Service Contract No 2007 / 147-446 - Swaziland

Old AgePhase one of the irrigation systems was installed in 1994, almost 19 years ago, and as yearselapsed, system efficiency reduces due to equipment wearing out. As a matter of urgencysome equipment must be replaced and the rest maintained for optimal performance. Apartfrom nozzles, sprinklers, due to old age, are underperforming. Some draglines have morethan the allowed tolerance of three joints and hydraulic valves are missing/broken pilots.These and other equipment has to be replaced.Possible ways of improving the hydraulic variation include readjustment of pressureregulating device (installing pilots on all Gulf valves) repair and/or removal of pinchedlateral/sub-main lines and the redesign of the hydraulic system.5 . 2 D e l i v e r y t e s t sThe following delivery tests were conducted:5.2.1 S p r i n k l e r d i s c h a r g eAccording to the ARC the difference in discharge in a specific irrigation block may not vary bymore than 10% from the average discharge, hence this evaluation. The discharge of thesprinklers was tested by collecting water into a container of known volume with a hose pipeconnected to the sprinkler nozzle. A minimum container size of 20 litres is recommended andtogether with a stopwatch the time it took to fill the container was recorded. The open end ofthe hose pipe was not held under water in the container, but also not so high that the watersplashed out of the container.Measurements were again taken at distances 0, L/4, L/2, 3L/4 and L on the lateral and thesprinkler line. The same points where pressure measurements were done were used and bytaking the time it took to fill the container, the discharge was calculated with the followingformula and results are shown in table 4.qe=average volume water measured incontaineraverage duration to fill container (sec)(litres)36001000…………… (10)m3/hourWhere q e = sprinkler discharge [m 3 /h]Maphobeni Farmers Association Report - 2009 Page - 43 -