L'agroforesterie consiste à mélanger sur la même surface des arbres et des cultures et nécessite que des relations de complémentarité s'établissent entre les deux espèces pour diminuer la compétition pour les ressources, notamment au niveau des interactions racinaires. L'objectif du travail de cette thèse était de tester et d'évaluer la possibilité de piloter l'enracinement de jeunes pêchers sous les racines de la culture associée (enherbement) afin d'établir une complémentarité dans l'utilisation des ressources du sol et en utilisant deux leviers: (i) un déficit hydrique modéré pour changer le patron d'allocation du carbone entre les compartiments aérien et souterrain en faveur des racines et (ii) la compétition interspécifique pour l'eau pour exclure les racines de l'arbre des horizons de sol superficiels et le contraindre à pousser en profondeur. Pour cela, un verger de pêchers composé de trois traitements (témoin bien irrigué, déficit modéré, déficit modéré + enherbement) a été installé en janvier 2013 et suivi pendant deux ans. La croissance du compartiment aérien a été suivie de manière dynamique sur la saison de croissance et des excavations racinaires ont été effectuées chaque année à la fin de la saison de croissance. Nos résultats montrent que tous les composants de la croissance ont été significativement réduit par le déficit hydrique très modéré. La combinaison d'un déficit hydrique modéré et d'un enherbement total ont réduit par quatre la taille des arbres au bout de deux années de croissance, réduction causée par deux mécanismes probablement additifs: (i) la compétition de l'herbe pour l'espace, réduisant le volume de sol prospectable par les racines de l'arbre et par répercussion le volume de l'appareil aérien et (ii) la compétition de l'herbe pour l'eau, qui en créant un dessèchement du sol, amène probablement le pêcher à générer des signaux racinaires à destination des parties aériennes pour réduire la transpiration par fermeture des stomates. Nos résultats sur les racines montrent que le développement du système racinaire du pêcher dans les conditions de notre étude pendant les deux premières années après la plantation est essentiellement plagiotrope. Le rapport racines/branches n'a pas été significativement modifié en faveur des racines sous l'effet du déficit hydrique mais la combinaison du déficit hydrique et de la compétition avec l'enherbement a diminué par trois la biomasse racinaire des arbres et exclu totalement les racines de l'horizon de surface (0-10 cm) au bout de deux ans. Cependant, la croissance racinaire se concentre majoritairement dans les 30 premiers cm de sol pour tous les traitements, mais une faible proportion du système racinaire totale (5%) des pêchers en condition hydrique non limitante dépasse les 70 premiers cm de sol (profondeur d'excavation maximale de l'étude) et est capable de prélever de l'eau jusqu'à 2 m de profondeur. Ainsi, nos résultats amène à penser que la séparation des systèmes racinaires entre l'arbre et la culture est très certainement une propriété émergente pilotable, à conditions de caractériser l'architecture racinaire de l'arbre et notamment sa plasticité chez des arbres jeunes. Des pratiques innovantes telles que l'installation des arbres par semis puis greffage au champ de la variété de production pourraient permettre de s'affranchir des traumatismes racinaires inhérents au mode de production des plants en pépinière. Il est également possible de moduler l'effet de la culture associée en sélectionnant des espèces et variétés dont la capacité compétitive souterraine est adaptée au stade de développement de l'arbre, en associant par exemple des espèces à faible capacité compétitive au début de son développement et à capacité compétitive graduellement plus importante au fur et à mesure qu'il grandit. / Agroforestry consists of association trees and crop in the same plot and requires that complementarity relationships be established between the two species in order to reduce competition, especially at the root level. The aim of this work was to test and evaluate the possibility of driving young peach tree roots under the roots of the associated crop (grass) in order to establish complementarity in resources uptake using two levers: (i) e moderate water deficit to change the carbon allocation pattern between shoots and roots in favour of roots and (ii) interspecific water competition to exclude tree roots from the first soil horizons and force them to grow at depth. To do so, we planted in January 2013 a peach tree orchard composed of three treatments (well-watered control, moderate water deficit and moderate water deficit + grass groundcover) which was monitored for two years. Shoot growth was dynamically monitored over the growing season and root excavations were performed each year at the end of the growing season. Our results show that all components of aerial growth were significantly reduced by the very moderate water deficit applied. The combination of a moderate water deficit and a grass groundcover led to a fourfold reduction in tree size after two years due to (i) grass competition for space, which reduced soil volume for the tree roots and consequently reduced shoot size and (ii) grass competition for water which by drying the soil led the tree to send root to shoot signals in order to reduce transpiration by stomatal closure. Our results on roots show that peach tree roots in the first two years of growth are mainly plagiotropic in the conditions of our study. The root/shoot ratio was not significantly modified in favour of roots under a moderate water deficit but combination of water deficit with grass competition led to a threefold reduction in root biomass et excluded tree roots from the topsoil horizon (0-10 cm) after two years. However, root growth mainly concentrated in the first 30 cm of soil in all treatments, but a small fraction of the root system (5%) in the control treatment was growing below the first 70 cm of soil (maximal excavation depth in our study) and was able to take up water up to 2 m depth. Thus, our results suggest that root system separation between trees and crop is a manageable emerging property, given that tree root architecture is characterized, and especially its plasticity in young trees. Innovating practices such as sowing trees and grafting them in the field could alleviate root injuries inherent to nursery practices. It is also possible to adjust the effect of the associated crop by selecting species and cultivars whose competitive ability is adapted to the tree age, by associating species with low competitive ability at the beginning of the tree development and with gradually more important competitive ability as the tree ages.

