The discharge from Lake Mälaren is regulated to keep the lake water level within limits set by a water decree. Despite this, in the year 2000 the lake water level rose above the upper limit. Studies conducted at the climate modeling unit Rossby Centre at the Swedish Meteorological and Hydrological Institute (SMHI) indicate that the inflow to the lake may increase in the future. A flood in the area will, among other things, strike infrastructure and residential districts. The aim of this study was to investigate the water levels of Lake Mälaren in future climates. In addition to this possible future expansion of the lake discharge though the sluice gates in order to keep water levels below limits set by the water decree and to prevent flooding of the shoreline were discussed. This was done by examining past lake and sea water level data and by using a discharge model to simulate future lake water levels resulting from high future inflow. The study was commissioned by SMHI. High lake water levels were reproduced fairly well by the discharge model, whereas it was more difficult to draw any coclusions concerning low lake water levels. The examination of data on past lake water levels demonstrated that the regulation of the lake discharge caused a reduction of the highest lake water levels, but above all an increase of low lake water levels. Data on past sea levels in the Baltic Sea showed high values during wintertime. In combination with future high inflow to Lake Mälaren during this season, this indicates that the greatest future flood risk may prevail during wintertime. The conclusion from the simulated future lake water levels was that the lake discharge needs to be expanded to prevent flood in the area. In all scenarios examined in this study, the lake water level will not rise above the upper limit set by the water decree if the discharge is increased to 1 370 m3/s, which almost corresponds to a doubling of the existing discharge of 710 m3/s. / Mälarens utlopp är reglerat för att kunna hålla vattenståndet inom acceptabla gränser. Trots regleringen översteg vattenståndet under vintern 2000/01 den högsta föreskrivna nivån i regleringsbestämmelserna. Studier som bedrivs på klimatforskningsavdelningen Rossby Centre på SMHI pekar på att det framtida inflödet till Mälaren kan komma att bli högre än vad det är idag, något som skulle innebära ännu högre vattennivåer i Mälaren. En omfattande översvämning av Mälarens stränder går bland annat ut över infrastruktur och bostäder. Problemet idag är att avbördningen genom sjöns utskov är för liten för att förhindra att översvämning uppstår. Att försöka skydda Stockholm mot vattnet med hjälp av skyddsmurar och invallning skulle bli alltför kostsamt. Ett bättre alternativ är istället att öka avtappningskapaciteten genom slussarna. Syftet med det här arbetet var att undersöka hur vattennivån i Mälaren kan komma att bli i ett framtida förändrat klimat. I samband med detta gavs ett underlag för diskussioner om kommande utbyggnader av Mälarens utlopp för att kunna hålla vattennivån under vattendomens högsta föreskrivna nivå även vid ett högre framtida inflöde. Detta uppnåddes genom att genomföra analyser med historiska vattenståndsdata och genom att använda en beräkningsmodell för avtappning, Mälarmodellen, för simulering av ett antal framtida inflödessituationer. Arbetet har genomförts på uppdrag av SMHI. Avtappningsmodellen återskapade de höga vattenstånden förhållandevis väl, medan det var svårare att bedöma hur precist den beräknade de allra lägsta vattennivåerna. Ett viktigt resultat från analysen med historiska data var att införandet av regleringen av Mälarens utlopp bidrog till att sänka de höga vattenstånden, men framförallt till att höja de låga. Ett annat resultat från studierna av historiska data var att vattenståndet i Östersjön antar högst nivåer under vintern. Detta i kombination med ett framtida högre inflöde till Mälaren under denna årstid indikerar att störst risk för översvämning kan komma att föreligga under vintern. För att säkert kunna hålla Mälarens vattennivå inom acceptabla gränser måste sjöns utlopp byggas ut. I alla scenarier som har undersökts i det här arbetet kan vattennivån hållas under den högsta föreskrivna nivån om avbördningen utökas till 1 370 m3/s. Det krävs alltså nästan en fördubbling av dagens avbördningskapacitet på 710 m3/s.

