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我国西部地区土地辽阔,人口密度小,大体可划分为黄土高原区、西北干旱区、青藏高寒区和西南山地丘陵区。西北地区东部为东亚季风控制,西南五省则多受西南季风影响。荒漠和无植被地区约占整个西部面积的35%,加之草原和稀树灌木草原所占面积,草原荒漠和无植被地区约占西部面积的1/2,可利用水资源明显不足。地质、生物和历史文献记录研究表明,约距今800万—900万年前随着青藏高原的隆起,我国西北干旱化和东部季风气候开始出现;约距今360万—260万年青藏高原加速隆升,奠定了我国西部干旱区和东部现代季风气候的基本格局。西北干旱气候虽有加剧的趋势,但在
The vast land in the western region of China has a small population density and can be roughly divided into the Loess Plateau, the arid northwestern region, the alpine region of the Qinghai-Tibet Plateau and the hilly area in the southwest. The eastern part of Northwest China is controlled by the East Asian monsoon, while the five southwestern provinces are mostly affected by the southwest monsoon. Desert and no-vegetation areas account for about 35% of the total western area. Combined with the area occupied by grassland and savannah grasslands, grassland deserts and no-vegetation areas account for about 1/2 of the western area, and the available water resources are obviously insufficient. Geological, biological and historical records show that from about 8 million to 9 million years ago, with the uplift of the Qinghai-Tibet Plateau, the arid northwestern China and the eastern monsoon climate began to emerge. The Tibetan Plateau about 3.6 million to 2.6 million years ago was uplifted , Which laid the basic pattern of the modern monsoon climate in the arid areas in western China and in the east. Although the arid climate in Northwest is aggravating trend,