The article presents the results of studying the water chemistry and the species structure of phytoplankton and higher aquatic vegetation of the cooling reservoir at the Kalinin Nuclear Power Plant (NPP), the lakes Pesvo and Udomlya being its components. It was established that the inflow of heated waters from the Kalinin Nuclear Power Plant to the lakes Pesvo and Udomlya had resulted in a significant change in the temperature conditions of the water bodies, an increase in water mineralization and the concentrations of hydrocarbonates, sulfates, calcium, and magnesium, as well as рН. The role of cryptophytae algae (Cryptophyta) has increased, and species of higher aquatic vegetation, unusual for this area have appeared.
The relationship between turbulent diffusion with Eulerian and Lagrangian scales of turbulence in natural flows is considered. An estimate of the depth-averaged Lagrangian time scale as a function of Eulerian scale is suggested. The vertical turbulent diffusion in open natural flows is studied. The mean velocity profile is described by a power law. On the assumption of flat flow under incomplete self-similarity of the global Reynolds number, a universal expression for the vertical transfer coefficient is obtained. This expression enables one to estimate the time and length of complete mixing using minimum experimental data. The coefficients of longitudinal and vertical diffusion in different rivers are compared with each other and the universal ratio of these coefficients is suggested.
The methodical approaches to the integral estimation of the biogenic diffuse export from urbanized areas have been developed and tested, using the Nizhny Novgorod area as an example in the absence of direct hydrological observations. The conditionally natural runoff of the Rakhma River, the catchment of which is mostly occupied by the present-day Nizhny Novgorod area, has been reproduced based on the RosHydroMet data on the Sundovik River-analog runoff for 2010–2017. The interannual distribution of the Rakhma River runoff has been analyzed, and the variations in the groundwater and surface runoff components have been estimated with regard to the joint impact of climatic and anthropogenic factors. The surface component of the Rakhma River runoff has been shown to increase twice while the groundwater component, to decrease by 38%. In this case the groundwater runoff value remains rather large (63 mm per year), accounting for 33% of the total river runoff. The calculations of the biogen export by the river into the Cheboksary Reservoir in different seasons, less the biogen input with wastewater, have been illustrated. The present-day diffuse export of biogens from the Nizhny Novgorod area has been roughly estimated. The export of mineral nitrogen (195 kg km–2) is maximal in the cold season and that of phosphorus (11 kg km–2), during the spring flood, respectively.
Homoacetogenic bacteria can play an important role in anaerobic degradation of organic matter in peatlands at low temperatures. However, little is known about the conditions when they come on the scene. We carried out incubation experiments with peat samples from a West-Siberian eutrophic fen in the presence and absence of inhibitor sodium fluoroacetate (CH2FCOONa) and proposed the employment of dynamic modeling to clarify the contributions of different groups of bacteria and archaea to the degradation of organic matter to CH4 and CO2. At the end of experiments, CH4 content in the headspace was 2.6–3.1 times higher than that of CO2; pH values of peat solution were between 6.5 and 7.0. Dynamic modeling of CH4 and CO2 and their isotopic signatures showed that CH4 was predominantly produced through homoacetogenesis and acetoclastic methanogenesis, while hydrogenotrophic methanogenesis played a minor role in the process. Inhibitor addition led to a change in the pathway of methane formation to H2-dependent methanogenesis. The comparatively large differences in the quantitative output of methane from different samples taken from the same field site were interpreted as a consequence of variation in the initial concentrations of biomass, cellulose, acetate, methane, and CO2. These differences also led to variations in the proportions of methane formed from acetate and H2/CO2.
The objective of this study was to provide the most accurate presentation of the behavior of a disastrous rain flood, which had resulted in destruction of a dam, casualties, and significant material damage. The problems set were solved by methods of numerical modeling in the two-dimensional setting applying the STREAM 2D CUDA software package. To calculate the rain flood, a catchment model of the Durso River was developed on a triangular non-uniform mesh, adapted to the river channel and the main inflows. To ensure direct numerical modeling of the dam’s destruction, a model was developed, which included the water area of the reservoir, the dam, composed of non-homogeneous earth material, and a downstream section of the river from the dam to the river mouth. The main results of the study were: the hydrograph of the water discharge of the rain flood, calculated by the actual precipitation data; a description of the washout of the earth dam composed of non-homogeneous materials, resulting from water spill over the dam crest, and a desctiption of the downstream spread of the breach wave.
The overland flow from different landscapes during flood season and its variations under the effect of agrotechnical activities and climate in the southern Russian Plain have been evaluated based on the analysis of data from water balance plots. The present-day overland flow in forest steppe and steppe regions has been shown to be several times less than that 50–70 years ago. At the same time, the infiltration runoff (perched-water and groundwater runoff) has increased. The structure of the present-day river runoff and the contribution of the overland flow, the runoff from a hydrographic network area, and the runoff of infiltration origin in individual natural zones to the formation of the river runoff have been determined. The export of biogens in the Volga and Don basins, including that in urbanized areas, has been calculated based on the analysis of water samples in different landscape zones. Such export from urbanized landscapes has been shown to contribute little to the total export of biogens in these basins. The volume of biogens of diffuse origin considerably exceeds that of biogens carried out by wastewater. However, this relationship may change for large rivers and reservoirs since river water carrying diffuse biogens mostly moves for a long time before it reaches the main river partially self-purified, whereas wastewater biogens mainly directly flow into large rivers.
