The Upper Vaal Water Management Area (Upper Vaal WMA) lies in the eastern interior of South Africa. This WMA includes the Vaal, Klip, Wilge, Liebenbergsvlei and Mooi Rivers and extends to the confluence of the Mooi and Vaal Rivers. It also includes major dams such as the Vaal Dam, Grootdraai Dam and Sterkfontein Dam. The southern half of the WMA extends over the Free State province; the north-east mainly falls within Mpumalanga and the northern and western parts in Gauteng and North West provinces respectively (DWAF 2004). Several wastewater treatment works (WWTW) located in this area do not meet the standard set by the present legislation that addresses proper treatment of water. This results in number of problems that affect the quality of water in this catchment. It was noted by the WRC (2006b) that with the challenges of implementation in an environment of shared responsibility, it is increasingly recognised that public/government institutions must foster institutional cooperation and interaction for efficient provision of public services, both at the policy-strategy level and the operational-implementation level. According to WRC (2006b), poor cooperation between institutions in the implementation of their interrelated mandates has resulted in inefficient utilization of scarce resources and/or endless disputes. In order to address this shortcoming, a study that investigated the effects of cooperative governance in the Wastewater Treatment Works (WWTW) in the Upper Vaal Water Management Area was initiated. The results of the research indicate a lack of cooperation between the three spheres of governance that participate in the sustainable management of water treatment in this area. / Thesis (M. Environmental Management)--North-West University, Potchefstroom Campus, 2013.

The Upper Vaal Water Management Area (Upper Vaal WMA) lies in the eastern interior of South Africa. This WMA includes the Vaal, Klip, Wilge, Liebenbergsvlei and Mooi Rivers and extends to the confluence of the Mooi and Vaal Rivers. It also includes major dams such as the Vaal Dam, Grootdraai Dam and Sterkfontein Dam. The southern half of the WMA extends over the Free State province; the north-east mainly falls within Mpumalanga and the northern and western parts in Gauteng and North West provinces respectively (DWAF 2004). Several wastewater treatment works (WWTW) located in this area do not meet the standard set by the present legislation that addresses proper treatment of water. This results in number of problems that affect the quality of water in this catchment. It was noted by the WRC (2006b) that with the challenges of implementation in an environment of shared responsibility, it is increasingly recognised that public/government institutions must foster institutional cooperation and interaction for efficient provision of public services, both at the policy-strategy level and the operational-implementation level. According to WRC (2006b), poor cooperation between institutions in the implementation of their interrelated mandates has resulted in inefficient utilization of scarce resources and/or endless disputes. In order to address this shortcoming, a study that investigated the effects of cooperative governance in the Wastewater Treatment Works (WWTW) in the Upper Vaal Water Management Area was initiated. The results of the research indicate a lack of cooperation between the three spheres of governance that participate in the sustainable management of water treatment in this area. / Thesis (M. Environmental Management)--North-West University, Potchefstroom Campus, 2013.

The draining of the Iraqi Marshlands is an example of the reorganization of a linked social-ecological system (SES) following a collapse. The goal of this study was to examine the utility of resilience as a water management tool through a case study of the Marshlands. Using the Four-Step Framework by Walker et al. (2002), it analyzed the Marshlands through the metaphor of the adaptive cycle, explored three possible future scenarios, created two models to characterize the system, and reviewed the implications of the analysis for water management in the Marshlands and resilience. This study found that resilience, and the Framework, could offer new perspectives for managing complex SESs. However, resilience is not useful during times of intense violent conflict, like war. It also found that there are resilient pathways to help the Marshlands reorganize. However, the Marshlands are very vulnerable and require strong institutional support to keep them from disappearing.

