Dynamics of typical agricultural landscape and its relationship with water resource in inland Shiyang River watershed, Gansu province, northwest China.

Shiyang River basin is located in Hexi Corridor, central-west Gansu province, northwest China. It is an area of typical arid to semiarid features. Based on the TM image of Liangzhou oasis and Minqin oasis in 1986 and 2000, this paper calculated and analyzed the changes of percentage and area of land use/cover types, and also have got the transformation matrix of the landscape mosaics. Dynamics of runoff and exploitation of groundwater, the most important factors influencing land use changes were also analyzed. The ratio of utilized water quantity in upper and middle reaches to that in lower reaches has increased largely from less than 2 before 1970 reached up to more than 8 since 1995; groundwater exploitation has developed progressively. As a result of overuse of groundwater, the groundwater table lowering obviously, the lowering rates reached up to 0.6-0.8 m/year in some place. In addition, the cropping patterns in study area were also distributed irrefficiently that if the planting percentage of water-wasting grain crops dropped to 50% in both oasis, it could save irrigating water by 1.2 x 10(8) m3 in Liangzhou oasis and 0.2 x 10(8) m3 in Minqin oasis one year.