This document records the methods used and results obtained to trace the
water flowing from the end of the cave system Sumidero de Cobadal to possible
springs at Fuente Aguanaz, Los Boyones and a river-side spring at Arronte.
Background information for this project is to be found in Proyecto:
Determinación de la Fuente alimentada por el río de El Sumidero
de Cobadal (Entrambasaguas), previously circulated.
2.1kg of dissolved Tinopal CBS-X optical brightening agent (OBA) was poured
into the underground stream at Cobadal. Cotton wool detectors at Fuente Aguanaz,
Los Boyones and Arronte were used to absorb the agent. Qualitative detection
was by fluorescence under UV light. A positive result was achieved at Fuente
Aguanaz between 5 to 7 days, proving that water from the downstream end of
the Sumidero de Cobadal flows underground to emerge at the rising of Fuente
Aguanaz, a straight line distance to Fuente Aguanaz of approximately 4.9km.
Optical brightening agents are widely used as water tracing chemicals due
to non-toxicity, strong absorption on cotton wool, ease of detection under
UV light where it glows blue, and lack of colouration to water. Tinopal CBS-X
OBA was ideal for use in this project as all three possible resurgences were
public water supplies.
The detectors were left in the resurgence water for up to 7 days where they
absorbed the OBA. Immersion for longer than this may have masked the fluorescence
with other contaminants. A check for background fluorescence involved checking
detectors every couple of days for 4 days before any OBA was added to the
water in Cobadal.
The people who handled the OBA took precautions when handling the detectors,
e.g. wearing gloves. OBA dust was kept to a minimum with thorough washing
and checking of hands and clothes with the UV lamp. It was found that once
the OBA was absorbed onto the skin, it neither washed out, nor was absorbed
onto cotton wool.
The time required for the project was over three weeks from background testing
to final removal of detectors. Moderately low water flow to moderately high
water flow conditions were observed throughout the test. Too little water
may not have carried the OBA quickly enough, and flood conditions would have
put the OBA into high level pools which would then re-contaminate the water
in a future flood.
The following documents can be found as pdf files
The original proposal document -
- Proyecto: Determinación de la Fuente alimentada
por el río de El Sumidero de Cobadal (Entrambasaguas)
- Technical details for Clariant
- Details of Dye Testing in Chapel-le-Dale
Equipment, methods and timings
UV lamp A combined torch and UV lamp for detecting forged banknotes
was obtained from Maplins.
(www.maplins.co.uk Ultraviolet mini
lantern, code ZC10L, price £9.99). This proved ideal throughout all
the tests, producing little visible light to confuse the test.
Detectors Cotton wool BP was cut into rectangles approximately 15
x 10cm and held inside 2 layers of chicken wire. Synthetic string was threaded
through the chicken wire and a "snoopy loop" attached. Twenty six detectors
were required; each was stored in a thin plastic bag. Each detector was tested
under the UV lamp before use. The cotton wool was totally clear of fluorescence
but specks of blue were noticed on some of the twists of the chicken wire.
(The specks were also visible after immersion but appeared to stay the same
size and, more importantly, did not affect the cotton wool).
(Photo showing lamp and
detector - Phil Papard)
Optical Brightening Agent Tinopal CBS-X optical brightening agent
powder was double-bagged in 300g portions and the plastic bags placed for
transport to Spain inside solid plastic boxes with press-fit lids. The lamp
was used to ensure that no OBA contaminated the external surfaces of the
An Internet search revealed some possible difficulties in dissolving the
powder straight into cold stream water. The OBA had to be dispersed into
the stream water as quickly as possible - carrying the OBA into the cave
as a colloid or solution was thought to be the answer.
Six 4 litre paraffin containers (with the original, close fitting lids) were
obtained. Approximately rectangular, each fitted snugly into its own tackle
sack for underground transport.
Method for dissolving the OBA powder: 3 litres of water in a large
pan was kept at approximately 70C over a gas stove. Cold water was dribbled
over 30g of the powder in a measuring jug and stirred with a spoon to create
a lump-free slurry. Some of the hot water was slowly added from the pan to
create a thinner slurry. This was then slowly poured into the pan, stirring
as it was added. Further portions were added using the same method until
it appeared that little more of the slurry would dissolve or disperse.
Approximately 350g dissolved in a total of about 3.5 litres of the hot water.
The concentrated solution was poured into the paraffin containers and allowed
to cool. The dissolving method was repeated for the other 5 containers ending
up with a total of 2.1kg of OBA dissolved in 21 litres of water.
Detection methods At each of the three resurgence sites, two detectors
(left and right) were used. Each was placed in a strong flow, possibly with
the flat face towards the current. At
Fuente Aguanaz the detectors
were attached to the iron grid covering the water collection pipe in the
cave upstream of the resurgence. At
Los Boyones in Secadura,
the detectors were placed close to the vertical abstraction pipe. At
Phil Papard), the detectors were placed over water welling up
from the stream bed within a metre of a grid over a stream bank opening.
Visits were generally made every two or three days to remove one detector
alternately, so that each overlapped the other, usually up to five days.
During the three weeks, one flood
episode (photo: Phil Papard) required almost complete
immersion at Los Boyones in order to recover a detector about 1.5m under
water. After that, the detectors at this resurgence were tied back to a much
The first 4 days were taken up with background testing to eliminate any OBA
in the water from, e.g. clothes washing. All detectors remained negative.
On "Day Zero", a team of eight cavers carried the 6 containers of OBA solution
into the Sumidero de Cobadal. It was
poured into the stream
(photo: Andy Morse) at the boulder chamber below the
5m pitch, more than a kilometre underground on a straight line bearing from
the entrance of 102º (Grid reference of this point is approximately
30T 0449764 4797788 altitude 168m). Although the OBA had started to precipitate
out of solution it quickly re-dissolved as it entered the stream water.
This table summarises the schedule of detector
placement and removal, along with the water levels and the results. The prime
result was the positive detection of the optical brightener at Fuente Aguanaz
after 5 - 7 days. The detectors at Fuente Aguanaz remained positive to the
time when all the detectors were removed from the resurgences on day 14.
All other detectors at the other resurgences remained negative throughout
We can conclude that the water disappearing at the end of the Sumidero de
Cobadal resurges at Fuente Aguanaz.
- It is also likely that any water sinking over the supposed underground
route of the water will also resurge at Fuente Aguanaz.
- Although the main conclusion is clear and unambiguous, it does not mean
that the water may not flow to other places at different water stages.
- The large size of the resurgence (1.5 x the flow from Boyones) suggests
a large catchment - perhaps up to Alisas - and an extensive network of cave
passages. Los Boyones has 43km of known cave passage behind it. At present,
there is only 1.5km behind Fuente Aguanaz.
- This map shows some of the water flows associated
with Fuente Aguanaz and Los Boyones.
The successful test was the result of a team effort from a number of people
who became involved. Thanks are due to all of the following:
Ian Chandler (who completed the detector exchange regime after most people
had returned home), Dave Cooke, Jenny Corrin, Penny Corrin, Harry Long, Lank
Mills, Andy Morse, Phil Papard, Andy Quin, Bill Sherrington, Pete Smith,
An Vanderplank, Dr Terry Whitaker, Jon Whiteley, Les Williams, and not least,
Fernando Fernández Labadie at the Dirección General De Obras
Hidráulicas Y Ciclo Integral Del Agua, Santander.
Juan Corrin, June 2006