Oxford University Cave Club

1998 Expedition: "Jultayu"

Picos de Europa, Spain

1998 Expedition Report - Contents

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Dye Tracing

Dye detecting is one approach used to investigate underground hydrology. A fluorescent dye, such as fluorescein is placed in an active stream and its route traced by placing activated charcoal detector bags in underground stream or at resurgences. This year we investigated the possibility that the caves in Area 9 drain to the 2/7 main drain. We placed dye in the small stream in 27/9 and dye-detectors in up and down stream 2/7 and at the Culiembro resurgence:

Upstream 2/7. Bags placed in pool just upstream of Big Ledge camp.
Downstream 2/7. Bags placed in pebbly bit of stream 10m before stream sinks.
Upstream Culiembro. Bags tied to rocks beyond deep water upstream of resurgence.
Downstream Culiembro. Bags to wire by resurgence.

Dye was placed in stream below third pitch of 27/9 on the 12/8/98, by Lev Bishop. A thunderstorm broke about two hours later. All the bags were placed by Jonathan Cooper, and most were retrieved by Jonathan Cooper or by people who had had no contact with dye. Bags were labelled and sealed in plastic bags on retrieval. Analysis was carried out by Jim Ramsden by soaking the bags in solvent (alcohol).

Location Bags In Out Trace
Up 2/7 2 Controls 1.8.1998 6.8.98 Negative
Up 2/7 1 Sample 6.8.98 14.8.98 Strong positive
Down 2/7 3 Controls 1.8.98 12.8.98 Negative
Up Culiembro 2 Samples 10.8.98 21.8.98 Weak positive
Down Culiembro 1 Sample 10.8.98 21.8.98 Weak positive

We, therefore, found that dye placed in 27/9 gave a strong positive trace to the upstream 2/7 within 2 days and a weak positive trace to both up and downstream detectors at Culiembro. The positive upstream trace at Culiembro would cause some concern except that water is known to resurge at a number of points slightly upstream of the main resurgence and that the detectors were not placed far enough upstream to avoid these. These show that at least some water in Area 9 drains to Culiembro via the 2/7 main drain. It also supports the hypothesis that the C4 stream may feed 2/7, since 27/9 lies roughly over the terminal sump of C4.

This opens up a number of exciting possibilities. Firstly, upstream exploration of 2/7 may push further into the mountain and reach the downstream end of the C4 sump. The unsurveyed passages found this year appears to head north west towards the C4 sump and the stream splits into two large feeders just prior to the limit of exploration. Secondly, 27/9 or other caves in Area 9 may provide an upstream entrance to 2/7, or even a high level link between upstream 2/7 and the C4 stream. It is not yet clear, whether, the 27/9 water joins the 2/7 stream as part of the hypothesised C4 water or as a separate smaller inlet. One interesting project for next year, may therefore be to carry out a trace from Area 9, with detectors at various locations along the 2/7 stream. Finally, it is already known that F64 and C4 drain to Culiembro, as dye placed in F64 in 1994 was traced both to the C4 stream and to Culiembro. There, therefore, is the possibility of a much larger system accessed either by 2/7 or via C4 and pushing upstream or by new entrances between the two known caves. Another interesting project, therefore, for future years is to carry out a trace from the Top Camp area (e.g. F2 or F7) to 2/7.