ملخص: The research presented in this thesis examines the possibilities of reducing, and ultimately eliminating, evaporation by groundwater control wherever shallow water tables occur in arid and semiarid regions. The understanding of vertical moisture movement and subsequent evaporation phenomena is important if practical methods for the reduction of evaporation are to be devised. This research reviews, develops and applies the relationship between the decrease of evaporation rate and the depth below ground level at which full groundwater saturation occurs. The first part of the thesis consists of an investigation and review of the relevant literature. The factors influencing evaporation of soil moisture are presented as internal and external controls. The assessment of evaporation is made by an application and development of the diffusion equation and the modified darcy equation for different boundary conditions. Another empirical assessment is made based on observations made on the flattened runoff terminals of a closed basin in an arid and semiarid region. The second part of the research examines the feasibility of lowering the water table in order to reduce evaporation. The evaluation of evaporation reduction is achieved by simulating the response of an aquifer to a system of pumped wells. The relationship between evaporation and water table depth that is derived in the first part of the thesis is used in conjunction with the multiple well system model to compute the total evaporation reduction from a specified area as a result of the induced drawdown. The effect of the aquifer and model characteristics on the reduction of evaporation is investigated. The last part of this thesis considers the application of the proposed technique for reducing evaporation and discusses the possible limitations. A cost method of optimization analysis method is also presented.

طبعة: London: University of London
لغة: إنجليزية
الوصف المادي: 271 p. ill. ;30 cm
الشهادة: Ph.D
مؤسسة مناقشة الرسالة: Departement of Civil Engineering

ملاحظة: Bibliogr.pp.264-271