• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 236
  • 49
  • 40
  • 25
  • 17
  • 7
  • 6
  • 4
  • 3
  • 3
  • 2
  • 1
  • Tagged with
  • 451
  • 175
  • 99
  • 89
  • 84
  • 50
  • 50
  • 48
  • 47
  • 46
  • 44
  • 43
  • 41
  • 39
  • 37
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
311

Integrated water resources management studies in the Mbuluzi Catchment, Swaziland.

Dlamini, Dennis Jabulani Mduduzi. January 2001 (has links)
Problems in the water sector range from degradation and depletion of water resources as a result of the impacts of land based anthropogenic activities, to the impacts of natural hydrological disasters and floods, while inadequate availability of water is at the core of most water related disputes in arid and semi-arid areas at local, regional, national and international levels. In the past, finding practical solutions for these problems fell neatly within the traditional scope of water resources management, which hinged almost entirely on economic viability of engineering oriented endeavors. However, a new set of management challenges has arisen following the high priority nowadays given to equity in water allocation and the protection of the natural environment above other issues. These new challenges have created a need for devising and adopting suitable management approaches, especially that would take social considerations into account. One of the approaches that provides promise relative to the new directions in dealing with contemporary water issues is integrated water resources management (IWRM). One objective of this study was to critically review the definitions and the fundamental principles of IWRM with the view of determining its applicability in developing countries and highlighting difficulties that may be faced regarding the adoption and implementation of this integrated approach. Swaziland is atypical example ofa developing country that is engulfed by the diverse water resources issues highlighted above and is currently engaged in updating water management legislation. Hence, Swaziland's experiences were used to put in perspective the key points and barriers regarding the adoption and implementation of IWRM. The catchment, the recommended spatial unit of IWRM, poses the first practical barrier, as catchments often cross both political and administrative boundaries, thereby creating the need for many water management problems to be solved across catchments with international security issues, cultural issues, different levels of development and different hydroclimatic regimes. The successful implementation of IWRM depends on effective participation of stakeholders. Lack of information flow between stakeholders of different backgrounds limits informed participation. Therefore, it is necessary to develop tools such as decision support systems (DSSs) that will foster easier multilateral information flow and aid decision making. IWRM requires information which itself should be managed in an integrated manner and be readily accessible. This is not always the case in developing countries with shortage of funds for data collection, manipulation and storage as well as adequately trained and experienced staff With the shortage of sufficiently long and reliable hydrological data for water management, the alternative is to synthesize records through hydrological modelling. Another objective of this study was to evaluate and test the suitability of the ACRU modelling system, a daily time-step agrohydrological model, to simulate catchment level hydrological processes and land use impacts as part of the assessment studies which form an integral part of integrated water resources management. ACRU was set up for the Mbuluzi, a 2958 km2 catchment in Swaziland. The catchment was subdivided into 40 sub catchments, after which the model was used for assessing both the impacts of land use and management changes on runoff yields and available water resources by evaluating present and future sectoral water demands, determining whether river flow from Swaziland into Mozambique meets the quantitative requirements of the international agreement existing between the two countries, and evaluating sediment yield and its spatial and temporal variation as well as its response to potential changes in land management. The physical-conceptual structure of the model, its multi-level adeptness regarding input information requirements, coupled with in-built decision support systems and generic default values make ACRU a suitable modelling tool in developing countries, as it makes it possible to obtain reasonable simulations for a range of levels of input information. Together with the model's multi-purpose nature, the ability of simulating ''what if scenarios", which was utilised in this study, makes it useful in the generation of information for IWRM. Future research needs which were identified include finding means of encouraging effective communication between scientists, water managers and other stakeholders, who may be "lay people". There is a need to conduct research that will lead to equipping ACRU with sediment routing and deposition algorithms, as well as routines to account more explicitly for dam operating rules and ecological issues, which would render its output even more useful in IWRM than the model's present structure allows. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2001.
312

Non point source pollution with specific reference to the Mkabela Catchment.

