Thesis (M.S.)--Western Washington University, 2010. / Includes bibliographical references (leaves 55-61). Also issued online.

Thesis (Ph.D.)--Technische Universiteit Delft, 2006. / Vita. Includes bibliographical references (p. 189-206).

In geographical hydrology the~e has been more interest in scientific rather than in practical application of mathematical models of catchment hydrology. This thesis emphasizes the importance of examining the potential of developments in scientific research programmes for practical hydrological applications, and in particular provides discussion upon the following five issues: 1 The application of hydrological models to ungauged catchments where no historical streamflow record is available for calibration. 2 The potential of hydrological models for routine and operational application. This application limits the data and computer resources which are available for use. 3 The development and application of a thorough model evaluation strategy which examines the suitability of a model in the context of a specific application requirement. 4 The selection of a conceptually sound model structure. S The development and evaluation of a suitable methodology for the incorporation of the spatial variability of catchments into hydrological" models. To provide a basis for the discussion of these five issues, this thesis provides the details of the modification of a currently used hydrological model, RYMO. The modification of this model involves the replacement of the empirical curve number model for runoff derivation with a physically based parameter infiltration model. A number of comparisons of HYMO and the modified version, HYM02, indicates that conceptual, parameter estimation, prediction, and sensitivity improvements have indeed been secured by the development of the modified model.

The research assesses the value of forecast information in operating a hydro-electric project with a storage reservoir. The benefits are the increased hydro power production, when forecasts are available. The value of short term forecasts is determined by comparing results obtained with the use of one month ahead perfect predictions to those obtained without forecasts but a knowledge of the statistics of the possible flows. The benefits with perfect forecasts provide an upper limit to the benefits which could be obtained with actual less than perfect forecasts. The effects of generating capacity and flow patterns are also discussed. The operation of a hypothetical but typical project is modelled using stochastic dynamic programming. A simple model of streamflow is formulated based on the historical statistics ( means and deviations). The conclusions are: The inflow forecasts can improve the operational efficiency of the reservoir considerably because of the reduction in forecasting uncertainty. The maximum release constraints affect the additional expected values. The benefits from the forecasts increase as the discharge limits reduce. Flow predictions in the high flow season are most valuable when the runoff in that time period dominates the annual flow pattern. However flow predictions at other times of the year also have value. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

Published Article / A functioning ecological system results in ecosystem goods and services which are of direct value to human beings. Ecosystem services are the conditions and processes which sustain and fulfill human life, and maintain biodiversity and the production of ecosystem goods. However, human actions affect ecological systems and the services they provide through various activities, such as land use, water use, pollution and climate change. Climate change is perhaps one of the most important sustainable development challenges that threaten to undo many of the development efforts being made to reach the targets set for the Millennium Development Goals. Understanding the provision of ecosystem services and how they change under different scenarios of climate and biophysical conditions could assist in bringing the issue of ecosystem services into decision making process. Similarly, the impacts of land use change on ecosystems and biodiversity have received considerable attention from ecologists and hydrologists alike. Land use change in a catchment can impact on water supply by altering hydrological processes, such as infiltration, groundwater recharge, base flow and direct runoff. In the past a variety of models were used for predicting land-use changes. Recently the focus has shifted away from using mathematically oriented models to agent-based modelling (ABM) approach to simulate land use scenarios. The agent-based perspective, with regard to land-use cover change, is centred on the general nature and rules of land-use decision making by individuals. A conceptual framework is being developed to investigate the possibility of incorporating the human dimension of land use decision and climate change model into a hydrological model in order to assess the impact of future land use scenario and climate change on the ecological system in general and water resources in particular.

No description available.

No description available.

