To measure this, you will need some form of a level. The Preferred instrument is an optical sight that has a level in it. This device allows one to sight a level line while looking through the optical sight. One such level is made by CST/Berger and is called a "Sight/Surface Level." Home Depot usually carries a fairly inexpensive one (around $20). If an optical level is unavailable, a short carpenter's level may be used. First, measure the height of your eye level (from the ground to your eye). Then start at the bottom end of your water source. Sight a level line and find where that line intersects the ground upstream. Have a second person mark that spot. Then stand at the marked spot and sight another line until it intersects the ground further upstream. Repeat this, counting the number of times you repeat it, until you reach the highest point of your water source. Now multiply the number of times it took to reach the source by the height of your eye-level. The result is your rise or head (Example: eye-level is 5 feet 6 inches. It takes 6 sightings to reach the source. 5 feet 6 inches times 6 equals 33 feet of rise or head.)