Water Distribution Uniformity Research Articles

Friction Coefficient for Center Pivot Systems

An important objective of any center pivot irrigation system is to achieve a uniform distribution of water delivered through the sprinklers. In this study friction coefficients are developed for designing center pivot irrigation systems using two of the most common methods used for estimating friction head loss in sprinkler irrigation pipelines. A center pivot system operating under field conditions was used to verify the analysis. In the analysis, the change of sprinkler discharges along the lateral affects the Reynolds number and hence the state of flow along the lateral has been taken into account. The calculation of friction coefficients and friction head losses from the two equations are compared with the field data.

Dosimetry of intravenously administered oxygen-15 labelled water in man: a model based on experimental human data from 21 subjects.

Models based on uniform distribution of tracer in total body water underestimate the absorbed dose from H2(15)O because of the short half-life (2.04 min) of 15O, which leads to non-uniform distribution of absorbed dose and also complicates the direct measurement of organ retention curves. However, organ absorbed doses can be predicted by the present kinetic model based on the convolution technique. The measured time course of arterial H2(15)O concentration following intravenous administration represents the input function to organs. The impulse response of a given organ is its transit time function determined by blood flow and the partition of water between tissue and blood. Values of these two parameters were taken from the literature. Integrals of the arterial input function and organ transit time functions were used to derive integrals of organ retention functions (organ residence times). The latter were used with absorbed dose calculation software (MIRDOSE-2) to obtain estimates for 24 organs. From the mean values of organ absorbed doses, the effective dose equivalent (EDE) and effective dose (ED) were calculated. From measurements on 21 subjects, the average value for both EDE and ED was calculated to be 1.2 microSv.MBq-1 compared with a value of about 0.5 microSv.MBq-1 predicted by uniform water distribution models. Based on the human data, a method of approximating H2(15)O absorbed dose values from body surface area is described.

Cablegation Evaluation Methodology

Cablegation is an automated furrow irrigation system in which the irrigation set moves at a slow, constant rate across the field. This constant movement allows time and space to be interrelated, which simplifies collection of furrow irrigation evaluation data. Specialized cablegation evaluation procedures are described and illustrated. Furrow stream advance and recession times and tailwater runoff rates can be measured at any point in time. Thus, average infiltrated depth and infiltration opportunity time can be easily determined. Water distribution uniformity can be estimated from infiltration rate at the time recession begins and infiltration opportunity times. The infiltration function can be estimated from average infiltrated depth and final infiltration rate.

Working Conditions of Sprinkler to Optimize Application of Water

It is surprising to note the lack of information usually given by manufacturers about their sprinklers, making it very difficult to correctly select a sprinkler and its working conditions when designing a sprinkler irrigation system or improving an existing one, using only the discharged volume and radius of throwing for every pressure‐nozzle combination. This paper shows the results of two studies made principally on three individual sprinklers: one measuring the single‐leg distribution curves and the other measuring the complete water distribution model of a sprinkler in windy conditions. Our purpose is therefore to establish a set of general rules valid for selecting a sprinkler. These rules must take into consideration the optimum working conditions that will maximize the possible uniformity of water distribution.

Surface‐Slope Effects on Sprinkler Uniformity

The slope of the soil surface has a significant effect on water distribution from sprinklers. Field tests were conducted to quantify the effects. A ballistic trajectory model was developed to simulate precipitation data for a sprinkler working on different ground slopes and at different sprinkler riser angles. The model uses precipitation data from a single sprinkler working on a zero slope plane under no wind conditions. The model is verified against measured data for a sprinkler operating on a slope. A study is made of the influence of sprinkler riser angle, nozzle angle, and soil surface slope on the uniformity of water distribution. Two different precipitation patterns, similar to Christiansen's sprinkler patterns B and E, are studied in detail. The results show that the sprinkler risers should be kept perpendicular to the soil surface to maximize the uniformity of water application and to minimize the erosion risk. Higher nozzle angles are preferable to lower nozzle angles when working on steep slope...

