No description available.

The distribution of macroinvertebrate communities is influenced by a myriad of abiotic environmental factors. However, many of these environmental factors do not occur randomly within a river system. Rather, they occur as a result of geomorphological processes that operate hierarchically to constrain the expression of environmental factors at successively nested levels. As a result of the hierarchical expression of geomorphological processes, environmental factors occur at characteristic scales within a river system and can be used to define spatial scales of river system organisation. Previous studies have examined multiscale patterns of benthic macroinvertebrate community distribution using scales of measurement such as ecoregions, catchments, rivers, reaches and functional habitats. However, none of these studies used scales derived from a geomorphological hierarchy to examine patterns of macroinvertebrate distribution. Given that macroinvertebrates are often deterministically influenced by environmental factors, and these environmental factors occur at characteristic scales within a geomorphological hierarchy, it is possible that the multiscale distribution of macroinvertebrate communities may correspond to the hierarchical arrangement of a river system. This study used scales of measurement derived from a geomorphological hierarchy to examine whether there was any congruence between the distribution of macroinvertebrate communities and the organisation of a river system at the catchment, zone, reach and riffle scales. The Upper Murrumbidgee River Catchment study area (13 005km/2) was divided into catchments, zones within catchments, reaches within zones and riffles within reaches. Macroinvertebrate collection was stratified across these scales according to a balanced nested hierarchical design, and environmental data were also collected at the catchment, zone, reach and riffle scales. Simultaneous multiscale treatment of biological and environmental data allowed identification of multiscale patterns of macroinvertebrate distribution in relation to the hierarchical organisation of a river system, as well as identification of hierarchical interactions between macroinvertebrate communities and environmental factors. Multivariate (ANOSIM, classification, ordination) and univariate (Nested ANOVA) statistical techniques were employed, and each analysis was performed at the species and family levels of taxonomy. Macroinvertebrate communities were highly similar within a reach, because this is the point in the geomorphological hierarchy where environmental conditions become more homogeneous, relative to larger scales. Conversely, communities were dissimilar at the larger zone and catchment scales because environmental conditions become more heterogeneous, relative to smaller scales. However, the reach within zone scale also represents the point where sampling reaches become distinct across the landscape, and the similarity of macroinvertebrate communities within a reach may also be related to the spatial proximity of samples. Hence, macroinvertebrate community distribution is only congruent with the smaller scales of river system organisation. Despite the lack of congruence between macroinvertebrate community distribution and the larger catchment and zone scales of river system organisation, there was a strong regional pattern of distribution in the Upper Murrumbidgee River Catchment. This regional-scale pattern self-emerges from biological information, and is larger than the geomorphologically derived catchment scale. Partitioning of macroinvertebrate data into regional groups subsequently revealed some congruence between macroinvertebrate distribution and the catchment and zone scales of river system organisation. An alternative hierarchy consisting of biological regions, biological clusters, geomorphological reaches and geomorphological riffles was marginally better able to capture patterns of macroinvertebrate distribution than the original catchment, zone, reach and riffle scales. Thus, consideration of the hierarchical organisation of stream systems from a purely physical perspective may fail to encompass scales that are relevant to biota, and biological information should be included as a primary hierarchical component of landscape-scale studies of macroinvertebrate distribution. The pattern of region and reach-scale macroinvertebrate distribution was matched by a general pattern of large catchment and local reach-scale environmental influence. This occurred despite testing of catchment, zone, reach and riffle-scale environmental variables against both the scaled and non-scale pattern of macroinvertebrate distribution. Macroinvertebrate communities were influenced by local reach-scale characteristics such as riparian vegetation character and channel morphology, but rifflescale hydrological variables were also associated with some headwater communities. However, macroinvertebrate communities also sit within a broader landscape context and are influenced by large catchment-scale factors such as landuse, or by factors indicating the geographical position of the sample or the size of the stream. The large and local-scale environmental variables that influence macroinvertebrates are related within a geomorphological hierarchy, and macroinvertebrates may respond deterministically to the same type of environmental factor expressed at different scales. These responses should not be treated as statistical correlates, but rather, they should be viewed in the context of a hierarchy of river system organisation. There was little difference in the overall scale-related findings between species and