Water Exchange in Small Riversheds With Severe Climatic Conditions During a Cold Period of a Year

Abstract

Presented are the results of experimental studies into the interaction between the surface and subsurface water in 16 mountain river basins of East Sayan and Lake Baikal as carried out by the Irkutskbased Institute of Geography during 1984‒1990. The research program included regular measurements of the thickness, area and volume of the surface and underground ice along the entire length of the valleys, pressure in closed lenses of underground waters, daily measurements of water discharges and chemical composition throughout the channel network. It was found that at the end of winter about 80‒90% of the area of the valleys of the rivers under study are covered by aufeis and by the seasonal subsurface ice of a different genesis. Furthermore, about half the volume of the seasonal ice corresponds to the surface ice (river ice and aufeis), and the other half to the subsurface segregated and injection ice. It was further shown that the period of formation of the main bulk of ice begins and ends earlier in the sections closer to the mouth. The “wave” of maximum intensity of ice formation gradually moves the river upstream. The ice volume is the last to form in the upstream components of the river network. At this time, the ice formation of the other area of the watershed has terminated or its main part has formed already. A cryogenic barrage phenomenon occurs, as a result of which the channel network receives subsurface water which, under normal conditions, is not drained by the river. The winter river runoff increases from 50% in the sections close to the source to 5‒10% at the mouth of the river.