The article describes the Ili River hydrological regime, provides an insight into multiyear and intra-annual changes in the discharge in the Ili delta head, given natural water flow versus water flow regulation. It shows the spatial distribution and re-distribution of runoff between delta watercourses and estimates the degree of delta submergence during floods. The article considers the findings in the studies of the water regulation function of the delta depending on forest coverage and offer projections related to further possible hydrological and morphological changes in the Ili delta.
For 11 large river basins (the Rhine, Tagus, Ganges, Lena, Upper Yellow, Upper Yangtze, Niger, Mackenzie, Upper Mississippi, Upper Amazon and Darling) located on different continents under a wide variety of natural conditions, series of annual river runoff were calculated by means of the land surface model SWAP for the period of 1962–2099. For the historical (base) period (1962–2005), meteorological forcing data were taken from the global WATCH data set. For the projection period (2006–2099), the results of simulations from five Atmosphere and Ocean General Circulation Models (AOGCMs: HadGEM2-ES, IPSL-CM5A -LR, MIROC-ESM-CHEM, GFDL-ESM2M, and NorESM1-M) obtained for four climate change scenarios of the RCP-family were applied. The obtained series of annual runoff for each river basin were used to calculate climatic values and standard deviations of annual runoff for four climatic periods (1962–2005, 2006–2035, 2036–2065 and 2066–2099), which were then averaged over all AOGCMs and RCP-scenarios and used to construct distribution functions of annual runoff (for each river basin and climatic period) approximated by the lognormal distribution function of random variables. The constructed annual runoff distribution functions were applied for estimating the probabilities of occurrence of extremely high and extremely low values of annual runoff for each river and climatic period.
A number of requirements for sediment transport formulas are considered for using in mathematical and physical models of alluvial channels. Some formulas (Bagnold, Petrov, Kopaliani) are analyzed and compared. It is demonstrated that the universal bed load transport formula should implicitly contain the Froude number. At the same time, the dependence of bed load discharge on the hydraulic resistance coefficient and the non-moving flow velocity increases the calculation error. However, these parameters, must be taken into account in simulating bed deformations for non-uniform sediments.
The study focuses on the specific features of the justice dealing with the results of measuring the characteristics of safety and quality of production, works, or services. It is shown that the error (uncertainty) that appears in such situations is a measure of data scatter and a source of legal uncertainty, which causes a risk of judicial errors. The level of such risk increases with increasing demands of economy to the standardization of the ever-decreasing values of characteristics evaluated with higher uncertainty. The study shows that a necessary condition for the rule of law in such cases is the risk-oriented approach to resolving arbitration cases.
Projected changes in river runoff due to possible climate change during the 21st century were simulated with making use of a physically-based land surface model SWAP and meteorological projections simulated by five Global Climate Models (GCMs) for each of four RCP scenarios. The Northern Dvina, Indigirka, and Taz river basins were used in the study. For each basin, 20 projections of changes in climatic river runoff were obtained for three climatic periods of the 21st century. The projected changes in climatic river runoff were analyzed together with the projected changes in climatic precipitation, incoming shortwave and longwave radiation, and evapotranspiration. The obtained hydrological projections were used to estimate their uncertainties resulting from the application of different GCMs and RCP scenarios.
The formation and distribution of river flow characteristics in the Don basin have been catholically analyzed, depending on the present-day climatic conditions in the central European Russia. The recent global warming is shown to have resulted in a change in the river flow formation conditions and water resources, as well as in a substantial transformation of the river water regime in the basin. The river water and groundwater chemistry in the basin in 1990–2015 has been considered at the main observation points. The dynamics of river water quality pollution level during the long period is presented. Water pollution characteristics, which make it possible to identify the water quality class and pollution level, have been used to give a generalized estimate of the water quality in the chosen river areas.
The space–time variations in the Oka basin water chemistry have been considered. The specific features in the river water and groundwater pollution along the Oka channel and its main tributaries have been determined. The distribution of the main pollutants and their sources along the river areas has been identified. Schematic maps of the hydrochemical flow and time variations in the main pollutants have been compiled. The main types of river aquatic organisms have been characterized, and their dynamics has been described depending on the level of river water pollution.
This paper presents the first thorough generalization of the recent change in annual peak runoff magnitude, variation, and timing in the North Caucasus. The patterns of the observed changes in the characteristics of peak runoff in the late XX–early XXI century are rather complicated, but show consistent structures over the territory. The main possible climatic drivers of the revealed changes in the tendencies are discussed, as well as the role of the observed change in the peak runoff in the context of flood danger in the region. The main peak runoff characteristics are re-evaluated for the first time for the whole region of the North Caucasus since the Volume of USSR Surface Water Resources series on this region issued in 1973.
