Winnats Head Sump 1 "The Lake"

[A_Northerner]

This is just a bit on info for anyone who has wondered what's in The Lake halfway down Winnats Head Cave, when I first started caving it always enticed me to wonder what was on the other side. It's been dived a couple of times in the past but I went for another look due to good vis. After the recent dry weather left the Lake, between Fox Chamber and The Sewer, tantalisingly clear (See photo below - clearer than I've ever seen it) I decided to take a dive in there. Previously reported dives were carried out in zero vis, with divers finding themselves totally submerged in very deep and very fine sediment at the bottom, unable to see their surroundings.

I assembled a team of SUSS Sherpas, and went for a look. After changing into completely new clean kit beside the sump, and testing my dive gear in the dry to preserve the vis, I swam to the far side to belay my line and dived down ahead of the inevitable avalanche of sediment that stirred up once I stepped into the pool.

I dived down to -9.5m, vanishing completely from view of the surface apparently, to find the 1m wide rift seen in the photo bells outwards to a diameter of 5m, but the roof being only 0.5m above a pyramid of silt that's accumulated in the centre. It seriously feels like being in the bottom half of an hourglass if that helps to visualise it.

I got about a minute of crystal vis at the bottom before the torrent of sediment engulfed me and I had to head back out.

Unfortunately the prospects here are pretty much nil. But it was a lovely dive for about 90 seconds.

It no longer looks like this, due to my diving. And it probably won't until we have another drought. I was glad to be able to have a look in these conditions. Maybe next time I'll remember to take a camera...

Thanks to those who carried.

 

[TLH]

Sorry for the dark photo, but this is how I always remember the lake. I always assumed that it was a wide arch heading under, not a slot.

Does the water level change much with the weather, and is this linked to the same water as the sump beyond the sewer?
(Sorry if these are daft questions, but there is quite the height difference between the two?)

Good effort getting your diving kit in there, it is known to be quite snug in places

 

[A_Northerner]

Does the water level change much with the weather, and is this linked to the same water as the sump beyond the sewer?

The level doesn't change much at all in my experience. The outflow towards the sewer seems to match the flow coming in from the collected percolation through the boulder choke below Fox Chamber. In dry weather it simply doesn't flow down the sewer and in wet weather the flow into it is never that massive.

The level difference in the photos is probably due to the mud slope slumping, which it definitely has done because the rock that the model is sat on in your photo is now further down the slope underwater. If the slope has slumped and lowered the outflow lip, the new level will be lower.

There's almost certainly no flow in from the other side, due to the flow in and out being the same (visually speaking, not measured).

A few fellow SUSS members who were interested in me diving this believe that the flow into the Sewer doesn't reach the terminal sump, so they're looking to continue exploration in the boulder choke beyond/below the Sewer.

 

[Goydenman]

that is incredible clear viz ..... great photo. Thanks for the update

 

[Stoney Boy]

I was one of the team when Phil Murphy dived it....it didn't look like that!