L’objectif du présent travail est l’analyse du fonctionnement des aménagements antiérosifs les plus répandus en Tunisie, les banquettes et les lacs collinaires. L’évaluation des banquettes a été basée sur leur caractérisation, le diagnostic de leur état, leur incidence sur le développement et la croissance de la culture de l’orge et leur impact sur certains paramètres physico-chimiques du sol. La reconstitution des apports hydriques, l’estimation des prélèvements pour l’irrigation et la détermination des apports solides moyens et exceptionnels ont été utilisés comme indicateurs pour l’évaluation des lacs collinaires. L’analyse diachronique a mis en évidence l’importance des cultures annuelles du périmètre aménagé en banquettes et la régression des espaces réservés aux terrains de parcours au cours du temps. Les résultats montrent que certaines banquettes ont été surdimensionnées tel que pour les écartements, les superficies des inter-ouvrages et leur longueur. Le diagnostic de l’état des ouvrages montre qu’une forte proportion des banquettes a été affectée par diverses formes de dégradation qui semblent être en rapport avec l’événement pluvieux exceptionnel de l’hiver 2003. L’évaluation des effets de l’aménagement en banquettes sur la production des céréales montre que la croissance, le développement végétatif et la production de matière sèche de la culture d’orge ont été significativement améliorés pour la zone située à proximité de l’ouvrage en comparaison avec la zone non aménagée. Après plus de trois décennies de la réalisation de l’aménagement, l’accroissement du rendement attribué à la mise en œuvre des banquettes a été évalué à 33% à proximité du bourrelet et à près de 10% en intégrant la superficie de l’ensemble de l’inter-banquette. Par ailleurs, l’aménagement en banquettes permet d’accroître la profondeur du sol, la teneur en matière organique, la capacité de rétention de l’eau, la fraction fine du sol et de réduire le taux de cailloux dans la zone limitrophe des ouvrages. Le taux de carbonates, le pH et la conductivité électrique semblent être non affectés par la mise en œuvre des banquettes. L’évaluation des prélèvements annuels, pour les besoins en eau d’irrigation, en moyenne durant la période de suivi, au niveau des lacs collinaires sur l’oued Fathiza I, l’oued Ras Rmal et l’oued Sned sont plus faibles que les apports effectifs indiquant une sous-utilisation de l’eau. Les apports moyens effectifs représentent entre 36% et 195% des apports estimés selon les ouvrages. Les apports solides moyens initialement estimés pour chacun des trois ouvrages ont été sous évalués se traduisant ainsi par une sédimentation prématurée. Les taux élevés de sédimentation risquent de compromettre la durée de vie des réservoirs. Les pertes de capacité, à la suite des précipitations exceptionnelles de l’hiver 2003, varient de 3,5% à 7,3% de la capacité initiale. Ces taux de sédimentation montrent l’impact des évènements paroxysmiques sur l’érosion au niveau des bassins versants de ces lacs collinaires. La spatialisation de la sédimentation à travers les cuvettes montre que l'essentiel du dépôt solide a lieu à l'amont des cuvettes. / Doctorat en environnement / info:eu-repo/semantics/nonPublished

