Small Lowland River Research Articles

Environmental Restoration and Changes of Sediment and Hydrodynamic Parameters in a Section of a Renaturalised Lowland Watercourse

In Europe, the routes of most watercourses were straightened and shortened, leading to the destruction and degradation of many natural environments. Currently, in places where it is possible, as part of the implementation of the Water Framework Directive, efforts are made to improve environmental sustainability, including improving the ecological condition of rivers. This paper presents the impact of three in-stream deflectors on changes in the section of a small lowland river—the Flinta (Poland)—where (from 2018 to 2023) detailed, systematic geodetic, and hydrometric research and an assessment of the ecological conditions were carried out. The presented results show the influence of deflectors on the initiation of fluvial processes in the transverse and longitudinal layouts of the channel. The river channel was narrowed from 6 to 5 m, and the current line shifted by almost 3 m. Changes were observed in the distribution of velocities and shear stresses, varying along the surveyed section of the river. In the first year after their application, an increase in velocity at the deflectors can be observed (from 0.2 m∙s−1 to 0.6 m∙s−1 in the deflector cross-section). In the following years, on the other hand, a clear decrease in velocity was observed in the sections between the deflectors (to 0.3 m∙s−1). The introduction of deflectors resulted in a significant increase in the values of shear stresses (from an average value of 0.0241 N∙m−2 in 2018 to 0.2761 N∙m−2 in 2023) and local roughness coefficients (from 0.045 s∙m−1/3 before the introduction of the deflectors to 0.070 s∙m−1/3 in 2023). Based on analyses of sediment samples, erosion and accumulation of bottom material were initially observed, followed by a subsequent stabilisation of particle size. Differences in grain size were observed, especially in the cross-section of the deflectors (increase in granularity d50% downstream of the deflector from 0.31 mm to 3.9 mm already 2 years after the introduction of deflectors). This study confirmed the positive impact of using deflectors on hydromorphological processes as deflectors facilitate the achievement of a good ecological status, as required by the WFD. The innovation of this paper lies in demonstrating the possibility of using small, simple structures to initiate and intensify fluvial processes, which may contribute to improving the ecological conditions of watercourses.

Response of functional diversity of fish communities to habitat alterations in small lowland rivers

AbstractFunctional diversity has proven to be more responsive than traditional taxonomic diversity to alterations for a wide set of communities, especially in aquatic ecosystems. Habitat alterations are among the most relevant causes of biodiversity loss in freshwater ecosystems, nevertheless their effect on functional diversity has been scarcely investigated so far. In this study, functional diversity of fish communities in the River Po basin, north Italy, were related to habitat quality at different spatial scales. Land use and riparian vegetation were identified as the most influent factors on freshwater fish functional diversity. On the other hand, habitat descriptors at smaller scale did not influence functional diversity of fish. The evidenced responses were driven by the contribution of exotic species, which maximized ecological niche occupancy, either by exploiting increased habitat heterogeneity or by interaction with native species. Moreover, traits filtering, disadvantaging large predators such as salmonids, was also observed in the studied communities, but likely this effect was related to other factors than habitat alterations. Overall, this study confirms that land use changes can be considered as valid proxies for anthropogenic alterations. Moreover, possible effects at ecosystem level, also related to the spread of exotic species, could be hypothesized, giving that traits mostly influencing the observed patterns of diversity in communities were related to trophic niche, a factor that has been associated with crucial processes like nutrient cycling or energy transfer.

Spatial Distribution Patterns of Zooplankton and Macroinvertebrates in a Small River under Strong Anthropogenic Pressure

The main objective of this study was to examine the spatial distribution patterns of aquatic invertebrates in an environment characterized by significant anthropogenic stress. During the entire research period, at all the sites, we noticed 72 taxa of zooplankton and 30 taxa of macroinvertebrates. Variation partitioning analysis reveals that the assemblages of planktonic organisms are much more determined by the time of sampling rather than by the site, in contrary to macroinvertebrates where the sampling time was only slightly more responsible for the composition of the benthic communities than the site. Spatial distribution of aquatic organisms in a small lowland river under strong anthropopressure shows significant deviations from the expectations of the River Continuum Concept (RCC). The benthic macroinvertebrate and littoral zooplankton communities exhibited a strong association with local site conditions, while, in contrast, pelagic zooplankton exhibited a strong dependency on drift and its production in the upper reaches of the river, leading to relatively consistent compositions downstream despite the highly altered river environment. To improve the biodiversity values and ecological state of a river, restoration treatments of bed and shore zones are required.