Berry, S. R. January 2011 (has links)
Non point source pollution (NPS) has long been the negated form of pollution within our natural systems. With an increase in the demand for quality crops and staple foods, there have been added pressures on water systems to cope with increasing NPS pollution (NPS-P). The effect and importance of scale on the assessment of NPS pollution has been identified as a pivotal component in the assessment of such pollutants, in particular the translation of processes from a field to a catchment scale. It has therefore become important to further investigate and research the processes involved in transporting and retaining pollutants at each measurement scale. A number of models have been developed for simulation catchments, however none of the suitably address the issue of NPS pollution and the translation of processes from the field through to the catchment scale. Each model researched fails to effectively address processes over varying scales, and tend to concentrate on a particular scale of observation. There is a distinct lack of a capable mechanism that assesses NPS pollution across varying scales within a catchment. The Water Research Commission (WRC) NPS-P project aims at eventually developing a successful model that addresses the issue of assessing NPS pollution across a number of different scales. This study aimed at assessing the loads of sediments and nutrients at different scales and included the establishment of a research catchment in the Mkabela Catchment outside Wartburg in KwaZulu-Natal, and the collection and interpretation of rainfall, runoff and nitrate data for a full year of sampling. The sampling provided valuable data for the calculation of pollutant masses and concentrations within the Mkabela Catchment. Non Point Sources are generally more dilute with suspended solids and nitrate in particular tending to have a high transport dependence upon summer events with a high intensity and low duration. A varying degree of scales were monitored during this study, ranging from plot to catchment scale in order to assess the varying influences on NPS Pollution (Nitrate and Suspended Solids). Monitoring was conducted through research mechanisms ranging from runoff plots at the plot scale to catchment scale flumes. It was found that scale has a varying influence on NPS pollution, with pollutant concentrations measured to be at a maximum at the field scale, with a value of 13.54mg/l of nitrate measured within the cane fields from event 3. Suspended solid values taken from within the water samples were most apparent at the plot scale, within the runoff plots, with a maximum of 2866.7mg/l measured during event 3 as well. It was evident from measurements and results obtained for each of the 10 sampled events that the main influencing factor of the nitrate concentrations and suspended solid values was the nature of the event. Summer rainfall events (high intensity and short duration) provided large overland flow volume that contributed largely towards the high concentrations of both nitrate and suspended solids, whereas the winter rainfall event (low intensity and long duration) contributed little to the concentrations of nitrate and suspended solids. In contrast to nitrate concentration, the largest nitrate loads by mass were measured during event 1 at the large catchment scale (Bridge 2), with a total cumulative load of 74.17kg nitrate estimated to have been yielded at the catchment outlet. The majority of nitrate are yielded from the agricultural lands where farming practices lead to the application of chemicals preplanting and post emergence. Suspended solids displayed a similar trend to that of nitrate, with an increasing cumulative yield measured throughout the catchment, resulting in a total 13414kg of sediment being measured at Bridge 2. It is interesting that Event 1 measured the largest cumulative loads for both nitrate and suspended solids; however it was recorded as an average intensity event (19.1mm/h) in comparison to the largest sampled intensity event of 165.9mm/h (Event 4) during the study. This may be attributed to the fact that the event coincided with the planting schedule of the sugarcane crops, and so the bare nature of the agricultural fields resulted in increased overland flow, and hence nitrate and suspended solid transportation. Data collected during all the events clearly show that the impoundment (a farm dam) acts as a water quality filter by retaining many of the nitrate pollutants when they enter the dam as channel flow. In summary, the controlling processes governing NPS-P movement varied through the differing scales, with crop size, artificial chemical application, nature of the event and timing during the year all contributing in varying manners at the differing scales. Future research within the WRC-NPS-P project should continue with sampling from the designated research points and add several more seasons of data to the already comprehensive first season of sampling. In addition, once a reasonable number of seasons have been sampled and analysed within the Mkabela Catchment, the initiation and development of an effective, representative scaled NPS-P model that addresses the movement and retardation of pollutants is necessary to be able to successfully model and predict the movement of NPS-P through catchment systems. In particular the effects of the controls afforded by such features as road crossings, wetlands and farm dams should be taken into account in the modelling of sediment and nutrient movement from field to catchment scale. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.
313

