Rainfall impacts all of us, from the lack of rain during times of drought to the dangers of flash floods when we receive too much rain too fast. For some interests - such as gardeners, farmers, and meteorologists - rain gauge data is critical information. For the rest of us, obtaining rain measurement information with a rain gauge is interesting and fun! Manual rain gauges are a simple tube, closed on one end and calibrated in inches to indicate the amount of liquid. A manual rain gauge must be hand-emptied after each precipitation event in order to ensure correct measurements. Rainfall amount is described as the depth of water reaching the ground, typically in inches or millimeters (25 mm equals one inch). An inch of rain is exactly that, water that is one inch deep. One inch of rainfall equals 4.7 gallons of water per square yard or 22,650 gallons of water per acre!