Large Watercourses Research Articles

Estimating and Analyzing The Stability of Brazilian Gnss Stations for Tectonic Studies

The detailed study of stresses and strains is fundamental for geophysical and geodetic studies, enabling the development of plate motion models, geodynamic processes and several proposals. GNSS positioning has been used to estimate these stresses and strains. However, for the accuracy required, it is necessary a rigorous assessment of the behavior of GNSS stations and their position time series. This paper aims to analyze the influence of the different types of geodetic monuments present in the Brazilian GNSS Continuous Monitoring Network by estimating and characterizing noise in the time series and investigating variables that can affect the stability of the stations to establish criteria for using this data in tectonic and geodynamic studies. The evaluation of 119 GNSS stations throughout Brazil indicates the significant presence of random walk noise in some of these stations, detected by analyzing the magnitude of the noise and the spectral index. It was found that the stations with unstable monuments have been observed for at least eight years and are mostly in coastal areas or under the influence of large watercourses.

Spatio-Temporal Variability of Water Quality in the Middle Danube—The Influence of Air Temperature and Discharge

Large watercourses are characterised by significant spatial and temporal changes in water quality due to both natural and anthropogenic impacts. The paper analyses changes in the Danube’s spatial and seasonal water quality in its middle part at five monitoring stations for the period 2018–2022. Examined water quality parameters include oxygen saturation (Os), ammonium (N-NH4), pH, 5-day biochemical oxygen demand (BOD), nitrate nitrogen (N-NO3), orthophosphates (P-PO4), suspended solids (SS), electrical conductivity (EC), and water temperature (WT). Furthermore, the analysis took into account the influence of two additional factors: air temperature (AT) and discharge (D). Throughout the entire period under study, all parameters were characterised by low concentration values, which met the environmental objective of good ecological status. The use of multivariate statistical methods allowed for the identification of EC, N-NH4, WT, Os, SS, and N-NO3 as determining the greatest spatio-seasonal variability of water quality in a selected section of the Danube. Regression models determined WT, EC and nitrogen nitrate changes as depending on AT, flow, and exposure time. Knowing models not only gives a better understanding of the dynamics of changes in water quality in the stretch of the Danube under study but potentially allows the prediction of these parameters based on easily measurable environmental variables.

MONITORING OF SEDIMENT POLLUTION FOR VARIOUS WATER BODIES IN THE UPPER VOLGA REGION

The problem of water body pollution with heavy metals is still relevant. From the viewpoint of technogenic load, the most hazardous pollutants are elements Hg, Cd, Zn, Pb, Cu, Cr, Co, Ni, Fe, Mn, and As. To systematize the research, the objects of different hierarchical levels were identified. Based on many years of experimental work, contamination of sediments with heavy metals was assessed for the Upper Volga system, i.e., Lake Seliger, an unregulated section of the Upper Volga, Ivankovskoe and Uglichskoe reservoirs. The largest taxon is the basin of the reservoir with the adjoining watershed area with cities and towns located on it, tributaries of various orders, smaller elements of natural and natural-technogenic relief. Urban and settlement agglomerations located on the coasts of reservoirs and unregulated areas or within watersheds are smaller in area, but no less significant in their role in water body pollution. Small rivers contribute to pollution/purification, which can contribute to the flow of both clean and polluted silty material into large watercourses. Different areal and temporal survey modes are offered for taxa of different hierarchy. The practical results of studies of the content in sediments of the listed objects of heavy metals – Cr, Co, Ni, Zn, Cd, Pb, As, Fe and Mn are presented. Described or provided references to the methods used in the experiments. The general picture of pollution is presented and the tendencies of its change in space and time are noted.

