The source of every river is its watershed. The origin of a river is the perimeter of its watershed. Rivers begin at the tips of tree leaves, at the eave of the house, at the crack in the sidewalk, at the crown of the road. Rivers begin where any dog stops at a stump, any cow pauses in a pasture. Rivers begin where we water the lawn and wash the car and pour out our stale cola in the parking lot.
Rivers begin wherever water touches the earth.
Because rivers do not have a point source, they may become polluted anywhere throughout the hydrologic cycle from ocean to air to soil. The integrity of rivers begins with the integrity of the earth itself. Air and ocean and land pollution are not separate ecologic problems. They are but the parts of the same problem and the seam that joins them is rising, falling, moving water. Rivers spring up from the oceans, fall from the sky, and seep through the earth.