family level. Family-level macroinvertebrate communities were similar within a reach and dissimilar among reaches, zones and catchments and there was a large regionalscale pattern of family-level community distribution. Local reach-scale and large catchment-scale environmental factors were most strongly associated with family-level macroinvertebrate distribution. Replication of these scale-related findings at both levels of taxonomy indicates that aggregation from species to family level does not result in loss of ecological information pertaining to primary hierarchical patterns. However, the difference between species and family level was pronounced when tracing the hierarchical occurrence of individual taxa, in the context of theories such as the landscape filters hypothesis and habitat based model. In particular, there was a shift in the scale at which families began to be removed from the hierarchy from the region to the smaller cluster scale. This shift was related to the lowered distinctiveness of familylevel regional macroinvertebrate groups, but also suggests that environmental filters may act differently on species and families. The use of family-level data is not recommended for the testing of theories of hierarchical taxon occurrence, because these theories rely on the accurate detection of precise macroinvertebrate-environment relationships. The use of scales of measurement derived from a geomorphological hierarchy provides a process-based foundation for marrying the biological and physical domains, and for examining the hierarchical interactions that may occur between these domains. However, the results of this study indicate that overlaying the biological and physical domains is not a straightforward task, because the biological domain may be influenced by factors other than the deterministic relationship between macroinvertebrates and environmental conditions. Regardless, this study has taken some basic principles of fluvial geomorphology and incorporated them into the design of a standard stream ecology study. Given the relatively advanced state of knowledge that exists individually in the disciplines of fluvial geomorphology and stream ecology, integration and application of concepts across disciplines represents an exciting future opportunity in aquatic science.

Salinity is a major determinant of where and how water resources are used worldwide. Natural salt pollution severely constrains the beneficial use of large amounts of water in Texas and neighboring states. High salinity loads in several major river/reservoir systems, including the Brazos River, originate largely from salt seeps and springs in isolated areas of the upper river basins located in the Permian Basin geologic region. Research objectives were (1) to improve salinity simulation capabilities of the Water Rights Analysis Package (WRAP) modeling system, and (2) to develop a better understanding of the occurrence, transport, and impacts of salinity in the Brazos River and Lakes Possum Kingdom, Granbury, and Whitney. Water volume budgets and total dissolved solids load budgets were developed for five river reaches covering 405 miles of the upper Brazos River. Methodologies were developed for creating and applying WRAP salinity input datasets. The WRAP modeling system was expanded and applied to the entire Brazos River Basin to investigate alternative modeling premises and impacts of salinity and salinity control measures on water supply capabilities. Water and salinity budget analyses of the Brazos River system based primarily on measured stream flow, reservoir storage, and total dissolved solids data compiled by the U.S. Geological Survey were performed to explore the characteristics of flow and storage volumes and salinity loads and concentrations in the river/reservoir system. WRAP salinity input datasets were developed based on results from the salinity budget study. One dataset was designed and applied specifically for testing salinity routing methods and calibrating salinity routing parameters. A second complete basin salinity dataset was developed and applied to simulate the Brazos River Basin for alternative management strategies. The results of the simulations demonstrate, for example, that previously proposed salt control impoundments can significantly reduce salinity loads and concentrations in the three reservoirs and at all locations on the Brazos River from the impoundments downstream to the Gulf of Mexico. The WRAP salinity simulation features are designed to provide flexibility in combining water quantity simulation datasets from the Texas Water Availability Modeling System or other sources, which may be very complex, with available salinity data which varies in extent and format between different river basins. The modeling capabilities demonstrated by the Brazos River Basin study can be applied in other river basins as well.

No description available.

Informal settlements are a natural and necessary part of urbanization. Occupied by victims of unsuccessful migration and viewed by the city dweller as a dystopia, these are incredibly self-sustaining parts of the city. Inhabited by the socially marginalised, informal settlements have been neglected in terms of infrastructure and public processes by the formal sectors. Recent efforts to deal with these settlements, like forced evictions, show evidence of social and spatial injustices inflicted on the inhabitants. By 2050, more than two-thirds of the global population will live in cities. Of those, one-third will live in sub-par informal settlements without their own right to the city. With this reality, is it time to reassess how we talk about informal forms of urbanization?

