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Water pollution is one of the most significant problems in the world today and is a global problem. Surface water pollution in streams and reservoirs is reflected in the deterioration of the quality of aquatic ecosystems, including those that occur in their vicinity or follow them. Lack of quality drinking water is one of the main causes of various diseases, which can lead to death, especially in developing countries. Therefore, it is important to detect water pollution in time and anticipate how it could develop and be transported in the stream. Measurements on a physical model are time-consuming and economically demanding, but for a given locality it can provide comprehensive information, including the proposal of possible measures and their verification. It is also a suitable approach for calibration and verification of mathematical models. One of the main tasks in the physical modelling of the spread of pollution in the stream was to find a suitable substance that would simulate the pollution without being aggressive towards the water pumping circuit. The method of electrical impedance spectrometry was chosen for its detection in the stream.

Full-width sharp-edged broad-crested rectangular weirs in the range 0.1 < h/L ≤ 0.3 situated in rectangular channels are frequently used in submerged flow conditions. To determine the discharge for the submerged flow, submergence coefficient and modular limit shall be known. This article deals with their determination upon a theoretic derivation and experimental research. The equation for modular limit has been determined from energy balance with simplifications. To validate it, extensive experimental research was carried out. However, the derived equation is too complicated for practical use which is why it was approximated by a simple equation applicable for the limited range. The equation for submergence coefficient was derived by modifying Villemonte’s application of the principle of superposition and its coefficients were determined using the data from experimental research of many authors. The new system of equations computes the discharge more accurately than other authors’ equations, with the error of approximately ±10% in full range of the measured data.

The paper presents the results of monitoring electrical properties of the soil of the body of the earth-fill dam of the Karolinka water reservoir in the fourth year after its reconstruction ended. Monitoring was carried out using the Z-meter device applying the electric impedance spectrometry method with the focus on seepage through the earth-fill dam of the water reservoir. Information about the changes that occurred in the dam body before and after the implementation of the measure (the construction of a cut-off wall when the dam was reconstructed in 2013) was obtained by monitoring the changes of the electrical resistances of the soil of the dam with time.

In the case of flow over rectangular broad-crested weir, where the inflow is realized by approach shaft, occurs influence of water surface level by approach flow velocity. The paper describes numerical model of flow including weir, approach and outlet shaft. Simulations of flow were created by 2D and 3D model with using three methods of turbulent modelling. In this paper a water surface level for each model setup is evaluated and then it is compared with measured values.

Shallow-water models are standard for simulating flow in river systems during floods, including in the nearfield of sudden changes in the topography, where vertical flow contraction occurs such as in case of channel overbanking, side spillways or levee overtopping. In the case of stagnant inundation and for frontal flow, the flow configurations are close to the flow over a broad-crested weir with the trapezoidal profile in the flow direction (i.e. inclined upstream and downstream slopes). In this study, results of shallow-water numerical modelling were compared with seven sets of previous experimental observations of flow over a frontal broad-crested weir, to assess the effect of vertical contraction and surface roughness on the accuracy of the computational results. Three different upstream slopes of the broad-crested weir (V:H = 1:Z(1) = 1:1, 1:2, 1:3) and three roughness scenarios were tested. The results indicate that, for smooth surface, numerical simulations overestimate by about 2 to 5% the weir discharge coefficient. In case of a rough surface, the difference between computations and observations reach up to 10%, for high relative roughness. When taking into account mentioned the differences, the shallow-water model may be applied for a range of engineering purposes. Modely mělké vody jsou standardem pro simulaci toku v říčních systémech během povodní, a to i v blízkém poli náhlých změn v topografii, kde dochází ke svislé kontrakci toku, jako například v případě přetížení kanálu, postranních přelivů nebo přetížení hrází. V případě stagnujícího inundace a pro čelní tok jsou konfigurace toku blízké toku přes široko-chocholatý jez s lichoběžníkovým profilem ve směru toku (tj. Nakloněné před a za svahem). V této studii byly výsledky numerického modelování mělké vody porovnány se sedmi sadami předchozích experimentálních pozorování toku přes čelní široko-chocholatý jez, aby se vyhodnotil vliv vertikální kontrakce a drsnosti povrchu na přesnost výpočtových výsledků. Byly testovány tři různé svahy proti proudu širokého hřebenu (V: H = 1: Z (1) = 1: 1, 1: 2, 1: 3) a tři scénáře drsnosti. Výsledky ukazují, že pro hladký povrch numerické simulace přeceňují asi o 2 až 5% koeficient propouštění jezu. V případě drsného povrchu dosahuje rozdíl mezi výpočty a pozorováním až 10% pro vysokou relativní drsnost. Při zohlednění uvedených rozdílů lze model mělké vody použít pro řadu inženýrských účelů.