Masters of Science / The thesis investigates the potential of the Rietfontein and Spitskop aquifer to meet a demand of 1000 m3/d (12 Lis) as an alternative water resource for the Rietfontein and Spitskop Community. Increasing demand for clean and hygienic drinking water puts more pressure on one of our most valuable resources and supplying all communities with surface water is an extremely difficult and costly task in rural areas like Rietfontein and Spitskop in South Africa. Therefore it is necessary that interim water supplies be found from local aquifers and be utilized to address water supply challenges. Groundwater may serve as a short-term and an interim water supply which may be useful during future dry periods. Abstraction of groundwater is sensitive to recharge. Due to semi-arid conditions in Rietfontein and Spitskop area, there is high rainfall variation and disparity each year. During the research, hydrocensus was carried out. Water samples for chemistry analysis were taken. Literature review and pumping test data was utilized from the previous studies done by different consultants (Botha, 2000, Vivier and Pretorius, 2003). A numerical groundwater flow model for the local aquifers in the area and surroundings was constructed focusing on recharge and abstraction scenarios for the water supply from the local aquifers. For Rietfontein and Spitskop area, the mean annual precipitation (MAP) is 617mm/year. To be assured and rational in determining aquifers ability to meet the required demand a recharge with ninety-five (95th ) percentile was recommended, which estimates the MAP of 308mm/year which is 50% lower than the average MAP of 617mm/year. For a period of ninety six (96) years, the data indicates a severe drought occurred four (4) times where the rainfall was even lower than 95th percentile level of assurance of recharge estimated. This gives a comprehensible indication that average mean is not ideal or steadfast stature when building a water supply numerical groundwater flow modelling. These aquifers can only be exploited and managed if a reliable method can be obtained to estimate their long-term sustainable potential, since the sustainable potential of these aquifers to supply the communities is dependent upon the recharge from rainfall. The results from a numerical groundwater flow model indicated that a combined potential from the local aquifer from eighteen (18) boreholes is sufficient to meet the required demand and a total of 2600m3 Id can potentially be abstracted from the aquifer. With ninety-five (95th ) percentile recharge rate of 308mm/year a numerical groundwater flow model shows that the rate of abstraction is 80% far less than recharge, which gives high level of assurance in terms of local aquifer water supply demand. The abstraction of the boreholes confirmed by a numerical groundwater flow model shows the least impact on the surrounding aquifer for an extended period of time. In the event of drought, the boreholes will see a decline in water level after two (2) months of pumping local aquifer. The water level will decline steadily from two (2) months to two (2) years with a change in water levels of up to 40m. The impact of the drought is minimal compared to recharge rate, which verifies less depletion of the aquifer. The local aquifer shows the potential of 3MLld can be supplied to the communities with an assurance level of 95th percentile of rainfall. Reliable quantification of groundwater recharge rate remains the main challenges the hydrologist experienced and further research is essential for improvement of groundwater management for the area concerned.

This thesis deals with the implementation of a system for measuring the amount of water in the tank using a 12V water pump. The whole system is controlled by the ESP32 microcontroller. The introduction deals with the theoretical analysis of various principles of measuring the level of liquids. The next part deals with the procedure of the construction of the measuring device and its theoretical analysis. The last part of the work deals with the control of the pump and the individual functions that provide this control. The ultrasonic distance sensor AJ-SR04M was chosen for the implementation of the device. The volume of water in the tank is calculated from its data. The ESP32 microcontroller provides system control via a web interface. The whole system was implemented and tested to measure the volume of water and its pumping in the IBC container.

Entering of thesis focuses on large-scale solar systems. Large solar-scale system will be used for heating water in public swimming pool. The pool is located in Brno - country. The pool is operated year-round. Great emphasis of the thesis is on the surface heat loss. Evaporation of water from the water surface is also applied in the experimental part of the thesis. In the calculations is used software for modeling the thermal microclimate of buildings and air conditioning design Teruna.

