Hydrological consequences of changes forest cover on watersheds of the Amur river basin

Observing the geographic environment change of watersheds is very important for understanding problem of influence on streamflow, which ranks fourth out of 23 hydrological problems highlighted at Vienna Catchment Science Symposium in April 2018. Watersheds of the Middle and Lower Amur, where main part of streamflow is formed, are covered with forests of various structures. Annual forest fires in the Amur basin lead to sharp decrease in transpiration and summarize evaporation, an increase in volume and rate of surface streamflow (slope) into river beds and, as a consequence an increase in river runoff. An increase frequency of fires entails a change in forest species composition. Despite fact that species of the stand within watershed grow up in same conditions (environment, climate, weather, fires) – total value of the areas of coniferous forests has a decrease, in contrast to deciduous species. This is consistent with the conclusions of Russian hydrologists about shift in Russia of the boundaries of middle taiga on north, which is justified by them using climatic models. Reduction of coniferous forests, which have a deeper root system and larger area of contact with atmospheric precipitation, contributes to a faster runoff of rainwater, contributing an increase streamflow. Moreover, a positive trend is also noted in synchronous dynamics of peaks of rain floods on the Amur near Khabarovsk. This corresponds to assessment of spatio-temporal variations of global terrestrial water storage changes of the Amur according measurements of the Earth’s gravitational fields by GRACE satellite, carried out by foreign researchers. It has been suggested that with a descending trend in areas of coniferous forests, conditions will persist, contributing to increase in streamflow during the period of monsoon and frontal cyclonic rains