The adaptive cycle metaphor provides insight into how and why social-ecological systems change. Literature on 'resilience thinking' has built upon this foundation and further developed the concepts of resilience, adaptation, and transformation to describe social-ecological system behavior. The resilience-thinking literature also describes systems that do not change, even when such change is desirable, as being in a trapped state. However, relatively little research has explored why such systems are trapped and how to free them. This thesis is the product of doctoral research which resolves how to identify, evaluate, and free a system caught in a maladaptive system trap. The study setting is water management in Grenada, a small island developing state in the southeastern Caribbean. Four research questions guide this study: (1) To what extent is Grenadian water management in a trap?, (2) To what extent is Grenadian water management transformable?, (3) Do current and recent interventions effectively foster or utilize transformability?, and (4) Which interventions should be pursued to facilitate transformation of water management in Grenada?. The study is informed by literature on social-ecological systems and integrated water resources management. Methodologically, the study is an explanatory single-case study of water management in Grenada, conducted from 2012 to 2013. The study utilizes data from semi-structured interviews (n=19), a questionnaire (n=180), a document review (n>200), and observation. The general strategy was to evaluate attempts to transform Grenadian water management within the 3-phase transformation framework described in the resilience-thinking literature. 'Points of failure' in transformation are defined as the cause(s) of a trap, and interventions to relieve the points of failure are proposed. Results indicate Grenadian water management is in a rigidity trap, although it exhibits some capacity to transform. A key point of failure of attempts to transform the Grenadian water sector into an integrated and holistic management system has been an inability to seize windows of opportunity to pass key legislation. I conclude the primary cause for this failure is poor fit among the problem, as perceived by various stakeholders, the proposed solution prescribed by water sector reform proponents, and political reality. In addition, reform proponents focus on advocating for reform to water sector professionals and do little to broker passage of legislation politically. Finally, reform proponents also assume legislation will be effectively implemented, which is not certain. Contributions specific to the Grenadian setting include a post-mortem on why efforts to reform the water sector have failed, described above. Five recommendations are made for future interventions to foster transformation of Grenadian water management: (1) engage residents as part of a vision to create political pressure for proposed solutions, (2) frame the problem with substantial resident input and focus, (3) craft solutions which take advantage of political realities such as funding restrictions, (4) anticipate and prepare for crises, and (5) enlist one or more people or organizations to serve as brokers. Empirical contributions include support for the three-streams framework of seizing windows of opportunity as fundamental to explain transformation of social-ecological systems. The primary conceptual contribution is the development of resilience thinking to illuminate ways to free trapped systems. I begin by providing a nomenclature to quantify and describe traps, which includes the type of trap, the degree of persistence and undesirability of the trap, and recent changes in these properties. Then, I develop a framework to assess transformability of a given system based on the existing 3-phase framework of transformation. When applied empirically, this framework illuminates points of failure of transformation, which I define as the cause of a given trap. Once identified, specific strategies can be devised to foster transformation and to break free of a trap.

An awareness of the effect of agricultural production on the environment has led to the development of policies to mitigate its adverse effects. This dissertation provides analyses of agri-environmental policies designed to protect environmental assets, as well as analytical decision-making tools useful for conducting policy evaluations. The first essay employs propensity score matching techniques to estimate the additionality of federal agricultural conservation programs for six conservation practices for farmers in Ohio. Additionality is an important measure of the effectiveness of conservation programs in inducing an increase in the conservation effort of farmers. Results suggest that additionality is positive and statistically significant for all six conservation practices. However, while programs achieve positive additionality for all practice types, a comparison between conservation practices reveals that certain practice types achieve higher percent additionality than others. Such results, coupled with information on the environmental benefits obtained per practice, could prove useful to program managers for improving the effectiveness of conservation programs. The second essay develops a new methodology to decompose the additionality measure into the two effects induced by conservation programs: expansion versus the new adoption of conservation practices. To do so, the relative contributions of two types of farmers, prior-adopters and new-adopters, are estimated. Results of the decomposition reveal that the additionality for prior-adopters is not significant for all practice types. Instead, additional conservation effort comes from new-adopters adopting new practices. Second, decomposition estimates suggest that practice types with a greater fraction of enrolled farmers that are new-adopters achieve greater percent additionality than those with greater proportions of prior-adopters. This suggests that a farmers? history in conservation adoption has a significant influence on additionality levels. The final essay analyzes the effect of recent instream flow diversion-guidelines on agricultural water security and streamflows within a decentralized water management regime. Spatially-explicit economic and hydrologic models are integrated to evaluate the tradeoffs between salmon bypass-flows and agricultural water security for three different diversion-guidelines within a northern-California watershed. Results indicate that the most restrictive diversion-guideline provides the greatest protection of bypass-flow days within smaller watersheds; however, within larger watersheds protection is not as significant. Water security, however, decreases sharply under the strict and moderate diversion-guidelines, especially during dry years. Overall, results indicate that greater focus should be given to protecting streamflows in the smallest watersheds, and meeting human water needs during dry years, when agricultural water security is impacted the most.

