Characteristics of hydrological cycle in relation to　environmental changes in Mongolian　grassland

Maki TSUJIMURA

Graduate School of Life and Environmental Sciences, University of Tsukuba, Japan

Mongolia is situated in arid and semi-arid region of northeast Asia, and the precipitation ranges from less than 50 mm/yr in the southern Gobi desert to more than 350 mm/yr in the northern taiga forest. The major region contributing to precipitation in Mongolia during the summer season is evaluated to be central Asia and western Siberia located to the northwest of Mongolia by a colored moisture analysis in which tracers are assigned depending on the region where the water vapor finally evaporated. The source of river water in central north and north east Mongolia is estimated to be a water fallen in the headwater regions by isotope tracer approach, and the river flowed down conserving chemical characteristics from the headwater to the downstream regions. The river water recharges dominantly groundwater in floodplain of mountainous basin, and especially the groundwater is major source of the drinking water in Ulaanbaatar, capital city of Mongolia. Mongolia is vulnerable region from the view point of the water resources, and a perspective of the water resources under the effect of climate change is discussed.