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. Anything that affects an upstream watershed eventually affects other sites downstream. A town that gets its drinking water directly from a river, for example, is acutely aware of upstream activities affecting its water quality, such as another town that's discharging effluents.
Watershed contamination is a serious problem for humans and wildlife.
Aquatic species are often the first to suffer from contaminated water. Slight increases in acidity can destroy the natural balance of water. A single instance of contamination, such as the spillage of industrial waste, can damage an aquatic food web for decades. In this simulation, students view an imperilled watershed and coastal area as a microcosm for environmental concerns involved in management decisions. They struggle with overlapping and conflicting uses of land and water.