Masters of Science / In South Africa and neighbouring countries such as Zimbabwe, Botswana, Angola, and Namibia, most river systems are non-perennial due to semi-arid or arid climatic characteristics. In such river systems, the interaction between groundwater and surface water is of significance in terms of developing appropriate methods for determining ecological water requirements among others. However, the interaction is not well understood in terms of the influence on the volume and quality of water on the gaining and losing water bodies. In past research, the importance of non-perennial rivers (NPRS) was neglected because these river systems were considered as systems of low ecological importance and economic value. However, an improved understanding of these systems illustrated that they provide habitat for diverse and unique flora and fauna. Therefore, the main research question that was posed for the study was what is the influence of river-aquifer interactions in non-perennial river systems in the semi-arid environment? The central argument was that unless we assess the interaction between surface water and groundwater in NPRS, we cannot improve on understanding of the role of groundwater on the NPRS. The aim of the study was therefore, to assess surface water-groundwater (river-aquifer) interactions in non-perennial river systems to provide an insight regarding how these water resources interact in semi-arid environments. To achieve the aim, three specific objectives were formulated, namely, to establish the groundwater contribution to the river system, to investigate the role of the river in recharging the underlying aquifer, and to develop a regional hydrogeological conceptual model of recharge mechanisms. To achieve the objectives of the study, samples were collected from boreholes, a dug well, springs, surface water and cumulative rainfall collectors during the summer and winter seasons. The samples were analysed for hydrochemistry and stable isotopic signatures (δ2H and δ18O). The intention was to identify where and when do river-aquifer interactions occur in the study area. Secondary data from records review and field data from hydrometric methods, ERT geophysical surveys and tracer techniques were also used to address the third objective.

Riverine landscapes are complex. More than just a single channel, they comprise a shifting mosaic of hydrogeomorphic patches with varying physical and biological characteristics. These patches are connected by water during flows of varying magnitude and frequency, at a range of spatial and temporal scales. Combined, landscape complexity and hydrological connectivity create biological diversity that in turn maintains the productivity, ecological function, and resilience of these systems. This thesis investigates the ecological importance of spatial heterogeneity and temporal hydrological connectivity in a dryland floodplain river landscape. It focuses on anabranch channels, and uses major carbon sources in these and adjacent landscape patches as indicators of ecological pattern and process. A conceptual model was proposed, describing the potential effects upon the distribution and availability of major carbon sources of: a) a spatial mosaic of hydrogeomorphic patches in the landscape (e.g. anabranches, river channel, and wider floodplain); and b) four primary temporal phases of hydrological connection during flow pulses (disconnection, partial connection, complete connection, and draining). This was then tested by data collected over a three year period from a 16 km reach of the lower Macintyre River (NSW/QLD Australia). Results were examined at multiple spatial scales (patch scale � river channel vs. anabranches vs. floodplain; between individual anabranches; and within anabranches � entry, middle and exit sites). The data indicate that spatial heterogeneity in the lower Macintyre River landscape significantly influences ecological pattern. Carbon quantity was greater in anabranch channels compared to adjacent river channel patches, but not compared to the floodplain; while carbon quality was greater in anabranch channels compared to both adjacent river channel and floodplain patches. Stable isotope analysis indicated that carbon sources that were predominantly found in anabranch channels supported both anabranch and river organisms during a winter disconnection phase. Other carbon sources found in the main river channel and the wider floodplain appeared to play a comparatively minimal role in the food web. Different phases of hydrological connection between anabranch channels and the main river channel were associated with differences in the availability of carbon sources. In the river channel, draining of water from anabranches (the draining phase) was associated with relatively high concentrations of dissolved organic carbon (DOC) and low concentrations of phytoplankton. Conversely, the disconnection phase was associated with relatively low concentrations of DOC and high concentrations of phytoplankton in the river channel. In anabranch channels and their waterbodies, the disconnection and draining phases were associated with high concentrations of both DOC and phytoplankton. Concentrations of these carbon sources were lowest in anabranches during the partial and complete connection phases. Different hydrological connection phases were also associated with changes in trophic status in the aquatic components of the landscape. On the riverbanks, relatively low rates of benthic production and respiration during the complete connection phase were associated with heterotrophy. The remaining phases appeared to be autotrophic. Benthic production on riverbanks was greatest during the disconnection phase, and respiration was greatest during the partial connection phase. In the anabranch channels, rates of production and respiration were similar during the disconnection phase, and were associated with heterotrophy in the anabranch waterbodies. The remaining phases appeared to be autotrophic. Respiration was greatest in anabranches during the disconnection phase, and production was greatest during the draining phase. Both production and respiration were lowest during complete connection. These differences and changes varied according to the landscape patch examined. At a landscape