Irrigation uniformity of level basins as influenced by variations in soil water content and surface elevation

Spatial variability in soils and surface elevation is an important consideration in the design and management of surface irrigated level basin systems. Field studies were conducted on a variable sandy loam soil in central Arizona to evaluate how the nonuniformities in the antecedent soil water content (prior to irrigation) and field surface level affected the uniformity of infiltrated water for a level basin irrigation system. Relationships between the soil water content and the sand, silt and clay fractions were described for a 4.2-ha experimental site, which was separated into 12 basins and planted to wheat in 1985 and 1986. Measured water distribution uniformities (average low quarter infiltrated depth/average infiltrated depth) were between 13–27% lower than that of an idealized uniformity of 98% where only infiltration opportunity time differences affect infiltrated depth uniformity. However, 0.51 to 0.68 of the variability in infiltrated depth could be explained by differences in the antecedent soil water content (0–1.0 m soil depth), while as much as 0.23 of the infiltrated depth variability, and 0.60 of the variability in deep percolation, was explained by nonuniformities in surface elevation. For a properly designed level basin system on sandy loam, distribution uniformities of 85% or more should be attained when 85% of the basin elevation is within ± 15 mm of the mean, provided the antecedent water content variability is on the order of 0.15 or less. However, those proposing to use level basins which have more extensive soil and water content variability should maintain a leveling precision, such that 100% of the basin is within ± 15 mm to attain high distribution uniformities.

Ridge tillage for managing irrigation water on the U.S. Southern Great Plains

Ridge tillage (furrowing) is widely used on irrigated land on the Southern Great Plains, especially on soils adapted to gravity flow, furrow irrigation. Ridge tillage is also used in conjunction with surge irrigation, limited irrigation, and precision water application techniques. This report reviews the effects of ridge tillage on irrigation water management and crop establishment. Furrow irrigation, made possible by ridge tillage, results in relatively uniform distribution of water in the field with length of run. Exceptions are on slowly permeable soils where infiltration at the lower end of the field may be low, and on moderately permeable soils where infiltration and losses to deep percolation may be high. Practices that result in more uniform water application on slowly permeable soils include allowing tailwater runoff, surge irrigation, deep loosening of the soil (especially at the lower end of the field), and precision water application. On moderately permeable soils, furrow compaction, surge irrigation, and precision water application practices help to reduce water losses resulting from high infiltration rates and deep percolation. The effects of these practices on water infiltration and irrigation efficiency are discussed. Also discussed are the advantages and disadvantages of ridge tillage for crop establishment.

An irrigation system for plots under a rain shelter

Rain shelters are important research tools for studying the soil-plant-water system. Much attention has been given to the design of these structures for the purpose of keeping water off plots; however, irrigation under these structures has not been widely reported. A simple irrigation system was developed from readily available materials for use under a large rain shelter. Solid set, lowvolume sprinklers frequently used by the turf industry were employed. Performance and evaluation tests showed that the system had uniform water distribution over the main-plot area of 4.6 × 6.2 m 2 plots, while minimizing overlap between adjacent plots. The water application rate achieved was approximately 25 mm h −1 for individual units. Christiansen uniformity coefficients ( cuc) were 83 to 85% for tested units. Water falling a distance of 0.7 m or less outside of a plot was less than 3 mm h −1, while at greater distances it was essentially zero.

UNIFORMITY OF LEPA IRRIGATION SYSTEMS WITH FURROW DROPS

Computer models for the movement and water delivery of low pressure center pivot and linear-move systems with furrow drops were used to compute water distribution uniformities. The models for small, 3-span, 170-m systems compared satisfactorily with field resuhs. The computed results for 396 m systems had lower uniformities than for the 170 m systems. Uniformities were lowest for furrow-check spacings of 0.5 m or less. As system speed increased, uniformities with short check spacings increased. At check spacings of 3 m or greater, speed had no effect with the center pivot but varied over a 10% range for the linear move. To obtain a uniformity coefficient of 0.8, check spacings needed to be at least 2 m. Uniformities were greatly improved if the alignment angles between spans, which controlled tower movements, were reduced from 0.7° to 0.4° or 0.25°. However, this caused more frequent movement of the center towers which requires more expensive equipment.

Space Shuttle solid rocket motor aft-end internal flows

Flow-visualization techniques were employed in a Vs-scale model of the Space Shuttle solid rocket motor to investigate the dominant aft-end internal flow patterns. The model included the two aft segments, the aft dome, and the convergent portion of the gimballed nozzle. The effects of blowing, which would result from gases produced by the burning propellant, were simulated through the introduction of a uniform distribution of water along simulated burn-back patterns representing the surface at three different times in a firing. It was found that the effects of vortices, shed from protruding inhibitor sections, upon flow a few diameters downstream were greatly diminished by the effects of wall injection. It was also found that the extent of circumferential flow resulting from the removal of a portion of protruding inhibitor was limited to the region near the missing portion. Strong circumferential flow in the aft dome was observed when no grain surface was present in the dome. This flow included nozzle-entrance vortices, which appear to result from interactions between the circumferential and toroidal flows associated with the submerged nozzle and the aft dome.

