Dynamics and driving factors on Hongjiannao lake in northern shaanxi province

The paper studied on dynamics and driving factors on Hongjiannao Lake since its formation with topographic map calculation, field survey and remote sensing technology. Based on the analyses on climate and land use, the main factor of lake change was found during 1981-2005. The results showed that Hongjiaonao Lake increased to 67km² with 5.5×10⁸m³ of water volume in 1960s from only 1.3km in 1920s. The lake shrunk sharply after 1990s while stable about 55-60km² during 1970s-1980s. The annual variations on lake area and water volume were 1.1 km² and 0.17×10⁸m³ respectively after 2000. The reduction of lake inflow mainly led to sharp decline in Hongjiannao Lake because of climate changes during 1981-1989 and 1994-2000. The reduction of rainfall runoff accounted for 73.7 percent of the reduction of runoff into the lake during 1981-1989. The amount of runoff reduction was five times than the actual amount of runoff during 1994-2000 when water consumption for human activities reduced 0.402×10⁸m³. Human activities on the vegetation coverage changes was mainly contributed to reduction of lake inflow during 1989-1994 and 2000-2004. Meanwhile, the construction of reservoir significantly reduced the water volume into the lake after 2004.