Climate change is bringing us periods of drought and periods of more excessive rainfalls as well as higher temperatures. Heat stress causes greater water demands in your garden, but you should irrigate only when rainfall is inadequate. How do you know when your new or established trees and shrubs need water? By installing a rain gauge.
Rainfalls can be highly variable from place to place in our area. How many times have you had a downpour and your neighbor less than a mile away has gotten only sprinkles? The official weather service’s instruments may be miles from your home and not all that helpful in knowing whether you need to water or not. A rain gauge can be a simple, inexpensive tool for determining if your specific property has received too little or too much water. Both can be problematic.
To choose the best instrument for accurately meeting your rainfall measurement needs, consider both the types of rain gauges available and where the gauge will be placed in the landscape.
Basic Collection Types of Rain Gauges
The many types of rain gauges fall into two basic categories: manual gauges that are read and emptied outdoors, and automated gauges that self-empty, record their readings, and send them to a digital display indoors.
Manual Rain Gauges
Standard manual rain gauges are typically clear acrylic or glass cylinders, usually marked in inches, centimeters, or millimeters, and are the cheapest and most straightforward option.
Some designs are less accurate than others. Plastic rain gauges that have a 4-inch diameter opening at the top are fairly accurate and are considered adequate for home use. Those who prefer more precision can follow the lead of The National Oceanic and Atmospheric Association (NOAA) weather observer network and use manual gauges with an 8-inch opening, which are considered the most accurate. Many of the plastic gauges that are “give aways” to the public are not 4-inch-diameter gauges. Gauges with smaller openings (some are as small as a test tube) give only a general, less accurate estimate of rainfall amounts.
Funnel-bucket gauges. These manual gauges have a more
sophisticated design. The funnel is typically a tapered shape, connected to a graduated cylinder that allows for the gradual expansion as the funnel fills with more rain. This cylinder sits in a bucket to catch the overflow. This type of rain gauge is recommended for amateur home weather observers by the National Weather Service. (https://weather.gov) Although considered more accurate than standard gauges, this type requires removal of the top funnel and self-emptying of the inner tube after each rainfall to take measurements.
Automated Rain Gauges
Tipping bucket gauges have a funnel that collects and channels the rainfall into a small teeter-totter-like container balanced on a seesaw lever. After a pre-set amount of precipitation falls, the lever tips, dumping the collected water and transmitting the data electronically to a digital readout somewhere in your home. Although the self-empty feature is helpful, these gauges may not be as accurate during heavy downpours or when power outages cause loss of data. The tipping bucket has a small drain that needs regular cleaning to remove leaves, algae or debris.
Weighing precipitation gauges consist of a storage bin, which measures precipitation mass via a sensor, measuring the weight of the rainfall. It can more accurately record during intense rainfall and can record snow or hail. Because they are more expensive and require more maintenance, they are not recommended for home use.
Wireless digital and home weather station rain gauges typically.
collect rain in a self-emptying bucket and transmit data collected to a unit inside the home. The weather stations have sensors that provide additional information such as wind speed, wind direction, temperature, and humidity. They are easy to use and handy for keeping historical records
Siting and Placement of Rain Gauges
Where you place a rain gauge can affect its accuracy. Proper siting often depends upon connectivity to wireless networks (if needed), maintenance accessibility, consideration of local wind patterns, and avoidance of physical obstructions. Here are some considerations:
- Place the gauge at least 2-5 feet off the ground on the side of a pole, a fence, or deck post in an open space. The top of the cylinder should be several inches above the top of the pole or post to avoid splash-back.
- The top of the rain gauge should be level.
- Keep your rain gauge away from obstructions that can keep water from entering, such as a tree branch. Mounting too close to your roof, trees, or buildings can cause inaccurate readings during heavy rain events. A general rule of thumb is to place the rain gauge twice the distance away from the height of the nearest obstruction (e.g., placing a gauge 20 feet away from 10-foot-tall trees).
- Don’t locate gauges on elevated sites, such as tops of knolls, to avoid wind turbulence problems that can cause the gauge to underreport actual rainfall. The windier the location, the greater the precipitation measurement error will be.
- Keep the gauge away from sources of artificial precipitation such as sprinklers.
In summary, the ideal location would be at a corner of your garden, deck or yard, free from excessive wind and any obstacles that might interfere with the collection of rain. An area that you walk past daily will help you remember to read and empty the gauge.
Tips on Using a Rain Gauge
Read the manual rain gauge at eye level, looking at the lowest point at the base of the curved rainwater surface (called the meniscus) and take the measurement at that point.
Whichever rain gauge you choose, develop a routine and record your rainfall measurement at the same time each day—just like brushing your teeth in the morning. Or keep it simple by recording and emptying a manual rain gauge on a weekly basis. Pick your day of the week to do this. Comparing the readings of your manual rain gauge with a weather station rain gauge can be useful.
After researching and reviewing the different models and what they offer, make it easy on yourself and pick one that will work for your lifestyle. The point is to collect reasonably accurate data specifically for your property. Regardless of which rain gauge you choose, it will help you avoid over- or underwatering your plants and conserve our precious water resources.
No matter where you landscape or garden, water is a resource that should never be taken for granted. Increasing the soil’s water-holding capacity by adding organic matter is another good way to make sure plants have water when they need it. Work on building your soil, set up a rain gauge, and start monitoring!
References
Accuracy of rain gauge measurements – NEWA, Cornell University, https://newa.cornell.edu/blog/accuracy-of-rain-guage-measurements/
Rain Gauges: What They Are, How They Work, And the Different Types of Rain Gauges, https://ownyourweather.com/what-is-a-rain-gauge/#google_vignette
Why Use a Rain Gauge? https://pikeconservation.org/rain-gauge
