Watershed Beginnings

What are the mechanisms that actually create creeks and rivers? Generally, whether the initial flow is from a spring or from rainwater pouring down the hill, a creek grows as it moves downhill. As you walk through this park, you'll notice mini watersheds inside this larger watershed that feed additional water into the creek as it moves further and further down the hill, which is why creeks and rivers are much larger at the mouth than at the headwaters, in addition to water spreading out when moving from a steep area to flat land.