Introduction

In 2022 the expedition obtained several TinyTag™ temperature data loggers[1] that could be left logging for over one year.  The need to log for over a year is important as several caves become inaccessible from September to May due to snow melt and general high water levels.  In addition, the expedition is limited to one or two trip a year for no more than a few weeks at a time.

There are many caves in the Tresviso – Andara area, some are resurgence caves at around 500m altitude and others high in the mountains between 1700m and 2000m in altitude.  The  loggers placed in entrances high up would be measuring the incoming, external, air temperature, whereas at the resurgence it would be water temperature.  Water temperature would be subject to several factors: how long the water was underground equilibrating with cave temperature and the temperature that it was when it entered the cave system.  The time underground will be related to flow (i.e., has it rained recently).

Some of the resurgence caves emit water from an unknown catchment area.  By monitoring the temperature, it may be possible to gain information about where the water came from.

Also considered were any other unique places.  For instance, a rift / trench in Cueva de la Marniosa occasionally forms a lake.  It may be possible to determine when and under what conditions this this lake forms.

Temperature loggers were place in the following locations:

The loggers were placed over a several days period in early September 2022, but were set to start logging on the 25 September 2022.  The loggers were collected over several days during September 2023.  It is assumed that no-one was in any of the caves from 25 September 2022 to 28 May 2023.  Between 28 May 2023 and 2 June 2023 three trips were made into Cueva de la Marniosa, although not in the vicinity of either logger.

Initial Results

Initially, using a day when all the temperatures have been stable (most likely following several weeks of dry weather).  The various cave temperatures can be compared, and trends observed.

The first trend to view is the logger for the Papoose Pitch in Cueva de la Marniosa. The detector is 1.1 km[2] from the known inlets at the head of the Sobra Valley with the bulk of that being open streamway (from Hall of the Mountain King).  The complete route is not known, but there is very little scope for sumps between the surface and the logger. 

Cueva de la Marniosa – Papoose

Graph: The trend of temperature at the streamway at foot of the Papoose pitch in Marniosa

Starting from the left of the graph there is a short spike downwards, this probably matches some rainfall and would indicate extra flow of colder water.  The temperature remains fairly level until a series of spikes downwards over winter.  Again, this would represent colder rain falling and potentially snow falling and melting.  The coldest two points are mid-January and mid-March, when it warms up again.  Further down spikes are then recorded, again representing rain on the surface.  The final reading is an upward spike which is the logger being removed from the cave.

Away from the downward spikes, the ‘summer’ temperature is stable at 7.4 C and the winter temperature drops to approx. 7.1 C away from spikes.  There is a step upwards of about 0.1 C on 15 July 2023 to a new stable of unknown origin.

Cueva de la Marniosa – Trench

Graph: The temperature trend at the bottom of the muddy trench in Marniosa.

The data on the trench in Marniosa is somewhat different.  Early on there is a very small spike upwards that corresponds to the downward spike on the Papoose pitch data.  It may be a small amount of water flow, or a change in air flow.  Of interest are the upward spikes which presumably indicate water ponding at the sensor.

The upward trend indicates the water was warmer than local cave temperature, i.e., the rain was warmer than the cave, suggesting the source is close to the surface (if the water was in a sump for significant time the temperature would be less remarkable and possibly negative).  Also, the width of the spike indicates how long the detector remained submerged.  During the period to the end of January 2023 there are three upward spikes.

During February 2023 and March 2023, the temperature change is more erratic with temperature change in both directions.  This may indicate snow melt as well as rainfall.

Finally, there is another ‘ponding’ event in mid-May with a similar signature to the events at the beginning of the data.  After mid-May the trend is flat indicating a dry summer.  Oddly, the nominal temperature at the end of 2022 (16/10/2022) was 7.07 C, whereas the nominal temperature in 2023 (23/6/2023) was 7.06 C, very slightly lower.

There are three isolated ponding events.  Once a pond is formed, it takes approx. one week (7, 5, 8 days) to clear.

Cueva de la Rio Chico

Graph: The Rio Chico temperature profile, next to the Papoose profile.

The water emitted by Cueva de la Rio Chico is warmer than the water at Papoose Pitch in Cueva de la Marniosa.  It is currently assumed that the sole source of water in Rio Chico is from the main sump 1.