The Czech Republic (CR) lies on the watershed divide of three seas-The North, Baltic and Black Seas. The watershed of these seas divides the territory of the CR into three international catchment areas (Labe, Odra and Danube). In conjunction with the fulfilment of obligations arising from the Convention of the European Economic Commission of the United Nations Organisation on the protection and use of transboundary watercourses and international lakes, an "International Commission" was founded in 1990-1998 for each international catchment area. The CR is a member of the International Commissions for the protection of these catchment areas. The purpose of the activity of these institutions is to support cooperation in water management at the level of international catchment areas. It is obvious that practically all significant watercourses in the CR drain water beyond its boundary on the territories of the neighbouring states, resulting in the fact that water sources in the CR are practically dependent on the amount and distribution of atmospheric precipitation. In the context of discussing changing climatic conditions, atmospheric precipitation of very different intensities increases the likelihood of the occurrence of extreme floods and dry episodes. The theme of protection from the consequences of floods and drought is part of joint debates of all three international commissions. The approach to the solution of the issues above, however, can be different because it is based on the current conditions of the given international catchment area. Many fields and areas give attention to the theme of threats posed by natural disasters created by flood situations and drought not only from the view of science. It is not possible to prevent floods or drought by the present scientific knowledge and technical options. In case of floods, it is possible to reduce their impact on the lives and property of inhabitants by constructing efficient flood control works. However, it is necessary to have in mind that even the best flood control measure will only be as reliable, efficient and safe as its weakest element will be reliable, efficient and safe. In many cases, this element is earth-fill dams. Therefore, it is necessary to have continuous and long-term information on their condition. When addressing the issue of drought in the CR, it is necessary to realise that the absolute majority of water sources depends on the retention and accumulation of water in the territory of the CR. At present, the impacts of drought and lack of water in the conditions of the CR are significantly mitigated by the existing water management infrastructure. However, it can be expected for the future that the existing water sources will not be sufficient. Not only the aspect of the potentially diminishing available amount of surface water and subsurface water in the CR will be problematic, but also the aspect of the unsuitable quality of water. Also from this aspect, it is possible to see the earth-fill dam as an element that helps retain and accumulate water in the landscape. The reality is that every inhabitant of the CR is a significant user of its water sources, and it is necessary to bear the responsibility for them. Unfortunately, people usually realise neither the significance nor the value of the discussed irreplaceable nature wealth for everyday life, nor the scope of activities and financial costs that are associated with this "matter of course". In this chapter, the team of the authors provides a view of international cooperation and its achievements when dealing with a project of applied research in the EUREKA programme, which was focused on the development and construction of monitoring technology enabling changes in water content to be monitored in a porous medium. The selected results are documented in a link to remedial measures applied to earth-fill dams of water reservoirs in the conditions of the CR, emphasising the use of the method of electrical impedance spectrometry. The authors are aware of the fact that it is only a fragment of the solution of the complex of the outlined issue. However, it is obvious that without the safe operation of water management works, the irreplaceable part of which is their monitoring, it is impossible neither to ensure water sources nor to manage them.

One ancient wisdom says, ‘He who does not know the past cannot create the future’. This is not only true for the peoples and countries, but also for every human activity and society. In the course of time, human society has often passed through booms and declines. However, the necessity for life was always the need for freshwater. Nowadays, when extremely dry months alternate with local torrential rainfall, water management is frequent, and construction of laboratories of water management was shown as a very wise act. The Faculty of Civil Engineering in Brno, Czech Republic, has its history reaching far back into the nineteenth century. Indisputably, the elaboration of the concept and the factual establishment of water laboratories is worldwide ground-breaking. Founder of the water laboratories in Brno is Prof. Ing. Antonin Smrcek, Dr. h. c. To defend the first laboratories in the Austro-Hungarian Empire, he used both his literary talent and knowledge of Czech and German languages in speeches at international congresses on dams and navigation. Prof. Smrcek was striving to contribute as effectively as possible to the development of his school and the Czech element in Moravia. Therefore, he became elected a deputy of the Moravian Land Diet (Parliament Assembly) and later also of the Vienna Reich Council where he collaborated, amongst others, with T. G. Masaryk. He stood up efficiently for the further extension of the Brno Technical College with mechanical, chemical, electrical, and cultural branches and carried through the chemical building on Žižkova Street. When appraising the life and work of Prof. Smrcek is becoming more and more aware of the legacy of our ancestors. With humility and pride, we invite you to take a short trip through the past and present of the water research laboratories in Brno. Let us be grateful.