Head Loss in Manifolds Or Trickle Lateral: Simplified Approach

Uniform distribution of water along a lateral or manifold is one of the primary objectives of a pressurized irrigation system designer. To design a system that will meet this objective requires establishing a relationship between pressure and flow rate. This requires knowledge of the head loss along the lateral or manifold. Total head loss from a lateral with sufficiently close outlets is considered. A simple analytical solution that gives a relationship between relative discharge and length, which, in turn, can be used to calculate the total head distribution along the lateral or manifold, is developed. Values calculated using this simplified expression compared very well with results of other, more complicated expressions. The approcah presented herein requires only the relative discharge at the two ends of a lateral or a manifold.

OBSERVATION OF WINTER INJURY TO THE ROOTS OF APPLE TREES ASSOCIATED WITH SPRINKLER IRRIGATION PATTERN

After the winter of 1985–1986, winter injury to the roots of young apple trees was found to vary with position relative to irrigation sprinklers in several orchards growing at a site in the Okanagan Valley in British Columbia. Trees closest to sprinklers sustained significantly less injury than those more distant to the sprinkler. Water interception by the tree trunk and leaf canopy appeared to prevent uniform water distribution, especially in the vicinity of the crown. The explanation for the effect of water distribution on tree survival was not clearly determined but it did not appear to involve direct effects of a drought stress on tree hardiness because the previous season’s growth, which is considered indicative of drought stress, was not always related to injury. Increase in root injury with distance from sprinklers probably resulted in lower heat capacity of the soil and subsequent lower soil temperatures during the winter. Implications of these observations on irrigation practices to increase winter survival of fruit trees are discussed.Key words: Malus × domestica Borkh., winter survival, soil moisture, freezing stress

Spray cultivation of seaweeds in recirculating brackish water

We have cultivated two species of brackish macroalgae and five Swedish and three New Zealand species of marine macroalgae. A new type of seawater spray method was developed and evaluated in a pilot-scale greenhouse on the small island of Furillen off Gotland in Sweden. Three tiers of netting were used, the seawater was recirculated and the salinity was adjusted to allow the cultivation of truly marine algae. Technically, the system worked well, achieving uniform distribution of water without clogging. Specimens tested grew well, although with low to moderate growth rates. The growth of epiphytes was limited, both on the algae and on the spray units. The macroalgae that are best suited to spray cultivation are those which are sufficiently rigid and buoyant to lie free on the net without retaining large amounts of water.

Trickle Lateral Hydraulics. I: Analytical Solution

An important objective of any trickle system is a uniform distribution of water delivered through the emitters. Computation of flow distribution requires knowledge of the variables such as pressure, flow rate, length of lateral, characteristics of the orifices, and frictional loss in the system. Several studies have been reported that establish these relationships. In each study, the primary solution is based on a discharge that is uniform, although ramifications of the manufacturer's variability have been modeled based on the derived hydraulic profile. Herein, we present an alternative treatment that includes a spatially variable discharge function as part of the basic solution.

The inventory and distribution of water on Mars

Terrain softening, fretted channels, debris flows, and closed depressions indicate that at least the upper 2 km of the cratered uplands at high latitudes (>30°) contain ice in amounts that exceed the porosity, estimated to be 10–20 percent. Theoretical studies, and lack of these features in the cratered uplands at low latitudes, suggest that the upper 1 km of the uplands at low latitudes is ice poor. However, valley networks indicate that water was present near the surface early in the planet's history, although in amounts smaller than at high latitudes. On the basis of these observations, the entire upper 1 km, planet-wide is estimated to have contained 75–125 meters of water at the end of heavy bombardment. From the volume of water needed to cut the circum-Chryse channels, and assuming uniform planet-wide distribution of water, the deep megaregolith is estimated to have contained at least 350 meters of water at the end of heavy bombardment, thereby giving a total minimum inventory of 425–475 meters planet-wide. Most of the water lost from the low latitude uplands by diffusion and in cutting the valley networks is now believed to be in the polar layered terrains. Most of the water involved in cutting the outflow channels is in the low-lying northern plains where a variety of features that have been attributed to ground ice is present. Since the end of heavy bombardment, a large fraction of the planet's surface has been overplated with water-poor volcanics, of which we have samples in the SNC meteorites. The younger volcanics have reacted extensively with the old volatile-rich basement. Part of the 10–20 bars of CO 2 and 0.1 to 0.3 bars of N 2 outgassed with the water was lost during heavy bombardment by impact erosion of the atmosphere and other processes. The remaining was fixed carbonates and nitrates and folded deep into the megaregolith during heavy bombardment.

