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 of fish 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.