This document includes three completed publications to represent Urban Agriculture as a ideal solution to meet the UN Sustainable Development Goals. The first publication (Weaver, 2017a) provided in Chapter Two examines the stormwater Best Management Practices (BMP) modelling parameters for the current EPA Stormwater Management Model (SWMM) as the first step to developing Urban Agriculture BMPs. The second publication (Weaver, 2015) provided in Chapter Three highlights how many high-rated scholars have identified agriculture as a critical driver for the planetary systems impacts we find with community development. The third publication (Weaver, 2017b) provided in Chapter Four breaks down a completely new definition for Urban Agriculture, as the foundational works disagree on meaning, resulting in an ambiguous definition. Together, these publications encourage engineers to model Sustainable Development options with green infrastructure (Weaver, 2017a), distinct from the Planetary Systems impacts of other contemporary options (Weaver, 2015), with a greater understanding of the social capital to engage stakeholders in meeting the UN Sustainable Development Goals (Weaver, 2017b).

Globally, the current state of freshwater resource management is insufficient and impeding the chance at a sustainable future. Human interference within the natural hydrologic cycle is becoming dangerously irreversible and the need to redefine resource managerial approaches is imminent. This research involves the development of a coupled natural-human freshwater resource supply model using a System Dynamics approach. The model was applied to two case studies, Somalia, Africa and the Phoenix Active Management Area in Arizona, USA. It is suggested that System Dynamic modeling would be an invaluable tool for achieving sustainable freshwater resource management in individual watersheds. Through a series of thought experiments, a thorough understanding of the systems’ dynamic behaviors is obtainable for freshwater resource managers and policy-makers to examine various courses of action for alleviating freshwater supply concerns. This thesis reviews the model, its development and an analysis of several thought experiments applied to the case studies.

