No description available.

Thesis (Ph. D. - Hydrology)--University of Arizona, 1984. / Bibliography: leaves 243-249.

A significant advantage attributed to surge flow irrigation is that for the same volume of water applied the stream will advance farther along the furrow than with continuous flow. This potentially will reduce runoff and deep percolation which will improve uniformity and application efficiency where this advance phenomenon holds. The mechanism for improvement in advance time has generally been ascribed to surface sealing and surface layer consolidation. However, these phenomena do not satisfactorily explain improved advance times in sandy soils. Widely used infiltration equations which require the determination of empirical coefficients are unsatisfactory as predictors of infiltration conditions of intermittent wetting. The Green-Ampt model and a simple redistribution model are combined into an analytical model to predict infiltration under surge irrigation. The model results are compared to infiltration tests on soil columns of three soils of different soil textures. Also the model and the experimental results from the soil columns are compared to predictions made by two numerical solutions of the Richard's equation. One of the numerical models includes the effect of hysteresis by the use of Mualem's model to predict the variation of moisture content with potential, the other numerical model neglects the effect of hysteresis. A comparison of the analytical and the numerical models shows good agreement in their predictions for the soils and surge cycles tested. A comparison of predictions made by all three models shows good correlation to the experimental results. Although the number of tests done on the analytical model were limited it appears to be nearly as good a predictor of infiltration as the numerical models. The greatest strength of the analytical model is that while the numerical models took many hours to do a single run, the analytical model took only a few minutes. Both model and experimental results indicate that there was no reduction in infiltration rates or volumes infiltrated with intermittent as compared to continuous wetting. Thus the reduction in hydraulic gradient is not a factor in the reduced infiltration observed by others.

Sampling and analysis of the soil moisture distribution and the overall water balance in an irrigated area are the central topics of this work. An experimental study was made in a 14-ha, border-irrigated, alfalfa field near Coolidge, in Final County, Arizona, during the summer/fall 1983. The water stored in the soil profile and its change with time were normally distributed, with coefficients of variation of about 10 and 25 percent, respectively. Temporal correlations were significant for storage (about .60), but absent in the other. Variograms were calculated to show the spatial structure of the distributions. An analogous statistical description was presented for the alfalfa yield. Also shown is a methodology to infer errors due to the field calibration of the neutron probe. Another task was to assess a methodology to minimize sample numbers for soil-water storage. Following the ideas of Vachaud and co-workers in France, it was verified that rankings of the measurements were approximately time-preserved. As a consequence, only a few key locations need to be sampled to evaluate the mean in those circumstances. Included also is an approximation to predict confidence intervals for estimating the mean, when such "representative sites" are used. Using irrigation inflow and rainfall, a procedure is defined to make use of the soil moisture data to evaluate irrigation efficiency and uniformity. Evapotranspiration (ET) distribution can also be assessed by soil moisture measurements, but only conditionally. For example, adaptation of the "field capacity" concept in the field study led to average daily ET rates in the range of 3-11 mm day⁻¹. ET and potential ET (PET) were also determined from weather data. Crop temperature was required in the ET calculation. Such a model, developed by Hatfield and co-workers, was judged satisfactory in our application, but not the Penman PET estimates. It is concluded that the ET model is promising, particularly if remote sensing of the temperatures is successful in the future. Also shown as a possibility is the use of plant temperature and pan evaporation data to infer crop water stress.

No description available.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

No description available.

Thesis (M.Env.St.)--University of Adelaide, Mawson Graduate Centre for Environmental Studies, 1998. / Bibliography: leaves 165-170.

The effect of furrow spacing on infiltration should be determined in order to properly design an irrigation system. The blocked furrow infiltrometer (BFI) and the flowing furrow infiltrometer (FFI) methods were investigated for this purpose in two areas upon a precision field furrow. Three irrigations were performed in each method. The initial and final soil moisture contents (before and after irrigation), the furrow cross-section (before and after irrigation), the inflow volume and the furrow water surface elevations (during irrigation) were measured in each test furrow. Cumulative infiltration and infiltration rates were determined for each irrigation. The results indicate that the FFI test furrows infiltrated more water than did the BFI test furrows for the same infiltration time. The infiltration rates were higher in the FFI test furrows than in the BFI test furrows until they approach the basic intake rate. The infiltration rates were also higher during the 0.90 m spacing tests than during the 1.80 m spacing tests. The 0.90 m spacing test furrows infiltrated more water than did the 1.80 m spacing test furrows.

A zero inertia mathematical model as described by Strelkoff and Katopodes (1977b) was used to simulate irrigations in blocked-end or ponded sloping borders. The model is based on the assumption that inertia is negligible. A linearization method was then used to decrease the difficulty and expense of the solution. The resulting mathematical expressions were solved with a double sweep technique. Border irrigations were simulated, using the model, for selected intake families (soil infiltration characteristics), required depths of infiltration, discharge rates, lengths, times of application, slopes, and roughness values. The output from the model, including the depth of infiltration, the maximum depth of flow at the upper end of the border, the maximum depth of ponding at the downstream end and the application efficiency, was used to develop the design charts for ponded sloping irrigation borders. These were combined with the operational input parameters to provide the design charts for a given intake family, slope and roughness. Since the same input parameters apply, the design charts developed can be used for ponded or free outflow borders. In cases of free outflow borders, ponding is replaced by runoff. Ponding can improve application efficiency over free outflow borders, provided that ponding affects a significant length of the border. Where runoff can not be reused, ponding or end-blocking a border strip is recommended. The maximum potential application efficiencies, on ponded borders, with adequate irrigation and minimum deep percolation were determined, with respect to intake family, required depth of infiltration, slope, roughness and length of run. A sensitivity analyses to evaluate the effect of infiltration showed that it is better to underestimate than to overestimate infiltration. The effects of roughness and slope on irrigation efficiencies and depth of ponding were also studied. A comparison of the Soil Conservation Service method for extended length, with blocked-end borders, and the maximum application efficiencies computed showed the SCS method to be satisfactory, provided that there is runoff adequate to irrigate the length extended.