Land degradation is a great threat to the Beshlo Catchment in Blue Nile Basisn, not merely as an environmental issue, but also a social and economic problem. In Gedalas Watershed (one of the micro catchments of Beshelo), land degradation, mediated by both biophysical and socio-economic drivers, is among the major environmental sustainability and social-economic development threats in the area. The threat is manifested in depletion of natural vegetations, water, soil and other natural resources; disruption of ecosystem functions, processes, integrity, and services. Given its particular vulnerability, watershed management activities have been in operation since the mid-1970s. Recently, the idea of Sustainable land management through integrated watershed development program has been initiated with the objective of reducing land degradation risks and ensuring food security at both the nationwide and family circle. Despite these investments and efforts, real evidences of success and failures of such efforts were not satisfactory explored. The objectives of this study were, therefore, to analyze the existing status and future prospects of sustainable land management and evaluates its implication on the environmental integrities and the local livelihoods specific to Gedalas watershed. For this effect, the study investigated the dynamics, deriving forces and implications of LULC, soil erosion and soil fertility status of the watershed, current status of watershed management practices, pertinent challenges and opportunities for practicing land management technologies and approaches that might help meet the sustainability requirements of SLM practices. In addition, the study explored factors that determine the willingness of farming households to undertake SLM practice. As the study carried in the coupled human-environment system of rural landscapes, interdisciplinary geographical approaches which integrats social and natural science methodologies were employed to deal with issues of land degradation-and-rehabilitation status comprehensively. The general findings of the study show that though it would be dificult to measure all the composite aspects of land degradation, some of the parameters considered in this study revealed that land degradation is a perpetuating challenge in the watershed. It is evidenced from the overall undesirable land use/cover changes i.e transition of 21.25% of Afro/sub alpine landscapes, 17.59% of the grasslands and 8% of shrub lands to either to cultivated land or settlement areas over the 1973–2017 period, which have unintended negative socio-ecological repercussions on the watershed; high annual mean soil loss value (which range from 37t/ha/year average values to 393 t/ha/yr soil loss rates on water courses) that exceed threshold level and a wide gap between the need for SLM and the actual achievement of SLM practices,including limited adherence to the idea behind contemporary land management policies and implementation principles and approaches. The study further revealed the presence of opportunities as well as a myriad of challenges that need to be tackled in order to achieve sustainable land management goals. The study colcludes that, though, some encouraging progresses have been observed in the SLM project sites; land degradation has remained a problem in the watershed. This calls for strenuous efforts to promote and assist wide scale adoption of SLM practices that address the pervasive land degradation problem and achieve land degradation neutrality as highlighted in sustainable development goals. / Department of Geography / Ph. D. (Geography)

Legal aspects of water retention in the landscape Abstract This diploma thesis deals with the legal aspects of water retention in the landscape in response to the current problems associated with impaired landscape retention capacity such as drought, erosion or floods. The author first outlines the factual and legal context of the issue, which is followed by an analysis of conceptual, administrative-legal and economic instruments of the Czech legal order that can improve water retention capabilities of the landscape. The diploma thesis analyses the relevant instruments of the Water Act, Forest Act, Act on the protection of agricultural land or Act on protection of nature and landscape. Consequently, it deals with the role of land-use planning, land consolidation and environmental impact assessment for the issue. The thesis includes comprehensive evaluation of the relevant legal regulation in terms of its effectiveness and possible proposals de lege ferenda.

This thesis is focused to determine water erosion of soil and drain from basin of štefanov stream. The basin of štefanov stream is unobserved with area 15,1 km2. After evaluation of current status is processed integrated design against the adverse effects of surface runoff.

No description available.

From the Proceedings of the 1974 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 19-20, 1974, Flagstaff, Arizona / An erosion prediction method that has recently received wide attention in the United States is the universal soil loss equation which is given as: a=rklscp. Where a = estimated soil loss (tons/acre/year), r = a rainfall factor, k = a soil erodibility factor, l = a slope length factor, s = a slope gradient factor, c = a cropping-management factor, and p = an erosion control practice factor. Data collected on the walnut gulch experimental watershed in southeastern Arizona were used to estimate these factors for semiarid rangeland conditions. The equation was then tested with data from watersheds of 108 and 372 acres. The predicted value of annual sediment yield was 1.29 tons/acre/year as compared with an average 1.64 tons/acre/year for 4 years of data for the 108-acre watershed, and a sediment yield of 0.39 tons/acre/year was predicted for the 372-acre watershed as compared with the measured value of 0.52 tons/acre/year. Although good agreement was noted between predicted and actual sediment yield, additional work is needed before the equation can be applied to other areas of the southwest.

From the Proceedings of the 1974 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 19-20, 1974, Flagstaff, Arizona / A stochastic model is presented for the prediction of sediment yield in a semi-arid watershed based on rainfall data and watershed characteristics. Random variables which lead to uncertainty in the model are rainfall amount, storm duration, runoff, and peak flow. Soil conservation service formulas are used to compute the runoff and peak flow components of the universal soil loss equation, and a transformation of random variables is used to obtain the distribution function of sediment yield from the joint distribution of rainfall amount and storm duration. Applications of the model are in the planning of reservoirs and dams where the effective lifetime of the facility may be evaluated in terms of storage capacity as well as the effects of land management of the watershed. In order to calibrate the model and to evaluate the uncertainties involved, experimental data from the Atterbury watershed near Tucson, Arizona were used.