2020 – May Metrics

2020 – May Metrics

As on 1st April, we can’t bring you any commentary on groundwater readings for 1st May. In the fullness of time, Affinity Water’s team will be out and about interrogating the automatic data-loggers and we should be able to extract the figures that Dave Anderson usually reliably collects for us on the day.

However, we do know that the Misbourne has continued to flow in full glory from top at Mobwell Pond all the way to join the Colne at Denham. And how good it has looked in the wonderful sunshine during lockdown. Many people have remarked how they have enjoyed its views while on their walks for exercise. Social distancing has sometimes been a little difficult to maintain on the paths between the Chalfonts!

Typically, groundwater levels in the chalk of the Chilterns can start to rise in late September to October and recharge continues until around mid-February to March. Rainfall during the next six months is largely taken up by evaporation and plants and does not make it through the soils to the chalk below. The graph below shows, year by year since 1992, total rainfall in the “recharge period” in blue, and total rainfall in the summer period in green. As can be seen, until this year there hadn’t been a strong recharge season for a good while – hence, as shown by the “extent of flow” picture, the river has struggled to make much of a showing during recent years. In terms of rainfall, this winter’s recharge has been well above average and it will be interesting to map that against groundwater levels when available and, particularly, to see how long flow will now keep going.

As always, I am encouraged by the rate of recovery of flow down the valley from Amersham after a dry spell being apparently more and more rapid since we first cleared the way 2008 to 2011 and again in 2012 to 2013 and again more recently – see the gradient of the recovery periods on the extent of flow picture below, especially the last few months.

In response to lots of questions, and several inaccurate comments seen on social media, we have just added a new page to our website called “The RIver Misbourne – Some Questions Answered” which attempts to explain some of the vagaries of our delightful but enigmatic stream. The link is here but, be warned, it is a large file. Alternatively, find it on the website at http://www.misbourneriveraction.org/node/51 where you can click onto the same pdf file. It has been reviewed by both a qualified specialist geologist and a hydrogeologist but, if you see any errors or have any questions, please be in touch – perhaps by our Facebook Page – Misbourne River Action – or direct.

Of course, we can’t be organising any work parties at the moment. Fortunately we had made substantial progress just before lockdown and the speed of the flow has forced a clear path so things aren’t too bad at present. As soon as the “All Clear” comes, we will be able to organise for some action to clear local restrictions.

Meanwhile, best wishes to all, however this dreadful pandemic is affecting you.

We hope to see you by, or in, the river very soon.

6 Mths Rainfall.jpg

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