Kenneth H. Solomon

Drop Size Distributions for Irrigation Spray Nozzles

DROP size distributions for irrigation spray nozzles, such as may be used in low or reduced pressure sprinkler systems, were measured with a calibrated stain technique. Similar data from other sources, measured with photographic or pellet techniques, were also obtained. The distributions were fitted with the upper limit log normal (ULLN) distribution function. ULLN parameters for each distribution are tabulated. Distribution characteristics such as the volume median drop size may be calculated directly from the ULLN parameters. A simple regression model for predicting ULLN parameters as functions of nozzle style, size and pressure is proposed and fitted to data for flooding and smooth flat plate spray nozzles. The fit of model to data was evaluated by comparing measured and predicted values for 50th (median) and 99th (volume) percentile drop sizes, and by directly comparing measured and predicted distribution functions. The distance between functions was defined analogous to the Euclidean distance between points in space, leading to definition of a pseudo r2 for the (functional) regression model. The fit between data and model for the two nozzle types was quite good. The models were used to explore the influence of nozzle size and pressure on drop size distributions for the two types of nozzles.

Global Uniformity of Trickle Irrigation Systems

ABSTRACT Asimulation model for the study of trickle irrigation uniformity was developed which treats the various equipment, system and other factors known to influence emitter flow rate variation. The model provides a tool for the assessment of global trickle uniformity in the sense that the assessment need not be spatially or otherwise restricted. A number of simulations were made to determine the sensitivity of global trickle uniformity to each of the determining factors. Emitter plugging, the number of emitters per plant, and emitter manufacturing variation are the most significant factors influencing the uniformity of trickle irrigation systems..

Water-Salinity-Production Functions

ABSTRACT WATER-salinity-production functions are mathe-matical expressions of the relationship between crop yield and the amount and salinity of applied water. If available, such relationships would be valuable aids to the study of water management practices throughout the arid West, where salinity can be a problem. This paper presents a model for constructing water-salinity-production functions based on our current understanding of crop response to water, crop salt tolerance, and the leaching process. Available theory and data from which to derive water-salinity-production functions are assessed, and a numerical example is given.

RELATING UNIT AND SUB-UNIT IRRIGATION PERFORMANCE

The relationship between on-farm and district-wide irrigation efficiency is not well understood. No analytical method exists to describe the relationship between performance parameter values for different geographic scales. Often on-farm efficiencies have different numerical values than district-wide or region-wide efficiencies. The ambiguous relationship between irrigation performance at differing scales is a frequent source of confusion, leading potentially to erroneous assumptions or policy decisions. A major item influencing irrigation performance over different geographic scales is the fact that tailwater (runoff) or drainage from one field may be reused on another, at least to the extent that the water quality of these flows is not limiting. Such reuse complicates the quantification of consumptive or beneficial uses of water. This article presents analytical expressions relating irrigation performance values for a unit and its constituent sub-units, when tailwater or drainage from one sub-unit may be reused on another. A simple numerical approximation to the exact relationship is also offered. Two irrigation performance parameters are considered: Irrigation Consumptive Use Coefficient (ICUC) and Irrigation Efficiency (IE). Expressions are presented for two cases: when there is a terminal subunit from which no further reuse is possible, and when non-consumed water from any sub-unit may be reused on some other sub-unit. Application of the theory is discussed.

Resource Utilization Efficiency

ABSTRACT IRRIGATION engineers are naturally concerned with efficient water use and financial economy. Yet, irriga-tion affects the use of many other important resources. Broadly applicable efficiency concepts that treat all the resources related to irrigation must be developed. This essay explores Resource Utilization Efficiency as a general notion and raises questions that will have to be answered by forthcoming research. Specific questions discussed include: What can we learn from the water use efficiency and economic indicators already developed? Why analyze resource use quantitatively at all? In what ways may efficiency measures be better evaluation tools than financial measures (e.g. profit)? What are the significant resources involved in the irrigation process? Should we treat renewable and nonrenewable resources differently? How can this effort help us to make trade-offs of conflicting goals or resource uses?