River Habitat Survey: Does This Help to Explain the Nature of Water Mite (Acari and Hydrachnidia) Assemblages?

In the European Union, assessments of the quality of the aquatic environment based on aquatic invertebrates are mandatory. Biological methods are supplemented with hydromorphological assessments of watercourses. There are many studies analysing the relationships between aquatic invertebrates and the hydromorphological assessment of the environment by the River Habitat Survey (RHS) method, but thus far, there has been no detailed study including water mites (Acari, Hydrachnidia) and the application of this method. In the present study, the following research hypothesis was put forth: a hydromorphological characterization of habitats is a significant element explaining the nature of water mite communities, and the RHS method can be used to predict the characteristics of Hydrachnidia populations in a river. The research was carried out in a small lowland river, the River Krąpiel (north-western Poland). Six locations were selected as representative of some state of habitat modification for the assessment of the hydromorphological conditions of the river and the collection of biological samples. The following conclusions can be drawn from the research: (1) the biology and ecology of water mites make them suitable as bioindicators of the environment, including hydromorphological modifications, and (2) the hydromorphological characteristics of habitats explain the nature of water mite communities in the river at the level of general population parameters (number of specimens and species), while at the species level, general regularities in water mite fauna distribution in river ecosystems, the continuity of the river ecosystem, and characteristics at a smaller spatial scale (habitat scale) better explain water mite community structure than the hydromorphological indices determined for a given site or section of the river.

The Water Flow Regime in the Weir Area for Vascular and Rush Plant Species Composition

The hydrotechnical construction, damming up the riverbed, creates two zones of hydraulic conditions, which affect the water discharge and sediment transport routes, as well as plant species composition, as a habitat answer to the hydraulic regime. This study examined the diversity of the vascular and rush plant species upstream and downstream of the weir. The Świder River, a small lowland river in Central Poland, was chosen as a study area. An examined river reach was located at 21 + 340 kilometers of the Świder River. Vegetation properties, plant species, and granulometric fraction composition were recognized at chosen cross-sections along the riverbed where specific hydraulic conditions could be met. The spatial distribution of vortices, smooth or rapid flow areas, and velocity pulsations influence the biotic environment, thereby affecting the species composition, quantity, and plant diversity. In the headwater zone, an environment more favorable to grain accumulation could be met, which was mixed with organic components in an agricultural catchment area. This phenomenon leads to creating favorable conditions for increased biodiversity. The present study demonstrated that small weirs could positively affect the composition of vascular and rush plants.

Water Quality in a Small Lowland River in Different Land Use

The paper describes water quality in the Raszynka River based on selected chemical parameters dependent on different land use. The research was carried out in the Raszynka River catchment, characterized by a small surface area (75.9 km2) and length (17.14 km). The river is a right tributary of the Utrata River. It is located in the Piaseczno and Pruszkow districts in the Mazowieckie voivodship. The dominant type of land use in the basin is agricultural land. Water samples were collected from 2017 to 2019 from previously designated research points at similar distances along the river. Selected physicochemical indicators examined in the samples include total alkalinity, electrolytic conductivity (EC), pH, and chemical oxygen demand (COD). Moreover, the concentration of selected substances was determined, including nitrogen compounds: NO3− (nitrates) and NH4+ (ammonium), TP (total phosphorus), and Cl− (chlorides). The results showed that the values of some of the examined indicators do not meet the standards set for first-class surface water quality. Indicators significantly exceeding the limit included ammonium, chlorides, and pH. The highest concentration of chlorides, ammonium, and nitrate was found in urbanized areas. The highest concentrations of total phosphorus and COD were determined in agricultural areas and total alkalinity in meadows.