scale, anabranch channels act as both sinks and suppliers of carbon. High rates of sediment deposition facilitate their role as sinks for sediment-associated carbon and other particulate, refractory carbon sources. Simultaneously, anabranch channels supply aquatic carbon sources from their waterbodies, as well as via processes such as inundation-stimulated release of DOC from surface sediments. Modelled data indicated that water resource development reduces the frequency and duration of connection between anabranch channels and the main river channel. This loss of landscape complexity via loss of connectivity with anabranches has the potential to reduce the total availability of carbon sources to the ecosystem, as demonstrated by a modelled 13% reduction in potential dissolved organic carbon release from anabranch sediments. This thesis has demonstrated the importance of spatial heterogeneity in riverine landscapes, by documenting its association with variability in the distribution and quality of primary energy sources for the ecosystem. It has shown that this variability is augmented by different phases of hydrological connectivity over time. Spatial heterogeneity and hydrological connectivity interact to increase the diversity and availability of ecological energy sources across the riverine landscape, at multiple spatial and temporal scales. This has positive implications for the resilience and sustainability of the system. Anabranch channels are particularly important facilitators of these effects in this dryland floodplain river system. Anabranch channels are �intermediate� in terms of spatial placement, temporal hydrological connection, and availability of carbon sources; of high value in terms of high-quality carbon sources; and relatively easy to target for management because of their defined commence-to-flow levels. Further research should be directed toward evaluating other ecological roles of anabranch channels in dryland rivers, thereby providing a more complete understanding of the importance of connectivity between these features and other patches. This knowledge would assist management of floodplain river landscapes at larger regional scales, including amelioration of the effects of water resource development.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: In this research a Real-Time hydrodynamic optimisation model of the Orange-Fish-Sundays River (OFS) system which uses real-time data in order to forecast release hydrographs, is evaluated. The OFS system stretches over three catchment areas in the Eastern Cape namely Great Fish, Little Fish and Sundays Rivers. The OFS supplies water from the Orange River through a 800 km system of canals, tunnels, dams and rivers to registered water users in this area. In order to cope with increasing pressures on water saving, water demand, water quality and dam safety, the Department of Water Affairs implemented this Orange Fish Sundays-Real Time (OFS-RT) system to calculate the optimal water flow, by running customised Danish Hydraulic Institute (DHI) MIKE11 software. The system utilizes an optimisation module that evaluates the simulated outcome at seven water release structures (dams, weirs and tunnels). Then during the optimisation process performs more adjustments to reach the objectives of the system to obtain the forecast release hydrographs. This OFS-RT model aims at target based objectives, using: (i) Hydras real-time field data of dam water levels, river flows and water quality from the area sent to the control office main computer at four hourly intervals via SMS and (ii) abstractors weekly water requests. This system takes irrigation and domestic demand into account as well as water quality, evaporation, rainfall, dam levels, dam safety, instream flow requirements and tributary flow. In order to manage the water flows through the OFS system the OFS-RT model forecasts the release hydrographs and uploads the predictions to a website to smooth operational procedures. The target outcomes were tested and evaluated during this research and it was found that the OFS- RT model succeeded in delivering release forecasts for the seven control structures to manage the OFS system. This research proved that management of river systems by using a real-time hydrodynamic model with optimisation is a useful tool for the optimal utilisation of water resources. / AFRIKAANSE OPSOMMING: Die doel van hierdie navoring is die evaluering van „n intydse hidrodinamiese optimiseringsmodel van die Oranje-Vis-Sondagsrivier (OVS) stelsel wat intydse data ontvang en loslatings hidrograwe verskaf. Die OVS stelsel strek oor drie opvangsgebiede in die Oos-Kaap: naamlik die Groot Vis-, Klein Vis- en Sondagsriviere en voorsien water vanuit die Oranjerivier deur „n 800 km stelsel van kanale, tonnels, damme en riviere, aan geregistreerde waterverbruikers in die gebied. Ten einde te voldoen aan die eise van waterbesparings, stygende vraag na water, die verskaffing van goeie water gehalte en damveiligheid, het die Departement van Waterwese „n intydse rekenaar model (OVS-IT) geïmplimenteer om die optimale watervloei deur middel van die aangepaste MIKE11 sagteware van die Danish Hydraulic Institute (DHI) te bereken. Hierdie stelsel maak gebruik van „n optimisering module wat die gesimuleerde uitkomste van verstellings aan sewe waterloslatingstrukture evalueer. Met optimisering word die verlangde hidrograaf deur verder aanpassings verkry. Data wat nodig is om die OVS-IT model se doel te bereik is: (i) Hydras intydse velddata van damwatervlakke, riviervloeie en water gehalte van die gebied ontvang deur die beheerkantoor se hoofrekenaar via SMS elke vier ure, en (ii) water verbruikers se weeklikse wateraanvrae Die stelsel neem die besproeiing en huishoudelike aanvraag in ag, sowel as soutgehalte, verdamping, reënval, damvlakke, dam veiligheid, stroom vloei vereistes en sytak byvloei. Die OVS se watervloei word beheer deur voorspelde loslatings hidrograwe, opgesom op „n webwerf wat die uitvoer prosedures aandui. Die intydse hidrodinamiese model met optimisering het volgens hierdie navorsing daarin geslaag om vir die beheer van die OVS stelsel, die loslatings van sewe beheerstrukture akkuraat te voorspel en bevind dat die model „n waardevolle instrument is vir die optimale bestuur van waterhulpbronne.

