Want an accurate, inexpensive, low tech way of recording rainfall? You can easily make your own with just some PVC pipe and items from your recycling bin.
Rain Gauge Basics
A rainfall gauge needs to collect rainfall in an open cylinder with a sharp edge. The water collected in this cylinder falls into a smaller collection cylinder below. The design should limit evaporation from the collection cylinder. The greater the difference in the cross-sectional area between the top and bottom cylinder, the greater the accuracy in the measurement.
This pop bottle rain gauge provides about a 78.5 to 1 ratio between the top and collection cylinders.
Step 1: Materials
1 liter clear plastic pop bottle
3 inch length of 4 inch PVC sewer pipe
4 inch PVC end cap
flat bottom clear ¾ inch pill bottle
Step 2: Cutting the Pop Bottle
Cut the barrel part of the pop bottle away from the top and bottom.
Keep both the barrel and top.
Step 3: Shaping the Funnel
Bevel an end of the 4” PVC pipe so that there is a sharp edge.
Step 4: Attaching the PVC to the Bottle Parts
Insert and glue with PVC solvent the bottom end of the PVC into the remaining rim on the bottle top. This makes a funnel with a PVC top with a sharp lip.
Glue the end cap onto the pop bottle barrel. This makes the bottom of the collection unit.
Step 5: Calibrate Your Rain Gauge
Calibrate the unit by first measuring and calculating the cross sectional area of the collection cylinder.
In our case the diameter of the PVC collector is 10.0 cm. This gives an area of 78.5 square cm. One mm of rainfall, results in 7.85 ml of water. This is now measured in a graduated cylinder.
The volume is converted into mm of rainfall.