Airthrey Loch EarthCache
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This Earthcache involves a walk around the loch, some observations and visual calculations.
In 1759, the Airthrey Estate was sold to Captain Robert Haldane of Plean. The 363-acre (1.47 km2) grounds and man-made loch were designed by Thomas White for the Haldane family in the late 18th century and both the loch and the castle remain today, largely as they were designed.
Artificial bodies of water are commonplace for functional water supply and for decorative purposes. Airthrey Loch may have been created for decorative reasons, although it is nowadays used for a variety of sporting pursuits at the university. An artificial body of water can be created when a valley is blocked with a dam or a low area is flooded.
This EarthCache examines the flow of water into and out of the loch. Water flows downhill, we all know that! The water here comes largely from the hills above the university and to the north of Bridge of Allan. But where does it go? Sometimes we don't always see with the naked eye where the water goes, but it must go somewhere.
The most common place to find fresh liquid water is under the Earth's surface, in a form called groundwater. Water from the surface seeps downward into the ground through tiny spaces or pores in the rock. At some point, though, it hits a layer of rock that no longer has pores, which stops the water from traveling downward. This rock is called impermeable because the water can no longer pass through it. The upper surface of the groundwater is called the water table. The water table will fall when there has been little rain in an area for a long time. The water table will also rise when it rains steadily for a long time. It is important to know how deep beneath the surface the water table is for anyone who intends to dig into the surface.
Airthrey Loch was not dug out of level ground in order to find the water table. Unless lined with an waterproof layer, the water will naturally seep down through any porous rock as far as the water table, therefore some water will disappear into the ground. If, however, the rock below the loch is impermeable without any pores, then the water in the loch will overflow at its lowest points of its banks.
To complete this EarthCache, you must answer the following:
1 - Walk the perimeter path around the loch and look out for water that is visibly entering or exiting the loch. Describe where these points are situated.
2 - Does there appears to be more water entering than exiting the loch on the day you make your visit?
3 - Using your answer to Q2, do you think this should have any effect on the water level? If so, should it be rising, and if not, why not?
4 - Looking at the contours of land around the loch, imagine how the land would have looked prior to the creation of the loch. Would the entry and exit points you see today have been different in the past? Where do you suppose the natural flow of water would have passed before the loch was created?
5 - Again, using the contours you see, what do you think might be the maximum depth of the loch, assuming no digging took place to deepen it, and where might this lowest point be located? A rough estimate will suffice.
6 - (optional) take a photo of yourself with your favourite view of the loch in the background.
Feel free to send the answers and log your visit at the same time. Any problems will be raised, but if you don't hear anything then please assume that your answers are good ones!
Additional Hints
(Decrypt)
Oevat nccebcevngr sbbgjrne! Gur cngu pna trg zhqql ng gvzrf.
Treasures
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