This weekend was the NPC AGM, so I took the chance of a trip down Grey Wife with Paul. After the last trip the way on looked like it needed washing through; there had been some rain during the week but the amount looked borderline. Past experience shows that a rainfall of 25 mm on a Thursday followed by dry weather can produce good diving conditions on Saturday or Sunday. The weeks biggest, local rainfall event was 15 mm.
After the usual enjoyable stomp down wide open passage we arrived at the sump and I kitted up. In Paradox Pond the vis was average but improved as the sumped passage was entered. It was clear that water had been flushed through the cave; the water was peat stained, the silt freshly rippled and vegetation hanging off the line. Unfortunately the main effect of the rainwater flush had been to bring in more silt without being powerful enough to shift it along. Thus space in the sump had been reduced and after several minutes of slow forward progress the dive was abandoned as an inefficient use of gas. After I surfaced Paul kitted up and searched the sump pool for other exits before having a quick go at the slot into the sump passage. No other passages were found and Paul pronounced himself happy with the slot.
All that can be done now is wait for a good dollop of rain, so if you are out walking in the Dales and you see someone doing a rain dance you are welcome to join in.
And this was useful information because now you know not to bother going into Grey Wife if there has been more than 15 mm of rain?
From this dive it looks like moderate rain can result in good diving conditions but does not move silt along the passage although it does bring more silt in. Considering the recent dives, no rain is good if the existing silt level is low. Dives several years ago showed that one heavy rain fall does move the silt about and can result in good dive conditions if followed by a dry spell :geek: