Chemical industries in Onitsha urban area of southeastern Nigeria have been discharging large quantities of effluents into surface streams. These streams are the primary sources of water used by poor households for domestic purposes. This study examines the effects of effluents on the physicochemical and microbiological characteristics of the recipient streams. This objective was achieved by collecting eight effluents and twenty-two water samples from control points, discharge lo-cations and exit chutes of the effluents for analysis. The results of the study characterised the effluents and their effects on the recipient streams. The effluents cause gross pollution of the streams as most of the parameters including pH, total dis-solved solids (TDS), turbidity, biological oxygen demand (BOD), chemical oxygen demand (COD), Mg, NO3, Fe, Cu, Pb, Cr, total heterotrophic count (THC) and total coliform group (TCG) returned high values that exceeded the World Health Organisation’s (WHO) benchmark from 2011 for drinking water quality. Only dissolved oxygen (DO), Na, Zn, Ca, and Na returned values lower than the WHO guideline. E. coli was found in all the samples; TCG was also high. This paper, there-fore, recommends that the effluent generating industries should treat their effluents before disposal.

One more time we would like to pay attention of especially of the hydraulic engineer audience to bankfull stage and discharge. Along the paper we show commonly accepted definitions of it and ways of calculations. It is difficult to determine the size of the bankfull flow level, that is why the authors are presenting many selected methods. Some of the methods allow the determination of biotic bankfull flow through the occurrence of zones of vegetation characteristic and based on the observation of the occurrence of ground beetles (e.g. the Woodyer and the Radecki-Pawlik and Skalski methods). Some of the methods – most popular- are using morphometric parameters (e.g. the Williams, the Hey and Thorne, the Gauckler-Manning and finally the Lambor methods).

We believe that the value of bankfull discharge would be accepted as a supporting tool for designers, hydraulics engineers and managers, especially those who care about river channel environment and cooperate with fluvial geomorphologists- and biologists as well as environmental agencies.

Extensive efforts have been made for many years by the power generating industry to replace conventional solid and liquid insulation with synthetic materials. Those measures are aimed at increasing the load capacity, improved fire safety and extending transformer life during exploitation. Modern insulating materials include aramid fibre-based paper and insulating fluids made of synthetic and natural esters. The paper presents research results of the electrostatic charging tendency (ECT) of mixtures of fresh and aged mineral oil Trafo En with synthetic ester Midel 7131 and natural ester Midel 1204. The measurements were taken in a flow-through system using the pipes made of metal, cellulose and aramid paper. The influence of the liquid flow velocity, the type of material of the measuring pipe and the mixture content on the level of the streaming electrification current generation was determined.

The Munin River (Svalbard) is a mountainous braided proglacial river. It drains from two valley glaciers developing an elongated channel belt and turning into a wide braided outwash fan before entering the main river. The Munin River is in its axial head supplied by the material from glaciers, and along the stream by material from lateral sources, i.e. braided outwash fan, debris-flow and fluvial-flow dominated fans. Detailed analyses of clast roundness showed that roundness suddenly changes to higher degrees in negative correlation with channel belt width and sinuosity of the channels. The roundness increases rapidly in sections with small channel belt width and low sinuosity, which can be seen in the bedrock gorge. On the contrary, the roundness does not change much in sections with large channel belt width and high sinuosity. The morphological changes of the channel belt are controlled by the bedrock morphology of the catchment, which is the main factor affecting the clast roundness in the Munin River. The nature of the lateral material sources and the downstream traction affect rather the individual gravel fractions.

Geometry of the fluid container plays a key role in the shape of acoustic streaming patterns. Inadvertent vortices can be troublesome in some cases, but if treated properly, the problem turns into a very useful parameter in acoustic tweezing or micromixing applications. In this paper, the effects of sinusoidal boundaries of a microchannel on acoustic streaming patterns are studied. The results show that while top and bottom sinusoidal walls are vertically actuated at the resonance frequency of basic hypothetical rectangular microchannel, some repetitive acoustic streaming patterns are recognised in classifiable cases. Such patterns can never be produced in the rectangular geometry with flat boundaries. Relations between geometrical parameters and emerging acoustic streaming patterns lead us to propose formulas in order to predict more cases. Such results and formulations were not trivial at a glance.

In the early days, consumption of multimedia content related with audio signals was only possible in a stationary manner. The music player was located at home, with a necessary physical drive. An alternative way for an individual was to attend a live performance at a concert hall or host a private concert at home. To sum up, audio-visual effects were only reserved for a narrow group of recipients. Today, thanks to portable players, vision and sound is at last available for everyone. Finally, thanks to multimedia streaming platforms, every music piece or video, e.g. from one’s favourite artist or band, can be viewed anytime and everywhere. The background or status of an individual is no longer an issue. Each person who is connected to the global network can have access to the same resources. This paper is focused on the consumption of multimedia content using mobile devices. It describes a year to year user case study carried out between 2015 and 2019, and describes the development of current trends related with the expectations of modern users. The goal of this study is to aid policymakers, as well as providers, when it comes to designing and evaluating systems and services.

Acoustical Driving Forces (ADF), induced by propagating waves in a homogeneous and inhomogeneous lossy fluid (suspension), are determined and compared depending on the concentration of suspended particles. Using integral equations of the scattering theory, the single particle (inclusion) ADF was calculated as the integral of the flux of the momentum density tensor components over the heterogeneity surface. The possibility of negative ADF was indicated. Originally derived, the total ADF acting on inclusions only, stochastically distributed in ambient fluid, was determined as a function of its concentration. The formula for the relative increase in ADF, resulting from increased concentration was derived. Numerical ADF calculations are presented. In experiments the streaming velocities in a blood-mimicking starch suspension (2 μm radius) in water and Bracco BR14 contrast agent (SF6 gas capsules, 1 μm radius) were measured as the function of different inclusions concentration. The source of the streaming and ADF was a plane 2 mm diameter 20 MHz ultrasonic transducer. Velocity was estimated from the averaged Doppler spectrum obtained from originally developed pulsed Doppler flowmeter. Numerical calculations of the theoretically derived formula showed very good agreement with the experimental results.

