Abstract: The so-called Lop Desert is distributed in the Lop Nor basin and its surronnding depressions with an area of about 50,000 sq.km The region is loeated at the innermost part of the Eurasian Continent and at the lowest part of the Tarim Basin. It is characterized by an extremely dry climate, an extremely sparse vegetation,a very rich salt-accumulation and a very low population density.Yet in ancient time it was the site of flourishing Loulan and other oases civilizations as well as the crossroad of the busy Silk Road.The dry climate of the region has been formed ever since late Cretaceous and early Tertiary. Since the Himalayan tectonic movement, coupled with the increasing uplift of the Tibetan Plateau, the desiceation has been greatly enhanced.The recent climatic trend is a continuation of slow desiccation; Yet under natural condition, the rate of desiccation is very slow and its impact on human society is negligible.The Lop depression was formed in early Quaternary. It is broadly delimited by the 900 m contour line wite its lowest point 778 m in elevation. Inside this extensive depressed area, theer smaller well-shaped depressions are identified——the Lop Nor dried basin, the Kara-holshin dried basin and the De-tama Lake basin.All these depressions have not been "wandering" during historical time. They have become lakes when filled with water and reduced to salt crust when dried.Nevertheless the braided lower channels of the Tarim-Konque-Cheerchen river system together with their end-lakes have been "wandering" during historical time. From the 2nd century B.C. to the 4th century A.D. the lower Tarim R. flowed eastward together with the Konque R. and emptied into the ancient Lop Nor.Then this combined channel turned southeastward, joined the Cheerchen R, and up to 1921 emptied into the ancient Kara-holshen Iake; the ancient Lr,p Npr was dry at that period From 1921-1952, due to human intervention, the Tarim and the Konque flowed into the Lop Nor again, with the ancient Karaholshen Lake dried up.From 1952-1972, the Tarim and the Konque were artificially separated. the latter continued to flow into the dwindling Lop Nor while the former, together with the Qarqan R., emptied into the Detama Lake. Since 1972, with the construcion of the Great West Reservoir near Takanlik, all lower channels of the Tarim-Konque-Cheerchen river system together with all end-lakes have dried up.Since the drying up of all lower channels and end-lakes the qualitty of regional environment has been greatly deteriorated.It has been featured bytwo "too little" and two "two much"——too little of water and vegetation andtoo much of salt and sand.Ef fective measures must be taken to combat these hazards as soon as possible.