Operational Evaluation of Village Level Irrigation Conveyance Systems

Abstract

ABSTRACT AN irrigation channel operational conveyance loss measurement teachnique is described which allows a determination of transient condition losses as well as a delineation of some types of steady-state losses. The technique is applied to Pakistan watercourse systems from which nearly half of the diverted supply is lost before it reaches the fields. Seven percent of the inflow to the extensive and intermittently used conveyance systems is lost to transient conditions such as initial infiltration into dry banks during channel filling, dead storage, and short-term bank breaches or outlet breaks. Transient losses are not measured by traditional conveyance loss techniques. The transient losses were highly dependent upon the length of channels filled and drained and can thus be reduced by reducing channel lengths or useage. Four percent of the inflow was lost to dead storage. Steady-state seepage rates were much higher than would be ex-pected and are probably the result of macropores in the channel banks. The operational evaluation technique is shown to be a valuable diagnostic tool.