How Much Water Agriculture Uses
One thing that really concerns water resource analysts is how much water agriculture uses. Agriculture uses a lot of water , more than all other water-using sectors of society. One of our gratest concern is the very high use of water by irrigation. This is because, in most cases the water used for irrigation can't be used afterward for other purposes, such as water supply for homes or industry.
Some forms of irrigation use water more efficiently than others. The efficiency of water use veries by region, crop, agricultural practice and technology. The least efficient types of irrigation are the surface methods. But think of how much water it takes for a traditional surface method like field flooding. It takes a lot of water to flood a field (1*).The water collects into ponds or basins, but than most of it either evaporates into the air or passes down through the soil into groundwater(2*) This means that, in lots of places, less than half of all the water applied to a field is actually used by he crop. The rest is lost to evaporation or to groundwater (3*)All of the flooding methods generally waste a lot of water-water that could otherwise be used for other purposes.
Fortunately, there are several irrigation technologies that are more efficient than poorly controlled abd highly wasteful flooding methods. They range from sprinkler systems to drip irrigation. In sprinkler systems, water is sprayed over crops and this provides and even distribution of water. New precision sprinkler technologies have greatly improved our ability to deliver water exactly when and where it's needed. However sprinkler systems are also a form of surface irrigation and just as in other surface methods, some of the water is still lost to evaporation.
REFERENCES
1*- S. Johannessen and C. A. Hastorf (eds.) Corn and Culture in the Prehistoric New World, Westview Press, Boulder, Colorado
2*-Schneider, Keith (September 8, 1989). "Science Academy Recommends Resumption of Natural Farming". The New York Times.