Eurasia is recognized as a region vulnerable the influence of global warming, in which annual mean air temperature significantly increased during the past few decades. To understand the influence of the global warming, it is primarily needed to access quantitatively changes in glacier and permafrost. Therefore, we selected Lena watershed covered by continuous permafrost as a study area and are studying the reason why long-term discharge in the Lena has been increased.

Lena watershed adjoining to Arctic Ocean has the area of 2,500,000 square kilometers, which is corresponding to the 9th in the world river. During the past 60 years, precipitation in Lena represented a decreasing trend, while river discharge increased. Meanwhile, precipitation and discharge in the last 20 years increased together. An analysis with snow water, soil moisture, active layer depth, evapotranspiration, and river discharge indicated that the increase of soil moisture caused by the increased precipitation and active layer depth largely contributed to the increase of river discharge in Lena.
The same research is expanding toward Ob and Yenisei for increasing our understanding for hydrological processes in the Arctic system.