Evolution of the Heihe River Basin oasis in the last 35 years

Taking the Landsat MSS(1975) TM & ETM+ (1990, 2000, 2005 and 2010) satellite images as the basic data sources, we extract the distributional information of oasis in the Heihe River Basin during 1975-2010. The results shows that: (1) Oasis expands from 1975 to 2010 and the growing rate especially quickly after the year of 2000, and Oasis reaches the top area of 8218.52 km<;sup>;2<;/sup>; in 2010. (2) Oasis is composed by cropland, forest, wet land, cities and settlement place in the study area. The cropland, which occupies about 60% of the oasis, and the cities and settlements expanded gently, and the forest and wet lands are changeful relatively.