Testing operational performance of a primary canal using hydrodynamic flow model during design stage
Date
2000-06
Authors
Savojbolagh, Saeid Khalaj, author
U.S. Committee on Irrigation and Drainage, publisher
Journal Title
Journal ISSN
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Abstract
The Shafurud Irrigation Project is located in the North Western part of Iran by the Caspian Sea. At present, traditional water courses are irrigating about 7,150 ha of paddy fields. Even though there are water shortages during low river runoff and peak growing season, it was decided to extend the area under paddy to about 12,300 ha in net. This is not possible without taking full advantage of the river runoff, and preventing the flow of a large volume of water to the Caspian Sea annually. Therefore, it was foreseen to construct a storage dam on one of the four rivers existing in the area, and three diversion darns on the other rivers. By taking full advantage of the river runoff through the diversion darns and provision of irrigation water during deficiency period from the storage dam, the goal can be achieved. The objective of this paper is to describe the design methodology adopted for the Shafurud primary canal by taking into account the operational performance of the system by using the MODIS hydrodynamic flow model. In the design of new primary canal, it was decided to investigate the effect of manual operation of secondary offtakes and impact of river runoff variation in two alternatives of automatic upstream and self-regulating downstream control systems during deficiency and sufficiency river runoff periods. The results of the simulation show that the unsteady flow phenomena has an important effect on the water delivery and operational efficiency of the system, specially in the case of alternative using an automatic upstream control. It was noticed that management by automatic upstream control is difficult, and during sufficient river runoff relatively more flow should be released from the storage darn as compared with its variant alternative of self-regulating downstream control system but due to topographical condition of the canal alignment with a few modifications it was considered to be a better design option. The idea of taking into account the operational performance of a new irrigation system at the time of design is becoming increasingly important every day, especially when it is realized that many old irrigation schemes do not function properly. One of the main reasons is that water distribution and unsteady flow conditions were hardly considered in their design.
Description
Presented at the 2000 USCID international conference, Challenges facing irrigation and drainage in the new millennium on June 20-24 in Fort Collins, Colorado.