Environmental Gradients Shaping the Freshwater Bryophyte Communities of Croatia (Western Balkans)

A comprehensive field survey of 527 sites on 293 watercourses across Croatia revealed 76 sites (14.42%) in which bryophytes were the dominant part of the macrophyte vegetation. Using classification and ordination analyses, we obtained five community types segregated across the gradients of several climatic, physiographic and water chemistry parameters. The Didymodon tophaceus–Apopellia endiviifolia and the Berula erecta-Cratoneuron filicinum communities were mostly confined to the clean and basic karstic rivers of the Dinaric Ecoregion under the influence of the Mediterranean climate, with the Didymodon tophaceus–Apopellia endiviifolia community being a tufa-forming community associated with the seasonally dry watercourses of small catchment areas and cascades along the larger karstic rivers, while the Berula erecta–Cratoneuton filicinum community was mostly associated with rivers with larger catchment areas and permanent flow. On the other hand, the Oxyrrhynchium hians–Chiloscyphus pallescens community and the Fissidens pusillus–Veronica beccabunga community were associated with eutrophic water restricted to small rivers of the Pannonian Ecoregion under the influence of the temperate climate and flowing over silicate bedrock. The most represented and widespread in Croatia was the Cinclidotus community, displaying the widest ecological range in the study. It was mostly associated with the relatively clean karstic rivers of large catchment areas belonging to the Dinaric Ecoregion, with the majority of the sites under the influence of a temperate climate with higher precipitation during the warm period of the year. The geographical patterns of the freshwater bryophyte communities showed that the relatively clean, fast and cold karstic rivers belonging to the Dinaric Ecoregion provide habitats that harbour a greater diversity of bryophyte communities than the watercourses of the Pannonian Ecoregion, where bryophyte-dominated communities are restricted to a small number of small lowland and semi-montane rivers and predominantly occupy periodically flooded microhabitats such as river margins.

ANALIZA WYBRANYCH CHARAKTERYSTYK HYDROLOGICZNYCH DWÓCH MAŁYCH ZLEWNI NIZINNYCH

Aim of the study: i. Comparison of characteristic discharges (mean and mean of annual minimum, i.e. mean low discharge) of small lowland river between two periods (1963-1990 and 1991-2020) estimated on the base of field measurements. ii. Comparison of specific discharges of two small catchments of various size in the period 1991-2020. iii. Evaluation of local indirect methods for estimation of mean and mean low discharge applied for the two small catchments. Material and methods: Since 1962, hydrological investigations have been conducted in a small lowland catchment of the Zagożdżonka River. The catchment area is characterized by agro-forested land use, and is located in the south part of the Masovia region, Poland. Continued monitoring of water stages and discharge measurement at the river gauge Płachty Stare were conducted for estimating daily and characteristic discharges for two periods: 1963-1990 and 1991-2020. Other methods were also used for both of the hydrological characteristics. They were based on maps of specific discharges from the Hydrological Atlas of Poland. Results and conclusions: Mean discharge of the Zagożdżonka River at the gauge Płachty Stare between the two periods decreased by 24%. Mean low flow decreased by 43%. Higher evapotranspiration, caused by climate change, i.e. temperature increase and higher ratio of forested area in the catchment, is indicated as the main reason of the changes. Mean specific discharge from the smaller catchment (at Wygoda gauge) was 36% less than from the larger catchment. The application of the indirect methods for estimation of mean and mean low discharges for the larger catchment seems to give satisfactory results.

Natural and Geomorphological Response of the Small Lowland River Valley for Anthropogenic Transformation

The regulation of small rivers and the consequent maintenance works are common in the Central European Lowlands. This article attempts to determine the relationship between the invertebrate fauna (and consequently the biocenosis) of the small lowland river valley and its landforms (morphodynamics) under the conditions of very large and rapid changes caused by river regulation and maintenance. On this basis, an attempt to analyze the response of the ecosystem to rapid transformations associated with engineering works was made. The study covered Kraska, a small river typical for Polish Lowlands, which has been regulated along almost the entire length. The results showed that, in the regulated sections, where the natural forms of the relief were destroyed, there were significantly fewer taxa and significantly smaller numbers of the specimen. Despite the clear negative impact of the regulatory work on the ecosystem, the river in some sections showed the ability to spontaneously restore certain geomorphic features.

