For some reason, watersheds seem to be popular places to put down pavement. Housing developments, grocery stores, and shopping malls require places to drive and places to park, which means those places end up getting paved. Where water used to infiltrate into the soil, trickle down through natural water-filtering aquifers and rejoin the reservoirs that serve our thirsty civilization, now rain falls on oily pavement. Paved areas prevent water from sinking into the soil beneath them and create deluges of polluted runoff that strip away topsoil, contaminate waterways, and eventually disrupt ecosystems for miles around all paved human developments.