Water is one of the main requirements for healthy plant growth. Most arid and semi-arid regions, however, suffer from insufficient and unreliable rainfall. In these areas a high rate of evaporation in the growing season is also common. When it rains in (semi-)arid areas, the rainstorms are usually heavy. The prevailing soils generally cannot absorb the amount of water which falls in such a short time. As a result rainfall in (semi-)arid areas is often accompanied by a large amount of surface runoff.
These climatic characteristics of (semi-)arid regions mean that it is important to use the limited amount of rainfall available as efficiently as possible. One way to do this is to use surface runoff (water harvesting). Another is to encourage infiltration and storage of rainwater (soil moisture retention or conservation). The advantages of water harvesting and moisture retention techniques in (semi-)arid areas may be summarized as follows. A higher amount of water available for crops may lead to a greater reliability and a higher level of yields. In addition, it can tide a crop over an otherwise damaging dry spell and it can make crop production possible where none is viable under existing conditions.
Version 2, 2003