عنوان مقاله [English]
Irrigation Researchers has recommended to change water delivery methods from rotational to on-request methods to enhance flexibility. The diversity of requests in the on-request method makes it difficult to plan and implement the water distribution. The intensified unsteady flow is a challenge concerning the hydraulic performance and flexibility of canals. Flow instability may be associated with excess or deficiency of water delivery, leading to poor performance contrary to the initial intention. Thus, the hydraulic performance of various on-request methods needs to be assessed before recommending them. In this research, based on classification of on-request methods three options are defined. To facilitate the evaluation of different options identical volume of water delivered to the turnouts during the irrigation cycle in all delivery rotations. To this end, out of the three delivery factors of flow rate, duration, and frequency, two factors are considered to be variable. An overall of 14 scenarios was defined by separating the conditions for increasing and decreasing demands. The scenarios were simulated and evaluated in the East Aghili canal using ICSS model. The results show that, even though with increasing the flexibility, unsteady flow behavior is increased, however, if the structures are adjusted accurately, the hydraulic performance of the canal would not be much different. The maximum deviation of water delivery to turnouts among scenarios is about 3% by volume. The lowest values of Adequacy and Efficiency indexes of water delivery are equal to: 0.970 and 0.968, respectively, and the highest values of Equity and Dependability indexes are 0.082 and 0.056, respectively, which shows that all of them are very close to their ideal values. Hence, regardless of the hydraulic behavior of the flow, different levels of flexibility can be achieved for a variety of on-request methods by correctly determining and performing the operation instructions.