Anthropogenic transformations of river ecosystems are not always bad for the environment: Multi-taxa analyses of changes in aquatic and terrestrial environments after dredging of a small lowland river.

Rivers are one of the most commonly transformed aquatic ecosystems. Most papers present significantly negative effects of activities such as dredging or channel regulation on the ecological status of rivers. The purpose of this work was to compare the response of various groups of invertebrates (Mollusca, Hydrachnidia, Odonata, Heteroptera, Coleoptera and Trichoptera) to an intervention involving dredging in conjunction with the removal of riparian vegetation. Habitat diversity increased after the dredging, and more individuals and species were caught than before the dredging. The increase in habitat diversity after the dredging translated into an increase in the species diversity of most investigated groups. Individual groups of invertebrates showed varied responses to the dredging, depending on the role of the terrestrial phase in their life cycle: the greater the role of the terrestrial phase in the life cycle, the more the group was affected by changes in the terrestrial environment following the intervention. In consequence, the intervention had the greatest negative impact on insects, and among these, on adult Odonata. The following conclusions can be drawn: (1) Dredging can benefit a previously anthropogenically transformed river ecosystem by increasing habitat diversity; (2) Odonata are particularly useful for assessing the impact of this type of intervention on invertebrate communities. They can be considered good indicators of habitat disturbances in both aquatic and terrestrial ecosystems.

Demonstration of an aggregated biomarker response approach to assess the impact of point and diffuse contaminant sources in feral fish in a small river case study

The assessment of the exposure of aquatic wildlife to complex environmental mixtures of chemicals originating from both point and diffuse sources and evaluating the potential impact thereof constitutes a significant step towards mitigating toxic pressure and the improvement of ecological status. In the current proof-of-concept study, we demonstrate the potential of a novel Aggregated Biomarker Response (ABR) approach involving a comprehensive set of biomarkers to identify complex exposure and impacts on wild brown trout (Salmo trutta fario). Our scenario used a small lowland river in Germany (Holtemme river in the Elbe river catchment) impacted by two wastewater treatment plants (WWTP) and diffuse agricultural runoff as a case study. The trout were collected along a pollution gradient (characterised in a parallel study) in the river. Compared to fish from the reference site upstream of the first WWTP, the trout collected downstream of the WWTPs showed a significant increase in micronucleus formation, phase I and II enzyme activities, and oxidative stress parameters in agreement with increasing exposure to various chemicals. By integrating single biomarker responses into an aggregated biomarker response, the two WWTPs' contribution to the observed toxicity could be clearly differentiated. The ABR results were supported by chemical analyses and whole transcriptome data, which revealed alterations of steroid biosynthesis and associated pathways, including an anti-androgenic effect, as some of the key drivers of the observed toxicity. Overall, this combined approach of in situ biomarker responses complemented with molecular pathway analysis allowed for a comprehensive ecotoxicological assessment of fish along the river. This study provides evidence for specific hazard potentials caused by mixtures of agricultural and WWTP derived chemicals at sublethal concentrations. Using aggregated biomarker responses combined with chemical analyses enabled an evidence-based ranking of sites with different degrees of pollution according to toxic stress and observed effects.

The influence of a dam reservoir on water quality in a small lowland river

The paper presents the effects of the dam reservoir in Komorów on the water quality in the Utrata river. The implementation of the adopted objective involved a comparison of water quality at two points, above and below the reservoir. The Utrata River is polluted with biogenic compounds throughout the whole section studied. COD content also indicates significant contamination exceeding permissible limits. A positive effect of the reservoir on water quality in the river was also observed in terms of the content of dissolved oxygen, with concentration increasing below the reservoir. The reservoir had a positive effect on reducing the concentration of total phosphorus in the water. Water in the Utrata below the reservoir showed higher values of chemical oxygen demand (CODMn) than above the reservoir. There were no differences in the concentration of NH4+ and NO3- ions in the water before and after the reservoir.

