5.b Water Balance on the Earth
The hydrological cycle shows that the input of water in any component of the biosphere should be equal to output.
r = E
where,
r = rainfall (precipitation)
E = evaporation
The total evaporation from the land (80 Tm/year) and oceans (420 Tm/year) is about 500 Tm/year. The total precipitation on the earth is also 500 Tm/year out of which 120 Tm/Yr falls over landforms and 380 Tm/Yr falls over oceans.
That means there is gain of 40 Tm/yr of water on land every year.
We need to manage our precious resource carefully