Due to shrinking surface area, Xinjiang's largest salt lake, Aibi Lake, has increased the desertification of the area and subsequently transformed into one of China's major sandstorm sources. According to the Bortala Forestry Bureau, water shortages have led to the shrinkage of the Aibi Lake surface. Three rivers including the Kuytun, which previously supplied 45.8 percent of the Aibi Lake water, dried up in the 1970s. Reduced supply of river water combined with severe lack of rain, about 90 mm per year, has caused a serious imbalance between the supply of lake water and evaporation.