Effects of Wind Velocity, Operating Pressure and Sprinklers Spacing on Distribution Uniformity in a Sprinkler Irrigation System

A. Bavi, S. Boroomand Nasab¹ and H. A. Kashkuli

Department of Irrigation and Drainage, Islamic Azad University, Ahwaz, Iran
Department of Irrigation and Drainage, Shahid Chamran University, Ahwaz, Iran
¹ Corresponding Author: Prof. Dr. S. Boroomand-Nasab
e-mail: boroomandsaeed@yahoo.com
 

Abstract

The study of an irrigation system makes the present status clear to the manager to be able to either continue or improve the system. It also indicates if there are logical, practical and economical reasons for improvement the systems.
Among parameters required for designing the sprinkler irrigation system, are operating pressure, layout, sprinklers spacing, uniformity coefficient and evaporation losses.
 In order to evaluate the effect of wind velocity, operating pressure, layout and sprinklers spacing on distribution uniformity, these experiments were conducted on omidiyeh research experiment station (ORES) Khououzestan, Iran. Three types of wind velocities (0-5, 5-7,> 7 m/s) , three average operating pressures ( 35, 40 , 45 m ), and three sprinklers spacing on lateral ( 15, 18, 21 m ) were applied . All the above treatments were simulated for rectangular, square and triangular layouts distribution uniformity, rate of evaporation losses under different conditions of wind velocity, air temperature, vapor pressure deficit, were estimated under various operating pressures ( 35, 40, 45 m ).
The results showed that, with an increase in wind velocity, the uniformity coefficient decreases and this relationship remains linear with wind velocities less than 7 m/s. The uniformity coefficient falls rapidly for wind velocities higher than this limit. Also increasing operating pressure from 35 to 45 m, under the condition of low wind velocities(>5 m/s),causes increase in the uniformity coefficient, but with increasing of average operating pressure, under strong winds (> 7 m/s) ,did not show a considerable change in the distribution uniformity coefficient. As a result the ratio of sprinklers spacing to diameter of coverage decrease and causes higher uniformity coefficient. Square layout produces a higher uniformity therefore it is recommended at the strong winds. The study also indicated that both the vapor pressure deficit and the wind velocity are important factors in estimating of evaporation losses.