0713 Aguanaz, Fuente
San Antonio 30T 446580 4801629 Altitude 78m Length 2046m Depth 31m

Updated 19th February 1999; 6th May, 16th October 2001; 5th November 2005; 15th May, 15th June 2006; 27th October 2007; 1st October, 8th, 19th, 30th November 2008; 6th May, 2nd, 18th November 2009; 26th June 2010; 6th January, 27th May, 5th October 2011

The cave is a major resurgence for the area and a large diameter pipe removes water supplying Santander. 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 951 litres per second. (The Matienzo / Riaño water resurgence at Los Boyones emits 650 litres per second on average. Unlike the 4 Valleys System, there is only one known feeder or cave which drains to the Nacimiento de Aguanaz).

An optical brightener test from the end of the Sumidero de Cobadal over Easter 2006 gave a positive result after 5 - 7 days during medium to medium-high flow. During the 6 or so visits over a fortnight the water levels were slow to react after some heavy rain, and even then only rose by approx. 7cm. Los Boyones rose by 120cm much more rapidly. The details of the test are found here. There is a possiblity that water from the Sumidero might drain to Torca La Vaca during low to normal flow, only passing over into Fuente Aguanaz during high stage. Some suggestions regarding water sources for Aguanaz are detailed here. In 2009 these possibilities were outdated when an inlet, apparently from La Gatuna, was explored.
The resurgence can emit large quantities of water, flooding the low lying ground around Entrambasaguas and beyond. One effect of the Whit 2008 flood was to jam leaves around the door of the new pumping station, which is probably 7m above the normal water level. A smaller flood in October of the same year was shown on national TVE news. (Photos here).

The resurgence area has an outdoor interpretation centre with 4 boards explaining about water and the environment. Further boards are in the old pump houses.

The water level at the bottom entrance is at about 50m altitude and is reached by walking down concrete steps. Sixty metres up behind this - reached by a track setting off on the right of the car park - is a hole below a scar in a depression which is where the pipe reaches to abstract the water. The entrance for cavers is another 70m south and starts as a route between boulders. The grid reference for this entrance was altered in 2008 and is that shown above. Just below the top of the rope climb, a hole was opened up in 2009, heading west. This turned out to be an alternative way down to the stream rather than any high level development.

The site is mainly swimming. Half way through, the water can be left and there is an inlet on the western side. This was pushed and resurveyed in the summer, 2009. Beyond the aven the inlet stream continues through an choke to two short ducks and a continuing stream passage which lowers to a flat out crawl with a slight draught. Before this, a climb out enters a large chamber / passage which may continue south beyond an unexplored pitch down. The area was reinvestigated and pushed on one trip at Easter 2010. "Had a good look round in the boulder choke. Could not find the main way on but found plenty of high level passage with deep holes in the floor. Possible ways on? About 250m unsurveyed?" About 150m were surveyed to 40m above the stream where the high level passage lies. See photos taken on this trip.
An inlet on the east was also explored, summer 2009, for 70m and ending at a too tight rift with no draught. A aven was free climbed 9m after a tight squeeze up to where it continued up out of sight.
The southern sump was dived at Whit 1995 and was passed in 5 to 6m visibility, after 35m, at a maximum 5m depth to a large sump pool on the other side. De- kitting occurs on a mud and boulder bank on the left. The continuation was then fully explored for 500m during the summer of that year and consisted of swimming and wading until the passage climbs several cascades to meet the unexpected sump 2.
The 25m long sump 2 was passed to approximately 300m of passage, ending at a boulder choke with a slight draught and one potential digging site. An extremely small, sharp sump continues at stream level. This was entered at Easter 2001 to an airbell to the right of the sump and then pushed in the summer to a "quite tight close down", 5m from the previous limit. Running water could be heard from the rockfall above. At Easter 2006, this seems to have been dived again.
There is a climb above sump 2 which needs attacking.
"The inlet on the left" after the second sump was pushed at Easter 2001. The passage continues tight through a few short climbs. A small chamber leads to a larger one with mud and boulder walls. A stream enters through the ceiling. The place smells of "outside".

Compared to Torca La Vaca, about 1.5km to the east, Fuente Aguanaz is a disappointment. There would appear to be no reason why this cave should not have (a number of) high levels. Perhaps the western extensions in 2009 have started to reveal these. More climbing up from the stream level and investigating avens is required.

There is apparently no account of the upstream passage from the middle entrance having been explored and, although some photos have been taken, the passage has not been surveyed.

A small hole on the east bank of the resurgence is the entrance to Invisible Cave, site 3283, a stream passage apparently not connected to Fuente Aguanaz but probably connected in the past as an inlet, before Fuente Aguanaz entrance cut back. A small, 4m long cave in a gully above the Aguanaz cavers' entrance was maypoled into in summer, 2009.

A diagram of the hydrology of the San Antonio - Hornedo - Cobadal area drawn after Easter 2011 can be found here.

Over three days in July 2011, the supposed upstream course of Fuente Aguanaz (or, at least, part of it) was dowsed. The furthest point reached was a small sink close to the entrance of the Sumidero de Cobadal. A number of inlets and sinks were also highlighted. See the links below.

References: Cawthorne R, 1987; anon., 1988 (logbook); material in file; anon., 1989 (logbook); Davis J and Corrin J, 1989; Corrin J, 1990; Corrin J, 1992b (survey); Corrin J, 1994b (survey); anon., 1995b (Whit logbook); anon., 1995c (logbook); Corrin Juan, 1995a (survey); Corrin Juan, 1996 (survey); García José León, 1997 (survey); Corrin Juan, 1997c; anon., 2001a (Easter logbook); anon., 2001c (Summer logbook); Corrin Juan, 2003a; Corrin Juan, 2003c; anon., 2005c (autumn logbook); Corrin Juan, 2006a; anon., 2006b (Easter logbook); Corrin Juan, 2007; Corrin Juan and Smith Peter, 2007; anon., 2008e (summer logbook); anon., 2008f (autumn logbook); anon., 2009a (Easter logbook); anon., 2009b (Whit logbook); Corrin Juan, 2010; anon., 2010b (Easter logbook); León García José, 2010 (survey); Corrin Juan, 2011; anon., 2011d (summer logbook)
Entrance pictures : middle entrance : top entrance :  bottom entrance
Underground picture(s): yes : optical brighener test 2006 : fossils 2009 : upstream from the middle entrance 2009 : western inlet extensions Easter 2010
Video: Resurgence and information boards   Exchanging cotton wool detectors during an OBA test  
Detailed Survey : 1:1000 (notes from 2009, 2010 to be drawn up)
Line Survey : on whole area survey (very small at northwest corner)
On area survey : Survex 3d file showing Hornedo and San Antonio areas (Easter 2010)
Dowsing reactions close to this cave : All dowsing reactions in the supposed Fuente Aguanaz catchment. (Article about the dowsing carried out in July 2011 can be found here.)
Survex file : yes (Easter 2010)
Passage direction rose diagram (Patrick Warren): yes