Dredging the 'duckpond.'

I was walking past the duckpond ( aka Paremuka Lake Stormwater Pond) the other day and discovered machines, dumpsters and equipment, all surrounded by fencing. Motor noise told me something was happening. I hurried over to find out what the hub-bub was about. I found out that it all had to do with Cabomba caroliniana. Well, mostly anyway. 

They are currently set up to dredge the smallest of the sections of the 'Lake.'  Periodic removal of the sediment that is carried into the stormwater pond is done to maximize its stormwater storage potential.

But, there is a second  and even more important reason that a careful dredging is necessary this time. This is one of two stormwater ponds in Auckland that has been invaded by Cabomba caroliniana, an aquatic weed that authorities believe was dumped into the pond from an aquarium. New Zealand takes unwanted species very seriously, and does whatever it takes to eliminate them when they're identified. 

One of the workers told me that this weed can be killed by saltwater, but introducing enough salt to do the job into this pond would also damage many other species and so that plan has been ruled out. 
(that's a two meter tall pipe in the background that brings water from up-stream stormwater ponds and from local street drains. The weed-eater/dredger is in the foreground.)

A view from the other side of the park. I was told that it will take about a month to complete this job.    -djf