Application rates from center pivot irrigation with current sprinkler types

Center pivot sprinkler irrigation is increasing in popularity in the United States due to the low labor requirement and ability to irrigate large fields. The main problem associated with pivots continues to be the inherently high application rates and tendency for runoff and erosion on medium- and fine-textured soils and rolling topography. Recently developed sprinklers or spray heads can produce high application uniformity with controlled drop sizes and medium sized pattern widths at medium to low pressures. A method is presented to predict the average and peak application rates at any point along a center pivot lateral for a particular type of sprinkler. The method can be incorporated with infiltration and center pivot design models to predict when runoff might occur. A computer program is available to aid in the design process and compare alternative configurations

Impact sprinkler pattern modification

Methods of modifying the water distribution pattern of an impact-drive sprinkler are described. A method of pattern modification called intermittent diffusion is introduced. A deflector attached to the drive arm intermittently diffuses the jet of a standard circular-orifice nozzle, producing desirable pattern shapes while maintaining a large pattern radius. Uniformity of application for both wind and no-wind conditions was evaluated using both the deflector and diffuse type nozzles. The deflector is beneficial for low pressure sprinkling, particularly under windy conditions. Equations were developed to predict the operating characteristics of the impact arm

Cablegation VI. The Waterbrake Controller

THE waterbrake was developed as a low cost means of controlling the plug speed in the cablegation automated surface irrigation system. The waterbrake is a simple hydraulic device requiring no external power source and can be built with locally available materials. The design equations are an extension of those presented in the previous papers. The cable reel design is also discussed

Too much of a good thing causes runoff problems

Center-pivot irrigation is used on about 550,000 acres in Idaho, and is growing in popularity because of its ease of operation. The majority of the 350,000 acres of Idaho potatoes are irrigated by center-pivot. The main problem with the use of pivots on Idaho's silt-loam soils and variable topography is their tendency to produce runoff

The WEPP model for runoff and erosion prediction under sprinkler irrigation

Potential runoff and erosion is a serious problem for some types of sprinkler irrigation systems, particularly traveling laterals and center pivots on medium– to heavy–textured soils operating on sloping land. Prediction of when runoff might occur is part of the system design process. The USDA–ARS Water Erosion Prediction Project (WEPP) model was tested with 3 years of field data under high–rate sprinklers in southern Idaho. Runoff and soil loss were measured on the upper, middle, and lower portions of a hillslope. The main parameter affecting infiltration and runoff was the effective hydraulic conductivity. Model predictions for average runoff and soil loss were improved when hydraulic conductivity values were adjusted to account for soil variability across the field. Runoff amounts were small, and prediction variability for individual furrows was quite high, but no more than would be expected from previous studies of infiltration variability. Soil loss predictions were unreliable for the small runoff amounts occurring in this study. The most reasonable use of WEPP for sprinkler irrigation would be for estimating when potential runoff might occur under center pivots for different soils, slopes, and crop management practices, and to determine limits on application depths and rates to avoid serious runof

Spraydrop kinetic energy from irrigation sprinklers

Information on the drop energy from sprinklers is important for choosing the optimum sprinkler type for a particular soil. Drop size distribution data were collected for different types of sprinklers with various nozzle size-pressure combinations using a laser-optical method. Drop velocities were calculated using a trajectory model. The overall drop energy per unit of applied water was calculated. A method was developed to estimate the kinetic energy for a particular type of sprinkler with a given nozzle size and operating pressure using nozzle size and pressure head as independent variables. The volume mean drop size was found to be a good predictor of overall kinetic energy. With no wind, the overall drop energy varied from about 5 to 25 J/kg. The smooth plate spray head gave the least drop energy, while the single nozzle, impact-type sprinklers gave the greatest. Wind was found to increase drop energy by as much as a factor of three, but nozzle elevation had a small effect on drop energ

Intake Rate: Border and Furrow

Water infiltration data which are to be used for evaluation, planning, or management of surface irrigation systems should be obtained by flooding or furrow-flow methods. This chapter describes methods that can be used for determining infiltration rates under actual operating conditions of border or furrow systems

Volumetric water drop evaporation measurement

A volumetric method was used to measure the evaporation loss of water drops larger than 0.3 mm diameter. This method, which uses microliter syringes, yields more accurate results than photographic measurement of changes in drop diameter. Evaporation data is presented for a range of drop sizes, air temperature, humidity and air velocity conditions

The WEPP model for runoff and erosion prediction under center pivot irrigation

The USDA Water Erosion Prediction Project (WEPP) Hillslope model was tested with data taken under traveling lateral irrigation in Southern Idaho. The main parameter affecting infiltration and runoff was the effective hydraulic conductivity. The model was found to predict average runoff and soil loss reasonably well for small slope areas (<40m) and can be used to analyze for potential runoff problems on steep critical areas within a larger field

Reservoir tillage for controlling runoff and saving energy

As energy costs have risen in recent years, sprinkler irrigation equipment has been designed to apply water at lower pressures. Some low pressure devices have been developed for use with set-move systems, but the most popular application has been on self-propelled systems such as center-pivot and linearmove systems. Although low pressure sprinkler systems reduce irrigation pumping energy requirements in most cases, their use can greatly increase the potential for runoff. Since the pattern diameter of low pressure sprinklers is less than that of high pressure sprinklers, water is applied over a smaller area. This increases the application rate, and can often exceed the soil water intake rate. (These relationships are explained in the BPA Irrigation Energy Efficiency sheet on "Irrigation Runoff Control Strategies.") If the water application rate exceeds the intake rate, surface ponding can occur. This surface water can move within the field from high areas to low areas. Runoff or wet and dry areas provide visual evidence of surface water movement, which results in crop variability and loss in crop production. These losses can be reduced by increasing intake rates and/or surface storage capacity of the soil so that all water is retained where it is applied