The human mechanism research of Minqin Oasis change in the lower reaches of the Shiyang River
石羊河下游民勤绿洲变化的人文机制研究

Based on social investigation material this paper analyses oasischange and its impact on Minqin Basin at the lower reaches of the Shiyang River in Hexi Corridor of western China.Furthermore,it discusses human mechanism caused oasischange in the context of human behaviorof water use and quantity balance of water use.Minqin oasischange is closely related to the expanding mechanism of traditional agriculture which can not be easily broken in a limited period of time.Howerver,if the human mechanism leading to environmental deterioration continues to exist, all human actions attempting to turn back the trend of the oasischange in the same area will have little effect. The worse trend of Minqin Oasisin the lower reaches of the Shiyang River is the process of the rapid decline of underground waterlevel, desertification, salinizification-alkalization and degeneration of vegetative cover that have greatly affected the agricultural production since the 1950s. The human factor causedthe oasischange is chiefly due to theunlimited demand of agricultural water use incited by the enlargement of farmland resulting from rapid population increase of the Shiyang drainage basin. The decrease of upstream runoff and the increase of water requirements have explained the decline of underground water level and the worsening of the underground water quality that caused the rapid salinizification and the rapid decline of the crop production,constituting one of the main reasons for farmland enlargement. All of these factors mentioned above are attributed to the degenerated vegetative cover and the disasterof the ecosystem.