Water Use Variability in Irrigated Level Basins

ABSTRACT AN understanding of the expected variability of crop water use under field-size, surface irrigation conditions is needed to improve irrigation designs and water management scheduling procedures. A 1985 field study evaluated water use variability under three irrigation schedules and two border lengths. High water distribution uniformities of 85% or greater with a level-basin irrigation system resulted in higher irrigation application efficiencies averaging 95% for a dry irrigation treatment compared with 89 and 83%, respectively, for medium or wet treatments on a wheat crop. A shorter irrigation border length of 190 m compared with 251 m did not improve irrigation water distribution or application efficiencies. Water use (evapotranspiration) was affected by irrigation application amounts but not border length, and water application and evapotranspiration variability were significantly correlated. The coefficient of variation in water use was nearly doubled on the drier than the wetter irrigation treatment with as much as 13% variability occurring on the dry treatment. The higher coefficient of variation in water use on the dry was attributed to primarily soil and crop factors. Spatial interdependence was exhibited for seasonal irrigation water applications and water use at distances of less than 15 to 30 m (50 to 100 ft) suggesting that these minimum spacings were needed for soil water measurements. Greater attention needs to be placed on improved irrigation management for reduced irrigation water applications in order to minimize the effects of spatial variabilities attributed to the irrigation system, soil, and crop parameters.

Mars: A water-rich planet?

Mars had outgassed at least 0.5 to 1 km of water, 10 to 20 bar of CO 2, and 0.1 to 0.3 bar of N 2. The volatiles that have been retained are mostly in the cratered uplands. Terrain softening, fretted channels, debris flows, and closed depressions indicate that at least the upper 2 km of the cratered uplands at high latitudes (>30°) contain ice in amounts that exceed the porosity, estimated to be 10–20%. Theoretical studies, and lack of these features in the cratered uplands at low latitudes, suggest that the upper 1 km of the uplands at low latitudes is ice poor. However, valley networks indicate that water was present near the surface early in the planet's history, although in amounts smaller than at high latitudes. The entire upper 1 km, planetwide is estimated to have contained 75–125 m of water at the end of heavy bombardment. The largest sink for water is the megaregolith below 1 km. Episodic eruption of water from the deep megaregolith cut many of the large outflow channels. From the volume of water needed to cut the circum-Chryse channels, and assuming uniform planetwide distribution of water, the deep megaregolith is estimated to have contained at least 350 m of water at the end of heavy bombardment, thereby giving a total minimum inventory of 424–475 m planetwide. Most of the water lost from the low-latitude uplands by diffusion and in cutting the valley networks is now believed to be in the polar layered terrains. Most of the water involved in cutting the outflow channels is in the low-lying northern plains where a variety of features that have been attributed to ground ice is present. A large fraction of the planet's surface has been overplated with water-poor volcanics, of which we have samples in the SNC meteorites. The younger volcanics have reacted extensively with the old volatile-rich basement. Some of the CO 2 and N 2 outgassed was lost during heavy bombardment by impact erosion of the atmosphere and other processes. The remaining was fixed carbonates and folded deep into the megaregolith during heavy bombardment.

Characteristics of vortex chamber oscillation device.

Fluidic Watering device was developed, to which self-oscillating phenomena are applied, and which has very simple structure. This device was named vortex chamber oscillation device. The jet is controlled only by a circular vortex chamber, and self-oscillation occurs by the pressure difference of the left and right parts of the vortex chamber. by the momentum balance of main jet, the critical pressure difference to switch the jet left and right was calculated. By the difference of the mass of air flow into the chamber through an air hole and flow out accompaning the jet, the time required for reaching the critical pressure was calculated, and the oscillation frequency was determined. This watering device attains appropriate size of water drops and uniform water distribution. This device was used for the SHINKANSEN to melt the snow on the tracks and the roofs of stations, and good results were obtained.

A Method for Preparing Small Soil Samples with Specified Bulk Densities and Water Contents

AbstractA centrifugation procedure is described for producing different degrees of compaction in both wet and dry soils. To ensure uniform distribution of water in the test samples, appropriate quantities of crushed ice are mixed with the oven‐dry soils 24 h prior to the centrifugation step.

Low-Pressure Water Distribution System in Irrigation Machines

ABSTRACT Alow-pressure water distribution system of an irrigation machine is presented. The system divides the water entering the machine equally between the emitters and continuously adjusts the speed of the machine to the entering flow rate so as to maintain a predetermined water application amount. While most existing control systems are based on flow regulators, this system includes a set of main and secondary gravitational distributors. Water distribution uniformity achieved is high (> 95%) at a relatively low pressure (30 to 50 kPa).