Background A watershed is any area of land that drains into a particular body of water.
All watersheds run into drainage basins, which, in turn, flow into the ocean.
All the world's inhabitants live in watersheds. Left alone, watersheds exist in natural balance with their environment. Rivers erode the highlands around them in a gradual process that helps maintain a natural dynamic balance. Human settlements, on the other hand, tend to accelerate erosion while further impacting on watersheds through land clearing, dam building, farming, and industry. An important thing to remember about watersheds is that they're single units, which are connected to other watersheds as they flow downstream.