• A hydrologic system analysis of the ground-water resources of the western desert, U.A.R. (Egypt)

      Salem, Mohamed Halim (The University of Arizona, 1965)
      An analysis of the cause-effect relationship of a free water table aquifer that changes laterally to an artesian aquifer was made for regions bounded internally by a circular cylinder. For a hydrologic system with a large pressure-head energy, development of the water resource by a single well is not the most practical approach and thus the study was extended to solve the problem of a line array of wells. The flow characteristic of the hydrologic system was divided into a regime of flow near the line array of wells which is titled the conduit regime, and a regime of flow distant from the line array, which is called the reservoir regime. This classification of flow type is based on the fact that the storage coefficient is not constant and accordingly the hydraulic diffusivity of the aquifer in the conduit region is much smaller than that in the reservoir region. Therefore, the mathematical continuity, which was assumed in previous analyses by other authors becomes discontinuous because linearity does not prevail throughout the flow system. The superposition principle, which is based on linearity and homogeneity, can not be applied to this non-linear system. By subdividing the flow system into the two regimes of conduit and reservoir, Carslaw's solution for the circular cylinder may be amplified by two integrations to achieve mathematical continuity of the whole system. The range that Goldenberg solved analytically for a similar problem was extended to meet practical requirements in the field of ground-water hydrology. A new approach was developed for the solution of the mutual interference problem of an infinite line array of wells. The interference is expressed in terms of what is called the discharge efficiency factor. The findings were applied to a hydrologic analysis of the ground-water resources of the Western Desert, U. A. R. (Egypt) in or der to describe its significance and importance in the design of systems for water resources development in extensive aquifers. The results aid also in defining the applicability limits of the theory of images, which has been used by several authors to solve for the interference problem of an infinite line array of wells.
    • Papago fields : arid lands ethnobotany and agricultural ecology

      Nabhan, Gary Paul (The University of Arizona, 1983)
      Papago Indian fields located in southern Arizona and northern Sonora, Mexico are examples of a food production strategy that was developed within the constraints of a water-limited environment. Although only a small percentage of the fields cultivated at the turn of the century remain in cultivation, extant fields are vestiges of an agricultural tradition that has persisted in arid lands for centuries. An examination of the documentary history of non-Indian observations of Papago agriculture and water control from 1697 to 1934 reveals numerous practices and features that are no longer apparent within or around remaining fields. Yet by learning from oral historical accounts of elderly Papago, and analyzing O'odham lexemes (native Papago terms) which guide farmers' management of fields, it is possible to gain a sense of folk science which Papago developed to successfully farm without permanent surface water reserves. Selected concepts from the folk science of the Papago are used as a point of departure in understanding the ecological processes which function within their fields. Standard field ecology methods were adapted to empirically test certain hypotheses relating to these ecological processes. Results include confirmation that Papago fields are situated in a variety of physiographic positions, and that ‘ak-ciñ arroyo mouth' farming is a misnomer. Papago crops exhibit many of the same drought-escaping adaptations as wild summer desert ephemerals for seed production during the brief summer rainy season, which varies from year to year in the date of its initiation. These adaptations greatly contribute to crop success. There are no significant differences in the diversity of herbaceous plants found in Papago fields compared to the diversity found in adjacent, uncultivated environments. Of the many nutrients analyzed in cultivated and uncultivated floodplain soils, only potassium was significantly richer in fields than in uncultivated floodplains; other differences were statistically insignificant. Floodwashed organic detritus, rather than the floodwaters themselves, appear to play the major role in renewing field soil fertility in certain localities. It is concluded that indigenous concepts which have long guided the management of traditional agricultural systems are of heuristic value in understanding how these farming systems function ecologically.
    • Scale effects in determining snowmelt from mountainous basins using a distributed approach for snow water equivalence and radiation, and a point snowmelt model

      Galarraga Sanchez, Remigio Hernan (The University of Arizona, 1995)
      Rates of snowmelt distributed across Emerald Lake watershed, an alpine basin located in the Sierra Nevada, California, were estimated for water year 1987 using a point snowmelt model applied to regions that were classified based on distributed snow water equivalence and net solar radiation (NSR). A 5-m resolution digital elevation model (DEM) and a 5-m classified digital terrain model of snow water equivalence (SWE) were resampled to coarser resolutions (25-m, 30-m, 50-m, and 100-m) using the nearest neighbor approach. These images were used to define other snowmelt physical parameters and the initial state of the snowpack before melting. Topographic parameters calculated at 50-m and 100-m resolution exhibited significant differences in their histogram distribution as compared to the 5-m DEM. The most important were variations in slope, aspect, sky view factor, and terrain configuration factor, which influenced radiation calculations and the definition of distributed parameters for snowmelt calculations. Elevations, however, did not change significantly from one resolution to the other. The distribution of topographic parameters modeled at 25-m and 30-m, remained almost unchanged. Four, seven and ten classes of snow water equivalence and net solar radiation were combined using a band interleave process to determine the maximum number of combined classes. The point snowmelt model was then applied to these areas, which shared similar SWE and NSR characteristics, to obtain hourly melt rates. Modeled snowmelt rates were compared to the total daily discharge observed at the outlet of Emerald Lake watershed. There was good agreement for resolutions S-, 25-, 30-, and 50-m but not for the 100-m OEM, as modeled net solar radiation was too high and water was released from the basin too early. Model performance using three tests (Nash-Sutcliffe criteria, sum of squares of the deviations and the sum of the absolute differences between observed discharge and computed melting) showed that the 30-m resolution OEM with combined classes of 7 SWE and 7 NSR provided the best snowmelt performance for this distributed approach. Finally, fractional snow cover area at one month intervals were estimated, showing that this approach offers the potential to model spatially distributed snow covered area in alpine regions.