Thesis (MA)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: This study investigated the extent of Water Sensitive Urban Design activities in the George municipality in the Western Cape Province, in South Africa. Water resource management in urban areas worldwide had become unsustainable with the widespread implementation of outsized infrastructure, environmental degradation and overuse of natural resources. The result was a concept called Integrated Urban Water Management (IUWM). IUWM encapsulates the entire water cycle from rainwater to surface water, groundwater and wastewater, as part of urban water management, and not as separate entities. There was worldwide response to IUWM, with the USA formulating Low-Impact Development (LID), the UK designing their Sustainable Urban Drainage System (SUDS), and New Zealand articulating Low Impact Urban Design and Development (LIUDD), all to improve urban water resource management. Australia responded with Water Sensitive Urban Design (WSUD). WSUD explores the design and planning of water infrastructural development in an urban setting, vital in Australian cities which experience continuous severe water shortage conditions. The WSUD approach aims to influence design and planning from the moment rainwater is captured in dams, treated, and reticulated to consumers, to the point of wastewater re-use, as well as stormwater use. Various techniques are specified as part of the WSUD approach namely: the installation of greenroofs, demand reduction techniques, stormwater management and the re-use of treated wastewater for irrigation and fire-fighting. These WSUD activities can be implemented from large-scale efforts with whole suburbs working together to manage stormwater by construction of wetlands, as well as small-scale change in design and planning, e.g., with household rainwater tank installation for irrigation and toilet flushing. With South Africa’s progressive legislation at a national, provincial and local municipal level, various WSUD activities can be implemented to aid and guide municipalities. The study aimed to investigate what type of WSUD activities the George municipality has implemented, and to what extent the activities had an impact on water consumption, since the drought in 2009. The reasons behind any lack of implementation were also explored. Proof of only eight WSUD activities implementation could be found. Water debtors’ data and bulk water data was sourced in order to determine the effect of the eight WSUD activities on water consumption. Bulk meter data could however not be used to correlate with the debtors’ data since readings from many bulk meters had not been recorded. Debtors’ data did prove however that the WSUD activities had a short-term impact on water consumption in the suburbs where it was implemented. The reasons given for non-implementation were not satisfactory. Recommendations are that the municipality should focus on better planning and implementation of diverse activities and that keeping records and data should be made a priority to determine any progress made. / AFRIKAANSE OPSOMMING: Hierdie studie ondersoek die omvang van die Water Sensitiewe Stedelike Ontwerp (WSUD) aktiwiteite in die George munisipaliteit in die Wes-Kaap, in Suid-Afrika. Waterhulpbronbestuur in stedelike gebiede in die wêreld het nie-volhoubaar geword met die grootskaalse implementering van buitenmaatse infrastruktuur, agteruitgang van die omgewing en die oorbenutting van natuurlike waterhulpbronne. Die gevolg was 'n konsep wat Geïntegreerde Stedelike Water Bestuur (IUWM) genoem is. IUWM omvat die hele watersiklus vanaf reënval, tot oppervlakwater, grondwater en afvalwater, as deel van die stedelike waterbestuur, en nie as aparte entiteite nie. Daar was 'n wêreldwye reaksie te IUWM, met die VSA se Lae-impak-Ontwikkeling (LID), die Verenigde Koninkryk se ontwerp van hul volhoubare stedelike dreineringstelsel (SUDS), en Nieu-Seeland se formulering van Lae-impak Stedelike Ontwerp en Ontwikkeling (LIUDD), om stedelike water hulpbronne beter te bestuur. Australië het reageer met Water Sensitiewe Stedelike Ontwerp (WSUD). WSUD verken die ontwerp en beplanning van waterbestuur infrastruktuur ontwikkeling, in 'n stedelike omgewing, waar dit noodsaaklik was in die Australiese stede wat deurlopende tekort aan water ervaar. Die WSUD benadering het ten doel om die ontwerp en beplanning te beïnvloed vanaf die oomblik reënwater in damme opgevang is, behandel, en aan verbruikers versprei word, tot by die punt van afvalwater hergebruik, sowel as stormwater gebruik. Verskeie