Measuring Rainfall On Roof

The catchment areais multiplied by the depth of rain that falls on it to give the total volumeof waterproduced.

Measuring rainfall on roof.

Estimate the rainfall per event in your area r by dividing the annual precipitation rate by the number of rain days per year. Roughly speaking 1 millimetre of rain over 1 square metre of roof equals 1 litre of water. In the united states a run of 12 inches 1 foot is used and pitch is measured as the rise of the roof over 12 inches. Although this calculation is simple in principle the units can make it a headache.

Find the average volume of rain depth x radius x radius x 3 14. Actually although we usually just say inches we really mean inches in the storm or inches in the last 24 hours or inches in some time period why does that matter. Multiply this by the rainfall to get the volume of rain. For example if it rained 35 4 inches in 2010 with 129 calculated days of rainfall you would divide 35 4 by 129 to get the average of 274 inches per event.

For instance a 7 12 roof pitch means that the roof rises 7 inches for every 12 horizontal inches. Xthen add up all of your measurements for example. Well obviously 1 inch of rain in a 15 minute period is a lot more water than 1 inch of rain in the last month. Calculate the average of the two diameters.

Factors such as evaporation wetting and soaking into the ground are not considered here. Find the area at the top of the bucket this is the area over which the rain is collected. This capacity can be calculated using the following formula. For example if you have a roof that measures 50 square metres that equals 500 000 square cm 1 square metre 10 000 square cm.

If your average rainfall was 25 inches year your annual collection potential is 1 120 x 25 28 000 gallons year. Measured amounts from the inner tube will be between a few hundredths up to one inch. For example on a 2 000 square foot roof you can collect 2 000 x 0 56 1 120 gallons inch of rain. If you re looking for average weekly rainfall over 4 weeks with recorded weekly rainfall totals of 20 inches 12 inches 6 inches and 25 inches we would say 20 12 6 25 63 the sum of the items by 4 the number of weeks 15 75 inches average weekly rainfall.

Annual rainfall in millimetres x roof surface area in square metres roof catchment capacity. Outside of the u s a degree angle is typically used. 1 00 inch 0 97 inches 0 88 inches 0 92 inches 3 77 inches xreport the total 3 77 measure rainfall of less than an inch from the inner tube. Assuming 5 cm of rain per hour.

Measure the diameter of the bucket at the bottom in the same way. Divide by two to find the average radius.