gen-define-watershed-boundaries-and-give-one-short-worked-exampl-641a

Define watershed boundaries and give one short worked example.

# Watershed Boundaries ## Definition **Watershed boundaries** (also called drainage divides or ridgelines) are the topographic lines that separate adjacent drainage basins. They define the perimeter of an area where all precipitation flows to a common outlet point. Water falling on one side of the boundary flows into one watershed, while water on the other side flows into a different watershed. **Key characteristics:** - Follow the highest elevation contours between drainage basins - Run along ridges, hilltops, and mountain crests - Water cannot cross these boundaries (flows away from them) - Can be determined from topographic maps --- ## Worked Example **Problem:** Using the topographic contours below, delineate the watershed boundary for outlet point A. ``` 100m _____ 100m | | 90m ___ | | ___ 90m | | | A | | | 80m | |__|___|__| | 80m | | ----_________---- 70m 70m ``` **Solution:** 1. **Locate outlet A** (given at 85m elevation) 2. **Identify high points** around A (100m contours form ridges) 3. **Draw boundary along ridgelines** connecting the 100m high points 4. **Verify flow direction**: All points inside boundary drain toward A; all outside drain away **Watershed boundary** = the line connecting the 100m elevation points around point A (forms a closed loop at the ridges)