Watershed

• A watershed is an area of land that drains or “sheds” water into a specific waterbody.
• Watersheds drain rainfall and snowmelt into streams and rivers.
• These smaller bodies of water flow into larger ones, including lakes, bays, and oceans.
• The speed the water drains to the central point depends on various factors such as type of soil, amount of plant life, and the steepness of the terrain.
• The boundary of a watershed is drawn by the natural landscape, such as hills or mountain ridges.
• Gravity pushes water from the higher mountains toward the lower river.

Sub-watershed

• Watersheds are broken down into smaller geographic units called sub-watershed.
• Large watershed may contain hundreds or thousands of smaller sub-watersheds that drain into the river or other water body.
• Therefore, watersheds of small streams are the sub watersheds of the larger streams.
• Simply, number of sub-watersheds form the watershed.