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The persistence of seagrass meadows depends on vegetation processes and the plants’ continuous response to various disturbances. Disturbance events cause discontinuities in the landscape (because the plants get dislodged) and affect vegetation processes as a negative response to sediment redistributions, eutrophication, and light reduction. In benign seagrass environments where biological disturbance is prominent, discontinuities in the landscape are also conspicuous though small, e.g., those caused by burrowing shrimps. Their bioturbation is known to affect plant dynamics, seagrass patch expansion, the benthos, processes at the sediment-water interface, and the export of organic matter. This study examined the role of small-scale disturbance by burrowing shrimps and its interaction with seagrass performance against a changing background of anthropogenically altered sediment dynamics. It established that the two types of burrowing shrimps – the alpheids and thalassinideans – both common in the seagrass beds, redistribute considerable quantities of sediment with significant substrate effects on depth gradients of organic matter, grain size, and nitrogen. The alpheids have a tight connection to the seagrass, i.e., they feed on it removing about 12 to 42% of primary production, but these do not necessarily affect the established clonal stands. The shrimps potentially deter seed and seedling growth and recruitment through burial, but this probably does not have a severe impact

The persistence of seagrass meadows depends on vegetation processes and the plants' continuous response to various disturbances. Disturbance events cause discontinuities in the landscape (because the plants get dislodged) and affect vegetation processes as a negative response to sediment redistributlons, eutrophication, and light reduction. In benign seagrass environments where biological disturbance is prominent, discontinuities in the landscape are also conspicuous though small, e.g., those caused by burrowing shrimps. Their bioturbation is known to affect plant dynamics, seagrass patch expansion, the benthos, processes at the sediment-water interface, and the export of organic matter. This study examined the role of small-scale disturbance by burrowing shrimps and its interaction with seagrass performance against a changing background of anthropogenically altered sediment dynamics. It established that the two types of burrowing shrimps - the alpheids and thalassinideans - both common in the seagrass beds, redistribute considerable quantities of sediment with significant substrate effects on depth gradients of organic matter, grain size, and nitrogen. The alpheids have a tight connection to the seagrass, i.e., they feed on it removing about 12 to 4 2% of primary production, but these do not necessarily affect the established clonal stands. The shrimps potentially deter seed and seedling growth and recruitment through burial, but this probably does not have a severe impact on the established stands that these shrimps inhabit. CRC

Arsenic, manganese and iron in drinking water at concentrations exceeding recommended guideline values pose health risks and aesthetic defects. Batch and pilot experiments on manganese adsorption equilibrium and kinetics using iron-oxide coated sand (IOCS), Aquamandix and other media have been investigated and modeled. Effect of manganese and iron loading on manganese removal and rate of oxidation of adsorbed iron and manganese have been studied. Aquamandix and IOCS demonstrated iron and manganese adsorption capacity that increases with increasing pH under oxic and anoxic conditions. Manganese loading and low filtration rate using feedwater with no nitrite favour non-uniform development of catalytic manganese oxide on media that subsequently enhances manganese removal.

This book presents the investigation of different architectures of integrating hydrological knowledge and models with data-driven models for the purpose of hydrological flow forecasting. The models resulting from such integration are referred to as hybrid models. The book addresses the following topics: A classification of different hybrid modelling approaches in the context of flow forecasting. The methodological development and application of modular models based on clustering and baseflow empirical formulations. The integration of hydrological conceptual models with neural network error corrector models and the use of committee models for daily streamflow forecasting. The application of modular modelling and fuzzy committee models to the problem of downscaling weather information for hydrological forecasting.

