Agricultural techniques for arid lands
Many of the techniques for agriculture in arid lands are not very different from those in other climatic zones. The unique problems of arid lands are almost entirely related to water or its effects over long or short times. Therefore, the discussion here revolves around two questions, "How to capture existing water", and "how to use water wisely".
How to Capture Existing Water. Much of the water that falls on arid lands is lost by runoff, deep penetration into sands, or by evaporation. Runoff can be captured for later use in natural or nature-like ways, or in manmade structures. These include the following:
1. Furrows, and diking of furrows, ditches, and pits following contours to slow the runoff of water and permit deeper penetration.
2. Similar structures reinforced by bench terraces, vegetative strips, or trees for alley cropping.
3. Crescent-shaped basins arranged to gather water for one or more trees.
4. Reservoirs of water, such as natural or constructed shallow basins along roads which capture runoff, earth structures that lead water into aquifers (underground streams), rock or clay-lined underground basins.
5. Other man-made structures. These include cisterns (household or community sized clay, stone, or concrete tanks, check dams (small structures that impede water movement in a stream), and conventional dams.
How to Obtain New Water. In many arid regions water can be obtained from wells. The depth of the well necessary to obtain water may vary a few to thousands of feet. Water in wells is either fossil (stored over impermeable layers for thousands of years), or from water that has entered the soil from rain, and is therefore stored rainwater. Both sources of water are limited and can be exhausted.
New water is also obtained by condensation from the air, either onto metal screens or plastic (the principle of the solar still) or onto foliage. Ingenious systems can be developed to capture this condensation. This source of water depends on nighttime temperatures that lower to the point of condensation.
How to Conserve Existing Water. Water that is conserved is just as valuable as water that is obtained, and is one of the best strategies for arid zones. There are many techniques, here presented only as lists.
[Ukrainian] [English] [Russian]