I denna rapport utreds olika metoder för att kunna reglera vattennivån i vattenkraftverket Avesta Lillfors i Dalarna. Två kraftverk ligger endast 900 m uppströms och detta gör att svarstiderna blir korta och regleringen blir lätt nervös. Att använda sig av vattennivåreglering i ett kraftverk för-enklar dess styrning då anpassning till inflödet sker automatiskt. En flödestabell har tagits fram genom mätningar i turbinen, med hjälp av Winter-Kennedy-metoden. Denna tabell används för att kunna fram-koppla regulatorn och därmed dämpa stora variationer i inflödet. Dessu-tom har en modell av älven skapats och testats med en återkopplad PID-regulator. Utefter dessa tester har lämpliga parametrar tagits fram, som ger önskad stabilitet, noggrannhet och snabbhet. Simuleringar har även gjorts med reglermetoden Fuzzy logic. / This report evaluates different methods to create a stable regulation of the water level in the hydro power plant Avesta Lillfors, in county Dalar-na. Another pair of plants are located just 900 m up the stream, which is why the regulation has to act fast. If the water level can be regulated and automatically adjust to the incoming flow, it facilitates the control of the plant. A flow chart is created from measurements in the turbine, using the Win-ter-Kennedy method. The results are used for feedforward control. A PID-regulator with feedback is also simulated in a model of the river. This helps finding the parameters that provide a stable, accurate and fast regu-lation. Fuzzy logic control has also been simulated.

Globally, a significant portion of energy comes from hydropower. However, harnessing hydro energy interrupts the natural state of river flows, thus affecting the ecological processes of the surrounding communities. In this thesis, a water level control model is described to sustain a desired head for a hydropower plant despite the nature of the stream flows. A scientific analysis is carried out on the physical set up of a hydropower reservoir via mathematical modelling. The study depicts that the amount of electric power, Pe(t) generated from a specific hydro reservoir is mainly controlled by the current water level, h(t) and its corresponding outflow volumes, fout(t). However, these two variables are largely constrained by the behaviour of the inflow volumes, fin(t). So, by relating the torque-force balance equations of all the dynamic elements involved we develop a mathematical model that maintains a steady water level at sustainable inflow rates. The Routh-Hurwitz stability criterion and the Final Value theorem are applied to decide the PD-control actions that stabilize the system. The penstock cross-sectional area, Ap is varied to attain the correct fout(t) for the desired h(t). The model behaviour is verified using Simulink simulation software. Eventually, the model accounts for hydroelectric power production patterns that depends on the nature of the stream flow rates.

Time-series forecasting is an area of machine learning that can be applied to many real-life problems. It is used in areas such as water level forecasting, which aims to help people evacuate on time for floods. This thesis aims to contribute to the research area of time-series forecasting, by introducing a simple but novel ensemble model: Force Linear to Exponential (FLEX). A FLEX ensemble first forecasts points that are exponentially further into the forecasting horizon. After this, the gaps between forecasted points are produced from said forecasted points, as well as the entire data history. This simple model is able to outperform all base models considered in this thesis, even when having the same amount of parameters to tune. / Tidsserieprognoser är ett område för maskininlärning som kan tillämpas på många verkliga problem. Det används i områden som vattenståndsprognoser, som syftar till att hjälpa människor att evakuera i tid för översvämningar. Denna uppsats syftar till att bidra till forskningsområdet tidsserieprognoser genom att introducera en enkel men ny ensemblemodell: Force Linear to Exponential (FLEX). En FLEX-ensemble prognostiserar först punkter som ligger exponentiellt längre in i prognoshorisonten. Efter detta produceras gapen mellan prognostiserade punkter från nämnda prognostiserade punkter, såväl som hela datahistoriken. Denna enkla modell kan överträffa alla basmodeller som behandlas i denna uppsats, även när den har samma mängd parametrar att ställa in.