Mapping Specific Constituents of an Ochre-Coloured Watercourse Based on In Situ and Airborne Hyperspectral Remote Sensing Data

It is a well-known fact that water bodies are crucial for human life, ecosystems and biodiversity. Therefore, they are subject to regulatory monitoring in terms of water quality. However, land-use intensification, such as open-cast mining activities, can have a direct impact on water quality. Unfortunately, in situ measurements of water quality parameters are spatially limited, costly and time-consuming, which is why we proposed a combination of hyperspectral data, in situ data and simple regression models in this study to estimate and thus monitor various water quality parameters. We focused on the variables of total iron, ferrous iron, ferric iron, sulphate and chlorophyll-a. Unlike other studies, we used a combination of airborne hyperspectral and RGB data to ensure a very high spatial resolution of the data. To investigate the potential of our approach, we conducted simultaneous in situ measurements and airborne hyperspectral/RGB aircraft campaigns at different sites of the Spree River in Germany to monitor the impact of pyrite weathering on water bodies after open-cast mining activities. Appropriate regression models were developed to estimate the five variables mentioned above. The model with the best performance for each variable gave a coefficient of determination R2 of 64% to 79%. This clearly shows the potential of airborne hyperspectral/RGB data for water quality monitoring. In further investigations, we focused on the use of machine learning techniques, as well as transferability to other water bodies. The approach presented here has great potential for the development of a monitoring method for the continuous monitoring of still waters and large watercourses, especially given the freely available space-based hyperspectral missions via EnMAP.

ЭКОЛОГИЧЕСКОЕ СОСТОЯНИЕ Р. ЗИМНЯЯ ЗОЛОТИЦА В ЗОНЕ ОПОСРЕДОВАННОГО ВОЗДЕЙСТВИЯ ГОРНО-ОБОГАТИТЕЛЬНОГО КОМБИНАТА

Introduction. Medium rivers play an important role in the environment: draining the large catchment area, they determine the water content and quality as well as hydrological conditions in large watercourses. The joint effect of such factors as the small size of these rivers and human activity disturbs the balance of ecosystems, thus increasing the vulnerability of the rivers. Significant negative changes tend to occur faster and stronger in river valleys. Our aim was to study the ecological state of the Zimnyaya Zolotitsa River ecosystem in the area of the indirect impact of wastewater from the mining and processing plant in the Lomonosov diamond field. Methods. In the course of the study, we used the standard methods for determining the main biogenic elements and oil hydrocarbons. Results. The paper provides data on the content of biogenic elements in water, pH value, dissolved oxygen and mineralization, as well as the content of oil hydrocarbons in water and bottom sediments. Conclusion. As a result of the studies, it was found that in the summer observation period, the concentrations of phosphorus, nitrogen and silicon salts as well as oil hydrocarbons did not exceed the maximum allowable values for fishery reservoirs.

Epigravettian in Eastern Bohemia

Until recently the Epigravettian occupation of Bohemia has remained relatively unknown. After re-evaluating an old assemblage from Ostroměř (first published by S. Vencl like the Ostroměř group of Late Palaeolithic) we can assign it to the Epigravettian cultural complex. A newly excavated site in Slatinky near Jičín probably dates to the Late Epigravettian, but only the specialised part of the site related to the production of microblades was excavated. Eastern Bohemian sites fit into the general form and framework of the Epigravettian stone industries with a dominance of short scrapers (often on flake) and a lower incidence of burins. Geographically, sites can be placed mainly in lower altitudes (256–400 m asl), while their number decreases with increasing altitude. There is no link to large watercourses, and on the contrary, the main ones seem to be rather smaller watercourses (sites are located 100–300 m from them) while at the same time it is clear that there was an effort made to search for places protected against adverse climatic phenomena. At the moment we can first provide a deeper insight into the Epigravettian site structure in Eastern Bohemia.

Influence of Hydrodynamic Regimes on Mixing of Waters of Confluent Rivers

At present, a significant weakening of the intensity of transverse mixing at the confluence of large rivers, which is observed in a number of cases, is widely discussed. Since the observed features of the confluence of large watercourses are not only of research interest but also of significant economic importance associated with the characteristics of water management at these water bodies, a large number of works are devoted to their study. Water resources management requires measures for the organization of water use which can be rational only under the understanding of processes occurring in water basins. To explain the phenomenon of suppression of the transverse mixing, which is interesting and important from the point of view of ecology, a wide range of hypotheses is proposed, up to the negation of turbulence in rivers. One of the possible mechanisms for explaining the suppression of transversal mixing can be the presence of transverse circulation manifesting itself as Prandtl’s secondary flows of the second kind. The characteristic velocity of these circulation flows is very small and difficult to measure directly by instruments; however, in our opinion, they can significantly complicate the transverse mixing at the confluence. The proposed hypothesis is tested in computational experiments in the framework of the three-dimensional formulation for dimensions of a real water object at the mouth of the Vishera River where it meets the Kama. Calculations demonstrate that, at sufficiently large flow rates, the two waters practically do not mix in the horizontal direction throughout the depth over long distances from the confluence. It has been found that a two-vortex flow is formed downstream the confluence, which just attenuates the mixing; the fluid motion in the vortices is such that, near the free surface, the fluid moves from the banks to the middle of the riverbed.

