Hydrology of the Black Mountains

gus horsley

New member
Has anyone done any work recently regarding tracing in the Llygad Llwchwr area?  I know that sinks up at Herbert's Quarry drain to the cave but have there been any conclusions drawn from this?  In addition, where does Pwll Swnd drain to?  I can't remember if anyone has done any tests in the latter region but I would imagine the water flows to the east somewhere.
Cheers
 

prahja

Member
Hi - can't remember about Pwll Swnd, but try to get a copy of the SWCC special publication on the Black Mountain. It goes into a fair bit of detail on the dye tracing, geology, etc of the Black Mountain. I don't have my copy handy as I am away from home at the moment. I think there are still copies available to buy at Pennwyllt - certainly there are copies in the library. Hope this helps...

Andy
 
If by special publication you mean the Black Mountain Cave Survey carried out for the BBNP by SWCC (and others?) members, then it is indeed a mine of information but I don't think it's for sale. Most of the hydrological information in it is available elsewhere anyway (eg back issues of Descent - sorry not to be able to give refs but I'm too far away from my copies).

One thing that interests me is that if you combine the hydrological info with the geological map, you see that the water flows east-west and that, initially, at the Herberts end, the dip is about 10 degrees to the southwest whereas at the Llwchwr (IIRC) it's more than twice that and to the southeast. Given the size of the resurgence, I always thought that this meant that there was a shedload of water barrelling up-dip to get out and the only way that kind of pressure could build up was through long sumps (ie don't bother digging at the Llwchwr end but further back east). This seemed to get some support from Mike Barnes' discoveries at Heaven's Door but since I'm no expert, I'd be interested to hear other thoughts.
 
Sorry, didn't really answer your question: to my knowledge there's been no recent dye-tracing. Also, I forgot to say that in addition to an apparent problem with the dip, the flow crosses at least three large faults running north-south and still results in a huge resurgence and reasonable flowtime ie the stream doesn't seem to be diverted by the faulting? Although there is a line of springs further to the south as I recall. Anyway, gotta go...
 

prahja

Member
No, not the cave survey project - there is an SWCC Black Mountain publication with a lot of history, geology, hydrology, cave info, etc, etc... published (at a guess) some 13 years ago - I believe there are still copies for sale (may be wrong though) and there are definitely copies in the library.

Andy
 

NigR

New member
gus horsley said:
I know that sinks up at Herbert's Quarry drain to the cave but have there been any conclusions drawn from this? 
In addition, where does Pwll Swnd drain to?

Dyetests from Herbert's Quarry to Llygad Llwchwr had relatively fast flowthrough times indicating lots of open passage.

Pwll Swnd resurges at Ffrydiau Twrch.
 
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