Last month, I was reporting flow along the whole stretch through the Chalfonts while noting the increasing amount of weed.   In the event, not many of us could make the work day but those who did carried out sterling work to clear a channel through the worst areas.  Now, a month on, flows are dramatically less and, in fact, zero through much of Chalfont St Peter.  The link between the villages is once more broken, with the stream from Chalfont St Giles now disappearing above Water Hall and, everywhere, the weed growth is prolific.

In these circumstances, it is a little more difficult to be enthusiastic about a work party in July.  However, it could be that there are some significant blocks upstream of Chalfont St Giles and specific problems elsewhere that would respond to a local blitz.  I intend to check out the usual spots in the next couple of days and a decision can be made at our next “not a meeting” which, by the way, is now changed again to Thursday 1st July at 19.45 in the usual spot to the right of the bar in the Three Pigeons, Austenwood Lane.  I look forward to seeing some of you there.   I will relay the outcome in a further circular.

The application for Heritage Lottery Funding for lining of target areas has been sympathetically received but, understandably, the funders say that they cannot move forward until the proposals have approval from Environment Agency.  As most of you are well aware, understanding of the EA’s position and requirements has been challenging us for many months and two expert members of the Chiltern Society/MRA are now drafting scoping proposals which we hope will enable clear discussion and finalisation of the purpose, detail and acceptance criteria for any further studies and surveys.   Meanwhile, flow measurements continue, with particular attention to the anticipated areas of loss.  (If you would like to join the “pool” of people undertaking this work, please let me know.  The measurements take about a day a month but obviously not everyone in the “pool” is needed every month).

One of the most frequent questions from people yesterday was around the whole issue of “Why does the Misbourne disappear downstream of Chalfont St Giles and reappear at Chalfont St Peter?”  A simplified answer which I usually give is as follows:

From the source at Mobwell, just north of Great Missenden to joining the River Colne at Denham, our river has three separate personalities – see the attached sketches.

 

 

 

 

 

 

1) From its source all the way to downstream of Amersham, it behaves as a fairly conventional chalk stream i.e. it is fed by groundwater in the chalk and it starts where this groundwater meets the surface.  At this point will be a spring but the point will move up the valley when groundwater level is high and down the valley in the summer.  So, from the Black Horse pub at Mobwell all the way down to Great Missenden is likely to be flowing in spring and dry in autumn – a “winterbourne” – with fairly constant flow from Great Missenden to Amersham.

2) From a little way downstream of Amersham to just before Chalfont St Peter, is usually a “perched stream”, i.e. the groundwater is some distance below the river bed and any flow is merely that from the upper reaches carrying on as if in a gutter.  In this area, the underlying chalk is more porous and fractured than higher up the valley and so, through this section, except when ground water levels are exceptionally high, water seeps back into the ground and often disappears completely.

3) From Chalfont St Peter to Chalfont Park it is once again a winterbourne. The start of spring fed flow moves seasonally between somewhere near Water Hall and the lake in Chalfont Park from which it flows reliably to the Colne.

inevitably, the detail is  more complex and some can be found on the website in the facts and figures section, which we are slowly expanding.