tegnieke word verskaf as deel van die WSUD benadering, naamlik: die installering van “greenroofs”, wateraanvraagbestuur tegnieke, en stormwater gebruik en hergebruik van behandelde afvalwater vir besproeiing en brandbestryding. Hierdie WSUD aktiwiteite kan implementeer word vanaf grootskaalse pogings met die samewerking van hele voorstede met stormwater bestuur deur die konstruksie van die vleilande, sowel as kleinskaalse verandering in die ontwerp en beplanning by huishoudings, byvoorbeeld met reënwatertenk installasie vir besproeiing en toilet spoel. Met Suid-Afrika se progressiewe wetgewing op 'n nasionale, provinsiale en plaaslike munisipale vlak wat munisipaliteite steun en lei, kan die verskeie WSUD aktiwiteite ïmplementeer word. Die studie is gemik om ondersoek in te stel na watter tipe WSUD aktiwiteite deur die George-munisipaliteit implementeer word, en tot watter mate die aktiwiteite 'n impak gehad het op die water verbruik sedert die droogte in 2009. Die redes agter 'n gebrek aan implementering is ook ondersoek. Bewyse van implementering van net agt WSUD aktiwiteite kon gevind word. Data van die water debiteure en grootmaat water meters is verkry ten einde die effek van die agt WSUD aktiwiteite op die water verbruik te bepaal. Grootmaat water meter data kan egter nie gebruik word om te korreleer met die data van die debiteure aangesien die lesings van baie grootmaat water meters nie aangeteken is nie. Debiteure se data het egter bewys dat die WSUD aktiwiteite 'n korttermyn-impak op die waterverbruik in die voorstede waar dit geïmplementeer is gemaak het. Die redes gegee vir nieuitvoering is nie bevredigend nie. Aanbevelings is dat die munisipaliteit moet fokus op beter beplanning en implementering van diverse aktiwiteite en dat die hou van rekords en data prioriteit gemaak moet word om vas te stel of enige vordering gemaak is.

A degradação ambiental do Noroeste do Estado do Rio de Janeiro tem se intensificado nas últimas décadas devido às práticas agrícolas não preservacionistas. Esta situação, que decorre do uso inadequado do solo, tem implicado em mudanças na oferta hídrica em grau variável nos municípios da região com prejuízos econômicos nas atividades dos pequenos e médios proprietários rurais e na qualidade de vida. A abordagem para enfrentar problemas deste tipo depende da participação efetiva das instâncias de governo e dos órgãos responsáveis pela gestão dos recursos hídricos. No âmbito da hidrologia os modelos hidrológicos com base no uso e ocupação do solo são ferramentas que podem auxiliar com ótimo custo e benefício a geração de informações em bacias hidrográficas, instrumentadas ou não. Os modelos são úteis ao planejamento e à tomada de decisão por possibilitarem a previsão de vazões e simulação de cenários sobre o uso do solo e qualidade da água. Neste sentido, o presente estudo pretende dar sua contribuição ao avaliar a adequabilidade do modelo SWAT simular o processo chuva-vazão na microbacia experimental de Santa Maria e Cambiocó, com 13,5 km2, localizada na região hidrográfica do rio Muriaé, afluente do rio Paraíba do Sul. O SWAT tem sido empregado em bacias agrícolas nos EUA, na Europa e, atualmente, na China, sudeste asiático e Irã, entre outros países, e na última década maior inserção no meio acadêmico brasileiro. A versão 2005 do modelo foi utilizada por meio da sua interface SIG para simular as vazões médias diárias com base na precipitação medida no intervalo de 15 minutos no período de 2005/2006. As vazões simuladas foram comparadas com as vazões observadas no exutório da microbacia. Foram testadas as ferramentas de análise de sensibilidade e autocalibração. O método de calibração manual foi usado para o ajuste por tentativa e erro. Os parâmetros ajustados corresponderam ao CN2 e ESCO. Os valores obtidos na calibração para os coeficientes estatísticos R2, NSE, PBIAS e RSR foram 0,80, 0,80, 7,02 e 0,45, respectivamente, indicando escore muito bom, o que foi confirmado pela inspeção dos hidrogramas. As saídas validadas para período diferente da calibração forneceram para os mesmos coeficientes os valores 0,84, 0,80, 25,92 e 0,44. Os dois primeiros, com escore muito bom. O valor de PBIAS, no limite do satisfatório, e RSR, muito bom. O desempenho permitiu concluir que a simulação com o SWAT foi adequada. Em relação às pesquisas que têm sido realizadas no Brasil os valores obtidos para os indicadores foram semelhantes, indicando a capacidade do modelo para novos estudos nesta microbacia que considerem os usos consuntivos e cenários de uso do solo. / The environmental