Submitted by Maike Costa (maiksebas@gmail.com) on 2016-01-05T12:09:06Z No. of bitstreams: 1 arquivototal.pdf: 8370454 bytes, checksum: 26479ee704fbe159e1994c81453039fa (MD5) / Made available in DSpace on 2016-01-05T12:09:06Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 8370454 bytes, checksum: 26479ee704fbe159e1994c81453039fa (MD5) Previous issue date: 2014-09-10 / The negative impacts caused by the use of process and land use on the banks of rivers and floodplains have been deteriorating the water health conditions, the environment and effect on landscapes. In urban areas, in particular, it is observed the degradation of rivers and water quality and aquatic biota. The interest in restoring ecosystems of waterways, both in urban and rural areas, is expanding worldwide, especially in developed countries. Similarly, areas of occupation in the coastal zone, those which tend to larger and denser occupation, have been a main concern of many governments. Therefore, models of environmental assessment of rivers have been developed and refined to allow the diagnosis and the selection of river restoration actions. The German method, called Mapping and assessment methods for the structure of Waters, developed in Bavaria, is used to map the quality of watercourses structure as a measure of its ecological integrity and indicates whether it is capable of supporting the dynamic processes of its bed. For the coastal zone, the Orla project’s methodology, developed by the Ministry of Environment of Brazil, uses the landscape units as elements of analysis in terms of urban occupation and provides grants for landscape analysis beyond the river limits and may complement fluvial analysis. Both methodologies contribute to perform a broader diagnosis of the current situation of environmental degradation, and may indicate which stretches and landscape units would need intervention to seek restoration or rehabilitation of these areas. In this work, these models were used to map the quality of the riverbed structure concerning its morphology, including the dynamics of the main river and the dynamics of wetlands, and also the marginal areas of low Jaguaribe River in its bed in the municipalities of João Pessoa and Cabedelo, on the south coast of the state of Paraíba. The results showed stretches of the river ranging from a totally altered state to little changed, concerning the stretch and the side occupation of the river channel. The extended marginal areas were classified into three types A, B, C of the Orla project, showing conformity with the classification obtained from the river system. / Os impactos negativos causados pelo processo de uso e ocupação do solo nas margens e planície de inundação dos rios vêm deteriorando as condições de salubridade das águas, do ambiente e com repercussão nas paisagens. No meio urbano, em particular, se observa a degradação dos rios e da qualidade da água e da biota aquática. O interesse em restabelecer os ecossistemas dos cursos d’água, tanto nas áreas urbanas quanto na rural, está se expandindo em todo o mundo, especialmente nos países desenvolvidos. De forma semelhante, a ocupação de áreas na zona costeira, as que apresentam tendências de maiores e mais densas ocupações, tem sido objeto de preocupação de diversos governos. Assim, modelos para avaliação ambiental de rios têm sido desenvolvidos e aperfeiçoados para permitir o diagnóstico e a seleção de ações de restauração fluvial. O método alemão, denominado Mapping and assessment methods for the structure of Waters, desenvolvido na Bavária, é utilizado para o mapeamento da estrutura da qualidade dos cursos d’água como medida da sua integridade ecológica e indica se o mesmo é capaz de suportar os processos dinâmicos de seu leito. Para a zona costeira, a metodologia do projeto Orla, desenvolvida pelo Ministério do Meio Ambiente do Brasil, se utiliza das unidades de paisagem como elementos de análise em termos de ocupação urbana e oferece subsídios para a análise da paisagem além dos limites fluviais, podendo complementar a análise fluvial. Ambas as metodologias contribuem para se realizar um diagnóstico mais amplo da situação atual de degradação ambiental, e podem indicar em quais trechos e unidades paisagísticas haveria necessidade de intervenção buscando a restauração ou requalificação dessas áreas. Neste trabalho, foram utilizados esses modelos para o mapeamento da estrutura da qualidade do leito fluvial, referente a sua morfologia, compreendendo a dinâmica do rio principal e a dinâmica das várzeas, além das áreas marginais do baixo rio Jaguaribe em seu antigo leito nos municípios de João Pessoa e Cabedelo, na zona costeira Sul do estado da Paraíba. Os resultados apontaram trechos do rio variando do estado totalmente alterado a pouco alterado, segundo o trecho e a ocupação lateral da calha fluvial. As áreas marginais estendidas foram classificadas nas três tipologias A, B, C do projeto Orla, apresentando concordância com à classificação obtida do sistema fluvial.

