I often use temperature as an indicator for different water sources. Surface water, at least in the top meter or so, can vary from frozen to almost air temperature in the summer and cools from the surface down in rivers and lakes. The sea may only reach about 17degrees if your lucky. However groundwater is often much more stable throughout the year, and a good rule of thumb is that groundwater, at least in Wales is about 11°C. Groundwater temperatures can be predicted by using the mean annual air temp (about 10°C) and adding 2-3°C for every 100m depth, so a groundwater from about 50m or so depth is likely to be around the 11-12°C mark. So armed with this – and my new toy – a FLIR C2 hand held thermal camera - I headed out to some cliff sections nearby.
Identifying groundwater seepages using thermal cameras is nothing new (see these slides from the EPA, 2008) however I am not sure it has been used for cliff face seepage mapping to identify bryophyte habitat/water supply –but then I could be wrong!
My aim was to see if the new camera could show temperature differences on a cliff face and perhaps identify groundwater seepages where tufa was forming (and bryophytes are living). Would this be any use for mapping or better understanding these habitats?
Below are my first few attempts, which I thought were worth sharing. The camera does show areas where groundwater seepage is occurring from the cliff, which correlate with the tufa and tufa mosses.
There are a few problems; the camera only records the surface temperature and this will change as soon as the water seeps out of the cliff and starts to equilibrate with the air temperature. In the summer this will have a warming effect and a cooling effect in the winter – thus choosing when to do this needs some thought. Perhaps repeat photography is needed throughout the year. The vegetation itself may alter the temperature as could small areas of shade. It would be useful to measure the water temperature in situ with a good old thermometer however these cliffs are just too dangerous to stand underneath.
Since reading Barrys blog about cow pats I thought that thermal imaging would certainly show up the temperature of the fresh pats quite nicely, I wonder what they look like in the winter and for how long they maintain a temperature different to the ambient air temp– are they acting as microclimates for bryophytes?
Happy for comments or suggestions.
DIGITAL PHOTOGRAPH: Cliff face groundwater seepage (west of Nash Point) with active tufa formation – Eucladium verticillatum and Didymondon tophaceus type habitat with lots of Maidenhair fern.