Kartläggning av översvämnignshotade järnvägstunnlar med GIS : En fallstudie av Norralatunneln

Erik, Fridholm, Johan, Sjögren January 2014 (has links)
In August 2013 the Norrala tunnel just north of Söderhamn was flooded, which caused a train stuck in thetunnel. In the future the intensity and the amount of rainfall are expected to increase in this area, which canlead to an increased risk of flooding. The purpose of this study was to use GIS to investigate whether it is possible to identify which railroadtunnels that are exposed to flooding during heavy rainfall. In order to investigate this, a GIS analysis wasperformed on the Norrala tunnel. The data used for this study was the National Elevation Model. The result of the study contains maps representing the catchment area for the tunnels and wetness index forthe north and the middle rescue tunnel. The flood analysis shows that the rescue tunnel that was flooded in August 2013 has a catchment area of1,1km², which is 20 times as big as the catchment area for any of the other tunnel entrances. The studyshows that GIS is a great tool for flood mapping. With the chosen method in combination with theNational Elevation Model, it is possible to identify tunnels that are exposed to flooding. The field study that was performed shows that the Swedish property map has flaws concerning hydrology.More than 90% of the water that ended up in the tunnel came from the west side of the highway E4,through a passage for wildlife. After the tunnel, the water was initially directed through a manmade streamthat follows the route of the property map. Further down, the manmade stream disappears and the waterthen follows the topography to the protection barrier nearby the tunnel. In the study, no calculations were made about the amount of water that flooded to the tunnel during theflooding in August 2013. Investigations of the climate change indicate that the amount of rainfall willincrease in the area. Therefore a further investigation is recommended, where the goal should be to protectthe tunnel from flooding. The method that has been used is applicable at any type of infrastructure. The Swedish TransportAdministration is recommended to use this method to investigate infrastructure and for future planning. / I augusti år 2013 översvämmades Norralatunneln strax norr om Söderhamn, vilket orsakade att ett tåg fastnade i tunneln. I framtiden förväntas intensiteten och mängden nederbörd att öka i detta område, vilket kan leda till en ökad risk för översvämning. Syftet med examensarbetet var att med GIS undersöka om det går att identifiera vilka järnvägstunnlar som är översvämningshotade vid kraftig nederbörd. GIS-analyser utfördes på Norralatunneln, där den Nationella Höjdmodellen användes som indata till undersökningen. Resultatet av studien innehåller ett antal kartor som redovisar avrinningsområden för samtliga tunnelmynningar och fuktighetsindex för den norra och mellersta räddningstunneln. Översvämningsanalysen visar att den räddningstunnel som översvämmades i augusti år 2013 har ett avrinningsområde på 1,1 km², vilket är mer än 20 gånger så stort som avrinningsområdet för någon av de andra tunnelmynningarna. Studien visar att GIS är ett bra verktyg för översvämningskartering och med den valda metoden i kombination med den Nationella Höjdmodellen är det möjligt att identifiera översvämningshotade tunnlar. Den fältstudien som genomfördes visar på brister i fastighetskartan gällande vattendrag. Mer än 90 % av vattnet som rann in i tunneln kom från västsidan av E4:an genom en älgpassage. Därefter leddes vattnet ner mot räddningstunneln via en grävd bäck som till en början följer fastighetskartans sträckning. Den tydligt grävda bäcken försvinner dock och vattnet följer därefter topografin till skyddsdiket intill tunnelmynningen.  I arbetet gjordes inga beräkningar på hur mycket vatten som flödade ner till tunneln i samband med översvämningen. Undersökningar av framtida klimat visar på att nederbördsmängden i området kommer att öka. Därför rekommenderas en vidare studie där målet borde vara att ta fram ett lämpligt alternativ för att skydda tunneln från översvämning. Analyserna som har utförts är tillämpningsbara även på andra typer av infrastruktur, därför rekommenderas Trafikverket att använda sig av metoden vid projektering och undersökning av infrastruktur.
314