Along the paper the new method called Invertebrate Bankfull Assessment method (IBA method) of determination of bankfull discharge is presented. The investigation of bankfull discharge using IBA were performed within one Polish Carpathian stream in the mountain region: the Ochotnica Stream. As an index of bankfull the existence of certain species of invertebrates was used which are present and resistant to specific water discharge conditions. The borders within a cross section of the mountain stream with a gravel bed were defined where characteristic invertebrates are present which are recognized as bankfull borders. Finally three invertebrates benches (IB-ms) were recognized which are characterized by very specific invertebrate species. Bankfull discharge was calculated up to this IB-ms and corelated using Canonical Correspondence Analysis with other values of bankfull calculated for a cross section using different bankfull.

There is a cascade of hydroelectric power plants built on the Váh River. From a water-management point of view, the natural channel is used to drain extreme discharges. During most of the year, discharges are regulated by water-management structures. These discharges are not used for energy-related purposes; therefore, it is important to determine the optimal discharge that will not negatively affect the ecosystem of the stream. The minimum balance discharge (hydro-ecological discharge) was determined based on the instream flow incremental methodology (IFIM) using the riverine habi-tat simulation system (RHABSIM). Input data were obtained from direct measurements on three reference reaches in the area between the cities Piešťany and Nové Mesto nad Váhom. Hydraulic flow characteristics were derived from three measurements at different water levels. Habitat quality was represented by ichthyofauna. Data to determine the habitat suit-ability curves of fish were obtained using a diving technique to collect video footage. The modelling resulted in the quanti-fication of the effect of discharge on ichthyofauna as a bio-indicator of habitat quality, which implied the need of 20 m3∙s–1 for a minimum balance discharge in summer.

This paper reports the preliminary results from the studies on the scanning electron microscopical studies on chrysophycean cysts collected in ponds and streams of King George Island (South Shetlands). The cysts play an important role as the survival developmental stages. Fifteen morphotypes are described, six of which are new for science. Particular attention has been paid to the anatomy of the pore, collar structure and to the ornamentation of the cyst surface.

The Brzanka Mountain Range in the Ciężkowickie Foothills has a dense river network. Unfortunately the contemporary maps contain only the names of some main rivers of the Brzanka Mountain Range. Local communities use the same set of names of rivers as cartographers, while studies in the historical geography of the Brzanka Mountain Range reveal a wealth of local hydronyms that have seemingly been forgotten. The article attempts both to reconstruct a set of hydronyms of the Brzanka Mountain Range and to explain their etymology. It shows that hydronyms change over time and that studies on local hydronyms can help restore the collection of the names of rivers in the Brzanka Mountain Range and provide interesting information related to the past of this region. Moreover, they reveal contemporary unknown facts related to the natural environment and settlement processes in the Middle Ages. A visual summary of the article is a map showing the Brzanka Mountain Range with its river network and associated hydronyms.

Non-point source pollution is a primary cause for concern globally. Various models have been developed to tackle this situation with much emphasis placed on best management practices. This practice has, however, proven to be insufficient to solve the NPS pollution situation. Existing non-point source models are watershed-based and complicated both in operation, parameter estimation and data requirements. A non-point source model is proposed using the concept of the Hybrid Cells in Series model. The model is a three-parameter model made up of three zones, which describes pure advection through time delay in a plug zone, with combined advection and dispersion occurring when the other two zones are considered as thoroughly mixed. The proposed model is tested using synthetic data and fi eld data from the Snake River, Colorado, USA, obtained from literature. Simulations were performed at four sample points; two from the tracer injection point along the Snake River before a confluence and two further downstream after the confluence. A regression analysis was carried out to determine the model’s capability to simulate pollutant transport for the four sampling points. The coefficients of determination are 0.98, 0.94, 0.84 and 0.97 while the standard error for each reach is 2.28E-2, 2.70E-2, 2.32E-2 and 9.35E-3 respectively. The results show good agreement between the measured and the simulated data. The response of the C-t profiles produced by the proposed model for both synthetic and field data demonstrates its ability to effectively simulate pollutant transport in natural rivers subject to non-point source pollution.

The very wet conditions of recent years in Europe have made it clear that measures will have to be taken in this century to prevent flooding. The question is how to manage groundwater in order to reduce the anticipated increased hydrological risk. Furthermore the surface water quality in the Netherlands is insufficient to meet the standards of the Water Framework Directive. The required improvements are difficult to reach, because the diffuse loads of nutrients from agricultural land can not be easily reduced. This demands for innovative solutions with respect to improve the surface wa-ter quality. In this pilot study the focus is on the purification in reed fields and use it as well to reduce the effects of the anticipated climate change. An experimental evidence on a practical scale is lacking and therefore in the woodland area of Lankheet in the eastern part of the Netherlands, 3 ha has been planted with reeds to purify the river water. The aim of the study is further to store the purified water in the groundwater in order to reduce climate change effects. For the hydrological situation a scenario study was set up, using a regional hydrological model to simulate the groundwater flow together with the water flow in a network of water courses. The analysis will give knowledge on the multifunc-tional use of such a system.