Non-regulated Rivers Research Articles

Characteristics of Cyanobacteria at Different Stages of Existence of the Kyiv Reservoir

The paper deals with the patterns of Cyanobacteria long-term succession at different stages of existence of the Kyiv Reservoir. The main ecological factors responsible for Cyanobacteria succession include current velocity, hydromorphological characteristics of the reservoir, the content of inorganic nitrogen (primarily of ammonium) and phosphorus, ΣN : P ratio, global climate changes, and the competition with higher aquatic plants in the shallow water zone. The trophic state of the hydroecosystem changed from mesotrophic (at the stage of the non-regulated river) to eutrophic (at the present time) depending on the intensity of Cyanobacteria development. With possible further deterioration of water quality, possible climate changes with an increase in water temperature within the range of even 1-2°C, the intensity of Cyanobacteria development will increase, especially in the pelagic zone of the reservoir, where they have practically no natural biological competitors.

USING THERMAL AND RGB UAV IMAGERY TO MEASURE SURFACE FLOW VELOCITIES OF RIVERS

Abstract. This study assesses the suitability to use RGB and thermal infrared imagery acquired from an UAV to measure surface flow velocities of rivers. The reach of a medium-scale river in Hungary is investigated. Image sequences with a frame rate of 2 Hz were captured with two sensors, a RGB and an uncooled thermal camera, at a flying height that ensures the visibility of both shores. The interior geometry of both cameras were calibrated with an in-house designed target field. The image sequences were automatically co-registered to account for UAV movements during the image acquisition. The TIR data was processed to keep loss-free image information solely in the water area and to enhance the signal to noise ratio. Image velocimetry with PIV applied to the TIR data and PTV applied to the RGB data was utilised to retrieve surface flow velocities. Comparison between RGB and TIR data reveal an average deviation of about 0.01 m/s. Future studies are needed to evaluate the transferability to other non-regulated river reaches.

Migrations of Young Fish in Regulated Rivers: Effects of Ecological Filters (Review)

Unlike in nonregulated rivers, new ecological filters are formed in artificial reservoirs: structures (gradient zones between biotopes) which affect the behavior and distribution of juvenile fish and therefore change parameters of the downstream migration. One distinct feature of such filters is their selective effect on different species and age groups of migrants when they pass boundaries between biotopes. The differential transparency of boundaries considerably affects the composition of migrants and dispersal of juvenile fish over biotopes. These suggestions are confirmed by the data of long-term studies on the downstream migration of juvenile Cyprinidae and Percidae in several reservoirs in Eurasia: Sheksna (Sheksna River), Ivankovo (Volga River), Kapchagay (Ili River), and Sarez (Murghab River) Reservoirs. The formation of ecological filters is shown in the zone of wedging-out backwaters (lotic–limnetic transformation) and in the zone between the littoral (resident) and pelagic (migratory) biotopes in the reservoir and in the near-dam broads. Emigration of juveniles from the reservoir depends on the location of the water intake (deep-water or surface) and overlapping of water intake zones with those of the spatial distribution of juvenile fish. The different selectivity of water intake sites of the hydroelectric power station located not far from each other and of a navigation lock forms different (in species and age composition) complexes of emigrants. The mechanisms and consequences of functioning ecological filters and ecological barriers are considered.

Vegetation encroachment ratios in regulated and non-regulated Mediterranean rivers (Spain): An exploratory overview

Vegetation encroachment is an expected response of rivers to a decrease in their flow variability and flood magnitude and frequency. It frequently occurs together with channel narrowing and a decrease in braiding, both of which are likely associated with different human alterations but most frequently with river damming. Vegetation encroachment ratios display a wide range of values according to local hydrologic and geomorphic contexts and dam operation management, and thus, they are very site specific. As vegetation interacts with fluvial processes, understanding the mechanisms that promote encroachment is important for predicting river trends and designing proper management and restoration measures. Our research aimed to explore the causal relationship between flow regulation and vegetation encroachment in Mediterranean rivers in Spain. We quantified vegetation encroachment and channel changes over the last 50 years in 13 river reaches, 5 of which corresponded to non-regulated rivers and 8 of which were located in rivers regulated by large dams. We analysed aerial orthophotographs from 1956, 1977 and 2011 or later up to 2014, according to image availability. We considered 1956 conditions as a reference and quantified ratios of changes in riparian vegetation cover, active channel width and braiding index over two periods, 1956–1977 and 1978–2011. We quantified the changes in the flow regime and clustered rivers according to their hydrological pattern, looking for potential hydrological drivers of the observed changes over time.Vegetation encroachment, channel narrowing and braiding decreases occurred in all the studied rivers. Significant differences in annual ratios between the studied periods were found for both vegetation encroachment and channel narrowing, but no statistically significant differences were found between the regulated and non-regulated rivers or between the hydrological river groups previously clustered by flow variables. After discussing existing literature, we suggest a multi-scale approach to understanding river changes over time, encompassing larger historical perspectives. We hypothesize a generalized hydrologic decline since the beginning of the 20th century affecting rivers at the broad-regional scale would be overlapping the effects of land cover changes (i.e., renaturalization) at the catchment scale in reducing flood intensity and sediment supply. River damming would reinforce these patterns at river segment scale, in turn overlapping the influence of local geomorphic and ecological features. This hypothesis, which should be tested by further research, may explain the constancy of encroachment and channel narrowing regionally reported but with a wide variety of change ratios, determining converging trajectories of Iberian rivers that have also been found in other regions.