Rainwater harvesting, the act of capturing and storing rain, is an ancient practice that is increasingly utilized today by communities to address water supply needs. This thesis examines whether domestic rainwater harvesting systems (DRWHS) can be a sustainable solution as defined by social, water quality, and technical feasibility for water security in semi-arid, rural environments. For this study, 50 surveys and 17 stored rainwater analyses were conducted in San Jose Xacxamayo, Mexico, in conjunction with my Peace Corps work of implementing 82 DRWHS. Results showed that all DRWHS were socially feasible because of cultural acceptance and local capacity. Water quality analyses showed that four DRWHS contained coliform bacteria; deeming water unfit for human consumption. Technical feasibility, examined through climate analyses, showed an average year-round reliability of 20-30% under current and future rainfall regime. The DRWHS can be a sustainable water supply option with roof expansion and treatment prior to consumption.

After the International Conference on Water and Environment in Dublin in 1992, the four socalled Dublin Principles created new managerial approaches for the water sector. This case study, which was conducted in the Limpopo Basin in Mozambique, examined the performance in the implementation of the principle related to “water development and management based on a participatory approach involving users, planners and policy makers at all levels”. The study was motivated by the fact that experience with the implementation of this principle in the Limpopo Basin of Mozambique has not delivered the anticipated outcomes. To this effect, this study analysed the history and performance of the decentralization process in the Limpopo Basin, and the factors that might have contributed to the outcomes we observe The methodology employed by the study was based on the framework for institutional analysis of decentralization reforms in natural resource management proposed by Dinar et al. (2005), Kemper et al. (2006), and Blomquist et al. (2008). This framework recommends that for the decentralization process to be successful, the following pre-requisites must be in place: (1) financial assistance from the state to enable basin level stakeholders to establish some of the organisations; (2) actors' participation and equitable representation of different segments of society, and acceptance of it from the communities; (3) the presence of basinlevel institutions, availability of forums for information sharing, communication and for conflict resolution; and (4) legitimacy, relevant human capacities and adequate financial resources among the River Basin Organizations (RBOs). The results from this study indicate that in as much as the Water Law, the Regulations of Water Services Provision and the Water Policy in Mozambique created the basis for the decentralization of water resources management, the operationalisation of the process has not been successful, considering that the prerequisites for an effective and sustainable decentralization process as postulated by Blomquist, Dinar and Kemper are still lacking. The study established that incentives for the decentralization process were not linked to the scarcity of water. The study further established that most prerequisites postulated by Blomquist, Dinar and Kemper were not satisfied, in particular: (1) the financial assistance from the state to enable basin level stakeholders to establish some of the organisations is inadequate; (2) the actors' participation and equitable representation of different segments of society with interest in water resources management is not satisfactory; and (3) the legitimacy, relevant human capacities and adequate financial resources for effective functioning of the Water Users Associations (WUAs) are still lacking. Copyright / Dissertation (MSc(Agric))--University of Pretoria, 2012. / Agricultural Economics, Extension and Rural Development / unrestricted

The Lake Kariba catchment area in southern Africa has one of the most variable climates of any major river basin, with an extreme range of conditions across the catchment and through time. The study characterized rainfall variability across the Lake Kariba catchment area, followed by describing prediction models for seasonal rainfall totals over the catchment and for inflows into Lake Kariba. The thesis therefore improved our understanding of rainfall variations over central southern Africa and provided evidence on how seasonal forecasts can be applied in order to potentially improve decision making in dam management. The prediction of the seasons in which floods or droughts are most likely to occur involves studying the characteristics of rainfall and inflows within these extreme seasons. The study started off by analyzing monthly rainfall data through statistical analysis. To determine the predictability of seasonal rainfall totals over the Lake Kariba catchment area, this study used low-level atmospheric circulation of a fully coupled ocean-atmosphere general circulation model over southern Africa, statistically downscaled to seasonal rainfall totals over the catchment. The verification of hindcasts showed that rainfall over the catchment is predictable at extended lead-times. Seasonal climate forecasts need to be integrated into application models in order to help with decision-making processes. The use of hydro-meteorological models may be proven effective for reservoir operations since accurate and reliable prediction of reservoir inflows can provide balanced solution to the problems faced by dam or reservoir managers. In order to reliably predict reservoir inflows for decision-making, the study investigated the use of a combination of physical and empirical models to predict seasonal inflows into the Lake. Two predictions systems were considered. First, antecedent seasonal rainfall totals over the upper Zambezi catchment were used as predictors in a statistical model for estimating seasonal inflows into Lake Kariba. The second and more sophisticated method used predicted low-level atmospheric circulation of a coupled ocean-atmosphere general circulation model downscaled to the inflows. Inflow hindcasts performed best during the austral mid-summer season of DJF (seasonal onset of inflows) and the autumn season of MAM (main inflow season). / Thesis (PhD)--University of Pretoria, 2015. / gm2015 / Geography, Geoinformatics and Meteorology / PhD / Unrestricted

