each of these and other concepts has shown some usefulness in some water situations–primarily in ponds. 

We need to understand what is going on at the bottom of the lake that is affecting the water above it. We know that there is a great deal of “muck” at the bottom of parts of Cross Lake.  Muck is sediment that has settled to the bottom and includes inorganic mineral content  (such as sand and silt)  along with much partially decomposed organic matter from sources such as dead Curleyleaf Pondweed and other plants, green and blue-green algae, fish remains and their waste products, leaves, grass, etc. 

The organic matter in the muck is very significant in understanding our water quality problems!  According to expert opinion, the bottom of lakes release more nutrients to the water column than what is currently coming in from the watershed!  The excessive nutrients “overfeed” undesirable blue-green algae and curleyleaf pondweeds.

As one DNR specialist said:  ‘This is not unique to Cross Lake, but you are dealing with the legacy of past practices.’ Runoff across bare earth has been caused by strip logging in the old days, road building, modern farming which has emphasized row crops of corn and soybeans rather than oats and hay, building cities, cabins and houses along the Snake River, its tributaries and the lakes. 

Everyone has a Curleyleaf Pondweed problem along the shore and quite a few people are dealing with it in May or June– preferably by cutting and removing it in order to prevent release of nutrients back into the water to “feed” blue-green algae.  This is good management. We would like to see many more people doing this. 

Blue-green algae are a more serious water quality problem–the ugly pea soup and smell bothers everyone, and the toxin it produces is potentially hazardous to swimmers and animals.  Unfortunately there is no tool, no weed-rake, to remove the algae.  What about algaecides?  Killing it in front of your dock is going to return nutrients back to the water, create another potential health issue and be useless in preventing these free-floating organisms from sweeping in with the waves from elsewhere in the lake.

PROPOSED PROJECT:

We are planning an experimental project in one northeast bay which has a long retention time (475 days), has a lot of nutrients, and has a lot of blue-green algae. We are seeking a grant to supplement our expense in purchasing equipment and supplies. 

If we are permitted by the DNR to begin the planned project (which includes aeration), we will be spending a great deal of time in setting it up in the lake and taking additional kinds of samples.  As advised by the DNR, determining if the project is successful will take careful planning and execution.  It is much more complicated than “putting it in the lake and let’s see if the water clears up!”  We want the project to be worthwhile and to improve water quality in a part of the lake that has taken the brunt of both human and natural forces.

In addition, we have grant money to supplement the purchase of some natural material cocoa rolls to be used as a filter where there is fast runoff of nutrient-rich soil through a gully and culvert and empties into Cross Lake in the northeast bay. The Pine County permit has been approved.

For your information:  Cross Lake Secchi disk readings in May 2009 were from 4 to 5 feet–excellent for that time of year.  Also, last September (probably at lake turnover) we had a reading of 8 feet at one location–a record high!  Rain affects lake level (and volume of water), this along with cooler water temperature and higher lake bottom oxygen levels, have much to do with water quality and resulting Secchi disk readings.   As you see, there are a lot of interconnected factors involving water quality. 

Jerry Trent

Water Quality Chair