Diversity of Fish and Zoobenthic Communities in Lowland River Related to the Factors of Hydromorphological, River Continuum and Pollution Disturbances

The response of zoobenthos and ichthyofauna to different levels of habitat degradation was estimated on a small lowland river. The level of fragmentation, the hydromorphological modifications of the watercourse bed, and the water quality of different river stretches were assessed as proxies of the degree of anthropogenic transformation of habitats. The degree of fauna similarity between the study sites, as well as the relationships between habitat quality and biotic indexes were estimated. A strong response of both assemblages to changes in environmental conditions was demonstrated, however, reaction to individual pressures differs. This confirms that these organisms are excellent, universal bioindicators and both groups should be used together. The key role of a well developed riparian zone in shaping the diversity of freshwater biota has also been demonstrated.

Environmental factors shaping assemblages of ostracods (Crustacea: Ostracoda) in springs situated in the River Krąpiel valley (NW Poland)

We investigated the ostracod assemblage structure in springs of a small lowland River Krąpiel valley. Environmental factors and the potential of ostracods as indicators of spring type were analysed. The analysis involved the type of spring, substrate, physicochemical parameters, and the river valley's hydrological status as environmental factors. A total of thirty ostracod species were recorded. The average count of ostracod individuals in a sample amounted to 100. The assemblages were dominated by juvenile Candona sp., juvenile Psychrodromus sp., Cypria ophtalmica, and Cypridopsis vidua. The spring species accounted for less than 1% of the individual counts, except for juvenile Psychrodromus sp. with 21% and Eucypris pigra with 4%. The average number of taxa per spring was 5. The ostracod assemblages were significantly influenced by limnocrene springs, spring flooding by the river overflow, the presence of coarse leaf litter, the presence of fine organic matter, a high content of NH4 as well as by BOD5, conductivity, pH, Fe, the river habitat modification index (RHM), the habitat modification score (HMS), and the river habitat quality (RHQ). The habitat conditions for the spring species appeared to be enhanced by the domination of mineral substrate over fine particulate organic matter, an elevated pH, the presence of leaf-derived organic matter, and the absence of flooding by the river. The spring species showed no association with the Krąpiel valley hydrological factors.

Changes of malacofauna in a small lowland river in eastern Poland

In 2016, the species composition and the structure of the dominance of molluscs in the Muchawka River (left-bank tributary of the Liwiec River) were assessed. The occurrence of 19 species of molluscs were recorded, including 11 species of snails and 8 species of mussels. The eudominant was Pisidium casertanum, which, only in the last two sites, constituted 43.1% of all molluscs. Two other species of molluscs from the Sphaeriidae family were also eudominants – Pisidium subtruncatum (22.8%) and Sphaerium corneum (10.3%). Snails were most frequently represented by the dominant Bithynia tentaculata, constituting 5.4% of all molluscs, and the subdominant Bathyomphalus contortus at 2.8%. Sixteen years after the first malacological analysis, an increase in species richness and differences in the dominance of molluscs were found in the Muchawka River. Clams from the Sphaeriidae family invariably dominated but with a different species composition. The disappearance of the protected Anodonta cygnea and Sphaerium rivicola has been noted, and the occurrence of the protected Unio crassus has also been noted.

Method for estimating the pollutant flow rate under diffuse pollution of small lowland rivers

In the present work, the model of diffuse pollution of the rivers by conservative components is considered on the basis of advection–diffusion equation. The asymptotic solutions of the equation are analyzed, and typical structures of stationary fields of pollutant concentration in the river are established. The model was tested using the measurements of pollutant concentrations on the reach of the lowland Barnaulka River (Russian Federation, Altai Region), with homogeneous composition of soils in the catchment. The method of optimization was used to calculate the mass flow rate of dissolved pollutants at different catchment areas of different lengths. The adequacy of the proposed model was checked using the determination factor. Based on the considered criteria, the method of splitting the complex concentration fields into elementary areas, within which the mass flow rate of pollutant can be considered unchanged, is proposed.