Long-term modelling of fluvial systems at the watershed scale: Examples from three case studies

To date, many numerical approaches are available in studying water flow and sediment dynamics along rivers from the reach to the watershed scale, based on various simplifications. The aim of the present research is to demonstrate how the so-called “morphodynamic quasi-equilibrium hypothesis” is effective in modelling riverine landscape morphodynamics evolution at the watershed scale, focussing on the long-term changes of longitudinal profile and bed grainsize composition of large alluvial rivers. A lumped 0-D, two-reach, two-grainsize model based on the Local Uniform Flow hypothesis and originally developed for reproducing fluvial changes at the historical time-scale, has been applied to three large watercourses to reproduce their long-term evolution, performing a sensitivity analysis based on the present conditions. Three morphometric parameters were analysed, aiming to describe the evolution of the longitudinal profile (concavity and aggrading) and the grainsize composition of the river bed (fining). Though the 0-D approach does not allow for a spatial distribution of the input parameters, namely the liquid and solid discharge, the modelling outcomes show reasonably good qualitative trends. At the scale of analysis (centuries to millennia) and for the chosen large sedimentary systems (thousands of kilometres long), which show high inertia to geomorphological changes likely owing to their longitudinal scale, the model can be helpful in detecting where the present conditions reflect a big disturbance to the “natural” trend. This initial detection method can provide additional insights in evaluating the capability of actual rivers to respond to the present external forcing, eventually reaching a quasi-stable configuration.

Rheophilic Macrozoobenthos Communities of the Southern Himalayas

The regional diversity of rheophilic macrozoobenthos communities in North India and Nepal has been studied based on material collected from 450 original quantitative samples in 160 small and large watercourses within the altitude gradient of 200–2800 m above sea level. A total of 22 types of communities from 5 classes are identified: rhithral (hard substrates at rapid flow), crenal (mosaic substrates of small watercourses), pelal (soft sediments), phytal (macrophyte beds), and rhipal (mosaic substrates of river bank edge). Many of the community types occur in different altitudinal temperature zones, but their composition and structure vary as the study proceeds further into the mountains. It has been shown that oriental tropical taxa dominate the lowland tropical zone, endemic subtropical taxa dominate the mid-mountain zone, and Palearctic (Central Asian) groups dominate the high-mountain zone. The key features of tropical rheophilic communities are described in comparison with temperate zone communities. The application of the Ramensky–Grime classification of ecological strategies to macrozoobenthos communities is discussed.

Influence of hydrodynamic regimes on mixing of waters of confluent rivers

At present, a significant weakening of the intensity of transverse mixing at the confluence of large rivers, which is observed in a number of cases, is widely discussed. Since the observed features of the confluence of large watercourses are not only of research interest, but also of significant economic importance associated with the characteristics of water management at these water bodies, a large number of works are devoted to their study. To explain this interesting phenomenon important from the point of view of ecology, a wide range of hypotheses is proposed, up to the negation of turbulence in rivers. One of the possible mechanisms for explaining the “suppression” of transversal mixing can be the presence of transverse circulation, manifested as Prandtl’s secondary flows of second kind. The characteristic velocity of these circulation flows is very small and difficult to measure directly, but they can significantly complicate the transverse mixing of the flow. In the present work, this hypothesis is tested on the basis of computational experiments in a three-dimensional formulation, performed for the configuration modeling of the Kama river at its confluence with the Vishera river. Calculations have shown that, at sufficiently large flow rates the two waters practically do not mix in the horizontal direction throughout the depth over long distances from the confluence. The reason for the weakening of transversal mixing is the formation of a two-vortex flow in the cross section below the confluence place. The fluid motion in vortices is such that, near the free surface, the fluid moves from the banks to the middle of the river.

