River In Ningxia Research Articles

Evaluating current drainage practices and feasibility of controlled drainage in the YinNan Irrigation District, China

The YinNan Irrigation District (YNID) is located in the upper reaches of the Yellow River in NingXia, China. Its drainage system was constructed between the 1950s and 1970s to maintain salt and water balances in the district. The system, however, has been reported draining the agricultural lands excessively, resulting in frequent irrigations and large amount of drainage discharge into the Yellow River each year. This paper presents a comprehensive analysis of current drainage practices in the YNID and discusses the feasibility of controlled drainage in order to mitigate the negative impact of agricultural drainage. Based on historical records and available information, drainage discharge has been estimated for different crop fields and ditches. The results show that for the major water use crop, rice, controlled drainage may reduce subsurface discharge through field ditches up to 94%. For wheat and corn, the benefit of controlled drainage is not significant because the major drainage discharge is directly through the main ditch system and the Yellow River channel. The rotational cropping nature and local water management tradition, however, make controlled drainage a very attractive option for water savings and reducing water pollution to the Yellow River.

Soil salinity in the irrigated area of the Yellow River in Ningxia, China

Soil salinity has plagued irrigated lands along the Yellow River in the arid Ningxia Hui Autonomous Region of China since shortly after the first canal was built in BC 214. By 1985, approximately 40% of the 300,000 ha of irrigated land was adversely affected by salt accumulation. Several factors have contributed to the increase in salinity. They include high groundwater tables caused by overirrigation, leaky main and lateral canals, and an inadequate drainage system. Other factors are the flatness of the terrain, the high level of the Yellow River during the flood season, widespread production of paddy rice, introduction offish ponds, and the presence of numerous lakes in the Yinchuan Plain. Effective methods of rehabilitating salt‐affected land have been devised but are not yet in wide use. Sediment from the highly eroded Loess Plateau complicates water control in the irrigation system. Despite the salinity problem, irrigation agriculture has prospered over the past 2,000 years.