small rivers
Recently Published Documents

Little is known about the microbial diversity of rivers that flow across the changing subarctic landscape. Using amplicon sequencing (rRNA and rRNA genes) combined with HPLC pigment analysis and physicochemical measurements, we investigated the diversity of two size fractions of planktonic Bacteria, Archaea and microbial eukaryotes along environmental gradients in the Great Whale River (GWR), Canada. This large subarctic river drains an extensive watershed that includes areas of thawing permafrost, and discharges into southeastern Hudson Bay as an extensive plume that gradually mixes with the coastal marine waters. The microbial communities differed by size-fraction (separated with a 3-μm filter), and clustered into three distinct environmental groups: (1) the GWR sites throughout a 150-km sampling transect; (2) the GWR plume in Hudson Bay; and (3) small rivers that flow through degraded permafrost landscapes. There was a downstream increase in taxonomic richness along the GWR, suggesting that sub-catchment inputs influence microbial community structure in the absence of sharp environmental gradients. Microbial community structure shifted across the salinity gradient within the plume, with changes in taxonomic composition and diversity. Rivers flowing through degraded permafrost had distinct physicochemical and microbiome characteristics, with allochthonous dissolved organic carbon explaining part of the variation in community structure. Finally, our analyses of the core microbiome indicated that while a substantial part of all communities consisted of generalists, most taxa had a more limited environmental range and may therefore be sensitive to ongoing change.

Abstract Zoobenthos organisms are directly related to the biogeochemical processes occurring at the bottom and in the water column of the channel. The paper presents the results of studies of the quantitative characteristics of the zoobenthos and the water quality of small rivers in the river basin of Shilka in the area of gold mining enterprises.

The results of long-term observations of the hydrochemical service of the Russian Meteorological Service on the content of dissolved oxygen in the rivers of Russia are considered. Data on the basins of the Amur, Lena, Ob, Volga for 1988-2007 is analyzed. We compared the average monthly oxygen concentrations above and below the sources of exposure – cities, large industrial enterprises – in total, about 100 paired sections were used. The study showed that in about half of these river sections, sometimes (in 14.8 % of cases) small changes in oxygen concentration (6.5-8.3 %) are observed. Wherein, both a decrease and an increase in oxygen concentration can occur below the sources of anthropogenic impact. The latter is typical for winter time, when the flow of heated wastewater into the river leads to formation of an air-hole and the flow of oxygen from the atmosphere into the water. Small rivers in cities experience the greatest stress; however, in general, for all the rivers under consideration, the anthropogenic change in the oxygen regime of the rivers is small and does not significantly affect the sustainability of the development of the territories.

AbstractSmall rivers support high levels of biodiversity, being especially sensitive to the effects of global change. Temporal records of community composition in minimally impaired streams can be used to explore trends in biodiversity in response to climate change and natural temporal variation. We approached the comparison of two time periods (2003–2008 and 2016–2020) to study whether the composition of diatom assemblages changed over time in twenty-three streams of the mountain range of Picos de Europa (Northern Spain). The stream’s water chemistry indicated significant decreases in N_NO3− and P_PO43− content over time. In these minimally disturbed streams, the specific diatom community was dominated by Achnanthidium pyrenaicum, Achnanthidium minutissimum and Cocconeis euglypta. PERMANOVA analyses did not identify significant changes in diatom assemblage composition between periods or river types. Diatom indices (e.g. IPS, NORTIdiat) indicated high or good ecological status and relatively high alpha diversity values were found in these mountain rivers during the studied years. Although diversity and evenness showed a significant decrease over time, the temporal stability of the river-type diatom reference community between the two periods should be considered as an indicator of biodiversity persistence of high importance when monitoring the ecological status following the reference condition approach.

The aim is to develop conceptual principles of sustainable development of the agrosphere and reproduction of degraded riverbeds of small rivers under climate change. Methods. Methodology and methods of system approach, monitoring, statistical analysis, and synthesis of scientific data. Results. It has been determined the ecological condition in Ukraine and the world has been by the manifestations of degradation processes in terrestrial ecosystems and small river basins on the principle of causation. It has been suggested the conceptual bases of restoration of channels of small rivers and their basins by carrying out engineering, culture-technical works in channels and floodplains of small rivers, the organization of adaptive landscaping of the territory, and also carrying out agro-, chemo-, bio- and phyto-meliorations in their basins without disturbance the basis of erosion and giving impetus to self-renewal of natural fauna and flora. In the processes of nature restoration, the leading role of domestic science in the methodological and methodological support of projects has been identified, and importance is attached to the restoration of natural biodiversity and biologization in agricultural systems. We proposed to create a state mortgage land bank with a concentration in it of land fees of ecological funds with the involvement of domestic and foreign investment. It is recommended to test the idea in several model pools of soil-climatic zones with further replication in Ukraine and the spread of technology beyond its borders. Conclusions. А systematic approach is needed to carry out reclamation works in the basins of small rivers is to implement the basin approach. To implement the program, the Verkhovna Rada of Ukraine must adopt the Law of Ukraine “On Agriculture, Sustainable Development of the Biosphere and Ecological Nature Management”, the project of which was developed at the NSC “Institute of Agriculture of NAAS”. The NSC “Institute of Agriculture of NAAS” with appropriate financial and personnel support on a multifunctional basis can perform the functions of a methodological center for the development of methodology and techniques of land management and reclamation in the process of restoring small river basins.