Putting bryophyte communities in the map: A case study on prioritizing monitoring of human pressure in riverscapes

Freshwater ecosystems support biological communities with high species richness and conservation interest. However, these ecosystems are highly altered by human intervention and threatened worldwide, making them a priority in conservation planning and biodiversity monitoring. Bryophytes, including several conservation-interest taxa, are recognized indicators of ecological status in freshwaters. We aimed to develop a framework for designing monitoring networks to detect trends in aquatic and semi-aquatic bryophyte communities, prioritizing high-conservation interest communities in different contexts of human pressure (specifically, resulting from the intersection of two criteria: (i) protection status and (ii) presence of a potential impact area).The framework consists of three steps: (1) Spatial modelling of biodiversity; (2) Spatial conservation prioritization; and (3) Model-assisted monitoring network design. Community-level modelling was used to model the distribution of the main bryophyte assemblages in the study area. A conservation prioritization software was utilized to identify areas with high conservation value. The monitoring network was designed using stratified random sampling and unequal-probability sampling techniques to target high conservation value sites distributed across different contexts of human pressure.We have identified four distinct community types, each characterized both by a small group of common and dominant species, and by small group of rarer, conservation-interest species. This typification of four species assemblages occurring in the study area, also highlighted those with potentially higher conservation-interest. The most valuable areas for the conservation of aquatic and semi-aquatic bryophyte communities coincide with specific environmental zones: mountainous areas in Lusitania, large watercourses in the Mediterranean North and some locations in the Mediterranean Mountains. Finally, we obtained a potential monitoring network consisting of 64 monitoring points, unequally distributed across different contexts of human pressure, privileging locations with higher conservation value.The framework presented here illustrates the potential of combining biodiversity modelling, spatial conservation prioritization and monitoring design in the development of monitoring networks. Namely, this framework allowed us to counter data deficiencies, to identify high priority areas to monitor and to design a monitoring network considering different scenarios of human pressure at a regional scale.This framework can also be valuable for conservation efforts as an approach to monitoring conservation-interest biodiversity features in anthropogenically modified riverscapes, which present different degrees of human pressure and the cumulative effects of these different impact elements. Moreover, this approach allows for the comprehensive monitoring of biodiversity values important for management at the national and regional levels. In addition, this framework is one of the first efforts in the development of monitoring networks that target aquatic and semi-aquatic bryophyte communities, a long-neglected plant group of high ecological and conservation importance in freshwater ecosystems.

Macrospatial Analysis of Early Scythian Fortified Settlements in the Right-Bank of Ukraine

Abstract The macrospatial analysis of fortified settlements in the right-bank of Ukraine allows for observations of a few regularities related to the location of sites along the rivers and watersheds. ‘Land’ settlements, e.g. Yakushyntsi or Mlynok, may have connected sites located along large watercourses, e.g. Trakhtemyriv, Rudkivtsi, which specialised in trade with the Greeks.

Modeling of River Width Variations Based on Hydrological, Morphological, and Biological Dynamics

AbstractOne-dimensional (1D) models can be applied, for engineering purposes, to long-term and large-scale morphodynamic simulations of entire river systems only if appropriate simplifications are introduced. This paper proposes an improvement of an existing simplified 1D model based on the local uniform flow hypothesis, coupled with a synthetic description of the transverse profile, which provides the active river width by analyzing the total and the vegetated widths of a watercourse, with assumed variables of the water flow. The overall density of the riparian vegetation, expressed in terms of biological carrying capacity, is predicted as a function of the local climate and some stresses due to interaction between hydrology, morphology, and biology. The constitutive equations have been deduced and the relevant parameters have been calibrated and validated against various hydrological and geometrical data, taken by satellite imagery covering two large watercourses located in tropical and subtropical area...

