Performance of 4mm impact sprinklers at different spacing within acceptable pressure ranges (250-350 kPa)

Abstract

Irrigation Engineers in Zimbabwe use the 12 m x 18 m spacing for the design of the sprayline, using 4 mm nozzle sprinklers. A study was conducted to determine performance and cost effectiveness of other spacings that can be used in sprinkler irrigation systems design. The main targeted spacings were a square layout of 15 m x 15 m and a rectangular layout of 15 m x 18 m. Water application uniformity and wetted diameter tests were done using the single line catch can layout method at 250 kPa, 300 kPa and 350 kPa using two locally manufactured (Toronto and Non Ferrous) and two imported (Rainbird and an Irriline) sprinklers. Highest coefficient of uniformity (CU) of 97 % and distribution uniformity (DU) of 95 % were obtained from a Rainbird sprinkler at 300 kPa. The lowest CU of 66 % and DU of 46 % were obtained from a Toronto sprinkler at 250 kPa. Highest wetted diameter (WD) of 32 m was obtained at 300 kPa from a Toronto sprinkler while lowest wetted diameter of 24 m was recorded at 250 kPa from a Toronto sprinkler. The results of CU, DU and wetted diameter showed that the 15 m x 15 m sprinkler spacing can be used in Zimbabwe under moderate wind conditions at 300 kPa, using preferably imported sprinklers for best application uniformity results.