SUMMARY Mangrove ecosystems thrive in (sub)tropical, intertidal areas where adaptations like vivipary and the hydrochorous dispersal of propagules become an absolute necessity. As propagule dispersal and early growth allow for the replenishment of existing stands and colonization of new habitats, many authors recognize the importance of these stages in structuring mangrove populations and communities. However, when it comes to the actual propagule dispersal and recruitment mechanisms, there is an apparent lacuna in the current understanding of mangrove ecology. The period between the mature propagule falling from the parental mangrove tree and the early growth of the established seedling, under various possible circumstances, remains in the dark. In this study we focus on this particular period by investigating both the places where these propagules end up as the pathways their dispersal units follow. And we go one step further. Mangrove forests are being destroyed worldwide at a threatening pace despite their tremendous asset to coastal human communities and associated biological species. The effect of human-induced (cutting and mangrove conversion to aquaculture ponds) as well as indirectly and/or ‘naturally’ evolving disturbances (sea level rise) on propagule hydrochory occupies an important place in this study. Dispersal of water-buoyant propagules of the family Rhizophoraceae and Acanthaceae (now including the Avicenniaceae) was studied in Gazi Bay (Kenya), Galle and the Pambala-Chilaw Lagoon Complex (Sri Lanka). The study sites differ both in tidal regime and vegetation structure, covering an interesting variety of ecological settings to examine propagule dispersal. Field data and experiments ranging from micro/ mesotopographical measurements and successive propagule counts to hydrodynamic and propagule dispersal experiments were collected or executed in situ. Two main methodological approaches were employed. Firstly, the question on mechanisms of propagule recruitment was addressed by statistically investigating the effect of microtopography, top soil texture and above-ground-root complexes on the stranding and self-planting of propagules (Chapter 2&3). Afterwards, suitability maps were created using Geographical Information Systems (GIS) to assess whether a particular mangrove stand has the ability to succesfully rejuvenate. Furthermore, the effect of degradation (tree cutting) (Chapter 2&3), sea level rise (Chapter 2&4) and microtopography-altering burrowing activities of the mangrove mud lobster Thalassina anomala (Chapter 3), was incoporated in the GIS-analyses. Secondly, the combined set-up of hydrodynamic modelling and ecological dispersal modelling was developed to simulate propagule dispersal pathways influenced by dispersal vectors (tidal flow, fresh water discharge, wind), trapping agents (retention by vegetation or aerial root complexes) and seed characteristics (buoyancy, obligated dispersal period) (Chapter 5&6). This type of approach provided the possibility to explore propagule dispersal within its ecological context, but was also applied to an implication of shrimp pond area restoration (Pambala-Chilaw Lagoon Complex, Sri Lanka) (Chapter 5) and to evaluate changes in propagule dispersal when sea level rises (Gazi Bay, Kenya) (Chapter 6). The main findings regarding propagule recruitment indicate that propagules are not distributed equally or randomly within a mangrove stand, yet species-specific distribution for anchorage occurs. Characteristics of the environment (microtopography, top soil texture and above-ground root complex) influence propagule recruitment in a way that complex root systems (e.g. pencil roots and prop roots) facilitate the entanglement of dispersal units and a more compact soil texture (like clay and silt) and a predominant flat topography creates suitable areas for stranding and self-planting of propagules. This combines effects of existing vegetation and abiotic factors on mangrove propagule establishment. Since propagule dispersal is not solely determined by species-specific propagule characteristics (e.g. buoyancy, longevity, etc.), I emphasize that propagule sorting by hydrochory has to be viewed within its ecological context. Propagule retention by vegetation and wind as a dispersal vector, deserve a prominent role in studies on propagule dispersal. The significance of dense vegetation obstructing long distance dispersal (LDD in its definition of this work), mainly in inner mangrove zones, supports our main finding that propagule dispersal is largely a short distance phenomenon. ‘Largely’ is here understood as quantitatively, not excluding epic colonization events of rare but important nature. In accordance with the Tidal Sorting Hypothesis (TSH) of Rabinowitz (1978a), smaller, oval-shaped propagules were found to disperse over larger distances than bigger, torpedo-shaped propagules. We can however not fully support the TSH because (1) these differences are no longer valid when comparing between torpedoshaped propagules of different sizes and (2) propagule dispersal is not always directed towards areas more inland, but can be strongly concentrated towards the edges of lagoons and channels Anthropogenic pressure on mangrove ecosystems, more specifically clear-felling or mangrove conversion to aquaculture ponds, imposes limitations on propagule recruitment due to reduced propagule availability and a decrease in suitable stranding areas where the architecture of certain root complexes, like prop roots and pencil roots, function as propagule traps. These types of pressure appear to have more severe consequences on propagule dispersal than the effect of sea level rise on mangroves. Mangrove forests, which are not situated in an obviously vulnerable setting, can be resilient to a relative rise in sea level if a landward shift of vegetation assemblages and successful early colonization is not obstructed by human-induced pressures. Also, and this renders mangrove forests vulnerable in spite of their intrinsic resilience, when the ‘capital’ of forest is severely reduced or impoverished as happens extensively worldwide, the ‘interest’ on this capital, understood as propagule availability, delivery and trapping, will not allow them to efficiently cope with sea level rise, putting sustainability of mangrove ecosystem services and goods at risk. In a larger framework of mangrove vegetation dynamics, knowledge on propagule dispersal will benefit management strategies for the conservation of mangroves worldwide, besides its fundamental interest to fully fathom the ecology of this particular marine-terrestrial ecotone formation.

"Major Subject: Water Management and Hydrological Sciences" Title from author supplied metadata (automated record created 2010-03-12 12:08:51). Includes bibliographical references.

"Major Subject: Water Management and Hydrological Sciences" Title from author supplied metadata (automated record created 2010-03-12 12:08:51). Includes bibliographical references.