Water harvesting. What is it and why?

Cotton, because it is drought and even salinity tolerant grows in some harsh, even extreme climates. However, cotton also yields best when there is some control over when it has access to water. Irrigated cotton yields more than purely rain-fed cotton for this reason. This is why we may seek to manage water or harvest water. To enable some control over the when to aid the crop.

Water harvesting may also have other benefits in increasing the available water for household use or growing food.

But cotton, the cash crop, will enable this to be paid for. So how does it work?

Rainfall in extreme and harsh climates may be brutish, and short. It may destroy the crop the farmer wants to grow. Managing fields to channel excess water away from crops, reducing immediate damage, and into some form of storage, or gathering scarce moisture around the plant are common ways.

Channelling is done by digging and directing water using natural slopes. Other management is by use of bunched up earth, bunds, stones and so on.

Seasonal rain courses can also be partially dammed.

The resulting boreholes, tanks and ponds can be protected by vegetation to reduce evaporation and lined with homemade brick or local stone to reduce water loss.

Here are some examples in action:

Peru

This lush vegetation in the desert of northern Peru is a result of water drawn from collection ponds covered by vegetation.

Benin

Cotton is planted into raised mounds to enable excess water to flow away and avoid seedlings being drowned.

This disused water pit could be used to collect rainwater and form the basis for a compost pit

Malawi

Potential water collection sire near cotton fields in Malawi. Rainfall could be directed down the slope and into a tank or along a channel

INDIA

Ditches and mounds with drainage draw rainfall away from crops and into storage.

Mounds around plants here retain scarce moisture for the plant. Gujarat.

Mr Sharma explains how here the mounds and slop work together to channel excess water towards storage wells and also feed the water table.

A collection tank for rainwater.