John Robinson has been charting changes in water levels in Wanstead Park since 2012. Here’s his graphic representation of what’s been happening.
Click on the Chsrt to examine it in more detail.
The bottom (x) axis is the number of days since recording began
The level in Perch varies seasonally as one would expect and it is currently at a normal level for the time of year.
The level in Heronry is very variable, presumably as a result of periods of pumping and periods without. The recent fall in water level is clearly linked to an absence of pumping over a long period as the City of London tried to get the level down to do the work on the dam. Pumping has now restarted. There appears to be no record of when pumping has taken place and by how much.
The level in the Ornamental Water has fallen over the last couple of years because there has been no input from the southern end and because water is continuing to seep away through its unlined bottom. A licence has been applied for to pump from the River Roding but we have no news as yet.