A "key" is a trench dug through porous soils, "keyed" into clay or bedrock, then backfilled with mixed, processed, nonporous soils, compacted to the top of the trench, essentially building an underground "wall", impervious to escaping water. Also called a "core trench", a "key'" or "keyway", this trench is placed strategically, where water tries to make its escape. Remember, we only borrow water for a time. Water always wants to leave, by seeking its path of least resistance, whether seeping through leaky dirt, or making its way to clouds via evaporation or sublimation, or through the digestive system of a creature. So, if you want to build a key, talk to local earthmovers, people who know your soils. Talk to the NRCS...they seem to know all the best earthmoving contractors. Here's the answer to your question...find an earthmover who knows your soils, how to build a keyway, and how to decide whether or not that's the answer to your problem. If your lake leaks to a certain level, then stops, a keyway certainly could be the answer. Find a pro you are confident in, and let him help you.
