ABSTRACT

Overoptimistic design values and assumptions in water supply and irrigation efficiencies has been said to be a major reason for the significant gap between the design service area and actual area irrigated of most canal irrigation systems in the country. In the cases, revalidation of design parameters forms part of a prudent approach to the formulation of irrigation modernisation plans. The number of experiment sites for percolation and ponding tests were determined in such a way that there was at least one for each major soil type, relative to location and every 100 ha of the service area. Without gauging stations, system officials for Balanac River Irrigation System acknowledged that the values they were using for available water supply were basically a result of guess work based on the approved water right of the irrigation system. The discharge rating tables determined for the flumes prior to 2000 were available at the National Irrigation Administration System Office.