Adopting controlled drainage practice in the upper reaches of the Yellow River Irrigation Districts, China

The YinNan Irrigation District is located in the upper reaches of the Yellow River inNingXia, China. Suffered from salinity problem prior to 1950s, an inclusive drainage system was constructed from 1950s to 1970s and has been used extensively for salt leaching. Theratio of drainage to irrigation water volume is as high as 60%. After years of leaching, salinity inmost area has been lowered substantially, total dissolved solids in drainage water during thegrowing season is generally below 0.9g/l. Nevertheless, the traditional practice continues andlarge amount of drainage water is directly discharged into the Yellow River each year. Ascontrolled drainage has been found beneficial in humid areas in drainage volume reduction andwater conservation, its application in irrigated agriculture is not straightforward due to thecomplex nature of salt and water balances in these areas. This paper discusses the feasibilityof adopting controlled drainage practice in the YinNan Irrigation District in order to mitigate theadverse impact of farm drainage. The analyses showed that for the major water use crop, rice,controlled drainage could be used to reduce water loss through field ditches significantly. Fordry land crops, however, the benefit of using controlled drainage is trivial because the maindrainage path is through main ditch system and the Yellow River channel.