117 Los Boyones
Secadura 30T 0455814 4799512  Alt. 50m Length 100m

Updated 13 February 1998; 19th Febrary 1999; 2nd May 1999; 5th November 2005; 14th May 2006; 6th May, 27th October 2007

The water found in Cueva de Carcavuezo (81), Cueva Llueva (114), Cueva Hoyuca (107) and part of Cueva de Riaño 1 (105) - the whole of the Four Valleys System (line survey)- resurges in the Secadura valley. In wet weather the water emerges from a number of openings along a 200m long front but in normal conditions the water resurges at Los Boyones. Major building and piping works were started in the mid nineties and an elevated walkway now passes the "resurgence front"  ending over the main resurgence pool where water is extracted and past over the hill to Moncallian. Trees surrounding the resurgence pool and visible in 1999 photo had gone by 2006. The treatment works is gated but, if locked, the gate can be easily climbed around.
The GPS for the extraction pipe is 30T 455815 4799517.

Information gleaned from the Dirección General de Obras Hidráulicas y Ciclo Integral del Agua in 2005 shows an average water flow from the resurgence over the previous 20 or so years of 650 litres per second. (The Fuente Aguanaz resurgence emits 951 litres per second on average. Unlike the 4 Valleys System, there are currently no known feeders or caves which drain to the Nacimiento de Aguanaz). At Easter 2006, an optical brightener test was carried out from the end of the Sumidero de Cobadal. A positive result was obtained at Fuente Aguanaz after a week and with no sign of optical brightener at this resurgence over a full fortnight. A paper detailing the methods, etc can be read here.

The small, excavated cave entrance is 5m above the normal resurgence and located just behind a large embankment of boulders which form part of the pumping station complex. The hole usually emits a strong draught.

A 5m pitch leads to a hole down into the boulder choke (which is unstable in places). The draught can then be followed between the boulders to the river at the base of a steep mud slope.

Various climbs at the top of the slope close down and the draught is lost.

In 1997 a pool of standing water leads to a way on upstream with deep water - not pushed.

Nearby, to the west, is Cueva 77A (site 154) which is all part of the difficult to explore resurgence complex.

References: anon., 1974b (logbook); Kendal Caving Club and Manchester University Speleological Society, 1975; Cope J et al, 1976; anon., 1977b (logbook); Corrin J et al, 1978; Manchester University Speleological Society, 1982; Mills L D J and Waltham A C, 1981 (survey); Corrin J S and Smith P, 1981; anon., 1981 (logbook); material in file; anon., 1989 (logbook); Corrin J, 1992b (survey); Corrin J, 1994b (survey); anon., 1996a (Easter logbook); Corrin Juan, 1997a; Corrin Juan, 1997b; anon., 1997b (logbook); Corrin Juan, 1997c; anon., 2005c (autumn logbook); Corrin Juan, 2006a; anon., 2006b (Easter logbook); Corrin Juan, 2007; Corrin Juan and Smith Peter, 2007
Entrance pictures :

Digital photos mainly around the resurgence pool, Easter 2006, during an optical brightener test from Cobadal. A1-A3 by Juan Corrin with Penny Corrin A2 and Ian Chandler A3 B1-B3 by Penny Corrin with Juan Corrin B2 and Ian Chandler B3 C1-H3 by Phil Papard with Juan Corrin, C2-D2, F2-G1; Ian Chandler and Jon Whiteley, e.g. E2 A1: Distant view of Los Boyones resurgence at the right hand end of the tree-lined river bank ending at an obscured building and track. A2-D3: Putting in cotton wool detectors during normal flow conditions. E1, F2-G1: Removing detectors during wetter conditions. E2,3,G2,3: Putting in detectors with a retrieval line. F1: Gated access to the treatment house.
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Underground picture(s):
Video: Retrieving a cotton wool detector during high water flow. (Phil Papard)
Detailed Survey :
Line Survey :
On area survey :
Survex file : yes