Spatial Changes of Minqin Oasis in the Northwest China over the Last 2000 Years

Based on the remote sensing images and GIS, this study focuses on understanding the spatial changes of Minqin Oasis over the last 2000 years, combining with the historical documents and maps, archaeological investigation, and field work. Having the interpreting keys and DEM been setup, the RS image was used to identify the distributing range and the archaeological survey data was used to determine the time of ancient oasis. The result shows that: Since this region was conquered by Han Dynasty in BC 210, the natural oasis was quickly changed into farmland. In the Wei and Jin Dynasties (AD 220-420), the reclaimed area reached to the first climax. Farmland deceased during the next 800 years from the South-North Dynasty (AD 420-581) to the Yuan Dynasty (AD 1271-1368) when nomadic people invaded. The second intensified development began in Ming Dynasty (AD 1368-1644) when the central government encouraged farmers in east China migrating to this oasis. This was followed by another more intensive development period in the Qing Dynasty (AD 1644-1911) and the irrigated area reached the largest of the whole the history which established the frame of modern Minqin Oasis. The irrigated oases developed in different dynasties located in different locations, with the trend to increase in scale. An intensive development period was always followed by a strong desertification thereafter.