I was at the Grand Falls of the Little Colorado in 1984 at a time of heavy water flow. We parked at a small picnic area just down from the Falls and walked up to admire the huge chocolate-like flow over the cliffs. When we got back to the car later we found that the extremely low humidity had worked to evaporate much of the water spray, which carried an abundance of plain old dirt...That "released" brown dirt coated everything down stream with layers of brown dirt. We had to use a fair bit of our water with paper towels to clear the windows! Great fun, but it's the very dry West, so take extra water.