Home – Home – Jornals – Geography and Natural Resources 2022 number 2

For the first time in the scientific literature, an analysis is made of the channel formation conditions and of the morphology and channel regime of the Lower Ob (within Khanty-Mansi Autonomous Okrug - Yugra) which in this context, in spite of its important economic and water transport significance, remains largely unexplored. The geomorphological structure of the valley determines downstream of the confluence of the river with the Irtysh the concentration of the river at the right valley side in a common channel producing single branches divided by straight unbranched sections shaped by river flow concentration along the right valley side and formation single branches, divided by straight unbranched sections. It is found that at the village of Pogrebennoe the broadening of the floodplain to 60 km is accompanied by the formation of a bifurcated channel (Malaya and Gornaya Ob), the distribution of water discharge in the main channels (up to four) and by numerous floodplain channels connected with one another and with the tributary, the Severnaya Sos’va river. In this connection, the water discharge of the main branches downstream decreases (by as much as 5 % of the total discharge in the Malaya Ob), there occur changes in the morphology of the channels of the branches of the bifurcated channel and in the parameters of their forms and in the intensity of reconfigurations and caving; the number and shallowness of river bars increase. It is established that the morphodynamic types are different in the common channel and in the branches of the bifurcated channel. The common channel is represented by one morphodynamically homogeneous section, with an absolute predominance of single bifurcations; the branches of the bifurcated channel are mainly meandering, and only the Gornaya Ob in the section along the valley side forms single bifurcations. On the boundary of the Khanty-Mansi Autonomous Okrug - Yugra and Yamalo-Nenets Auonomous Okrug the river is concentred in two main branches (Malaya and Bol’shaya Ob). We obtained hydrological and morphological relationships between the parameters of channel bends of the channel of the branches of the bifurcated channel and the branches of single bifurcations and their discharge during floods. However, the relationships are unstable, because they are disturbed due to the variability in water discharge within one form and local conditions.