degradation in the Northwest region of the State of Rio de Janeiro has intensified in the last decades due to no preservationist agricultural practices. This arises from inappropriate land use that has been associated to changes in water supply to a varying extent in the Regions municipalities. These, has leaded to economic losses in the activities of small and medium rural homeowners, and quality of life decaying. The approach to address such problems depends on the active participation of government bodies and agencies responsible for water resources management. Hydrological simulation models can assist with great value and benefit to the generation of information in basins, instrumented or not. Models are useful for planning and decision making as they allow the discharges forecasting and simulation scenarios on land use and water quality. In this context, the study aims to make a contribution to assess the suitability of the rainfall-runoff component of the SWAT model in the Santa Maria and Cambiocó catchment, with 13.5 km2, located in Muriaés river basin, a tributary of the Paraíba do Suls river basin. SWAT has been employed in agricultural basins in the U.S., Europe, and currently in China, Southeast Asia and Iran, among other countries, and had in the last decade greater insertion in the Brazilian academia. The 2005 version of the model was used through its GIS interface to simulate the daily mean discharges based on rainfall measured at 15 minute intervals from 2005/2006. Simulated and observed discharges at catchments outlet gage station have been compared. Tools for sensitivity analysis and calibration were tested. Manual calibration adjustment was conducted with CN2 and ESCO parameters. The values obtained by calibration for the statistical coefficients R2, NSE, PBIAS and RSR were 0.80, 0.80, 7.02 and 0.45, respectively, indicating "very good" score. This was confirmed by inspection of hydrographs. The validation period for the different outputs provided the coefficients 0.84, 0.80, 25.92 and 0.44. The R2 and NSE matched a very good score. The PBIAS was at the limit of satisfactory and RSR, very good. The results showed that SWAT simulations were appropriate comparing with others studies in Brazil. The model can be recommended for further studies in this catchment for modeling consumptive uses and land use scenarios.

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No. of bitstreams: 1 soldera_bc_dr_rcla.pdf: 1339538 bytes, checksum: f6e8c82c512ffcd9256c246fffb800fb (MD5) Previous issue date: 2017-10-24 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Este trabalho apresenta um novo conceito, denominado Água Compensável (AC), que permite mensurar o uso da água a partir da alteração de sua qualidade e quantidade, abrindo as portas para a criação de instrumentos econômicos para sua gestão. O conceito baseia-se em um princípio simples, inovador e abrangente, para que possa ser utilizado de forma ampla por governos, empresas e cidadãos para quaisquer atividades humanas que envolvam o uso de água. A AC é um conceito ao qual pode ser atribuído valores obtidos por uma equação proposta e seguindo uma metodologia também proposta. A AC apoia-se no conceito denominado Pegada Hídrica Cinza ou Água Cinza, que por sua vez está inserido dentro do conceito Pegada Hídrica (Water Footprint). Para exemplificação do uso do conceito, utilizou-se a área de estudo das Bacias Hidrográficas dos rios Piracicaba, Capivari e Jundiaí (PCJ). Esta escolha deveu-se ao fato desta ser uma área que apresenta importante desenvolvimento econômico, muitas vezes com urbanização mal planejada e indústrias de grande porte estabelecidas, gerando impactos na qualidade e quantidade dos recursos hídricos, que indicam a necessidade de melhores planejamento e gestão do uso da água. O trabalho consistiu em levantamentos, compilações, elaboração de bancos de dados, interpretações e análises para determinação da AC para uma gama de solutos potencialmente contaminantes, oriundos de atividades antrópicas. Os solutos selecionados foram: nitrogênio, fósforo, Demanda Bioquímica de Oxigênio (DBO), Demanda Química de Oxigênio (DQO) e gorduras totais. Foram efetuados os cálculos e análises das AC para solutos gerados por diversas atividades realizadas nas Bacias PCJ e por dois estudos de casos específicos, indústria de bebidas (cerveja e refrigerante) e indústria de alimentos (laticínios e abate animal). É importante salientar que o conceito AC deve ser estimado mesmo para valores de concentrações para solutos que estejam abaixo do padrão de