Les mollusques sont des indicateurs de perturbations anthropiques et environnementales. Ce groupe de macroinvertébrés représente en outre une source importante de nourriture pour les poissons et les oiseaux aquatiques du littoral. Les hypothèses de cette étude sont que la communauté de mollusques est influencée indirectement par les tributaires agricoles et/ou par des variables environnementales (comme la dessiccation et l'exposition aux vagues) puisque ces perturbations sont susceptibles de modifier leurs sources alimentaires et leur habitat. Les indicateurs de la réponse des mollusques aux agents perturbateurs sont la composition, la diversité, la densité, ainsi que la biomasse des espèces. En septembre 2013, des mesures de paramètres physico-chimiques de l'eau ont été réalisées, et des échantillons de mollusques et de végétation aquatique ont été prélevés à 14 sites le long des rives du lac Saint-Pierre (Fleuve Saint-Laurent, Québec, Canada). Le long de la rive nord, les sites fortement exposés à l'action du vent, situés à de plus grandes élévations, affichaient une plus faible densité, biomasse et richesse spécifique de mollusques que les sites de la rive sud, en milieu plus abrité et profond. Les sites physiquement perturbés étaient caractérisés par de faibles biomasses en macrophytes submergés. Les sphaeriidae apparaissent comme des exceptions à ces patrons, montrant une abondance plus élevée aux sites presque dépourvus de macrophytes. Bien que les variables physiques et l'habitat exercent une influence déterminante sur les communautés de mollusques, les gastéropodes et les moules unionidés étaient également affectés par la dégradation de la qualité de l'eau dans le panache des tributaires agricoles. La richesse, la densité et la biomasse des gastéropodes étaient négativement influencées par des teneurs élevées de matières en suspension et de fer dissous. Les résultats de notre étude montrent que la communauté de mollusques du lac Saint-Pierre est directement affectée par l'émersion périodique, l'exposition au vent, et indirectement par l'effet de ces variables physiques sur les macrophytes qui constituent leur habitat. / Molluscs are indicators of anthropogenic and environmental disturbances and constitute an important food source for littoral fish and aquatic birds. The main hypotheses put forward for our study are that the mollusc community is impacted by the agricultural tributaries and/or by physical variables (desiccation, exposure to waves) through changes in food and habitat. The indicators used were mollusc species composition, diversity, density, and biomass. Over the course of two weeks in September 2013, we sampled physical/chemical water variables, collected aquatic vegetation and molluscs at 14 sites on both shores of Lake Saint-Pierre (St. Lawrence River, Quebec, Canada). Sites located at higher elevations, subjected to recent water level fluctuations, and exposed to wind fetch along the north shore, had lower gastropod and unionid mussel richness, density, and biomass than less-exposed sites located at lower elevations along the south shore. These physically disturbed sites were characterized by low biomasses of submerged macrophytes. Sphaerid clams appeared to be notable exceptions to these patterns, showing their highest abundances at sites almost devoid of macrophytes. In spite of the fact that physical and habitat variables exerted a strong effect on mollusc communities, gastropod and unionid mussels were additionally affected by degraded water quality originating from agricultural tributaries. Gastropod richness, density, and biomass were negatively influenced by high levels of total suspended matter and dissolved iron. Our results show that the mollusc community in Lake Saint-Pierre was primarily affected by the direct influence of periodic emersion, wind exposure, and indirectly through the effect of these physical variables on macrophyte habitat.