The Impact of Climate Change on the High Water Levels of a Small River in Central Europe Based on 50-Year Measurements

Climate change affects many elements of the natural environment and strongly influences the hydrology of rivers. In this study, we investigated trends in temperature, precipitation, and the water level characteristics in the small lowland river Lebiedzianka in northeastern Poland for the 50 year long period of observations (1970–2019). We recorded significant increase in air temperature and potential evapotranspiration, but the annual sum of precipitation did not change. We found significant downward trends for annual runoff. The results show a steady decrease in the number of days with high water levels. These changes caused by global warming will have a strong impact on forest habitats associated with high water levels and periodic inundations. In Europe, many of these precious habitats are protected under the Natura 2000 network as sites of high heritage value; nevertheless, their sustainability will be at risk due to the ongoing changes in their hydrological regime.

Changes in the quality of a small lowland river in Poland under the influence of pollution and a dam reservoir located in its course

Abstract The study on a small lowland river was conducted in order to determine changes in water quality under external loading (inflow of treated wastewater, runoff from agricultural areas) and the location of a dam reservoir in its course. The 21 km long River Pogona (Greater Poland, Poland) is a small tributary of the Obra Canal in Kościan. In 2004, in its valley, the Jeżewo Reservoir, with an area of 78 ha, was utilized to supply the flow in the Obra Canal during the dry season and to irrigate agricultural areas. The river is also a receiver of treated sewage from the sewage treatment plant in Karolewo. The research, carried out in 2017 at six sampling stations in its course, showed that the discharge of treated wastewater resulted in an increase in conductivity, concentration of ammonium nitrogen, nitrites and total nitrogen in the waters of the River Pogona. On the other hand, the location of the Jeżewo Reservoir in its course contributed to an increase in water temperature, pH, dissolved oxygen, chlorophyll-a and nitrite concentration in the outflowing river. The results showed that the inflow of treated wastewater from the sewage treatment plant, surface runoff from the catchment area and the Jeżewo Reservoir formed in its course, influenced seasonal and spatial changes in the water quality of the River Pogona.

Microplastics in freshwater fish from Central European lowland river (Widawa R., SW Poland)

In contrast to marine organisms, the presence of microplastics (MPs) in freshwater animals remains insufficiently studied. The aim of this study was to identify the occurrence of MPs in the digestive tracts of two fish species from a small lowland river (Widawa R., SW Poland). In total, 202 gudgeons and 187 roaches were collected, of which 54.5% and 53.9% had ingested MP-like particles, respectively. Feeding type and behaviour, sex and capture site (above or below the dam reservoir) did not affect the number of fish with MP-like particles.

Modeling of River Channel Shading as a Factor for Changes in Hydromorphological Conditions of Small Lowland Rivers

The ecological water quality in rivers and streams is influenced both by the morphological factors (within the watercourse channel and by the dynamic factors associated with flow), as well as biological factors (connected with the flora and fauna characteristic of its specific area). This paper presents an analysis of the effect of river channel shading by trees and shrubs on hydromorphological changes in a selected reach of the Wełna River, Poland. The analysis was conducted on two adjacent cross-sections (one in a reach lined with trees, the other in an open area with no tree or shrub vegetation). Data were collected during field surveys in the years 2014 and 2019. According to the Water Framework Directive, the Wełna River represents a watercourse with small and average-sized watershed areas, with sand being the dominant substrate of the river bottom. Flow volume, distributions of velocity in the sections, as well as substrate grain-size characteristics and river bottom morphology, were determined based on field measurements. In the study, the leaf area index (LAI) of vegetation was measured in the reach lined with trees, while the number and species composition of macrophytes were determined in the investigated river reaches. Moreover, a digital surface model (DSM) and Geoinformation Information System GIS tools were used to illustrate variability in shading within the tree-lined reach. The DSM model was based on Light Detection and Ranging (LIDAR) data. The results of this study enable us to establish the relationship between river shading by vegetation covering the bank zone, and changes in hydromorphological parameters of the river channel.