The influence of several parameters on the incipient motion of gravels has been carefully examined from theoretical and experimental standpoints. The effect of the longitudinal bed slope is significant and well described with existing methods. This analysis shows that the effects of the grain Reynolds number and relative submergence are negligible for turbulent flows over hydraulically rough boundaries. Laboratory experiments for homogeneous gravels on a plane bed provided detailed measurements of both mean flow velocity and velocity fluctuations for the analysis of the lift and drag coefficients. This analysis of the lift and drag coefficients enables a better evaluation of the Shields parameter for incipient motion as a function of the angle of repose . The theoretical developments presented in this paper are corroborated by the results of our laboratory experiments as well as many others available in the literature.

Broad-crested side weirs have been the subject of numerous hydraulic studies; however, the flow field at the weir crest and in front of the weir in the approach channel still has not been fully described. Also, the discharge coefficient of broad–crested side weirs, whether slightly inclined towards the stream or lateral, still has yet to be clearly determined. Experimental research was carried out to describe the flow characteristics at low Froude numbers in the approach flow channel for various combinations of in- and overflow discharges. Three side weir types with different oblique angles were studied. Their flow characteristics and discharge coefficients were analyzed and assessed based on the results obtained from extensive measurements performed on a hydraulic model. The empirical relation between the angle of side weir obliqueness, Froude numbers in the up- and downstream channels, and the coefficient of obliqueness was derived. Boční přelivy se širokou korunou byly předmětem četných hydraulických studií, nicméně proudění na koruně a před přelivem v přítokovém korytě ještě nebyl plně popsány. Také součinitel průtoku bočních přelivů se širokou korunou s různým úhlem půdorysné šikmosti nebyl precizně určen. Experimentální výzkum byl proveden za účelem popisu charakteristik proudu za malých hodnot Froudova kritéria v přítokovém korytě při různých průtokových stavech. Tři varianty s půdorysnou šikmostí přelivu byly podrobeny výzkumu. Charakteristiky proudu a součinitel průtoku byly určeny na základě změřených dat. Empirická závislost součinitele průtoku na úhlu půdorysné šikmosti a podílu Froudových kritérií v přítokovém a odtokovém korytě byla stanovena.

The paper gives short information about the results of monitoring the electrical properties of an earth-fill dam during the application of a nutrient aqueous solution used in the method BioSealing. Monitoring is carried out using a Z-meter device when applying the method of electrical impedance spectrometry and, in some cases, is part of a system of monitoring seepage through the earth-fill dam of the water reservoir by its administrator. Information about the changes that take place in the body of the dam during the movement of the water level in the reservoir or after the influence of weather changes or human activity are given through the monitored changes in the electrical parameters of the soil of the dam with time.

This paper is concerned with the determination of the relationship for the calculation of the discharge coefficient at free overflow over a rectangular sharp-edged broad-crested weir without lateral contraction. The determination was made on the basis of new measurement in a range of the relative thickness of the weir from 0.12 to 0.30 and newly in a large range of relative height of the weir extremely from 0.24 to 6.8 which greatly expands the application possibilities of low weirs. In addition, the effects of friction and surface tension on the value of the discharge coefficient were evaluated as well as the effect of the relative thickness of the weir. The new equation for discharge coefficient, expressed using the relative height of the weir, was subjected to verification made by an independent laboratory which confirmed its accuracy. Článek je zaměřen na určení součinitele průtoku při dokonalém přepadu přes pravoúhlý přeliv se širokou korunou bez bočních kontrakcí. Stanovení bylo provedeno na základě nových měření v rozsahu relativní tloušťky přelivu od 0.12 do 0.30 a nově za velkého rozsahu relativní výšky přelivu, což významně rozšiřuje aplikační možnosti tzv. nízkých přelivů. Současně byl určen vliv tření a povrchového napětí a vliv relativní tloušťky přelivu. Nová závislost byla ověřena nezávislou laboratoří.

