Plants can apparently stop water changes... it's been done. Albeit, this is on a large scale... Make sure you read the whole thread (tons of pages), but you'll get the point.
http://www.monsterfishkeepers.com/forums/showthread.php?t=95787&highlight=ponds+concrete
http://www.monsterfishkeepers.com/forums/showthread.php?t=95787&highlight=ponds+concrete