A rain gauge is a device that accurately measures precipitation. Your children can use common household objects to create a rain gauge. They can regularly measure the amount of rain and then record their findings in a journal. A rain gauge can be a do-it-yourself science project, a component of a weather station for kids or a device to help them estimate the water requirements of a garden.
The Gauge's Function
When your child gauges rainfall, she’s recording the depth of precipitation accumulating over a set time period. Because you can’t accurately measure rainfall in natural places for various reasons -- ground absorption of rain, evaporation or the run-off of precipitation into streams or lower ground -- a rain gauge is required. The gauge typically consists of a cylinder with a scale -- millimeters or inches -- running vertically along its side. Your child can place the rain gauge in a secure outside location that is unobstructed by tree branches, building eaves or electrical cables.
Two Types of Gauges
The two main types of rain gauges have different shapes. The first type is cylindrical with straight sides. When using this type of gauge, the height of captured precipitation equals the actual amount of rainfall. If your child collects an inch of rain, she records a rainfall measurement of 1 inch. The second type of rain gauge has a funnel top and is best suited for capturing small amounts of precipitation. To measure rainfall, you have to use a ratio of the cylinder’s diameter to the funnel’s diameter. For example, if the ratio is 1:5, then 10 inches of water captured in the cylinder equals 2 inches of actual rainfall.
Building a DIY Gauge
Have your kids gather a 2-liter soda bottle, scissors, tape and pebbles. Begin by cutting off the top half of the bottle just below the point where the bottle’s shape starts to narrow. Place pebbles in the bottle’s bottom to weight it down. Invert the bottle's top half and insert it into the bottom half. Match the rims of the top and bottom halves and then tape them together. Attach a piece of tape that runs from the top of the bottle to the point just above the stones, or the base of the gauge. Position a 12-inch ruler to the side of the bottle so its zero-line matches up to the gauge’s base. Use a marker to draw every 1/8-inch or 1/4-inch mark, and then number each inch. Add water to the gauge until the water reaches its baseline or zero point. By doing so, your child can measure additional water -- captured rainfall -- from the zero line.
Have your child monitor the rain gauge on a daily basis. She should measure rainfall at the same time everyday. For an accurate measurement, your child needs to be at eye level with the gauge. After recording the rainfall on a chart, she should empty the gauge, according to “ScienceWorks for Kids: Weather, Grades 4-6+,” by Mike Graf and Michelle Rose. Alternatively, she can subtract the current reading from the previous day’s reading to arrive at accumulated rainfall. She can also describe rainfall as heavy, moderate or light. While heavy rainfall is more than 0.3 inch of rain per hour, moderate rainfall ranges between 0.1 and 0.3 inch of rain per hour. Light rainfall is lower than 0.1 inch of rain per hour.