Document type: DU ETD
Collection: Geology Theses  
Title An Energy Balance Index Of Potential Evapotranspiration With Application To An Irrigated Arid Region
Author(s) Walker, Wayland Joseph
School/Department Department of Geography
Institution University of Denver
Degree Type Master's
Degree Name M.A.
Type of Resource text
Degree Date 1967-1
Digital Origin reformatted digital
Rights Statement All Rights Reserved
Reason for Restrictions No restrictions
Type of Restriction Author permission required for access
Keyword(s) Geology
Abstract The fundamental problem underlying this study is a threatening world food crisis that may accompany the population explosion of the twentieth century. Temperate and tropical regions have historically been able to supply adequate food, fiber and forage supplies to meet demand. Arid regions by necessity are now being developed at a quickening rate. With increased technology these dry regions not only have the potential to meet the challenge but could eventually surpass the agricultural yields of temperate and tropical zones. A multitude of interdisciplinary soil, plant, water, and social studies are required to bring arid zone technology to the point of fruition. These studies run the gamut from theoretical through basic and applied research. The diversity of information and new knowledge needed is manifold. This thesis is primarily concerned with one important aspect of the expansive problem, namely, the loss of water to the atmosphere. The limiting combined loss of water to the atmosphere by evaporation plus transpiration was termed, by C.W. Thornthwaite, potential evapotranspiration. Numerous scientists, it is shown, have contributed to the study of this phenomenon. They have, by and large, concluded that only four climatological factors influence the global rate and quantity of water loss to the atmosphere. These four factors are solar radiation, temperature, humidity, and wind. For arid regions, solar radiation and temperature are deemed adequate indices of potential evapotranspiration. An energy-balance index of potential evapotranspiration is set forth using solar radiation and temperature as basic ingredients. The empirical formula proposed appears consistent with theoretical energy balance foundations. A procedure for bridging the gap between potential evapotranspiration and crop consumptive use is presented. The methodology used leans heavily upon the work of Blaney, Criddle, and Fireman, noted workers in this field of study. Indigenous characteristics which should be considered in applying the proposed index and methodology to an arid region are stated to be; (1) Cropping Intensity (2) Cropping Pattern (3) Cropping Period (4) Culturable Area A simple case study of the Northern Zone of West Pakistan shows how the foregoing information can be put together to predict future Irrigation water requirement and thereby open the door to intelligent planning in arid irrigation economies.
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