The paper deals with the determination of the basic characteristics of flow at the crest of a rectangular broad-crested weir and in detail with the characteristics of flow separation at the upstream edge of the weir crest. The determination of the characteristics is made on the basis of measurement of the water surface level, the pressure head and the velocity field using the Particle Image Velocimetry method. The characteristics are expressed dimensionless in relation to the energy overflow head and the critical depth.

The paper deals with research focused on description of flow structure in front of broad-crested weir. Based on experimental measurement, the flow structure in front of the weir (the recirculation zone of flow and tornado vortices) and flow structure on the weir crest has been described. The determined flow character has been simulated using numerical model and based on comparing results the suitable model of turbulence has been recommended. Příspěvek se zabývá výzkumem zaměřeným na popis struktury proudu před přelivem se širokou korunou. Popisuje strukturu proudu před přelivem (recirkulační oblast proudu a tornádové víry) a na koruně přelivu. Struktura proudu byla simulována numerickým modelem a na základě porovnání výsledků byl doporučen vhodný model turbulence.

Even though broad-crested side weirs have been subjected to numerous studies, guidance for discharge coefficient determination for broad-crested side weirs still has not been clearly given. Experimental research was carried out to describe the flow conditions in front of a trapezoidal broad-crested side weir at low Froude numbers in the approach channel for various combinations of inflow and overflow discharges. Three side weir variants with different oblique angles were studied. Flow characteristics at the side weir were analyzed and assessed based on the results obtained from extensive measurements performed on a hydraulic model. The empirical relation between the coefficient of obliqueness, the angle of side weir obliqueness, and Froude numbers upstream and downstream of the weir was derived.

The paper deals with selected procedures used to calculate the shape of compact nappe during free overfall from a smooth horizontal channel with rectangular cross section. Calculated and measured water surface and velocity conditions in the end section, the level of water surface upstream in front of the end section and the shape of the compact part of an overfall nappe are described for a particular compared case. Článek pojednává o vybraných postupech výpočtu tvaru neprovzdušněné části paprsku při volném přepadu z hladkého vodorovného koryta obdélníkového příčného profilu. Pro konkrétní porovnávaný případ jsou popsány vypočtené a změřené hladinové a rychlostní poměry v profilu koncové hrany, průběh hladiny protiproudně před koncovou hranou a tvar neprovzdušněné části přepadového paprsku.

The use of environmentally-friendly materials in hydraulic engineering (e.g. the stone lining of weirs at levees) calls for the more accurate estimation of the discharge coefficient for broad-crested weirs with a rough crest surface. However, in the available literature sources the discharge coefficient of broad-crested weirs is usually expressed for a smooth crest. The authors of this paper have summarized the theoretical knowledge related to the effect of weir crest surface roughness on the discharge coefficient. The method of determination of the head-discharge relation for broad-crested weirs with a rough crest surface is proposed based on known discharge coefficient values for smooth surfaces and on the roughness parameters of the weir. For selected scenarios the theoretical results were compared with experimental research carried out at the Laboratory of Water Management Research, Faculty of Civil Engineering (FCE), Brno University of Technology (BUT). Používání přírodě blízkých materiálů ve vodním hospodářství (např. kamenná opevnění povrchu přelivů v ochranných hrázích) vyvolává požadavek přesnějšího stanovení součinitele průtoku pro přelivy se širokou a hydraulicky drsnou korunou. V dostupných literárních pramenech je součinitel průtoku přelivů se širokou korunou obvykle vyjádřen pouze pro hladký povrch koruny přelivu. Autoři článku shrnuli teoretické poznatky týkající se vlivu drsnosti povrchu koruny přelivu na součinitel průtoku a navrhli metodu pro stanovení způsobu hydraulického výpočtu konzumční křivky přepadu přes přeliv se širokou a drsnou korunou. Postup vychází ze znalosti součinitele průtoku přelivu s hladkou korunou a charakteristik drsnosti. Pro vybrané scénáře byly teoreticky vypočítané hodnoty porovnány s výsledky experimentálního výzkumu uskutečněného v Laboratoři vodohospodářského výzkumu Ústavu vodních staveb, Fakulty stavební, Vysokého učení technického v Brně.