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Harvesting of Duckweed 2019

Posted: September 6, 2019


Pilot project taking place in some ponds

Have you been walking by the Eagle Creek ponds this week and wondered what is happening?  The equipment you see is being piloted to see how well it can remove excessive duckweed from our ponds.  It is important to remember that the aquatic vegetation is a natural part of pond ecosystems.  It is only when that growth becomes excessive that it can create problems.  Removing or harvesting the duckweed offers an opportunity to remove nutrients from the aquatic system so they will not contribute to excessive plant growth in subsequent years and ultimately to algae blooms in Lake Winnipeg.  

You might be wondering….

Why now and why not earlier in the season?

This is the first available time slot the contractor had available.  The City of Winnipeg uses this contractor to remove excessive vegetation growth from their ponds and because the City has seen conditions similar to ours the contractor has been fully occupied until just this week. The RM approached the City of Winnipeg this spring to see if there might be an opportunity to work with its contractor.  We are grateful that the City has been able to release the contractor to us to trial the use of the equipment.  


Does removing excessive duckweed growth at this time of year do any good?

By removing the duckweed we are removing the phosphorus from the system that otherwise would fall to the bottom of the pond once the duckweed dies.  These nutrients would then be available to feed aquatic plant growth the next year.

What does the RM hope to learn for next year?

One of the things we are looking forward to is being able to calculate the amount of nutrients – specifically phosphorus – that is being taken out of the system with removal of the duckweed.  The International Institute for Sustainable Development has taken samples and will be calculating just how much phosphorus is being removed in this manner.  Knowing this information will assist to determine when and how best to deploy available resources.

What is happening to the duckweed that is being removed?

The duckweed is being disposed of at the compost pile at the Transfer Station where it will be allowed to dry out before it is transferred to a compost facility to finish the composting process.  Once fully composted it will make an excellent source of slow releasing fertilizer for soil amendments.  

Can the excessive growth of other aquatic plants be removed this way?

It depends.  The equipment requires adequate space and depth and a suitably strong enough launch pad to carry the weight of the equipment and not cause a bank failure.  The other factor to consider is what will happen if we remove one type of vegetation?  For example, if we completely removed submerged aquatic plants they may be replaced with excessive algae growth.  

Is there other equipment that might also work?

The RM is investigating other options that might work on duckweed and other species so this is unlikely to be the last trial that you will see.  

Where can I get more information and keep up to date on developments?

Keep checking our website under the tabs for Residents/Environment and Climate for information under Ponds.  



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