Das litorale Makrozoobenthos ist eine bedeutende biotische Komponente in Seen und trägt substantiell zur Biodiversität und Funktion von Seeökosystemen bei. Allerdings unterliegt das Litoral zunehmenden anthropogenen Nutzungen, deren ökologische Auswirkungen jedoch kaum quantifiziert wurden. In dieser Doktorarbeit wurde untersucht, welche Bedeutung maßgebliche Umweltfaktoren auf die Zusammensetzung des litoralen Makrozoobenthos haben, und wie sich anthropogene Nutzungen auf die Zusammensetzung und Funktion des Makrozoobenthos auswirken. Die Zusammensetzung des Makrozoobenthos wurde durch die Uferstruktur, Trophie und das hydrodynamische Regime bestimmt. Die faunistische Ähnlichkeit zwischen Habitaten war jedoch signifikant geringer als zwischen Trophiestufen, so dass die Uferstruktur, und nicht die Trophie, einen größeren Einfluss auf das Makrozoobenthos hat. Strukturelle Degradation führte zu einer Reduktion der Habitatheterogenität, was eine signifikante Verringerung der Diversität und eine signifikant veränderte Artenzusammensetzung verursachte. Infolgedessen war die Komplexität der Makrozoobenthos-Nahrungsnetze an degradierten Ufern signifikant geringer als an natürlichen Ufern. Erhöhte Wasserstandsschwankungen führten zum Ausfall von Wurzelhabitaten und der damit assoziierten Makrozoobenthos-Gemeinschaft. Schiffsinduzierter Wellenschlag führte zur Verdriftung des Makrozoobenthos von ihren Habitaten bereits bei geringen Sohlschubspannungen. Die Effekte von Wasserstandsschwankungen und schiffsinduziertem Wellenschlag wurden jedoch durch Habitate mit hoher struktureller Komplexität verringert. Mit dieser Doktorarbeit konnte ich ein mechanistisches Verständnis darüber erarbeiten, wie anthropogene Nutzungen die Wirkungsbeziehungen zwischen Umweltfaktoren und Artengemeinschaften verändern und welche ökologischen Auswirkungen dies hat. Diese Kenntnisse können als wissenschaftliche Basis zur Bewertung von anthropogenen Beeinträchtigungen des Litorals dienen. / Littoral macroinvertebrates are an important biotic component of lakes by contributing substantially to the biodiversity and functioning of lake ecosystems. Humans alter the littoral and riparian areas for various purposes, but the resulting ecological impacts on littoral macroinvertebrates have not been quantified. In this thesis, I investigated the significance of key environmental factors for littoral macroinvertebrate communities and how human alterations of these environmental factors impact the structure and function of macroinvertebrate communities. Macroinvertebrate community composition was significantly related to littoral structure, trophic state and the hydrodynamic regime. The significantly higher compositional dissimilarities among habitats than among trophic state suggested that littoral structure was the more important driver of community composition. Structural degradation caused a significant reduction of habitat heterogeneity and resulted in a significant reduction of species diversity and a significant altered community composition. This caused a significant reduction of macroinvertebrate food web complexity and substantial alterations of the trophic base of the food webs. Climate-change induced water level fluctuations resulted in the loss of root habitats and the specific community associated with this habitat. Ship-induced waves had substantial direct effects, since macroinvertebrates were detached from their habitats by waves even at moderate shear stress levels. However, the impacts of water level fluctuations and ship-induced waves were mitigated by the presence of habitats with high structural complexities. This thesis provided a mechanistic understanding of how human activities alter relationships between environmental factors and biotic communities. This knowledge can be used to develop scientifically sound approaches to assess the persistent human impacts on lake ecosystems.

From the Proceedings of the 1971 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 22-23, 1971, Tempe, Arizona / The development of tree-ring chronology for bristlecone pine (Pinus aristata), stretching over 8,200 years, has been used to calibrate the radiocarbon time scale. An extensive deposit of driftwood in Stanton's cave in the grand canyon was estimated to have been deposited on the cave floor about 12,000 years ago on the basis of the 4,095-year radiocarbon age of a split-twig figurine on the surface of the cave floor. However, the initial driftwood specimen gave the surprising C-14 age of 35,000 years. A tree-ring dating study was therefore undertaken on driftwood in the grand canyon in order to: (1) evaluate the driftwood deposit in Stanton's cave; (2) provide a basis for interpreting c-14 dates from canyon archaeological sites; and (3) document a technique for deriving some concept of pre-dam hydrology, especially maximum high water levels. The percentage of dated specimens found indicated that the approach was feasible. A likely interpretation of the seemingly early c-14 dates at archaeological sites is that prehistoric man used old driftwood, as does modern man in the canyon. Tree-ring dates from wood above the pre-dam high water mark indicate that maximum 100-year flood evidence can be obtained.