lançamento em corpos d’água, cujo efluente ao qual se incorporam tenha sido previamente tratado. Este raciocínio é suportado pela lógica de que, para alcançar um padrão sustentável a responsabilidade sobre qualquer alteração da qualidade da água, pela adição de massa de soluto, deve ser extensiva à sua remoção ou pela compensação por esta remoção, quer ela venha a ser realizada natural ou artificialmente, quer por diluição ou eventual degradação natural, ou por tratamento da água. Em todos os cálculos realizados neste trabalho pôde-se verificar o elevado volume de AC e o quanto isto pode colocar em risco a qualidade e quantidade da água. É evidente que massas de solutos sempre serão lançadas nos corpos hídricos, porém pode-se fazer com que estas massas não sejam suficientes para elevar a AC e contribuir com a má qualidade do rio. O conceito de AC é simples e poderoso, permite a mensuração do impacto antrópico ao recurso hídrico e abre a possibilidade de valoração da água por meio de compensações realizadas pelos diversos usuários. / This work presents a new method, called Compensable Water (CW), that allows to measure the water use by altering its quality and quantity, opening the doors for the creation of economic instruments for its management. The concept is based on a simple, innovative and comprehensive principle, so it can be widely used by governments, businesses, citizens and any human activities involving the use of water. CW is a concept that can be attributed values obtained by a proposed equation and following a methodology also proposed. The CW concept is based on Water Footprint and Grey Water Footprint concept. To exemplify the use of the SW method, we used the study area of the Piracicaba, Capivari and Jundiaí (PCJ) Hydrographic Basins. The choice of the area was due to the area presents an important economic development, often with poorly planned urbanization and large industries, generating impacts on the quality and quantity of water resources, and these factors indicate the need to improve the water use management. The work consisted of surveys, compilations, databases, interpretations and analyses to determine the SW for a range of potential contaminants from anthropic activities. The selected solutes were: Nitrogen, Phosphorus, Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD) and total fats. Calculations and analyses were carried out for the CW generated by several human activities in the PCJ Basins and for two case studies, beverage industry (beer and soft drink) and food industry (dairy and animal slaughter). It is important to emphasize that the CW must be estimated even for concentration values of solutes that are below the discharge pattern in water bodies whose effluent to which they are incorporated has been previously treated. This reasoning is supported by the logic that to achieve a sustainable standard, the responsibility for any change in water quality, by the addition of solute mass, must extend to its removal or compensation, whether it comes to be carried out naturally or artificially, either by dilution or eventual natural degradation, or by treatment of the water. The results show there is a high volume of CW and it is posing in risk the quality and quantity of water. It is evident that masses of solutes will always be released into the water body, but these masses cannot be enough to raise the CW volumes and contribute to the poor quality of the river. The CW concept is a simple and powerful tool for the measurement of the anthropic impact on water resource and allows the valuation of the water through compensations made by water users. / 165799/2014-5

Situé dans la partie sud du Sénégal, le bassin de la Casamance dispose de potentialités rizicoles importantes. Malgré les contraintes causées par les aléas climatiques, les populations locales ont su pratiquer la riziculture dans les zones de vallée. En revanche, la persistance des effets négatifs a eu pour conséquence la prise de conscience de la nécessité de protéger les zones rizicoles contre l’avancée du sel et de maîtriser les quantités d’eau précipitées. C’est dans ce contexte qu’une multitude de petits barrages a été mise œuvre en Casamance par différents acteurs au développement. Cette thèse fait le point sur l’état du choix de la politique d’aménagement hydro-agricole dans le bassin de la Casamance. En effet après un peu plus d’un demi-siècle d’intervention, le constat de l’insuccès des programmes de développement de la production du riz dans les bas fonds demeure.Elle propose une grille d’analyse de la