基于数字遥感图象的民勤绿洲20年变化研究

对1973年MSS、1987和1994年TM数字图象进行目视判读，以人机交互的方式勾绘了三个典型年代民勤石羊河下游的绿洲分布图，利用GIS软件进行了面积量算，并对三个年代的绿洲分布图进行迭加覆盖处理，获得绿洲分布变化图和面积变化数据。结果表明，20年来绿洲面积经历了选缩小后回升的变化过程；绿洲的空间分布有从下游向上游方向迁移的趋势；绿洲内部结构由受自然-人工渠（河）道控制向受人工渠道-井位控制转变；绿洲质量在下游明显恶化。

Study on the Change of Minqin Oasis Since Recent Twenty Years Based on Digital RS Images

Based on the visual interpretation of the digital images acquired respectively in 1973, 1987 and 1994, the distribution maps of Minqin Oasis at the lower reaches of Shiyang River are drawn for these three typical years, the area of the oasis is calculated by using GIS software, the distribution maps of the oasis change are overlain, and then the change data are obtained, The results are as following: (1)From 1973 to 1994, the area of Minqin Oasis experienced a prior reduction and a subsequent enlargement. The former was mainly caused by increase of the area of the abandoned farmland and the degeneration of the natural and artificial vegetation within and around the oasis due to the reduction of stream water volume, and the latter was mainly caused by enlargement of the irrigated area from the great increase of groundwater extraction. (2)In the spatial distribution, Minqin Oasis downstream from Hongyashan Reservoir has a tendency of moving upstreamward, it is not only enlarged in the upstream marginal zone of the oasis, but also towards the hinterland of the deserts in a plot way by drilling wells because of the continuous degeneration of the ecological environment and the increase of the abandoned farmland at the lower reaches, and of the convenience of diverting stream water for irrigation at the upper reaches and the great increase of groundwater extraction. (3)The change of Minqin Oasis is the reflection of the environment change in Shiyang River watershed, to research on it has an important significance for the research on regional environment change.