Grow with the flow : Hydrological controls of riparian vegetation in boreal stream networks

Kuglerová, Lenka January 2015 (has links)
What drives species diversity across landscapes is one of the most fundamental questions in ecology. Further, understanding the mechanisms underlying species diversity patterns is important not only for forming and challenging ecological theories but also essential for appropriate landscape management and effective nature conservation. This thesis focuses on patterns of vascular plant, moss and liverwort species richness and composition in relation to water flow in boreal-forest catchments, focusing mostly on riparian zones (RZs), that is terrestrial areas bordering streams and rivers. I addressed some of the most essential questions related to the ecology of riparian vegetation including the role of stream network position, groundwater (GW) flow paths, substrate availability, upland perturbations, and stream restoration. I also investigated how riparian soil processes and habitat properties relate to these factors in order to provide a holistic understanding of riparian dynamics. The results showed that the species richness and composition of riparian vascular plants, mosses and liverworts are strongly influenced by position along the stream network, GW discharge, presence of variable substrates in RZs, and by stream restoration. Generally, more species were found downstream in the network, at sites with inputs of upland GW, sites with high diversity of substrates (e.g., open mineral soil, rocks, stones, wood and bark), and along streams restored after channelization. This thesis also describes how riparian habitat properties responded to position in the landscape and human impacts, thus providing mechanistic links between plant species diversity and riparian processes across spatial scales. These ecological insights are further implemented into numerous recommendations for freshwater and upland management in boreal Sweden. Given that streams and rivers connect landscape elements both longitudinally and laterally I argue that management plans should be designed for entire catchments instead of individual river segments. Ignoring the connectivity of streams as well as the high connectivity of riparian areas to uplands via GW flows may result in failure of restoration, mitigation and/or protection actions. Further, during forestry operations more emphasis should be placed on GW discharge areas along streams and rivers, because they represent important ecological and biogeochemical hotspots in the landscape. The riparian buffers left along streams in boreal catchments affected by forestry are presently insufficiently wide and often uniform in width. This threatens the assemblages of species in GW discharge hotspots and the ecosystem services they provide. Overall, this thesis describes a holistic picture of riparian diversity patterns and riparian processes in boreal landscapes, acknowledges and elaborates on current ecological theories, presenting new patterns in biodiversity, and offers management guidelines.
315

Institutional overlaps in water management in the Eerste River Catchment.

Nleya, Ndodana January 2005 (has links)
In this minithesis I have investigated overlapping mandates as a source of management failure in water management in South Africa in general and Eerste River Catchment in particular. I analysed major legislation which deals with water management to find out how duties and responsibilities are apportioned in the various pieces of legislation. I also undertook an exercise of evaluating roles and responsibilities played by various organs of state in water management from national government, Provincial Government of the Western Cape through to local government, in this case the Municipality of Stellenbosch and the City of Cape Town. It emerged that there were a number of areas of overlap, ambiguously defined mandates, conflict and that these were impeding on decision making in water management. In order to test the framework built above, I then applied it in the Plankenbrug River, a tributary of the Eerste River. Through analysis of newspaper clippings over a period of 4 years I was able to reconstruct conflict over ill-defined mandates in the various aspects of the management of the catchment which showed that<br /> there were differences in roles of the different state organs operating in the catchment. Water management conflict emanated from lack of congruence in the various legislation and differences in the interpretation of legislation. The various state organs seem to be aware of the constitutional duty of cooperative government that engenders state organs to work co-operatively in order to meet their developmental mandates. It seems however that the state organs were merely interested to be seen to be in conformity with this duty more than actually solving the issue as this was seen as something to be tackled at a higher level.
316

A GIS-based landscape analysis of dissolved organic carbon in boreal headwater streams

