THE BASICS
Let’s start with the precipitation part of the cycle (see illustration). Precipitation is water that falls to earth under gravity when atmospheric water vapour condenses to form clouds. The main forms of precipitation are rain, drizzle, sleet, snow, ice pellets, graupel (also called soft hail) and hail. Precipitation can have two fates: it can be so light that it evaporates before it reaches the ground (these so-called virga are seen as wispy streaks of rain under a cloud) or it can reach the ground. The precipitation that falls on the ground either infiltrates into the soil or flows over the surface, ending up in rivers and streams (called run-off). Run-off is lost to the livestock farmer, as it does not contribute to veld production even though it can be measured in the rain gauge.
The water that infiltrates into the soil will do one of three things: percolate deep into the subsoil and replenish the groundwater; evaporate directly from the bare soil surface back into the atmosphere; or be absorbed by plants and transpire back into the atmosphere.
This story is from the November 20, 2020 edition of Farmer's Weekly.
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This story is from the November 20, 2020 edition of Farmer's Weekly.
Start your 7-day Magzter GOLD free trial to access thousands of curated premium stories, and 8,500+ magazines and newspapers.
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