August 2012

How to Read your Rain Gauge Introduction A rain gauge is an instrument that is used to measure the amount of rainfall in a given area over a specific amount of time. It helps you to know exactly how much it is raining. Data from rain gauges can be collected for a gardener's personal use, or for use by scientists or weather professionals. Regardless of why rainfall data is being collected, it is important to be able to read a rain gauge correctly. Instructions 1. Make sure the rain gauge is empty before the rainfall event you want to measure occurs. It is good practice to empty the rain gauge after each time it is read. 2. Lift the rain gauge to eye level. Whether you stoop to examine the gauge or you lift it up, the top of the water line must be at your eye level to ensure you are reading it accurately. 3. Record the height of the water. The surface of the water will be slightly curved because its surface tension tends to make it stick to the sides of the container. This is known as a meniscus. Read the height of the water at the base of the meniscus. Most rain gauges will have numbers that are divided into tenths of inches. For example, if your rain gauge is filled to the .50 line that means that .5 of one inch or one-half inch of rain has fallen. 4. If rain has fallen, but there is little to no water in it, then record that a "trace" of precipitation fell. 5. Empty the rain gauge for the next measurement.

Placement of your Rain Gauge Rain gauges must be placed within a clear, open area. Do not place rain gauges in spaces where there are trees or buildings that can block rainfall because this may result in incorrect readings. Ideal placement of your Gauge ♦ In open areas, place rain gauge twice as far from obstacles as they are high. ♦ In developed areas, place far from obstacles as they are high. ♦ In open areas place the gauge top about two feet off the ground. ♦ In developed areas place the gauge top about five feet off the ground. Points to Remember when Reading your Rain Gauge

Be Accurate

♦ The most important thing is to make sure the rain gauge is empty before you start recording the rainfall. ♦ If it already has some water inside then this will alter the readings. Empty the rain gauge every time you read it. Reading it every day will help you to get into a routine.