Water Levels

[badger]

maybe before this goes of topic hope to get some sensible answers,  was in mendips weekend just gone, had four groups down funnily four different caves, so those that went down longwood and gb had lots of water, the video of the waterfall had more water going down it then I have seen for a long time. those that went down eastwater and swildons no water at all, in fact swildons entrance series completely dry.
so was wondering if there was an obvious reason, other than it rained over one side of mendip and not priddy side?
is this something other cavers have noticed.

 

[mikem]

Friday eve not much water down GB, none at all in Swildon's. However, GB & Longwood have still had a small flow all summer whilst Swildon's & Eastwater haven't had any - the 20mm on Sat morning obviously wasn't enough to start them running, but did increase those that already were.

Mike

 

[Les W]

We really have had very little water on Mendip for months now. I don't know if Bristol Water are still pumping upstream from Swildons but that might account for the lack of flow there. Eastwater has a new swallet upstream of the entrance and water is not seen in the cave unless it is high flow.
Taken together that might explain it over the Priddy side.

 

[badger]

saturday the water at eastwater was dissappearing down in between the tyres.
when went in to swildons no sign of water in the entrance stream, by the time I came out was possibly an inch. by the time went down on sunday, the water had all but dissappeared just visable between thepebbles.
gb hadnot quite a raging torrent but was high enough to rope the waterfall and as I understand enough water to make the bottom of the ladder dig wet highhighnot sure.
I know longwood react's quickly to water, so perhaps gb does,
maybe it is that all caves in that area react quicker to some others on mendip

 

[whitelackington]

The Charterhouse caves are under the Blackdown Massive,  Highest part of Mendipshire, which is quite steep sided.
Presumably rain is likely to run down the steep slopes and straight into engulfment.

 

[Les W]

When the ground is dry run off will be instant. Longwood and GB have large, well defned catchments. They respond quickly to rain and drop just as quickly after.
Swildon's drainage is more difuse and Eastwater is now always dry except in times of very high flow.
I would guess that you must have been in the Charterhouse caves just after the downpour . Swildon's will respond but much slower and if BW are pumping then the water might not even make it to the cave.

 

[Naomi S]

That's interesting and explains why the waterfall in GB was trying to spit us off and Swildons is still dry to rolling thunder!

Where do BW pump from then and when do they do that?  What would happen if they just stopped?  I can guess but my question really is do they tell us cavers before they do this?  Is this why there is a flood warning for Longwood from BW in the MU?

 

[Les W]

Bristol Water pump from boreholes upstream of the entrance but normally don't pump. In times of drought/low water conditions they tend to hit all their sources to keep up with demand so there is a good chance (though not definite) that they are pumping now.
Also Swildons drainage, although larger in area is much flatter than that of the Charterhouse caves so runoff is slower and there is more oportunity to soak into the ground.

There has never been a problem for cavers from the pumping at Swildons (except for low/no water) but it is possible if they stop pumping at Longwood that a pulse could flow down the cave and catch somebody unawares at a low bit, hence the warning.

 

[whitelackington]

As it is raining over Mendipshire today,
perhaps young cavers can be dispatched into both Longwood and Beastwater,
then we will know?

 

[badger]

I find myself back on mendip this weekend, not sure what has been happening weather wise in mendip but Sussex we have had already well over the average rain fall for the month, What has the weather been this week in mendips, weather forecast for the weekend suggest Friday will be the worse than scattered showers? And most importantly how has any weather if been sustained effected Swildons,?

 

[Burt]

Hi Badger

Mendip weather at the moment terrible; squally heavy showers every 10 minutes or so. Was up at Ubley Warren this morning and couldn't see across the yard at times the rain was so heavy.

The pond which feeds Swildons is still very low, and the resurgence flow at Cheddar looks as if it's high summer rather than mid autumn. However if it rains constantly today and tomorrow the levels may rise, but as Les rightly points out there has been little serious rain on Mendip for months, so the ground is still soking up in places.

I have, however, a sneaking suspicion that the stream which feeds Swildons at the entrance has found an easier way underground (as they do) and will not return. I hope this isn't the case though.

 

[badger]

something we had wondered if this might be the case, but if that is the case where would this then show in swildons. be interesting to see this weekend.
We also have had a very dry summer in sussex, but all local streams are running quite high today, though have not heard any flood warnings but if we have another day of torrential rain think some could flood.
the Met Office weather reports tomorrow, sat and sun much better than the week so far so maybe the streams will have chance to recover.

 

[Les W]

Swildons currently has plenty of water for the first time since about April/May(ish) 
Currently a normal winter level stream