Selecting geomorphic variables for automatic river segmentation: Trade-offs between information gained and effort required

Identifying river segments with apparently distinct geomorphic characteristics but relatively homogeneous internal features may be critically helpful in designing network analysis for characterization, environmental assessment and river management. Automatic segmentation procedures using geographic tools and statistical methods provide objective and replicable results. In particular, multivariate procedures may be appropriated for different purposes such as coping with the multiple dimensionality of river systems. Although there is an increasing number of studies dealing with segmentation using different sets of morphological variables, the influence that the selected variables have on segmentation results is rarely assessed. In this context, we defined five combinations of frequently used geomorphic variables (i.e., channel slope, active channel width, valley bottom width, channel confinement and specific stream power), and compared the obtained segmentation results. We study the upper Esla River network, covering a total length of 294 km, with the largest two rivers regulated by large dams. Variables were measured at successive river sections 200 m apart. Five segmentation results were obtained in which we compared the number and characteristics of the segments, and the internal variability and the suitability of predicting river dynamics (i.e., occurrence of bare and vegetated gravel bars). The number of segments per kilometer of river and their average length were different among segmentations but varied much more across rivers than across segmentations. In general, segmentations including channel slope and active channel width performed better in predicting the occurrence of bare gravel bars than segmentations based on stream power or valley confinement. When splitting the initial data set into regulated and non-regulated segments, differences in predicting the occurrence of gravel bars were found, with better results in the case of non-regulated rivers. Channel slope and active channel width showed a reduced explanatory power for the regulated reaches. Finally, we conclude that primary geomorphic variables such as channel slope and active channel width were more efficient than secondary variables such as stream power, which may encompass more information but needed additional data and the use of empirical models, with greater effort and much uncertainty. In the case of regulated rivers, automatic segmentation including the affected variables (e.g., active channel width) may help in detecting differences in geomorphic sensitivity to river adjustments across the resulting segments downstream from the dams. Our results offer valuable insights into the selection of geomorphic variables for river segmentation analysis, in which trade-offs between the information gained and the effort required must be considered according to the respective research targets.

Effects of flow regulation in the life-cycles of a Mediterranean cyprinid species, the Iberian chub (Squalius carolitertii Doadrio, 1988)

