MRA: July Jetstream

Inevitably, the lack of rain is having a significant effect on the river.  The EA attended several fishkills reported last month, though these were less than on some previous occasions.  The upper winterbourne flow has now receded towards Little Missenden while the lower winterbourne is just about hanging on through the Chalfonts for the moment.  Despite the good flow enjoyed for the past three years, we should remember that there has only been flow through CStPeter on 1st August in 14 of the last 33  years, though that ratio is improving, probably due to reductions in abstraction.

On the other hand, the weather forecasters tell us that the present hot and dry spell is the result of the jetstream being further north than usual and I read that, in turn, this reflects the Northern Atlantic Oscillation (NAO) index – the pressure difference between the Azores and Icelandic weather systems.  Long term readers of my waffle will remember there was once a university scholar studying the NAO who considered flow in the Misbourne closely reflected an NAO cycle.  Unfortunately, we lost touch – possibly because they found extreme difficulty in developing conclusions from the NAO index as it can flip in a few days or stay steady for months.  In my view, a somewhat erratic cycle undoubtedly exists with there usually being 5 to 7 years between highs and lows, floods and droughts, but being rapidly masked by climate change.   I have spent a few hours this month similarly failing to graphically match it to the NAO index!

Several supporters, enthusiastically led by Trish Mallet have been busy identifying and removing Invasive Non-Natural Species (INNS) with “balsam bashes” along the river.  The principal INNS target is Himalayan Balsam – the purple one, which forms stands and outcompetes natural species in many waterside locations throughout England with devastating results – e.g. the Rivers Wye and Rother.   Its sister, Orange Balsam is also an INNS and, while a lesser concern, it is nevertheless seemingly becoming more common along the Misbourne and the team are keen to remove it as well.  Where found, the thankfully less common but more noxious Japanese Knotweed and Giant Hogweed are being expertly treated.  Another issue is floating pennywort in the lower reaches where the Colne Catchment Action Network is researching treatments.

The Riverfly monitoring teams have continued their outstanding work and are now including temperature measurements with their records of different types of inverterbrate.  The graph below shows the EA “alarm” trigger levels, the recent average scores and the notional target scores (RICT) for a river in near perfect ecological health.  Yes, the figures do beg a number of questions for investigation.  The blue dashed line at 71% of RICT describes a river in “Good” condition per the Water Framework Directive – perhaps a minimum target for “Mending the Misbourne”.  

Other “Citizen Science” groups have been out looking for traces of water-voles to map the extent of populations along the river and MoRPh surveys have been undertaken to record pre-project conditions for proposed projects.  We are now looking for volunteers to help with routine flow measurements and also “mud-spotting” – i.e. simply recording how clear the water is at particular locations associated with weather events.  We would love to hear from you.

At the recent fun “not-a-meeting”, it was agreed that there were quite a few potential targets for work parties viz;  ‘balsam bashing” as above, continuing clearance near Bottom House Farm Lane, maintaining a channel through the watercress in the “sheepfields” downstream of CStG, routine attention near the CStG Greyhound and the old ford, and debris removal in Amersham.  

There is a “balsam bash” in Chalfont St Peter this Tuesday morning 21st (more help welcome), and we noted the following as possibles for tackling this list: Weds 22nd, Saturday 25th, Weds 29th, Saturday 1st August, Weds 5th August, Weds 12th and Saturday 15th.   Please let me know which work for you and I’ll select the three or four with the most takers.  While we couldn’t cope with the numbers if everyone on our supporters list turned out even once a year, it’s always nice to see new faces and many hands do make light work.  (If none of these dates work for you, but you fancy doing something, why not use the WhatsApp to ask for company own a particular date? – I will endeavour to provide RA’s and kit in the same way as usual)