In this thesis, several modelling approaches are explored to represent spatial pattern dynamics of aquatic populations in aquatic ecosystems by the combination of models, knowledge and data in different scales. It is shown that including spatially distributed inputs retrieved from Remote Sensing images, a conventional physically-based Harmful Algal Bloom model can be enhanced. Also, Cellular Automata based models using high resolution photographs prove to be good in representing aquatic plant growth. Multi-Agent Systems can capture well the spatial patterns exhibited in GIS density maps. A synthesis modelling framework was developed to include biological/ecological growth and diffusive processes, and local effects in conventional modelling framework. The results of the complementary modelling paradigms investigated in this research can be of help in achieving a sustainable environmental management strategy.

This thesis presents the development and validation of a novel three-dimensional sediment transport and morphological numerical model suitable for coastal regions. The thesis discusses the modelling of both suspended and bed-load transport of non-cohesive sediment, important aspects of the morphological updating scheme, and approaches used to model the three-dimensional effects of waves on coastal hydrodynamics. Results of several validation studies are presented and the model is shown to perform well in several theoretical, laboratory, and full scale test cases. Application of the model and acceleration techniques to the complex and dynamic entrance to Willapa Bay, WA, USA is also critically analysed and discussed. A new method to select a representative morphological tide for coastal environments containing significant diurnal tidal energy is presented.

Due to relatively high phosphorus removal efficiency and economy, the enhanced biological phosphorus removal (EBPR) in activated sludge wastewater treatment systems is a widely applied process to control and prevent eutrophication in surface water bodies. However, the EBPR process can be prone to suffer of upsets and deterioration. Since glycogen-accumulating organisms (GAO) compete with polyphosphate-accumulating organisms (PAO), which are the microorganisms that perform the biological phosphorus removal process, the proliferation of GAO has been linked with the instability of the EBPR process. Based on laboratory- and full-scale experimental work as well as mathematical modeling, this research contributes to get a better understanding about the environmental and operating conditions affecting the PAO-GAO competition and, therefore, the EBPR process performance and stability.

Ungauged catchments can be found in many parts of the world, but particularly in sub-Saharan Africa. Information collected in a gauged catchment and its regionalisation to ungauged areas is crucial for water resources assessment. Especially farmers in semi-arid are in need of such information. Inter and Intra-seasonal rainfall variability is large in these areas, and farmers depend more and more on additional surface and groundwater resources for their crop production. As a result, understanding the key-hydrological processes, and determination of the frequencies and magnitudes of stream flows, is very important for local food production. This is particularly true for the ungauged Makanya catchment in Tanzania, which is the subject of this study.

In this dissertation, the role of subsurface drainage to reduce waterlogging and salinity problems in irrigated agriculture in arid and semi-arid regions has been analysed and recommendations on how to improve subsurface drainage practices have been formulated. The study contains a synthesis based on eight case studies covering subsurface drainage practices in Egypt, India and Pakistan. Professionals can use these recommendations to improve planning, design, implementation, and O&M practices. The recommendations can also help to address issues related to an enabling environment (who will pay the costs of drainage?) and the changing roles of institutions to improve farmers’ participation and organization.

Since the last two decades, the most prominent institutional change for the water and sanitation sector is neo-liberalism. This book analyses the effects of neo-liberal institutional changes on the strategies and performances of water providers. In this regard, studies are executed in the Netherlands, the Netherlands Antilles, the United Kingdom and Italy on what water providers can do, want to do and actually do. It is concluded that neo-liberal institutional changes matter for the strategies of water providers, but that no conclusion can be reached with respect to performance effects.

This thesis presents powerful machine learning (ML) techniques to build predictive models of uncertainty with application to hydrological models. Two different methods are developed and tested. First one focuses on parameter uncertainty analysis by emulating the results of Monte Carlo simulations of hydrological models using efficient ML techniques. Second method aims at modelling uncertainty by building an ensemble of specialised ML models on the basis of past hydrological model’s performance. Methods employed include artificial neural networks, model trees, locally weighted regression and fuzzy logic. The application of the methods to several real-world case studies demonstrates the capacity of machine learning techniques for building accurate and efficient predictive models of uncertainty.