Local influence of south-east France topography and land cover on the distribution and characteristics of intense rainfall cells

The Greater Lyon area is strongly built up, grouping 58 communes and a population of 1.3 million in approximately 500 km2. The flood risk is high as the territory is crossed by two large watercourses and by streams with torrential flow. Floods may also occur in case of runoff after heavy rain or because of a rise in the groundwater level. The whole territory can therefore be affected, and it is necessary to possess in-depth knowledge of the depths, causes and consequences of rainfall to achieve better management of precipitation in urban areas and to reduce flood risk. This study is thus focused on the effects of topography and land cover on the occurrence, intensity and area of intense rainfall cells. They are identified by local radar meteorology (C-band) combined with a processing algorithm running in a geographic information system (GIS) which identified 109,979 weighted mean centres of them in a sample composed of the five most intense rainfall events from 2001 to 2005. First, analysis of spatial distribution at an overall scale is performed, completed by study at a more detailed scale. The results show that the distribution of high-intensity rainfall cells is spread in cluster form. Subsequently, comparison of intense rainfall cells with the topography shows that cell density is closely linked with land slope but that, above all, urbanised zones feature nearly twice as many rainfall cells as farm land or forest, with more intense intensity.

A phytometer study evaluating the effects of stream restoration on riparian vegetation

AbstractChannelization of streams and rivers to facilitate timber floating has cut off riparian zones from the channel, covered them with coarse sediment and resulted in less flooding. Restoration measures aiming to counteract these impacts are expected to create a higher, more natural hydrological variability and enhance site quality for riparian plants. In a long‐term field experiment, we evaluated the effect of flooding regime on riparian plant performance by measuring survival and biomass increment of two transplanted phytometer species, a grass (Molinia caerulea) and a forb (Filipendula ulmaria). We also analysed the number and duration of flooding events in channelized and restored stream and river reaches with an indirect method using diurnal temperature oscillation. We found that flow duration was higher, with significantly more flood events at restored compared with channelized sites in medium‐sized and large watercourses, particularly during the summer months. Phytometer performance was better at restored sites, and it was positively correlated with duration and frequency of summer flooding, indicating that more but less intense floods after restoration improved site conditions for phytometer growth. This may not only result from an increased heterogeneity in channel morphology caused by the return of boulders but can probably also be attributed to a reduced current velocity at restored sites. Flood variables were more often correlated with other abiotic variables at restored than at channelized sites, which points to an increased land–water connectivity as a result of restoration. Copyright © 2015 John Wiley & Sons, Ltd.

Fractal Dimension of the Hydrographic Pattern of Three Large Rivers in the Mediterranean Morphoclimatic System: Geomorphologic Interpretation of Russian (USA), Ebro (Spain) and Volturno (Italy) Fluvial Geometry

By applying fractal geometry analysis to the drainage network of three large watercourses in America and Europe, we have calculated for the first time their fractal dimension. The aim is to interpret the geomorphologic characteristics to better understand the morphoevolutionary processes of these fluvial morphotypes; to identify and discriminate geomorphic phenomena responsible for any difference or convergence of a fractal dimension; to classify hydrographic patterns, and finally to compare the fractal degree with some geomorphic-quantitative indexes. The analyzed catchment of Russian (California, USA), Ebro (Spain), and Volturno (Italy) rivers are situated in Mediterranean-climate regions sensu Koppen, but with different geologic context and tectonic styles. Results show fractal dimensions ranging from 1.08 to 1.50. According to the geological setting and geomorphic indexes of these basins, the lower fractal degree indicates a prevailing tectonics, active or not, while the higher degree indicates the stronger erosion processes on inherited landscapes.

Establishing physico-chemical reference conditions in Mediterranean streams according to the European Water Framework Directive

Type-specific physico-chemical reference conditions are required for the assessment of ecological status in the Water Framework Directive context, similarly to the biological and hydro-morphological elements. This directive emphasises that natural variability of quality elements in high status (reference condition) needs to be quantified. Mediterranean streams often present a marked seasonal pattern in hydrological, biological and geochemical processes which could affect physico-chemical reference conditions. This study establishes general physico-chemical reference conditions (oxygenation, nutrient, salinity and acidification conditions) for different Mediterranean stream types. 116 potential reference sites located in 23 Mediterranean catchments in Spain were sampled in spring, summer and autumn in 2003. All sites were subjected to a screening method for the selection of reference sites in Mediterranean streams (Mediterranean Reference Criteria) and classified using a pre-established stream typology that establishes five different stream types (temporary streams, evaporite-calcareous at medium altitude, siliceous headwaters, calcareous headwaters and large watercourses). Reference conditions (reference value and reference threshold equivalents to high-good class boundary) were calculated using two different methods according to the availability of reference sites: the reference site 75th percentile approach of all reference sites and the 25th percentile of the population approach. The majority of the studied potential reference sites (76 out of 116) were selected as reference sites. Regarding type-specific reference conditions, only siliceous headwaters could be considered different from the rest of stream types because lower conductivity and pH. All reference stream types presented seasonal differences as regards some parameters, except for temporary streams due to the high natural variation of this stream type. For those parameters which presented seasonal differences in a specific stream type, the least restrictive values were proposed as reference conditions.

