Thesis (Ph. D.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 116-126). Also available on the World Wide Web.

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Ph.D. / Wetlands play an integral role in the hydrological cycle and biodiversity. Despite this, wetlands have been neglected in terms of research and monitoring in South Africa. This lack of research has become even more insufficient when it comes to endorheic wetlands. Endorheic wetlands in South Africa are known as pans. Pans are isolated depressions that for through wind erosion are generally shallow and lack an integrated drainage. Water gain is depended on rainfall and surface runoff and water loss is largely due to evaporation. Pans can be either ephemeral in nature or can remain inundated for long periods of time. There are close to 5000 pans in the study area of the Mpumalanga province of South Africa. An estimated 40% of these pans are perennial in nature. The little information on the ecology of pans is all focussed on those systems that are ephemeral. The lack of knowledge is, however, not restricted to the ecology of perennial pans but also the management tools available for these ecosystems. Whereas a variety of methods are available to determine the quantity and quality of water needed to sustain riverine systems (and wetlands connected to rivers), there are no such methods for pans. Especially important is the lack in standardised methods to assess the ecological integrity of perennial pans. This is important as perennial pan ecosystems are increasingly under threat from an increase in coal mining and agricultural activities in Mpumalanga. Coal mining activities have increased in the study area due to both an increase in energy demands and the ease of mining coal deposits in the study area. The lack in standardised methods could be as a direct result of the lack in knowledge of the ecology of the perennial pans. The aim of this study was thus to develop standardised methods for assessing the ecological integrity of perennial pans in Mpumalanga by studying the ecology of the pans. The study thus uses a fundamental approach to reach certain applied goals. To achieve the aim, a total of nine pans were included in the study of which seven were surveyed seasonally for two years and two were sampled on a single occasion. Five of these pans were located in the Mpumalanga Lake District (MLD) and were in a relatively pristine condition. The other four pans were impacted either by agricultural activities, mining activities or both. During these surveys, various components of the ecosystem were studied. These components included the spatial and temporal variations in the abiotic components like the physico-chemical characteristics, habitat quality and quantity, and the sediment characteristics. It also included the spatial and temporal variations in the vegetation communities surrounding the pans and the aquatic invertebrate communities within the pans. The aquatic invertebrate communities were assessed based on a taxonomic approach (diversity) and functional approach (biological traits).

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Copies of author's previously published articles inserted. / Bibliography: leaves 317-359. / xxii, 360 leaves : ill. (some col.), maps (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Examines the generality of the Flood Pulse Concept as a model for the role of flow in large floodplain rivers of all climatic zones and reviews the literature on hydrology-biology relations, with particular reference to the ecology of riverine fish. Using techniques of ordination, clustering and analysis of similarities (ANOSIM), examines the relations between flow variability, econology and climate in large rivers worldwide. Using a fie-year database for Cooper Creek in Central Australia, relates structures of fish, macroinvertebrate and zooplankton assemblages and indices of fish health and behaviour to hydrology at several spatial and temporal scales. These relations are established using multivariate techniques, univariate correlation and regression, and neural networks modelling. / Thesis (Ph.D.)--University of Adelaide, Dept. of Zoology, 1999

Copies of author's previously published articles inserted. / Bibliography: leaves 317-359. / xxii, 360 leaves : ill. (some col.), maps (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Examines the generality of the Flood Pulse Concept as a model for the role of flow in large floodplain rivers of all climatic zones and reviews the literature on hydrology-biology relations, with particular reference to the ecology of riverine fish. Using techniques of ordination, clustering and analysis of similarities (ANOSIM), examines the relations between flow variability, econology and climate in large rivers worldwide. Using a fie-year database for Cooper Creek in Central Australia, relates structures of fish, macroinvertebrate and zooplankton assemblages and indices of fish health and behaviour to hydrology at several spatial and temporal scales. These relations are established using multivariate techniques, univariate correlation and regression, and neural networks modelling. / Thesis (Ph.D.)--University of Adelaide, Dept. of Zoology, 1999

