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How do I find the line of highest elevation on a topographic map that separates one watershed from another?

1. How would you use a topographic map to calculate the amount of water a certain watershed could collect and contribute to its river? 2. How is it possible for water to get in the gravel and below the clay, even though clay is watertight? 4. If water is drawn out faster than the aquifer can recharge, what happens to the well?

Public Comments

1. Q: How do I find the line of highest elevation on a topographic map that separates one watershed from another? A: You follow the elevation contours up the hills until they stop. Where they stop (& would decrease down the other side), then you will find a boundary of watersheds of one stream from another. Q: How would you use a topographic map to calculate the amount of water a certain watershed could collect and contribute to its river? A: You can work out the area of the watershed by means of elevation contours & then you multiply that area by the average known rainfall of the area. This will give a volume which will equal the total of the watershed's discharge over a specific period of time. Q: How is it possible for water to get in the gravel and below the clay, even though clay is watertight? A: With difficulty!! This is an unusual situation as generally impervious clays lie beneath the gravels. It could be very possible that water may be derived directly from a spring which flows through pervious gravels that lie beneath clay. Q: If water is drawn out faster than the aquifer can recharge, what happens to the well? The level in the well goes down meaning that anyone drawing water will need to drop their bucket deeper in order to recover water.