The Atmospheric Water Resource over the Qilian-Heihe Valley

On the base of weather station data and the NCEP/NCAR reanalysis data, atmospheric water resource over the Qilian-Heihe Valley was analyzed, and the result shows that, the less water vapor transport source and the divergence of atmospheric stream eld are main cause for resulting in the little water vapor content over the Qilian-Heihe Valley. Annual mean atmospheric water vapor content over the Qilian-Heihe Valley is merely 30% and 40% over the south of the Yangtze River and the middle of North China, respectively. Because of its high elevation and high precipitation e ciency, the Qilian Mountains area has plentiful precipitation. And the lower surface temperature and evaporation make the surface water material gather easily and thus form runo . As for the Heihe Valley, for the low precipitation efficiency, there is little precipitation and its value is corresponded to the surface evaporation. Thus its contribution to the surface water is very small. In the grid of 2.5°×2.5° over the Qilian-Heihe Valley, annual influent and effluent water vapor amount are 668×109 and 650×109 m3, respectively. The net influent water vapor amount is 18×109 m3. The influent water vapor takes on reducing tendency and with an obvious descent in period of the 1970s-1980s. In the recent 40 years, because the air temperature over the Qilian-Heihe Valley is rising and the atmospheric water vapor content is descending, the decrease of precipitation would be inevitable.