The Decision Analysis Interview Approach in the Collaborative Management of a Large Regulated Water Course

There are always conflicting goals in the management of large water courses. However, by involving stakeholders actively in the planning and decision-making processes, it is possible to work together toward commonly acceptable solutions. In this article, we describe how we applied interactive multicriteria decision analysis (MCDA) in a collaborative process which aimed at an ecologically, socially, and economically sustainable water course regulation policy. The stakeholders' opinions about the alternative regulation schemes and the relative importance of their impacts were elicited with the HIPRE software. Altogether, 20 personal interactive decision analysis interviews (DAIs) were carried out with the stakeholders. Our experience suggests that the DAIs can considerably improve the quality and efficiency of the collaborative planning process. By improving communication and understanding of the decision situation in the steering group, the approach helped to develop a consensus solution in a case having strong conflicts of interest. In order to gain the full benefits of the MCDA approach, interactive preference elicitation is vital. It is also essential to integrate the approach tightly into the planning and decision-making process. The project's home pages are available to the public at http://www.paijanne.hut.fi/.

Defining criteria to select reference sites in Mediterranean streams

The European Water Framework Directive establishes the need to define stream type-specific reference conditions to identify “high ecological status”. Methods for selecting reference sites using a priori criteria have been proposed by many authors. A review of these criteria revealed that the most relevant criteria for streams and rivers were those related to riparian vegetation, diffuse and point sources of pollution, river morphology and hydrological conditions and regulation. In this work, we propose 20 criteria that reflect the characteristics of Mediterranean streams and their most frequent disturbances for the selection of reference sites in Mediterranean streams in Spain. We studied 162 sites located in 33 Mediterranean basins belonging to five stream types. Of the locations, 57% were selected as a priori reference sites by having applied the proposed criteria. Reference sites were identified for all stream types except for “large watercourses” which includes the lower reaches of some rivers in this study area. This a priori selection of reference sites was subjected to validation using the macroinvertebrate community by applying of an IBMWP threshold, which is considered to be an indicator of undisturbed sites in Mediterranean streams. This approach determined that whole of this selection (100%) could be considered valid reference sites. Furthermore, we identified differences in the reference conditions for each stream type on the basis of macroinvertebrate assemblage composition.

Concordance between ecotypes and macroinvertebrate assemblages in Mediterranean streams

Summary1. According to the guidelines of the European Water Framework Directive, assessment of the ecological quality of streams and rivers should be based on ecotype‐specific reference conditions. Here, we assess two approaches for establishing a typology for Mediterranean streams: a top‐down approach using environmental variables and bottom‐up approach using macroinvertebrate assemblages.2. Classification of 162 sites using environmental variables resulted in five ecotypes: (i) temporary streams; (ii) evaporite calcareous streams at medium altitude; (iii) siliceous headwater streams at high altitude; (iv) calcareous headwater streams at medium to high altitude and (v) large watercourses.3. Macroinvertebrate communities of minimally disturbed sites (n = 105), grouped using UPGMA (unweighted pair‐group method using arithmetic averages) on Bray–Curtis similarities, were used to validate four of the five ecotypes obtained using environmental variables; ecotype 5, large watercourses, was not included as this group had no reference sites.4. Analysis of similarities (anosim) showed that macroinvertebrate assemblage composition differed among three of the four ecotypes, resulting in differences between the bottom‐up and top‐down classification approaches. Siliceous streams were clearly different from the other three ecotypes, evaporite and calcareous ecotypes did not show large differences in macroinvertebrate assemblages and temporary streams formed a very heterogeneous group because of large variability in salinity and hydrology.5. This study showed that stream classification schemes based on environmental variables need to be validated using biological variables. Furthermore, our findings indicate that special attention should be given to the classification of temporary streams.