ABSTRACT
The need for flood control usually follows the settlement of people on the rich soils of a floodplain. The paddy cultivation of lowland monsoon Asia and the ancient irrigation systems of the Nile and Euphrates were dependent mainly upon river regimes with a violent warm-season flood. Streamflow or flood routing provides a means of translating a hydrograph from an upstream to any downstream point so as to express the effects of the intervening channel and valley storage. Flood control demands considerable accommodation space to be left inside reservoirs, whereas irrigation demands the maximum water storage. The application of water to the soil, or irrigation, is undertaken mainly to grow crops in dry climates and in humid climates with a marked dry season. From early times water-power was used to drive revolving wheels, such as norias for irrigation and, by means of shafts, stones for grinding cereals and pulses.
