A friend of mine who farms in England recently took this photo of an ancient dewpond on his land and commented that,
"It's not so very long ago that this pond would have been a vital water supply for animals wintered in an outlying building at the top of the hill. These days this is about as much water as we ever see in it."
Being an interfering busybody, I immediately suggested that he figure out why it was drying up and attempt to restore it, and posted a couple of links that might or might not help.
http://www.rexresearch.com/dewpond/dewpond.htm http://www.scribd.com/doc/12799817/Permaculture-in-Humid-Landscapes http://www.youtube.com/watch?v=lsWKyv9Hbak http://www.small-farm-permaculture-and-sustainable-living.com/permaculture_slope_and_aspect.html He replied that,
"In geography at school I was taught that local lore suggested that the dewpond name was misleading and they were carefully sited on the top of the water table just back from the edge of escarpments. This would stack up quite well with the siting of this example. Due to this I'd always assumed that drier winters and water abstraction had lowered the water table which along with silting had stopped this one filling. Your link along with some that I found last night suggests that it may be more complicated. I think that some careful spadework may be in order" Then true to his word, he promptly set out with a spade and dug a hole, reporting back that,
"I dug a 3 foot deep hole without finding anything. 24 hours later this is what it looked like. I suspect that the "magic" is down to the water table in this particular case."
This is a contour map of the area for anyone who might be interested.
"Most of the contour to the north and west is manmade. I think that the natural contour line would sit between the pond and the hedge to it's south-east side.
We're unlikely to recreate an open pond here as any poaching around it could encourage liver fluke in the livestock. However if I could drop in a cistern and pipe the water it should raise the level at which our free farm water supply can operate by just over 25 metres. That's a pretty enticing prospect!
At present I'm considering digging deeper and putting in a vertical 6 inch pipe to monitor water levels throughout the year. The major obstacle could be the fact that I'm fairly certain that the water table has risen over the last decade and it could easily fall again over the coming years." Does anyone have any experience or relevant information that might be of use in the restoration project? Is the water table likely to be the only factor involved in this dew pond or does it rely on a combination of factors? Is digging out the silt all that is going to be necessary to restore it or will it need lining with layers of clay and straw as suggested by some of the links?
I'd love to hear other people's thoughts on this!