Event Abstract Back to Event Effects of flow regulation in the life-cycles of a Mediterranean cyprinid species, the Iberian chub (Squalius carolitertii Doadrio, 1988) Carlos M. Alexandre1*, Teresa Ferreira2 and Pedro R. De Almeida3 1 Escola de Ciências e Tecnologia, Universidade de Évora, MARE - Centro de Ciências do Mar e do Ambiente, Portugal 2 CEF - Forestry Research Center, Portugal 3 Universidade de Évora, Departamento de Biologia, Escola de Ciências e Tecnologia, Portugal River regulation tends to modify flow patterns, causing a reduction of discharge variability and disturbing environmentally cued life cycles of fishes. The objective of this study was to assess the changes in some of the most important life-cycle patterns of a resident freshwater fish species, the Iberian chub (Squalius carolitertii Doadrio 1988), caused by the hydrological alteration promoted by Vilarinho das Furnas Dam on River Homem. From May 2010 to June 2011, three sites were sampled in River Homem and three in River Vez, a nearby non-regulated river, selected as reference. Bi-monthly and fortnightly fish samples from the Iberian chub populations inhabiting the two selected rivers were collected and analyzed for fish age, growth and reproduction. River regulation operating in River Homem, for water derivation purposes, homogenized the flow pattern of the studied watercourse, causing a reduction in the magnitude and variability of monthly flow volumes that resulted in a set of bio-ecological deviations observed for the studied species. Shortly, seasonal pattern of gonad development was similar for male chubs from both rivers but distinct for females, particularly during the reproductive season. Moreover, female chubs inhabiting the non-regulated river presented higher fecundity but smaller oocytes than regulated river females. Seasonal pattern of fish condition was similar between the two rivers but chubs from the regulated river presented, globally, smaller values than the non-regulated river population. Findings from this study are important to understand the derivation in biological patterns imposed by regulated rivers on freshwater fish species and to be used as guiding elements for flow requirements implementations. Acknowledgements The authors wish to thank Ana Ferreira, Catarina Mateus, Joana Ribeiro, Marta Candeias, Marta Lourenço, Nuno Andrade, Paula Valadas and Tadeu Pereira for their assistance during multiple sampling campaigns and laboratorial sessions. This study had the support of the Fundação para a Ciência e Tecnologia (FCT) (Pest-OE/MAR/UI0199/2011). C. M. Alexandre was funded with a PhD grant (SFRH/BD/66081/2009) by the FCT. Keywords: Fish life-cycles, Streamflow, flow regulation, Iberian chub, Mediterranean rivers Conference: XV European Congress of Ichthyology, Porto, Portugal, 7 Sep - 11 Sep, 2015. Presentation Type: Oral Presentation Topic: Life Cycles, Migration and Connectivity Citation: Alexandre CM, Ferreira T and De Almeida PR (2015). Effects of flow regulation in the life-cycles of a Mediterranean cyprinid species, the Iberian chub (Squalius carolitertii Doadrio, 1988). Front. Mar. Sci. Conference Abstract: XV European Congress of Ichthyology. doi: 10.3389/conf.fmars.2015.03.00002 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 03 Nov 2015; Published Online: 04 Nov 2015. * Correspondence: Dr. Carlos M Alexandre, Escola de Ciências e Tecnologia, Universidade de Évora, MARE - Centro de Ciências do Mar e do Ambiente, Évora, 7004-516, Portugal, cmalexandre@fc.ul.pt Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Carlos M Alexandre Teresa Ferreira Pedro R De Almeida Google Carlos M Alexandre Teresa Ferreira Pedro R De Almeida Google Scholar Carlos M Alexandre Teresa Ferreira Pedro R De Almeida PubMed Carlos M Alexandre Teresa Ferreira Pedro R De Almeida Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Food resources and cyprinid diet in permanent and temporary Mediterranean rivers with natural and regulated flow

AbstractThis study addresses the differences in food availability, diet and feeding activity of the Iberian barbel, between permanent and temporary nonregulated rivers, and the effect of flow regulation on feeding parameters. A total of 267 adult barbels were seasonally collected in four nonregulated and regulated rivers from permanent and temporary basins, and their gut content was analysed. Locally available food sources were evaluated across sites and seasons. Barbels from the permanent nonregulated river exhibit a more variable and diversified diet in which invertebrates assumed a large importance, especially during high flows. Barbels from the temporary nonregulated river presented a more uniform diet composed of plant material and detritus, particularly in drought seasons. Flow regulation affected different flow components in both systems, but the effects on food resources and barbels' diet were similar, resulting in an intra‐annual stabilisation of resource availability and fish diet, with a higher consumption of plants and detritus. Changes in fish diet and feeding activity in both nonregulated and regulated rivers were strongly associated with the seasonal variability of streamflow components, particularly between low‐ and high‐flow periods, and with the reduction in flow variability in the case of dam regulation. Results from this study can be used to improve guidelines for flow requirement implementation.

A systematic overview of the coincidences of river sinuosity changes and tectonically active structures in the Pannonian Basin

As tectonic movements change the valley slope (low-gradient reaches of valleys, in sedimentary basins), the alluvial rivers, as sensitive indicators, respond to these changes, by varying their courses to accommodate this forcing. In our study sinuosity values, a commonly used characteristic parameter to detect river pattern changes, were studied for the major rivers in the Pannonian Basin in order to reveal neotectonic influence on their planform shape.Our study area comprises the entire Pannonian Basin (330,000km2) located in eastern Central-Europe, bounded by the Alps, Carpathians and Dinarides. The studied rivers were mostly in their natural meandering state before the main river regulations of the 19th century. The last quasi-natural, non-regulated river planforms were surveyed somewhat earlier, during the Second Military Survey of the Habsburg Empire. Using the digitized river sections of that survey, the sinuosities of the rivers were calculated with different sample section sizes ranging from 5km to 80km. Depending on the bank-full discharge, also a ‘most representative’ section size is given, which can be connected to the neotectonic activity.In total, the meandering reaches of 28 rivers were studied; their combined length is 7406km. The places where the river sinuosity changed were compared to the structural lines of the “Atlas of the present-day geodynamics of the Pannonian Basin” (Horváth et al., 2006). 36 junctions along 26 structural lines were identified where the fault lines of this neotectonic map crossed the rivers. Across these points the mean sinuosity changed. Depending on the direction of the relative vertical movements, the sinuosity values increased or decreased. There were some points, where the sinuosity changed in an opposite way. Along these sections, the rivers belong to the range of unorganized meandering or there are lithological margins.Assuming that the rivers indicate on-going faulting accurately, some places were found, where positioning of the faults of the neotectonic map could be improved according to the sinuosity jumps. However, some significant sinuosity changes cannot be correlated to known faults. In these cases other factors may play a role (e.g., hydrological changes, increase of sediment discharge also can modify sinuosity). In order to clarify the origin of these changes seismic sections and other geodynamical information should be analyzed to prove or disprove tectonic relationship if hydrological reasons can be excluded.