situation générale à partir d’une étude à plusieurs dimensions : une dimension politique portant sur l’échelle nationale et régionale, une dimension socioculturelle basée sur le local et une dimension technique qui se rapporte aux petits barrages. La synthèse de ces trois entrées permet de formuler des modèles d’intervention mieux adaptés au contexte et aux réalités locales. / Located in the south of Senegal, the Casamance basin has a significant potential for rice production. Despite climatic constraints, the local people practice paddy cultivation in the valleys. However, the persistence of negative effects has resulted in the awareness of the need to protect the rice-growing areas against the advance of salt and to improve the use of rainfall available. It is in this context that a number of small dams were built in Casamance by various development actors.This dissertation assesses the hydro-agricultural planning policies in Casamance that were implemented during the last five decades. This appraisal is quite bleak: most of the rice production development programmes did fail in lowlands. This Ph.D. proposes a framework for analyzing the overall situation through a multi-dimensional study: a political dimension at the national and regional levels, a socio-cultural dimension based on the “local”, and a technical dimension referring to small dams. The synthesis of these three entry ways enables to propose intervention models better adapted to the local context and realities.

Les micropiles à combustibles sont envisagées pour remplacer ou prolonger l’autonomie des batteries dans les dispositifs nomades. Dans ce domaine, la miniaturisation très poussée a abouti à la réalisation de prototypes planaires multi-cellules d’une puissance de 3 à 5 W. La différence d’architecture par rapport aux piles à combustibles « classiques », l’absence d’auxiliaires de fonctionnement et l’utilisation direct de l’air ambiant comme réactif amènent de nouvelles problématiques au niveau de la gestion de l’eau produite. Le travail de cette thèse porte sur la caractérisation de la gestion de l’eau et l’augmentation de la durée de vie d’un système de micropiles à combustible planaire « à respiration », à température ambiante. L’impact prépondérant de la thermique a été mis en avant, au niveau des points de fonctionnement (noyage aux faibles densités de courant et assèchement aux forts courants) comme au niveau local (gradients entre cellules). Les phénomènes d’assèchement et de noyage ont été étudiés grâce à l’imagerie neutronique. Un des principaux phénomènes observé est la rétrodiffusion d’eau vers l’anode suite une condensation au niveau de la cathode, conduisant à une importante perte de puissance. Une étude de la dégradation lors de fonctionnement longue durée a permis de montrer qu’une mauvaise gestion de l’eau favorise la corrosion d’éléments métalliques, conduisant à une diminution des performances. Une solution visant à éliminer ces phénomènes a été développée et implémentée avec succès. L’intégration du microporeux développé lors de cette thèse a permis d’atteindre une dégradation de 0,1 mV/h sur 2500 h de fonctionnement à 3,5 W. / Micro fuel cells have been considered as potential substitute or complement to batteries for nomad systems, in order to enhance their autonomy. Miniaturization of these objects led to the development of multi-cells planar arrays delivering 3 to 5 W. The specificities of this design compared to the “conventionnal” fuel cell stack architecture, coupled to the removal of peripheral components and the use of ambient air as oxidant, comes along with new challenges concerning water management. This work is focused on the characterization of water management and the lifetime improvement of a planar air-breathing fuel cell array at ambient temperature. Thermal effects have been demonstrated to be of first order concerning the operating conditions (flooding at low current density and drying-out at elevated one) and the local heterogeneities (between cells). Drying-out and flooding have been investigated using neutron imaging. One of the major phenomena observed is back-diffusion linked to water condensation on the cathode side, leading to anodic water accumulation and concomitant power decrease. Investigation of the degradation during long term operation pointed out corrosion of metallic elements as the major issue involved in performance decrease. Development and successful implementation of a solution to counter these troubles led to a limited degradation of 0.1 mV/h during a 2500 h operation at 3.5 W.