A study of anthropogenic seasonal rivers in China

Natural rivers may be classified into two flow durations, perennial and seasonal. However, due to strong human activities, some perennial rivers in north China have been changed into seasonal rivers, among which the most striking examples are the lower Yellow River, the lower Yongdinghe River and the lower Hutuohe River in North China Plain. These rivers can be regarded as a new category of rivers, and termed anthropogenic seasonal river (ASR) in the present study. The transformation from perennial rivers to ASRs occurs under the influence of both natural factors and human activities. In the zones with some specific combination of environmental settings, the transformation from perennial to ASRs is most likely to occur. These zones can be regarded as sensitive or susceptible zones of ASRs. In the present study, three sensitive zones of ASRs have been identified, i.e., the transitional zone from arid to semiarid climates, the zone of “superelevated river” (i.e., a river whose bed is higher than the floodplain behind the artificial levees) development, and the zone with unbalanced land–water coupling. To a great degree, the formation of ASRs in these susceptible zones is the result of the excessive water diversion by human beings for irrigation and other water demands during low-water seasons. This study shows that the major anthropogenic seasonal rivers in China such as the lower Yellow River and Haihe River, and some of their tributaries are all located in these susceptible zones.