Hydropower is the world’s largest source of renewable electricity generation. Hydropower plants with reservoirs provide flexibility to the power systems. Efficient planning techniques improve the flexibility of the power systems and reduce carbon emissions, which is needed in power systems experiencing a rapid change in balance between power production and consumption. This is due to increasing amount of renewable energy sources, such as wind and solar power. Hydropower plants have low operating costs and are used as base power. This thesis focuses on weekly planning of hydropower in systems with large volumes and varying power generation and a literature review and a maintenance scheduling method are presented. The topic of hydropower planning is well investigated and various research questions have been studied under many years in different countries. Some of the works are summarized and discussed in literature reviews, which are presented in this thesis. First, some reviews are presented, which covers several aspects of hydropower planning. Literature reviews for long term, mid term and short term planning, respectively, are described. Maintenance scheduling in power systems consists of preventive and corrective maintenance. Preventive maintenance is performed at predetermined intervals according to a prescribed criteria. This type of maintenance is important for power producers to avoid loss in electricity production and loss in income. The maintenance scheduling for hydropower plants prevent these phenomena since spill in the reservoirs and wear on the turbines can be avoided. Usually, the maintenance in hydropower plants is performed on the turbines or at the reservoir intake. A deterministic and a stochastic method to solve a mid term maintenance scheduling problem formulated as a Mixed Integer Linear Programming using dynamic programming is presented. The deterministic method works well in terms of computational time and accuracy. The stochastic method compared to the deterministic method yields a slightly better result at the cost of a need for larger computational resources. / Vattenkraft är världens största källa till förnyelsebar elproduktion. Vattenkraftverk med magasin erbjuder flexibilitet till elkraftsystem. Effektiva planeringsmetoder förbättrar flexibiliteten hos kraftsystemen och minskar koldioxidutsläppen, vilket är nödvändigt i kraftsystem som utsätts för snabb förändring med obalans mellan produktion och konsumtion av effekt. Detta beror på ökad andel förnyelsebara energikällor, som vind- och solkraft, i kraftsystemen. Vattenkraftverk har låga driftkostnader och används som baskraft. Den här avhandlingen fokuserar på veckoplanering av vattenkraft i kraftsystem med stora volymer och varierande kraftproduktion, samt en litteraturstudie och en metod för underhållsplanering presenteras.    Ämnet vattenkraftplanering är väl undersökt och varierande forskningsfrågor har studerats under många år i olika länder. En del av arbetena sammanfattas och diskuteras i litteraturstudier, vilka presenteras i den här avhandlingen. Först presenteras några litteraturstudier, som täcker flera aspekter av vattenkraftplanering. Litteraturstudier, för långtids-, medeltidsplanering, respektive korttidsplanering beskrivs.    Underhållsplanering i elkraftsystem består av förebyggande och korrigerande underhåll. Förebyggande underhåll utförs vid förutbestämda intervall enligt förbestämda kriterier. Denna typ av underhåll är viktig för att kraftproducenter ska kunna undvika förlorad elproduktion och förlorad inkomst. Underhållsplaneringen för vattenkraftverk förebygger dessa fenomen, eftersom spill i magasinen och slitage på turbinerna kan undvikas. Vanligen utförs underhållen i vattenkraftverken på turbinerna eller vid intaget i magasinet. En deterministisk metod och en stokastisk metod att lösa ett medeltidsplaneringsproblem, formulerat som ett blandat heltalsprogrammeringsproblem presenteras. Den deterministiska metoden fungerar väl i termer av beräkningstid och noggrannhet. Den stokastiska metoden jämfört med den deterministiska metoden ger ett något bättre resultat dock till priset av ett behov av större datorresurser. / <p>QC 20220920</p>