Andersson, Jan-Olov January 2009 (has links)
In boreal catchments, stream water chemistry is influenced and controlled by several landscape factors. The influence of spatially distributed variables is in turn dependent on the hydrological scale. Headwater streams have larger variability of water chemistry, and thus together represent a large biodiversity, and therefore need to be monitored in official environmental assessments. One objective of this study was, using Geographical Information Systems (GIS), to analyse co-variation between landscape variables and water chemistry and to determine which of the landscape variables have a major influence on the concentration of dissolved organic carbon (DOC) in headwater streams. Another objective was to find a simple method for predicting sources of DOC, using official map data and publically available GIS applications. Totally 85 headwater catchments (0.1-4 km2) in the county of Värmland, western south Sweden, were used in the study. Water chemistry was analysed for water sampled at low, medium and high flows, and landscape variables were extracted from official map data sources: topographic maps, a digital elevation model (DEM, 50 m grid), and vegetation data. Statistical analyses showed that topography (mean slope and mean topographic wetness index (TWI)) and wetland cover often correlated well with DOC in headwater catchments. Official map data could satisfactorily extract landscape variables (mean slope, mean TWI) that were useful in predicting stream water chemistry (DOC). A high-resolution elevation model, which was generated by interpolation of photogrammetric data, was used to calculate and evaluate two different wetness indices and their ability to predict the occurrence of wetlands in six catchments of different sizes and topography. The SAGA (System for Automated Geoscientific Analyses) wetness index (SWI) gave substantially better results than the TWI. The effects of resolution of DEMs on calculations of the SWI were investigated using 5, 10, 25 and 50 m grids. The results showed that SWI values increased with increasing cell size. The near linear increment of mean values for resolutions 10-50 m suggests a independence of terrain type and catchment size, which supported previous findings that indicated that mean slope and mean wetness index calculated from coarse elevation models may be used for prediction of DOC in headwater streams.
317

A distributed conceptual model for stream salinity generation processes : a systematic data-based approach

Bari, Mohammed A. January 2006 (has links)
[Truncated abstract] During the last fifty years mathematical models of catchment hydrology have been widely developed and used for hydrologic forecasting, design and water resources management. Most of these models need large numbers of parameters to represent the flow generation process. The model parameters are estimated through calibration techniques and often lead to ‘unrealistic’ values due to structural error in the model formulations. This thesis presents a new strategy for developing catchment hydrology models for representing streamflow and salinity generation processes. The strategy seeks to ‘learn from data’ in order to specify a conceptual framework that is appropriate for the particular space and time scale under consideration. Initially, the conceptual framework is developed by considering large space and time scales. The space and time scales are then progressively reduced and conceptual model complexity systematically increased until ultimately, an adequate simulation of daily streamflow and salinity is achieved. This strategy leads to identification of a few key physically meaningful parameters, most of which can be estimated a priori and with minimal or no calibration. Initially, the annual streamflow data from ten experimental catchments (control and cleared for agriculture) were analysed. The streamflow increased in two phases: (i) immediately after clearing due to reduced evapotranspiration, and (ii) through an increase in stream zone saturated area. The annual evapotranspiration losses from native vegetation and pasture, the ‘excess’ water (resulting from reduced transpiration after land use change), runoff and deep storage were estimated by a simple water balance model. The model parameters are obtained a priori without calibration. The annual model was then elaborated by analysing the monthly rainfall-runoff, groundwater and soil moisture data from four experimental catchments. Ernies (control, fully forested) and Lemon (53% cleared) catchments are located in zone with a mean annual rainfall of 725 mm. Salmon (control, fully forested) and Wights (100% cleared) are located in zone with mean annual rainfall of 1125 mm. Groundwater levels rose and the stream zone saturated area increased significantly after clearing. From analysis of this data it was evident that at a monthly time step the conceptual model framework needed to include a systematic gain/loss to storage component in order to adequately describe the observed lags between peak monthly rainfall and runoff.
318

Analyse multi-échelle des processus d’érosion hydrique et de transferts sédimentaires en territoire agricole : exemple du bassin versant de la Canche (France) / Multi-scale analysis of water erosion processes and sedimentary transfer in agricultural territory : example of the Canche river catchment (France)