Day-to-day water management is challenged by meteorological extremes, causing floods and droughts. Often operational water managers are informed too late about these upcoming events to be able to respond and mitigate their effects, such as by taking flood control measures or even requiring evacuation of local inhabitants. Therefore, the use of weather forecast information with hydrological models can be invaluable for the operational water manager to expand the forecast horizon and to have time to take appropriate action. This is called Anticipatory Water Management. Anticipatory actions may have adverse effects, such as when flood control actions turn out to have been unnecessary, because the actual rainfall was less than predicted. Therefore the uncertainty of the forecasts and the associated risks of applying Anticipatory Water Management have to be assessed. To facilitate this assessment, meteorological institutes are providing ensemble predictions to estimate the dynamic uncertainty of weather forecasts. This dissertation presents ways of improving the end-use of ensemble predictions in Anticipatory Water Management.

Seawater desalination is a rapidly growing coastal-based industry. The combined production capacity of all seawater desalination plants worldwide has increased by 30% over the last two years: from 28 million cubic meters per day in 2007—which is the equivalent of the average discharge of the River Seine at Paris—to more than 36 million cubic meters per day in 2009. Seawater desalination is an energy-intensive process. It furthermore consumes considerable amounts of natural resources in the form of chemicals and materials, and may have negative effects on the marine environment due to the discharges of concentrate waste waters and residual chemicals into the sea. The growing number of desalination plants worldwide and the increasing size of single facilities emphasizes the need for greener desalination technologies and more sustainable desalination projects. Two complementing approaches are the development and implementation of best available technology (BAT) standards and best practice guidelines for environmental impact assessment (EIA) studies. While BAT is a technology-based approach, which favors state of the art technologies that reduce resource consumption and waste emissions, EIA aims at minimizing impacts at a site- and project-specific level through environmental monitoring, evaluation of impacts, and mitigation where necessary. The dissertation contains a comprehensive evaluation and synthesis of the potential environmental impacts of desalination plants, with emphasis on the marine environment and aspects of energy use, followed by the development of strategies for impact mitigation. A concept for BAT for seawater desalination technologies is proposed, in combination with a methodological approach for the EIA of desalination projects. The scope of the EIA studies are outlined, including environmental monitoring, toxicity and hydrodynamic modeling studies, and the usefulness of multi-criteria analysis as a decision support tool for EIAs is explored and used to compare different intake and pretreatment options for seawater reverse osmosis plants.

This study provides a hydrology based assessment of (surface) water resources and its continuum of variability and change at different spatio-temporal scales in the semi-arid Karkheh Basin, Iran, where water is scarce, competition among users is high and massive water resources development is under way. The study reveals that the ongoing allocation planning is not sustainable and essentially requires reformulation, with consideration of spatio-temporal variability and observed trends in the streamflows regarding flood intensification and decline in low flows. The development of innovative methods for quantification of the hydrological fluxes (i.e., regionalization of model parameters based on similarity of the flow duration curve and the use of areal precipitation input in the hydrological modeling) helped better understanding and modeling the basin hydrology. The investigation of scenarios for upgrading rain-fed areas to irrigated agriculture, using SWAT, recommends the promotion of in-situ soil and water conservation techniques. Conversion of rain-fed areas to irrigation causes significant reduction in the downstream flows, and requires additional considerations such as less development in the upper catchments, practicing supplementary irrigation and developing water storage. The knowledge generated is instructive for hydrological assessment and its use in water resources planning and management in the river basin context.

This study shows that BF is an effective multiple objective barrier for removal of different contaminants present in surface water sources including bulk organic matter and organic microplollutants (OMPs) like pharmaceutically active compounds and endocrine disrupting compounds. It was found that biodegradation and adsorption play primary and secondary roles, respectively, in the removal of OMPs during soil passage. Furthermore, using field data from BF sites and chemical properties of OMPs, models were developed to estimate the removal of OMPs during soil passage.