Meaning of mm of Rain

1 mm (millimeter) of rain means that an area of 1 square meter will have a layer of rain 1 mm thick.

In terms of volume:
1 mm rain = 1 liter of rain in an area of 1 square meter

For farmers:
10 mm rain = 10 liters per square metre of the field

Rain in 1 Hectare of Field
A rainfall of 1 mm supplies 1 litre of water to each square metre of the field. Therefore, with a rainfall of 1 mm over 1 hectare of field, the total amount of water is 10, 000 litres or 10 cubic meters.

10 mm of rain over 1 hectare field will have a total of 100, 000 litres or 100 cubic meters, the equivalent of 10 water trucks (assuming a commercial Water Bowser Truck capacity of 10,000 Liters).


CONVERSION:
25 mm = 1 inch

1 hectare = 10,000 square metres (100 m by 100 m)
1 hectare = 0.01 square kilometres (1% of sq km)
1 hectare = 2.47 acres (2.5 approx.)

1 acre = 0.4047 hectare (2/5 of a hectare)



RAIN MEASUREMENT: How is rainfall measured
http://en.wikipedia.org/wiki/Rain_gauge


RAIN IN AGRICULTURE, CROPS
http://www.fao.org/docrep/r4082e/r4082e05.htm