Use of numerical modelling for management of canal irrigation water

Flow regulation and distribution structures play an important role in the overall management of irrigation canals. In this paper the solution of one-dimensional Saint Venant equations of continuity and momentum was applied to a secondary canal in the Abazai Branch of the Upper Swat Canal Irrigation System, North West Frontier Province of Pakistan. The system has been changed from supply based to crop based. The aim of the study was to firstly evaluate the performance of canal outlets under different discharge conditions. The second aim was to assess the response of any modifications in the dimensions of the canal outlets on water distribution under different discharges. Five cases of 100, 80, 70 and 50% of design discharge were tested. The additional operational option of opening and closure of the canal was also evaluated. It was found that under the existing configuration of the canal, the majority of the canal outlets were not drawing discharges according to their allocations for all the four discharge levels. Modifications in outlet dimensions improved the outlet performance. The best performance of canal outlets was obtained under 100 and 80% of the design canal discharge after modifications. In the periods of low irrigation demand, the study recommends opening and closure of the canal instead of operation at lower than 80% of design discharge. Copyright © 2006 John Wiley & Sons, Ltd. Les ouvrages de controle et de repartition des debits jouent un role important dans la gestion d'ensemble des canaux d'irrigation. Dans cet article la resolution d'equations unidimensionnelles de Saint Venant de continuite et impulsion a ete appliquee a un canal secondaire de la branche Abazai du Upper Swat Canal System dans le Nord-Ouest du Pakistan. La gestion du systeme par la ressource est passee a une gestion par la demande (des cultures). Le but de l'etude etait d'abord d'evaluer la performance des emissaires sous differentes conditions de debit. Le deuxieme objectif etait d'evaluer l'effet de modifications dans les dimensions des emissaires sur la distribution de l'eau en faisant varier le debit. Cinq cas de debit d'equipement (100%, 80%, 70% et 50%) ont ete testes. l'option supplementaire d'ouverture et de fermeture du canal a egalement ete evaluee. Il a ete trouve que dans la configuration existante du canal la majorite des emissaires ne transitaient pas le debit prevu pour les quatre niveaux de debit etudies. Des modifications apportees a leurs dimensions ont ameliore leurs performances. La meilleure performance des emissaires a ete obtenue pour 100% et 80% du debit d'equipement du canal apres modifications. Dans les periodes de moindre demande d'irrigation, l'etude recommande l'ouverture et la fermeture du canal plutot que son fonctionnement a des debits inferieurs a 80% du debit d'equipement. Copyright © 2006 John Wiley & Sons, Ltd.