This study is focused on the comparison of streamflow composition simulated with three well-known rainfall–runoff (RR) models (ECOMAG, HBV, SWAT) against hydrograph decomposition evaluated with End-Member Mixing Analysis (EMMA). In situ observations at two small mountain testbed catchments located in the south of Pacific Russia are used. All applied RR models and EMMA analysis demonstrate that two neighboring catchments disagree significantly on the mutual dynamics of the runoff sources. The RR models' benchmark test is based on proximity to EMMA hydrograph composition. Different aggregation intervals (season, month, and pentad) were applied to find a reasonable generalization period ensuring the clarity of results. ECOMAG is most conformable to EMMA outcome; HBV reflects flood events well enough; SWAT exhibits distinctive behavior compared to the other models. It is shown that, along with standard efficiency criteria of simulated and observed runoff proximity, EMMA analysis might provide useful auxiliary information for the validation of modelling results.

Causes of the abrupt burst of iron discharge by the Amur R. and its tributaries in the late 1990s are analyzed. A conclusion regarding the likely climatic cause of this phenomenon is substantiated.

Presented are the results of adapting and testing the method of the genetic disintegration of the runoff hydrograph based on the use of natural chemical tracers in the framework of the End-Member...

The development of methods for studying river runoff formation to integrate the up-to-day instruments of point hydrological–hydrochemical observations with new concepts and modern simulation means is...

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.

Water quality degradation and eutrophication of lakes are global ecological and environmental concerns, especially shallow lakes. This study collected hydrochemical data from 2935 samples of the Chinese part of Xingkai (Khanka) Lake, based on 40 published papers spanning the period from 2001 to 2023. Using the water quality index (WQI), improved geo-accumulation index (Igeo), and redundancy analysis (RDA), we analyzed the overall contamination characteristics of the water environment in Xingkai Lake. Additionally, we explored the impact of climate change and human activities on the lake’s water quality. The results showed that the annual WQI for Xingkai Lake ranged from 47.3 to 72, with a general downward trend, indicating improving water quality. Notably, the average WQI in May and total nitrogen (TN) content decreased significantly, signaling further improvement in water quality. The average concentration of TN in sediments was 1401.3 mg/kg, reflecting mild contamination. The Igeo values for the heavy metals Hg and Cr were greater than 1, indicating moderate contamination, while the Igeo values for Cd and Pb were between 0 and 1, which is in the range of uncontaminated to moderately contaminated. Land use and climate change (average annual temperature and annual precipitation) were key factors influencing water quality, with cumulative explanatory ratios of 67.3% and 50.1%. This study utilized land-use change as a metric for human activities, highlighting the potential impacts of climate change and human activities on the water quality of Xingkai Lake. It offers vital insights for the sustainable management of Xingkai Lake and provides valuable references into the management of similar transboundary lakes.