For example, sandy soils allow the ground to soak up water faster. This reduces surface runoff, but can affect ground water. Clay soils, on the other hand, are tighter and do not allow as much water infiltration. This can lead to more runoff and soil erosion. Whether your watershed drains into a stream or lake, the area nearest the water greatly affects water quality.
Wetlands also act as natural sponges to absorb peak flows of water and reduce flooding.
Many fish and wildlife species rely on wetlands for rearing their young, and for food and shelter. To fully understand your watershed, you'll also need to consider how it is used. Land uses and trends. All activities within the watershed have an impact on its natural resources. Cities, homes, roads and factories modify the watershed and affect its natural resources.