Any type of simple, plastic rain gauge will do for this project. The rain gauge should be able to hold at least 6 inches of rainfall. Below are illustrations of several common types of home/garden rain gauges.
These type of rain gauges are relatively inexpensive ($10-$30) and can be found at most hardware/garden centers or online.
Tipping bucket gauges ($40-$60) are also perfectly appropriate for Rainlog.org. A review of three inexpensive digital rain gauges taken from the Nov/Dec 2005 issue of Southwest Hydrology can be found here.
Contact us at help@rainlog.org if you have questions on buying a rain gauge or have trouble finding one.
Read the water level at the vertical line down the center of the gauge, to the nearest two decimal places (i.e. 0.35 inch). The smallest line divisions are hundredths of an inch for precipitation measuring 0.00″ to 0.20″, then two hundredths of an inch from 0.20″ to 1.00″, and finally five hundredths of an inch from 1.00″ to 6.00″. Within the 0.20″ to 1.00″ range, read to the nearest 0.01″ by counting measurements that are halfway between the lines.
The most critical issue in collecting good rainfall data is the location of your gauge. Site your gauge in an open area away from obstructions such as trees or overhangs, and in an area protected from high winds. Mount your gauge on a post at a height of 3 to 5 feet with the gauge extending several inches beyond the post. Make sure that the top of the gauge is level. Make sure the post is not in an area where rainwater can indirectly splash from sheds, equipment, carports, etc. If you have a large area, consider installing several rain gauges.
![[A rain gauge on a post]](/assets/images/setup.gif)
Ideal rain gauge installation
Keeping a small amount of mineral oil in the gauge will retard evaporation over the day. The mineral oil will float on top of the rainfall as it accumulates in the gauge and form a barrier to evaporation.
Note: The volume of mineral oil you add will depend on the type of gauge you are using. The surface area of the gauge opening is different depending on the size and shape of the gauge. A wedge-type gauge has increasing surface area with increased depth of rainfall , so be sure to add a volume of oil that will be sufficient to form a layer when the gauge is almost full. Filling an empty wedge-type gauge to 0.05″ appears to be enough oil to slow evaporation. Other cylinder/rectangular gauges should have a layer of oil that is 0.01″ thick. Experiment with what works best for your gauge.
We suggest using mineral oil because it is non-toxic and relatively stable. It can be safely emptied with accumulated precipitation in your yard. Other oils may be toxic and not recommended. Mineral oil will break down in direct sunlight and at high temperatures. Keep an eye on the mineral oil amount and wash out your gauge each month to remove residues.