I noted the planting by the edge of the new river in the extended park area last week. Now the BBC has spotted this new wetlands and you can see the TV report here (time codes 5:04 to 7:05: https://www.bbc.co.uk/iplayer/episode/m000csmw/bbc-london-evening-news-23122019#t=5m4s
These types of ponds mostly capture road run-off, probably in no small measure from the very busy A40 road close to the park. This carries microparticles of plastic, bitumen, car tyres, oils and other organic undesirables and in the past this was directly drained into the river Brent and hence the Thames. Now at least it has a chance to settle to the bottom of the ponds before discharge.
Before you ask, it is hoped that plantings such as those we did last week will play a role in processing these organics so that they do not simply accumulate in the ponds. After all, we have seen how dogs are now seen frolicking in them; I do hope they are given a good soapy hot bath when they get home. Ducks and swans also now occupy them (the ponds, not the baths). Before we know it, we will be constructing a bird watcher’s hide for the visitors!