Abstract Comparative analysis of methods of obtaining electricity from a renewable energy source is carried out. Various designs and op-tions for small hydroelectric power plants have been proposed. Positive and negative factors of structures under consideration and their impact on the environment are analyzed. The main characteristics of the flow (speed, head) for the choice of the optimal variant of hydroelectric power plant have been determined. Three variants of impellers for free-flow hydroelectric power plants are proposed with a comparison of the efficien-cy of each variant. An analysis was carried out and an impeller based on a Darrieus rotor was selected for further research. Simulation was performed in the Flow Simulation program. The initial data for the design of Darrieus rotor operating in a liquid were the diameter and width of the impeller. The calculations involved a rotor with straight and swirling blades. The swirling blades rotor is self-starting. In the course of the calcula-tion, the speed of the liquid flow approaching the rotor and the rotor speed were changed. As a result of cal-culation, the value of the positive moment for self-starting was determined, which occurs at an incident flow velocity of at least 1.3 m/s.

Abstract Considering the dilution of sewage and the interaction between river water and bottom sediments, a mathematical model for the conversion of pollutants in water bodies has been developed. Taking the small rivers in northern Vietnam (Ban Thi River and Dai River in the Red River Basin) as an example, it shows that more than 60% of the chemical composition of the river waters studied is determined by the interaction of the following factors: Co-precipitation of sediments and trace elements on solid particles, and sediments at the bottom of the river. The impact of water runoff is first manifested in the change of solid runoff, and to a lesser extent in the process of regulating the water, which takes longer to establish equilibrium in the solution. On the basis of the proposed model, a simplified version of the model and a standardized pollutant discharge method have been developed for whether there is an option of river water chemical composition observation data. In this case, the influence of interaction with bottom sediments is indirectly considered through the structure of the model and its parameter values. The simplified model was tested with the Jinjiang River in the Poyang Lake Basin as an example.

Abstract Information and geoinformation technologies can be widely used on inland waterways and water transport facilities. Solving problems related to monitoring the state of water quality, its changes as a result of anthropogenic impact, forecasting the quality of water resources, analyzing water consumption and wastewater disposal – this is not the whole list of opportunities that open up to the user when creating a cartographic basis for the geoinformation system of a river basin. Mathematical and cartographic modeling of content and conventional signs is the basis of the method for creating electronic maps. Basin maps of large and small rivers represent models of the studied objects and intermediate links between the objects and the researcher. Information about the situation in the river basin is constantly changing. Electronic maps have an indisputable advantage over paper ones in their ability to transmit this information in real time, constantly making any changes that occur in the study area. Various analytical operations can be performed with information that is entered into the GIS and applied to an electronic map of the river basin. The possibilities of GIS technologies in creating a cartographic basis for the river catchment area will affect the ability to transfer the assessment and management system of water resources and water quality to a more modern and high-quality information level, taking into account the real capabilities of the current control system in the field of environmental management.

AbstractArctic rivers drain ~15% of the global land surface and significantly influence local communities and economies, freshwater and marine ecosystems, and global climate. However, trusted and public knowledge of pan-Arctic rivers is inadequate, especially for small rivers and across Eurasia, inhibiting understanding of the Arctic response to climate change. Here, we calculate daily streamflow in 486,493 pan-Arctic river reaches from 1984-2018 by assimilating 9.18 million river discharge estimates made from 155,710 satellite images into hydrologic model simulations. We reveal larger and more heterogenous total water export (3-17% greater) and water export acceleration (factor of 1.2-3.3 larger) than previously reported, with substantial differences across basins, ecoregions, stream orders, human regulation, and permafrost regimes. We also find significant changes in the spring freshet and summer stream intermittency. Ultimately, our results represent an updated, publicly available, and more accurate daily understanding of Arctic rivers uniquely enabled by recent advances in hydrologic modeling and remote sensing.

Large Amazonian rivers impede dispersal for many species, but lowland river networks frequently rearrange, thereby altering the location and effectiveness of river-barriers through time. These rearrangements may promote biotic diversification by facilitating episodic allopatry and secondary contact among populations. We sequenced genome-wide markers to evaluate histories of divergence and introgression in six Amazonian avian species-complexes. We first tested the assumption that rivers are barriers for these taxa and found that even relatively small rivers facilitate divergence. We then tested whether species diverged with gene flow and recovered reticulate histories for all species, including one potential case of hybrid speciation. Our results support the hypothesis that river dynamics promote speciation and reveal that many rainforest taxa are micro-endemic, unrecognized and thus threatened with imminent extinction. We propose that Amazonian hyper-diversity originates in part from fine-scale barrier displacement processes, including river dynamics, which allow small populations to differentiate and disperse into secondary contact.