As rainfall and irrigation water use is measured in mm, what is the vol of say 10 mm of rain?

Question

Also, when providing water for irrigation (domestic or commercial), the quantity of water to be used is shown in mm. None of the "great scientific minds of our time", however, show what this quantity of water is in terms of volume (gallons or litres). Why is that?

Farmers can't easily tell how much water is in 900 mm or 12 inches, but thats what all the literature shows! And, last time I looked, no conversaion table could convert mm (length) into litres (volume), so whay do they keep persisting in misleading info?

Answer 1

The volume of rainfall can be calculated as hectare-mm or acre-inches in an area or watershed.

The equation is:
rainfall volume = hectares in watershed x mm of rain
rainfall volume = acres in watershed x inches of rain

Answer 2

The reason that it doesnt convert is because a rain gauge shows only the amount of rain in a specific area, in order to calculate the volume you would have to know the entire area that the rain has covered which is impossible to get a precise answer because rain doesn't fall consistantly over entire areas. The gauge is just a simple way of showing farmers an estimate as the the amount of rain that has covered their fields for that specific rain storm. The length in a rain gauge is only one dimension, there is also either the diameter if it is round or length by width by height if square. So it can be figured out.

Volume is the entire area plus depth so say it is a small field and that it is 1200 inches (100 ft) by 2400 inches (200 ft) and the rain gauge shows that it rained 3 inches (as an average over the entire field) then the volume of water would 1200X2400X3=or 8,640,000 inches cubed or 5,000 ft cubed.

There are 231 cubic inches in one US gallon. Since a cubic foot is 12 by 12 by 12 inches, a cubic foot has 1728 cubic inches. Thus one cubic foot = 1728 cubic inches = (1728/231) gallons = 7.48 gallons.

So the volume in gallons would be 7.48X5000=37,400 gallons was rained on that particular field during that rain storm assuming that it did rain 3 inches over the entire field.

Answer 3

Volume is rainfall in mm times the area that you are irrigating. For example, 10 mm (0.01 m) of rain over 1000 square metres would be 0.01 m x 1000 m^2 = 10 m^3 of water = 10000 litres.

Answer 4

its a 2 cm graduated cylinder...each mm is 314.15 mm cubed if I did my math good. through fact all and sundry makes use of a 2cm diameter graduated cylinder then all and sundry's length in mm is an identical.