Povodí Labe (Czechia)

Significant changes in long-term hydrological values have been observed, resulting in an increase in the proportion of wastewater discharged from wastewater treatment plants (WWTPs) in watercourses. During periods of reduced flow, this proportion can exceed 50% of the flow in the receiving watercourse. For most parameters, concentrations increase in the watercourse downstream of the WWTP, thereby deteriorating water quality (nutrients, chlorides, conductivity, coliform bacteria, dissolved substances). However, the assessment is less clear-cut for some parameters. With decreasing flow, the differences in concentrations upstream and downstream of the WWTP discharge increase for most parameters. A notable increase in water temperature and pH downstream of the WWTP is observed during the warmer months, accompanied by a more rapid decomposition of organic matter. This results in smaller differences for ammonium nitrogen, and conversely, larger differences in its concentrations during the colder months.In addition to the well-known problems with nutrients, the situation with increasing salinity of watercourses may also worsen with more frequent occurrences of low flow periods. Unlike nutrient parameters, salinity parameters do not have targets for good ecological status set in the Czech Republic, so they are not included in the assessment of the status of water bodies and no measures to improve their ecological status need to be proposed. Phosphorus and chloride concentrations exhibit a marked increase downstream of the WWTP throughout the whole year.The paper will present the impacts of discharges from WWTPs that have been selected as significant for the Czech Republic in the Plan for Managing Drought and Water Scarcity in the Czech Republic. These examples are used to find flow rates that would eliminate the combined impact of drought and wastewater treatment plant discharges on the ecological status of the affected surface water bodies. The results of an assessment of the impact of the first stage of reconstruction of the largest WWTP in the Czech Republic, which treats wastewater from the capital city of Prague, on improving water quality in the Vltava River will also be presented.

Abstract The spatial distribution of suitable habitats and dispersal abilities of the constituent taxa jointly affect the structure of metacommunities in standing freshwaters. Most studies exploring spatial effects on aquatic metacommunities, however, focus on at most a few taxonomic groups. Within two consecutive seasons, we studied spatial patterns in the species richness and composition of three passively dispersing and three actively flying freshwater invertebrate groups (rotifers, microcrustaceans and molluscs vs. hemipterans, aquatic beetles and odonates) in a metacommunity system consisting of 42 newly or recently created fishless pools in a highly heterogeneous Central European sandstone landscape consisting of deep valleys and steep ridges. We hypothesized that the extent to which these dispersal barriers affect invertebrate groups depends on their dispersal mode, and that the ability of each group to colonize new habitats is affected by the landscape morphology. Moreover, we predicted that the history and age of the pools would play a major role in structuring of invertebrate communities. Following the classical island biogeography pattern, habitat size (measured as pool surface area or depth) was the key characteristic influencing species richness for each of the six studied groups (range of explained variation: 10%–58.7%). The number of nearby aquatic habitats (i.e., potential colonization sources) was also an important determinant of species richness for molluscs (18.8%), crustaceans (36.4%) and aquatic beetles (27.2%). After pool size, the most important factor influencing species richness was the presence and functional composition of aquatic macrophytes in the pools, which affected the species richness of odonates (25.2%), aquatic beetles (12.2%), rotifers (11.1%), and crustaceans (8.3%). Valley distances between localities, defined as the shortest distance that avoids crossing steep ridges, explained consistently slightly more variation in species composition (2.6%–12.6%) than did Euclidean distances (1.0%–10.1%) for all six groups. Spatial variables (the valley distance matrix, position of pools within clusters in the landscape, and the number of nearby aquatic habitats) explained more variation in species composition (3.4%–25.4%) than local pool characteristics (2.8%–9.4%) or temporal variation (0%–7.6%) in all taxa except hemipterans, whose species composition was almost equally affected by local (3.3%) and spatial factors (3.4%). We conclude that landscape‐level spatial structure in our study area affects the dispersal and metacommunity assembly of both actively and passively dispersing invertebrates more than studied pool characteristics or temporal variation. The observed congruence between groups with different dispersal modes is likely because flying insects follow similar dispersal routes as the key animal vectors of passive dispersers. Our study highlights the importance of including relevant topography features in studies of aquatic metacommunities in complex and heterogeneous landscapes, even for taxa considered to be efficient dispersers.

Environmental analysis at trace levels is a new field of research in the Czech Republic since about ten years. New methods have to be adapted, pollution sources have to be investigated and quality assurance has to be established. The improvement in the detemination of trace substances in the Elbe river, mainly that of organic pollutants, is shown. A first insight on an international level is given into the origin of pollution in the Czech part of the Elbe river and the analytical work provided by the Czech water research institute and one of the most important monitoring laboratories.

Sintered negative electrodes for nickel-cadmium secondary cells were studied. Model electrodes prepared by means of three different impregnation methods were evaluated. It was demonstrated that the impregnation procedure may affect properties of active mass and the service life of electrodes in a significant way.