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Accurate predictions of water surface elevation (WSE) in rivers at high spatial and temporal resolution are important for flood/drought risk assessment and flood/drought forecasting and management. WSE in a river is controlled by three main factors: discharge, riverbed geometry, and hydraulic roughness. In remote and poorly instrumented rivers, discharge and riverbed geometry are highly uncertain and WSE is therefore hard to predict. ICESat-2 laser altimetry provides accurate elevation transects across the river at very high spatial resolution (70 cm along track). This paper demonstrates how ICESat-2 elevation transects can be used to parameterize a basin-scale hydraulic model of a continental-scale river. The workflow is demonstrated for the transboundary Amur River in North-East Asia. Simulated WSE is subsequently validated against a large dataset of in situ and satellite altimetry observations, and we demonstrate that the model can reproduce available WSE observations throughout the basin with an accuracy of 1–2 m. [ABSTRACT FROM AUTHOR]

The Amur River is one of the largest rivers in Asia and the world. The initial data on major, trace geochemistry of the bulk composition of recent sediments from upper, and middle Amur River suggests that concentrations of most major and trace elements in the Amur sediments correspond to the upper continental crust. However, there are significant differences in the bulk composition of recent sediments in different river parts, e.g. ƩREE, (La/Yb)n, Eu/Eu*. Besides, from "Upper Amur" down the river to "Amur–Zeya valley" the values of indices CIA, CIW, PIA, V increase, whereas STI and R values decrease. Farther down the river to "Khingan canyon" the opposing process occurs. That may be explained by the changes of river reaches, namely from mountain to valley and contrariwise. The statistical analysis results show a significant positive correlation of ƩREE with indices PIA, CIA, CIW, and a significant negative correlation with STI and R indices. Eu/Eu* values have a positive correlation with WIP. The correlations may be explained by the peculiarities of sorting and transporting river sediments, not chemical weathering. [ABSTRACT FROM AUTHOR]

Background. This study was initiated for the morphological comparison of two species of recently described Amur graylings collected in the unique zone of their sympatry. This provided an infrequent opportunity for the estimation of the species-specific morphological diversification not determined by environmental conditions dissimilarity. This study aimed to compare the seismosensory systems of two species of Amur grayling, the lower Amur grayling, Thymallus tugarinae Knizhin, Antonov, Safronov et Weiss, 2007, and yellow-spotted grayling, Thymallus flavomaculatus Knizhin, Antonov et Weiss, 2006, collected in sympatric habitats with the inclusion of the published data on other northeast Asia grayling species. Materials and methods. The comparative study was based on samples of T. tugarinae and T. flavomaculatus specimens collected at species sympatric habitats in the middle stretch of the Anyuy River, one of the biggest tributaries of the Amur River. The lateral line system was stained, the topology was examined, and seismosensory system canal pores were counted. Differences in canal pore numbers between examined species were estimated with Wilcoxon signed-rank test. Also, cluster analysis was carried out. Results. Examined sympatric species were found to differ in the number of pores and secondary canaliculi topology but were similar to geographically distant grayling species. Conclusions. The results revealed sympatric morphological divergence of studied species and demonstrated parallelism of interspecies variability of examined features which are likely determined by conditions of species ecological optima. Comparative morphological analysis of the species and forms with questionable taxonomic status should be carried out using material that is collected in different parts of the habitation areal, paying special attention to the sympatry zones, if there are any such cohabitation regions, because the environmental factors have similar effects on all of the analysed species within such zones. [ABSTRACT FROM AUTHOR]