[Truncated abstract] Runoff generation behaviour and flooding in a lake dominated catchment are nonlinear, threshold-driven processes that result from the interactions between climate and various catchment characteristics. A complicating feature of the rainfall to runoff transformation, which may have implications for the flood frequency, is that the various surface and subsurface flow pathways are dynamic, heterogeneous and highly nonlinear, consisting of distinct thresholds. To understand the impact of threshold nonlinearities on the rainfall-runoff transformation in such catchments, a systematic examination was carried out to investigate runoff generation behaviour of the catchment itself, the overflow behaviour of a lake in combination with the catchment draining into it, as well as the lake organisation within a lake chain network. Three storage based thresholds were considered: the catchment field capacity storage governing catchment subsurface stormflow, total storage capacity governing catchment surface runoff, and lake storage capacity governing lake-overflow. ... Through these investigations, this thesis has provided valuable insights into the process controls of lake-overflow events and the associated flood frequency behaviour in lake dominated catchments. In particular, the relative roles of climate, soil depth, the soil?s drainage capacity, as well as the relative geometry of the lake vis a vis the contributing catchment, in the determination of the dynamic characteristics of lake-overflow events and associated flood frequency behaviour have been highlighted. In addition, the importance of lake organization, as expressed in terms of the average ratio of catchment area to lake area and the spatial variability of this ratio from upstream to downstream, and their impact upon connectivity and flood frequency have also been explored. The outcomes of this study highlight the importance of thresholds governing flood frequency, and provide insights into the complex interactions between rainfall variability and the various threshold nonlinearities in the rainfall-runoff process, which are shown to have a significant impact on the resulting flood frequency curves. The improved understanding of these process controls will be useful in assisting the 1 management of the catchment-lake system in the study region, and in regions elsewhere. In particular, the outcome of this study can provide guidance towards the adoption of various management strategies for lake chain systems by illustrating the effects of potential flow interruption and retardation as ways to assist in flood prevention and mitigation, whether it is aimed at decreasing the frequency of occurrence of lake overflows, or merely decreasing the flow magnitude for a given return period.

O objetivo principal desta pesquisa foi desenvolver um modelo de simulação dinâmica para a valoração ecológica de serviços ecossistêmicos hídricos, baseado em princípios de Dinâmica de Sistemas com o auxílio do software STELLA. A hipótese básica adotada foi que: a valoração ecológica dos serviços ecossistêmicos deve contar com uma ferramenta integradora dos elementos envolvidos na modelagem ecológica como requisito básico para compreensão da dinâmica ecossistêmica que gera fluxos de serviços ecossistêmicos hídricos (SEH). Os SEH são os benefícios gerados a partir das complexas interações, entre os componentes do ciclo hidrológico e que tem a ver com a preservação tanto em quantidade como em qualidade da oferta de água. O modelo foi desenvolvido, através de uma análise sistêmica dos processos ecossistêmicos compreendidos dentro do ciclo hidrológico, foram determinadas as principais variáveis e suas respectivas inter-relações, de acordo com a estrutura desse ciclo. Essa estrutura foi representada no diagrama causal, que serviu de base à elaboração do diagrama de estoque e fluxo, por meio do qual se estabeleceu o modelo matemático que permitiu efetuar a simulação numérica. A escala temporal de aplicação do modelo é diária e foram efetuadas 365 simulações, o que permitiu estimar fluxos anuais de SEH. O modelo foi parametrizado na sub-bacia das Posses, Município de Extrema, Minas Gerais; aqui esta sendo implementado o primeiro projeto piloto, baseado na relação floresta-água, de pagamentos por SEH do Brasil. Foram examinados 36 cenários, com o objetivo de avaliar o impacto que têm variáveis como: textura de solo, altura da vegetação, índice de área foliar e profundidade do lençol freático na geração dos fluxos de SEH em água na superfície, infiltrada e armazenada; porém foi avaliado como estes incidem de forma quantitativa na manutenção da oferta de água disponível. O modelo desenvolvido permitiu aumentar a compreensão dos fluxos de SEH, o que representa uma ferramenta de elevado potencial de aplicação nas fases de definição de âmbito, de avaliação de alternativas e monitoramento de esquemas de pagamentos por SEH no Brasil. / The main objective of this research was to develop a dynamic simulation model to valuate ecological hydrological ecosystem services. The principles of System Dynamics were applied using the software STELLA. A basic hypothesis was adopted: ecological valuation of ecosystem services must use a tool to integer all the elements involved in ecological modeling, as a basic requirement to understand the ecosystem dynamic that generates water fluxes as hydrological ecosystems services (HES). HES are the benefits generated from complex interactions that occur within the hydrologic cycle; those interactions deals with the preservation of available water, in quantity and quality. The model was developed after a systemic analysis of the ecosystem processes involved in the hydrologic cycle; pointing out the main variables and the interrelations that constitute it. Then, the structure of those relations was represented in a causal diagram; becoming the base to built up the stocks and flows diagram. This later diagram established the mathematical model that allowed the numerical simulation. The time step of the model is one day during 365 days, estimating annual water HES. The model was parameterized at Poses sub-watershed, Extrema County, Minas Gerais. In Extrema was established the first payment for HES project in Brazil, based on the relationship between forest land and water availability. Thirty six scenarios were studied considering surface, infiltrated and stored water services fluxes; affecting the availability of water. The objective of those scenarios was to evaluate the impact that variables such as: soil texture, vegetation height, leaf area index and groundwater depth have on water flux generation. The model developed enables to increase the understanding of HES fluxes, becoming a tool with a broad spectrum of applications during the stages of assessing and scoping alternatives for payment of environmental services and to monitor HES programs in Brazil.

Thesis (Ph. D.)--Utrecht University, 2008. / Vita. Includes bibliographical references (p. 131-140).