On the first few days there is the same spike downwards indicating the same rain picked up at the Papoose sensor.

Graph: The relative drop of the first spike 29/9/2022

The onset of the temperature drop at Papoose is about 30 minutes before Chico.  Also, the drop at Chico is slower.  The difference in absolute time may simply be the difference in the time it rained over the catchment, more measurements would need to be made before distance of travel can be inferred (if at all possible).  However, the slowness of response of the Chico detector indicates a larger volume to fill before the full temperature effect is visible.

Note also, the rise and second drop eight hours later that lasts some hours, may represent a second route from the surface to the resurgence.

In November there are upward spikes with no matching spike at Papoose.  Although there are other occurrences of these spikes they are not isolated from other events.

Graph: The temperature spikes in Rio Chico

The spikes could represent localised rain (note the temperature change is the reverse), and it is possible for rain to fall on the Chico catchment, but not the Sobra valley, however, the reverse would be expected also.  The cave could be drafting in (against the flow of water) bringing warm exterior air to the detector.  More investigation is required here.

From April 2023 to August 2023, we see a general increase in temperature from 8.0 to 8.6 C unlike the Papoose trend.

In general, Chico has more oscillation in temperature than Papoose and the initial analysis is not as clear.

Cueva de la Cabeza de Vaca

Cueva de la Cabeza de Vaca (Cowshead Cavern) is a resurgence cave with a similar stream to Cueva de la Rio Chico.  It is 2.5 km up and the other side of the valley.

Graph: Cueva de la Cabeza de Vaca and Cueva de la Rio Chio comparison

Similar to the Chico result, there are spikes (downward) that don’t match the flow at Papoose.  There are spikes that match the same at Rio Chico, but there are other spikes that don’t correspond to anything in Chico or Papoose. 

There are also oscillations early in the period that have an approximately daily frequency.  They are also present later in the year.  This may be caused by proximity to the entrance, in future the logger should be placed further in to the cave.

Graph: Cueva de la Cabeza de Vaca

The data over the year is less clear than the Papoose logger.  There are rain events on Papoose that don’t show on Cueva de la Cabeza de Vaca (early June 2023).  This could be localised rain, suggesting the catchment is away from the Sobra valley.

There is also a lot of external temperature logged, again moving the detector further into the cave is suggested.

Cueva del Nacimiento

Nacimiento is known to take water from the high Andara caves.  It is also fed by the Marniosa – Papoose stream, although the Papoose stream is only a small fraction (2%?) component of the Nacimiento stream.

Graph: Cueva del Nacimiento data

The most visible difference with the Nacimiento data is the range between summer and winter conditions.  The water temperature spikes down to 4 C several times during winter. It is likely that the low temperature is related to water coming from the high peaks and being a significant amount of snow melt.  Note that neither Cueva de la Rio Chico nor Cueva de la Cabeza de Vaca show such low spikes in temperature, indicating their catchment (which is unknown) is much lower in altitude.

The first spike, as seen at Papoose, may show a minute early drop, but it is over 10 hours later before the drop is seen in Nacimiento.

Graph: The first spike in Nacimiento compared to Marniosa – Papoose

The very small drop would be from local rain, a small component of the flow from Nacimiento.  The later drop is possibly the rain arriving later in the high peaks, but also the time for the flow from the high peak to reach the resurgence.  More spike events would need to be investigated to get an average flow time (hoping the prevailing direction the rain spreads is either known or random).

During the spring and summer, the temperature increases.  At Papoose there is very little change, perhaps the low flow and the source equalise quickly.  In comparison Nacimiento is warming quite rapidly.

Graph: Comparing the warming trend across the three caves

Conclusions

There is still much information to be extracted from the data.  The Cueva de la Cabeza de Vaca sensor needs to be moved further into the cave to avoid external temperature fluctuations.  The only catchment that originates in the high peaks is Cueva del Nacimiento.

[1] Tinytag Plus 2 – TGP-4017 https://www.geminidataloggers.com/data-loggers/tinytag-plus-2/tgp-4017

[2] Straight line distance between the Silvestre Pot entrance and the bottom of Papoose Pitch