Kentucky sank 1,700 used Christmas trees in one 92-acre lake to give fish new places to hide
Residents donated about 5,000 trees last winter; the state anchors them underwater in clusters and posts the GPS points so anglers can find them.
Kentucky
Most water feeding Mammoth Cave starts outside the park; 700-plus dye traces put 60% of its catchment there
The Turnhole Spring basin alone covers about 94 square miles, roughly 16% more than the whole national park, so farms, roads and towns upslope drain straight into the cave.