No description available.

In this study social network analysis is used to empirically map out existing collaborative social networks influencing water governance in the Mkindo catchment, in Tanzania. I assess how existing social networks may affect the capacity to govern water and explore how knowledge about these networks can be used to facilitate more effective or adaptive water resources management. The study is the first of its kind to apply social network analysis to organizations influencing both blue water (the liquid water in rivers, lakes and aquifers) and green water (the soil moisture used by plants) at the catchment scale. Using a questionnaire and semi-structured interviews, social network data for 70 organizations was generated. With the help of social network analysis software1, the reciprocated collaborative interactions within the water governance network were traced, to better understand how the network facilitates and constrains individual actors, as well as the whole network, in managing water resources. Results show that there is currently no organization that coordinates the various land and water related activities at the catchment scale. Furthermore, there are important actors influencing water governance at the catchment scale, but they are not adequately integrated to the formal water governance system. Water user associations (WUA’s) are in the process of establishment, and could bring together actors presently not part of the formal governance system. However, at the moment the establishment of WUA’s seems to follow a top-down approach that fails to consider the existing informal organization of water users that are revealed through this social network approach. Instead of imposing institutional arrangements I argue that it is more promising and effective to identify and build on existing social structures. Social network analysis can help to identify existing social structures and points for interventions to increase the problem solving capacity of the governance network.

Groundwater seepage to surface water is an important process to peatland ecosystems; however, the processes controlling seepage zone distribution and magnitude are not well understood. This lack of process-based understanding makes degraded peatland ecosystems difficult to restore and problematic for resource managers developing a sustainable design. Degraded peatlands, particularly abandoned cranberry farms, often have drainage ditches, applied surface sand, and decreased stream sinuosity to artificially lower the water table and support agriculture. These modifications disconnect the surface and groundwater continuum, which decreases thermal buffering of surface water significantly. The combination of a decreased influx of thermally buffered groundwater, a naturally low surface gradient, minimal canopy, and strong solar input causes surface water temperature extremes that degrade ecosystem health. Through strategically incorporating the natural processes to restore groundwater discharge to restored surface streams, surface water temperature extremes will be buffered promoting a healthy, resilient wetland ecosystem. Therefore, it is critical to understand the spatial hydrogeologic constraints that induce groundwater seepage. Here we examine the spatial relationship between surficial groundwater seepage and the subsurface hydrogeologic structure within a mineraltrophic peatland environment. We use multiple field methods to develop a process-based conceptual model of the ground water seepage development at the site; these methods include geophysical, thermal, and isotopic techniques. The results indicate that there are two distinct forms of groundwater discharge to the peatland platform: diffuse lower-flux marginal seepage and discrete higher-flux interior seepage. Both types of groundwater discharge develop through interactions with subsurface peatland basin structure, specifically when the basin slope is perpendicular to the regional groundwater gradient. These observations also allow insight into the formation of the groundwater discharge through time. The strong correlation between the subsurface basin structure and surficial groundwater expression will allow resource managers to more efficiently locate groundwater seepage on large, complex sites, and develop comprehensive management and restoration strategies for these critical ecosystems.

No description available.