Blog Post: Secchi Disc is go!

Secchi disc in Porth Yr Ogof
Photo: Mike Thomas

The secchi disc is in!

Following several false starts due to weather and quite a bit of discussion about how to do it, we've finally attached to secchi to a pot of concrete and found somebody else to drag it into the cave for us!

In seriousness, we're grateful to Mike Thomas, a CDG diver, for agreeing to take the disc in today and try some visibility measurements. He was headed over to Porth Yr Ogof for a dive in any case and I was heading to the next valley to take a group caving at Little Neath River Cave - where we also took a photo of sump 1 (station 7).

Mike pulling the Secchi disc into a fast flowing
Tradesmans Entrance, PYO

I ran over to Porth first to drop off the secchi and took some photos of Main Entrance (Station 4), Tradesman's Entrance (Station 3) and the River levels (Station 6).

I had been wondering, now that the secchi was about to be in place, whether there was any value in keeping the above ground stations. They all form part of the Porth story but seemed unlikely to change very much. Besides, this is a diving project after all.

Porth Main Entrance - in front of the new rock fall!

I considered dropping the surface observations and stations and only keeping the underwater ones - until I visited Main Entrance today!
I was very surprised to see what looked like a very recent collapse. A huge boulder blocked the path to the cave entrance and several other large, tv sized rocks had come down.
So much for nothing changing!
I'm inclined to keep the surface observations as part of the project for now - it just got interesting!

New rock fall by Main Entrance, PYO

Please take care when visiting Main Entrance - there is another massive   boulder just 'hanging' there above the path...

Mike took two viz measurements, one with a hand held light monkey (4m) and one with a helmet mounted Rude Nora 2 caving/diving torch (3m). He had already been upstream and was keen to point out that these were not 'true' visibility readings.

Significant rock falls close to PYO Main Entrance

He also noted one very white trout and shot some video - and also 2 bullheads.
This (in comparison to other reports) is quite a small amount of life, so it will be interesting to see if the abundance improves by the time another diver reports in.

Meanwhile, over in the next valley, I visited Sump 1 of LNRC (Station 7) and my eagle eyed cavers spotted a bullhead in the shallows. No trout this time though (that we could see). No foam and pleasingly, no diesel/paraffin smell. The white substance on the mud bank near the sump (@rescue dump) has almost gone.