The article discusses the role of sulfite-reducing clostridia in methane and hydrogen oxide formation in bottom sediments. The examined materials have been accumulated in the course of expeditions carried out at 25 water objects and streams of the subarid zone of the Southern ETR with different mineralization and the degree of anthropogenic stress, as well as via an experiment aimed at detection of the ability of sulfite-reducing clostridia to produce reduced gases. In the majority of samples of bottom sediments in water objects of the Southern ETR, including mud sediments of lakes that are used for therapeutic purposes, the amount of sulfite-reducing clostridia exceeds the normative levels by an order of magnitude. The maximum abundance (106–107 CFU/g) was recorded in the nearshore zone of the southeastern part of the Taganrog Bay, thus implying fecal pollution. As a rule, the highest abundance is restricted to the higher (0–2 and/or 2–5 cm) layers. A close relationship was found to exist between the concentrations of methane and hydrogen sulfide, as well as the abundance of sulfite-reducing clostridia in the bottom sediments. The results of the laboratory experiment imply the ability of sulfite-reducing clostridia to produce methane and hydrogen sulfide. It is supposed that sulfite-reducing clostridia, as well as methanogens and sulfate-reducing microorganisms, participate in the generation of methane and hydrogen sulfide in situ in bottom sediments and therapeutic muds.
The applicability of the previously developed technique for simulating the runoff hydrographs of northern rivers to the Ob River, which has largest basin area among Russian rivers and flows under severe conditions of the Western Siberia, has been investigated. The technique is based on a land surface model SWAP (Soil–Water–Atmosphere–Plants) with input data based on global data sets on land surface parameters and meteorological forcing data derived from observations at meteorological stations situated within the Ob basin. The uncertainty of Ob runoff has been evaluated. The potentialities of SWAP model in reproducing the long-term dynamics of the mean snow water storage in the Ob–Irtysh basin have also been studied.
Chemistry variations in the rivers are key indexes of weathering mechanisms. This paper presents a chemical variation examination of water samples acquired from 11 Taiwanese rivers to assess the relationships between chemical and physical weathering based on the variations of major dissolved ions. One salient relationship is illustrated by the discovery that huge amount of water discharge is the vital factor associated with the dilution of ion concentrations. The total dissolved solid discharge from the investigated rivers is approximately 10 Mt/yr, prominently, 60% of the dissolved ions are attributed to the outcrop of silicate. Finally, it is noted that only 4% of the total dissolved solid discharge is observed in the total delivered material in river water, which is practical with the characteristics of weathering mechanism, most of the materials transported into river water undergo little chemical weathering.
The short-term, seasonal, and interannual variations in the abundance and species composition of the Black Sea metazoan microzooplankton have been analyzed at the open coastal area and the mouth of Sevastopol Bay in 2009–2015. Whatever the time scale, the temperature factor played the main role in abundance variations. In particular, the coincidence of two-year periodicities in the sum of active temperatures and the abundance of copepod-invader Oithona davisae at the year-to-year scale have been demonstrated. Variations of wind speed and direction have been shown to be significant factors in the short-term variations of microzooplankton abundance. The general species diversity of the community was found to depend significantly on the abundance of the invader species.
In the present study, long-term monitoring data were collected from the study area of the Kaoping River Basin, Taiwan. Specifically, data from six selected groundwater level stations and six precipitation stations in the vicinity were collected between 1997 and 2014. The standardized groundwater index (SGI) and standardized precipitation index (SPI) were then used to analyze the region’s drought characteristics. The results revealed that continuous droughts occurred in the river basin from 2003 to 2005. The trend for 2014 further indicated that the drought situation in the region would worsen in terms of severity. After calculation and analysis of the cross correlation function between the SGI and the SPI, a positive correlation was identified between the maximum cross correlation function (q max) and the duration of the drought event. The larger the q max value, the longer was the duration of the drought, and vice versa. The study also found that the q max value varied with geographical locations: it was smaller for the various measuring stations located along the Qishan and Laonong rivers, but it tended to be larger for stations located beyond the Ailiao River. Thus, this study reckoned that if a drought event were to occur in the latter area in the future, its duration would be relatively longer. The findings of this study could also serve as future reference for the water resources management of the Kaoping River Basin.
Four global climate scenarios of the family “Special Report on Emissions Scenarios” of the Intergovernmental Panel on Climate Change, which correspond to the specified scenarios of economic, technological, political, and demographic development of the human civilization were used to develop forecast versions of meteorological forcing data dynamics in the Ob–Irtysh basin in the XXI century. The obtained data were used to simulate the variants of possible changes in water balance components in this river basin up to mid-XXI century. The calculation technique is based on the use of land surface model SWAP and a generator of climate scenarios MAGICC/SCENGEN. The changes in the annual runoff of the Ob, governed by possible global climate change are compared with its natural variations caused by weather noise.