Patault, Edouard 16 November 2018 (has links)
L’érosion hydrique est un processus majeur de dégradation des sols dans le monde avec des conséquences multiples : perte de terres agricoles, envasement des cours d’eau, coulées boueuses. En France, la région Hauts-de-France est la zone la plus touchée par ces pertes en terres qui peuvent dépasser les 10 t ha-1 an-1. Si les processus à l’origine de ces transferts sédimentaires ont été largement étudiés par la communauté scientifique ces dernières années, il reste néanmoins des verrous liés aux variabilités spatio-temporelles. De plus, l’efficacité des politiques récentes de lutte contre l’érosion n’est pas quantifiée. Cette étude propose une analyse de la variabilité spatio-temporelle des transferts sédimentaires selon plusieurs échelles (1-1000 km²), et une première évaluation de l’efficacité des politiques d’aménagement au sein d’un bassin du Nord de la France (la Canche ; 1274 km²). Une station de mesure haute-fréquence, a été implémentée à l’exutoire d’un sous-bassin versant de la Canche (la Pommeroye ; 0,54 km²) pour quantifier les transferts hydro-sédimentaires sur deux années hydrologiques contrastées. Selon nos résultats, les transferts varient de 29,4 à 70 t km-2 an-1. 40% du flux est exporté au cours de 3 épisodes érosifs majeurs (sur 48 enregistrés) et les paramètres forçants sont liés à la durée d’un épisode pluvieux et la quantité de précipitations. Sur ce même bassin, la prédiction spatiale à l’échelle centimétrique des transferts hydro-sédimentaires a pu être effectuée via le nouveau modèle d’érosion des sols WATERSED (BRGM) et l’efficacité d’un plan d’aménagement de lutte contre l’érosion a été quantifiée. Nos résultats permettent de valider l’opérabilité du modèle sur ce territoire. Les transferts sédimentaires à l’échelle du parcellaire agricole peuvent atteindre les 76 t km-2 pour un évènement donné et sont influencés par l’état de surface du parcellaire agricole. Une réduction significative (jusqu’à 84%) des transferts par les aménagements d’hydraulique douce est également observée. A l’échelle du bassin de la Canche, l’utilisation de traceurs chimiques et spectrocolorimétriques dans un modèle de mélange (Sed_Sat ; USGS) a permis d’évaluer d’une part les contributions des affluents de la Canche et d’autre part les contributions des sols et des berges (respectivement 30-70%). Des variations spatio-temporelles significatives ont pu être observées et les résultats tendent à montrer un potentiel impact positif des politiques récentes d’aménagement du territoire. Cette étude montre également que de nouveaux traceurs liés à la signature spécifique des particules magnétiques sont particulièrement prometteurs dans ce contexte pour tracer un signal d’érosion des sols. A terme, ces données pourraient être incluses dans des approches sediment fingerprinting. L’analyse selon plusieurs modalités spatio-temporelles et le couplage expérimentation/modélisation améliore donc notre compréhension de la dynamique des transferts sédimentaires sur le bassin versant de la Canche. Cela fournit des résultats essentiels pour orienter les futures politiques de lutte contre l’érosion des sols. / Water erosion is a serious concern in global land degradation leading to multiple consequences: loss of arable lands, siltation of streams, mudflows. In France, the Hauts-de-France region is the most affected area, and soil loss can exceed 10 t ha-1 yr-1. Although hydro-sedimentary processes have been widely studied by the scientific community, there is still a lack of knowledge in the understanding of the spatio-temporal variabilities. Additionally, the effectiveness of recent erosion control policies so far cannot be quantified. This study proposes an analysis of the spatio-temporal variability of sedimentary transfer at different scaling (1-1000 km²), and an initial assessment of the effectiveness of management policies within a northern France catchment (the Canche river, 1274 km²). A high-frequency monitoring station was implemented at the outlet of a Canche sub-catchment (the Pommeroye, 0.54 km²) to quantify the hydro-sedimentary transfer over two contrasted hydrologic years. According to our results, sediment yield varies from 29.4 to 70 t km-2 yr-1. 40% of the flux is exported during 3 major erosive events (out of 48 recorded) and the forcing parameters are related to the duration and the amount of rainfall. In this sub-catchment, the centimeter-scale spatial prediction of the hydro-sedimentary transfer was carried out using the new soil erosion model WATERSED (BRGM) and the effectiveness of an anti-erosion management plan was quantified. Our results validate the operability of the model in this context. For a given event, sediment transfer can reach 76 t km-2 yr-1 in agricultural plots and are strongly depending on the soil surface state. A significant reduction (up to 84%) of sedimentary transfer by the anti-erosion plan was also observed. At the scale of the Canche catchment, the use of chemical and spectrocolorimetric tracers in a mixing model (Sed_Sat tool; USGS) evaluated the contributions of the Canche tributaries and sediment sources contributions (i.e. channel banks and soils; 30-70% respectively). Significant spatio-temporal variations have been observed and the results show a potential positive impact of the recent management policies. This study also shows that new tracers related to the specific signature of magnetic particles are promising in the context to trace soil erosion. For further analyses, this data could be included in sediment fingerprinting approaches. Thus, this study based on several spatio-temporal modalities and the coupling of experimentation and modelling improves our understanding of the Canche hydro-sedimentary dynamics. It provides essential results to guide the future erosion control policies.
319

