ABSTRACT
If conditions preclude safe, productive, rainfed cultivation, and if there is no suitable groundwater and rainfall collection and concentration is impractical, it may still be possible to develop stream-flow to support irrigation. Streams seldom flow constantly year-round, and in some cases they may fluctuate from year to year; also they may not pass close to land which is suitable for irrigated cultivation. The problem of inconstant flows may be solved by engineering (the construction of dams or barrages) or by watershed management or by both. To date, engineering approaches have usually been adopted and this seems likely to remain so for the immediate future. The solution when rivers do not run near the land it is desired to irrigate is to build a canal, pipeline or aqueduct and divert the water to where it is needed; this is increasingly being done and on an ever-growing scale and over longer distances.