Evaluation of the ecological status of an impaired watershed by using a multi-index approach

The objective of this study was to use an integrative approach to assess the ecological status of a small river impacted by multiple sources of disturbance. The River Febros (NW Portugal) is a small and highly impacted non-regulated river; approximately 44% of the watershed area is dedicated to agriculture, but there is also some urbanization. Environmental status was evaluated using a new multi-index approach, combining quality indices for water (Water Quality Index (WQI)), benthic macroinvertebrates (Iberian Biological Monitoring Working Party Index (IBMWP)), and human modification (Riparian Forest Quality Index (QBR)); Ecological Status River Mediterranean Index (ECOSTRIMED); River Habitat Survey (RHS)). Surveys were carried out between October 2002 and 2003, along four stretches of the main course of the river for physicochemical characteristics, as well as water microbiology and macroinvertebrates. Water quality was poor at all sites (WQI averaged 30.4%) and decreased downstream. The RHS (assessment of instream habitats and the river corridor) and the QBR quantification displayed the same trend. Macroinvertebrates diversity was permanently low with only the most tolerant insects taxa present; oligochaetes dominated. The ecological status of River Febros was well represented using the experimental assessment system, where a downstream decrease in condition was noticeable (in spite of a lower water quality upstream). Our results emphasize the importance of assessing several components of disturbed ecosystems in order to ascertain overall quality and the importance of promoting improvement of the riparian gallery as a buffer against multiple agents of disturbance.

Morphodynamique fluviale actuelle d'origine anthropique : exemples dans le bassin de la Loire (France) / Human impacts on present day fluvial morphodynamics: examples from the Loire river basin (France)

Résumé Dans le bassin de la Loire, les modifications de la dynamique fluviale liées à des actions anthropiques sont très variables dans l'espace selon la taille des cours d'eau et l'utilisation du sol. Les têtes de vallons évoluent en fonction de l'occupation du sol : incision et recul de tête si le couvert végétal protège bien le sol, accumulation dominante si l'érosion sévit sur les versants. Les rivières de rang 2 à 4 apparaissent plutôt stables en l'absence d'aménagements, comme les recalibrages ou les dérivations. En revanche, les cours principaux enregistrent une incision importante, mais inégale dans le sens longitudinal.

Évolution estuarienne d'une rivière régularisée en climat sub-boréal : la rivière aux Outardes (côte nord du golfe du St-Laurent, Québec)

The sedimentological evolution of the Rivière aux Outardes estuary was modified considerably during and after the construction of the hydroelectric dams on the river. Prior to 1965, the dominant river discharge was 1350 m3/s and the flood peak reached 2700 m3/s. Between 1965 and 1975, during the building activities, it fell to 430 m3/s and since 1955 it remained steady at 555 m3/s. Now, the variations range from 1300 m3/s during discharge periods to 0 m3/s during some filling periods. The most significant variations in the river discharge related to the creation of the reservoirs have modified the sedimentary equilibria and it is the aim of the present study to improve our understanding of the flow of the non-cohesive materials in the estuary.Before regulation, the sedimentary processes were dominated by seasonal variations of the river regime: the floods flushed out the fine material from the estuary. Between 1965 and 1975, the river discharge decreased, and the tidal wedge moved upstream. The erosion rate of the cliff edges decreased during working periods of regulation and the entry of marine material was increased particularly at the mouth of the river. The influence of the swell and the tide is more important than the effect of the river discharge.In the present estuarine system, the sedimentary budget is positive and the source of non-cohesive materials has been changed since the regulation of the river. The principal hydrodynamic processes in the estuarine environment of the Rivière aux Outardes are compared with those of non-regulated rivers in a subboreal climate, such as the Rivière St-Jean and the Rivière La Grande rivers. [Journal Translation]