Multi-scale effects of hydrological and landscape variables on macrophyte richness and composition in British lakes

Sun, Junyao January 2016 (has links)
Macrophytes are an integral component of lake littoral zones and play an irreplaceable role in maintaining the ecological balance of wetlands. Recent research has highlighted the role of lake-scale environmental factors (or “filters”) and catchment- and/or landscape-scale processes in explaining variation in macrophyte communities across different scales. In this work, the effects of land-use and connectivity on macrophyte communities were explored at two contrasting spatial scales (i.e. local catchment scale and topographic catchment scale). At the local catchment scale, the results revealed strong scale-dependency. The effects of land use on macrophyte richness were most apparent at fine spatial scales (within 0.5 to 1 km) and significantly outweighed the importance of hydrology. In terms of growth form composition, the effects of hydrological connectivity were stronger than those of land use, with the greatest effect observed at an intermediate distance (~ 5 km) from the lake. The study on the hydrologically-connected lake pairs indicated that environmental filters were more influential in explaining species turnover than lake connectivity. Interestingly, geographical connectivity explained more of the variability in species turnover than hydrological connectivity. Moreover, the relative importance of environmental filters and lake connectivity to species turnover was very sensitive to the degree of human disturbance. The multi-scale interaction analyses indicated the effect of lake alkalinity on macrophyte composition is strongly influenced by catchment scale variables including hydrological features and land use intensity. The turnover in macrophyte composition in response to variability in alkalinity was stronger in catchments with low lake and stream density and weaker in catchments with a more highly developed hydrological network. Lake abiotic variables were found to have more influence on macrophyte composition in lowland catchments with a higher intensity of human disturbance. Moreover, the catchment-scale factors promoting the establishment of different communities were found to vary between catchments depending on lake type, the degree of environmental heterogeneity and hydrological connectivity.
320

Analýza maloobchodních příležitostí a ohrožení na Strakonicku / Analysis of retail opportunities and threats in Strakonice region

BAJTOVÁ, Jitka January 2012 (has links)
Principal objective of my authorized work has been to make analyse of retail´s opportunities and threat in section of quick high turnover goods in Strakonice. Information, which has been obtained, base on the analyse and observation, to write to the simulation software RetailOpportunitySim, to introduce screenplay of development and base on the results from the software to propose suitable actions for chosen retail´s subject. To calibrate the software was necessary to define the market geographically and define the real structure of the settlement. Survey was carried out and observations of the retail units on my chosen market. Scenarios were defined hypotheses were confirmed or rejected by software. The scenarios were applied to the retail unit Gastro.

Page generated in 0.0686 seconds