A brief geographical description is provided for Lake Khanka and its drainage basin where the Russian part accounts for more than 90% of the area. Sixteen rivers on the Russian territory and eight rivers on the Chinese territory flow into the lake. Only one river, Sungacha, flows out of the lake; it is a border river and connects Lake Khanka with the Ussuri river. A historical analysis of the water level dynamics in Lake Khanka for the last 10 thousand years showed that rises of the lake water level, shore erosion, an increase in flood frequency and duration, and an increase of the degree of waterlogging of the valleys corresponded to warm climatic phases. The cold phases showed a decrease in hydraulicity of the rivers and in the lake level, and an enhancement in aeolian processes in the coastal zone of the lake and its river valleys. Seismic processes and changes in groundwater flow can also be responsible for changes in the lake water level. Morphostructural analysis indicates a potentially high seismic activity of this territory and risks of magnitude 8 earthquakes. In the 20^th century, the natural processes of water level fluctuations in the lake began to be influenced by anthropogenic factors, such as the water withdrawal for irrigation of paddy fields and streamflow control. The territory of China within the Lake Malaya Khanka drainage basin is the home for extensive paddy systems which are supplied with water from the Muling river basin. The water is then directed to Lake Malaya Khanka, and through the drain facilities it enters Lake Khanka. In fact, an inter-basin transboundary water transfer is carried out, which can affect significantly the water level in the lake. Characteristics of the existing nature management practices in the Russian portion of the lake drainage basin, and also lake pollution assessments are given. The main geo-ecological problems in the Lake Khanka transboundary drainage basin associated with water level fluctuations, geodynamic processes and environmental pollution are identified. Geo-ecological problems are considered to mean changes in natural processes accompanied by the transformation of separate natural components and landscapes in general, and causing, as a rule, negative consequences for humans and for various forms of nature management. The primary and related components of the geo-ecological problems highlighted. The main directions of comprehensive research within the framework of cooperation between the People’s Republic of China and the Russian Federation in order to work out the plan for governance of sustainable nature management in the transboundary drainage basin of Lake Khanka are suggested.

Antecedent moisture conditions are essential in explaining differences in the translation of flood-producing precipitation to floods. This study proposes an empirical residual-oriented antecedent precipitation index (RAPI) to estimate and further link antecedent moisture conditions with flood predictive uncertainty. By developing a fully kernel-based residual error model without functional presumptions, the proposed RAPI is calibrated as the regressor of the deterministic model residual. Furthermore, the MI-LXPM algorithm is applied to search for optimal parameters in mixed-integer constraints. The rationality of the proposed framework is demonstrated by its application to a case study in South-East China. The quality of probabilistic streamflow predictions is then quantified using reliability, precision, and the NSE of the prediction mean. The results show that the RAPI closely connects to the uncertainty of hourly flood prediction as a proxy of antecedent soil moisture. The influence of RAPI is mainly on the precision and unbiasedness of flood prediction. Compared with the deterministic model output, the RAPI provides a better flood prediction of small to median flood events as a regressor. Along with the proposed date-driven residual error model, the framework can be applied to any pre-calibrated hydrological model and help modelers achieve high-quality probability flood prediction.

The study is focused on the specific features of ice regime in Amur lower reaches and the structure of ice surface in branches of different size and dynamic state. The main features of ice stratigraphy in different parts of the river have been identified, and ice cover characteristics have been found to show considerable heterogeneity across the channel. Quantitative data on the concentration of terrigenous material in the ice and its distribution within the ice mass have been collected. The amount of terrigenous material was estimated in the ice in Amur lower reaches, from where it is largely exported into the Sea of Okhotsk during spring ice drift.

It has been established that the formation of the relief of the Lower Amur region is due to the long history, differentiated tectonic movements, climatic features, and a complex permafrost pattern. Despite the low elevations of the mountain ridge tops, numerous traces of Quaternary glaciation, relict permafrost forms, and active manifestation of modern cryogenic processes on the highest peaks of the mountains have been found there for the first time. Data on the distribution and occurrence of permafrost strata within the Udyl’-Kizi and Evoron-Chukchagir lowlands point to their relict nature. Specific features of erosion-accumulative processes of mountain taiga rivers in the monsoon climate zone, caused by significant seasonal unevenness of the runoff, have been revealed. It is shown that the Amur River bed, crossing vast lowlands, forms complex floodplain-channel branches, in which the water flow and sediment deposits are being constantly redistributed between the branches. An assessment is given of the role of uneven floodplain sedimentation played in the emergence of various forms of mesorelief. The features of the formation of the floodplain and floodplain lakes under conditions of a deficit of traction load within the Lower Amur Lowland are revealed.