Assessing the Performance of Subinja Irrigation Scheme in the Wenchi Municipality of the Brong Ahafo Region of Ghana

Performance evaluation of an irrigation system is the analysis of certain measurements taken in the field while the system is operating under actual field conditions. The principal indices for evaluating the performance of any farm irrigation system are uniformity, adequacy and efficiency. The overall aim of the evaluation process was to identify the operational problems associated with the solid set sprinkler irrigation system. The study was therefore carried out in 2011 to evaluate the application and water storage efficiencies, as well as the distribution and uniformity coefficients of Subinja Irrigation scheme in the Wenchi Municipality. Forty (40) catch cans or containers with diameter of 120 mm and a height of 140 mm were laid out on a grid having suitable square spacing 3 m× 3 m in order to determine the application rate. It was discovered that the sprinklers operate at an average application rate of 15.63 mm/hr whilst the soils also have an average infiltration rate of 11.73 mm/hr leading to runoff on the field. Distribution Uniformity and Christiansen’s Coefficient of Uniformity were 60.4% and 75.63% respectively indicating that the irrigation was performing below standard. The average depth of water applied was lower than the root zone deficit resulting in storage efficiency below 100%.The application efficiency was very low at the percentage of 43.5. Problems militating against the scheme include inadequate maintenance of the system, leakage from joints, inadequate supply of sprinkler equipment and poor supervision