Irrigation Offtake Sensitivity

Monitoring and effective operation of control structures are of importance in a modern irrigation system. Previously developed sensitivity indicators can be useful tools for better management of irrigation systems. The influence of lateral canal water depth on the offtaking and ongoing discharges were simulated and evaluated using a simple model in the Doroodzan irrigation system in south-western Iran. Results confirmed the influence of water level changes in the lateral irrigation canal on offtake and cross-regulator discharge. Results obtained also led us to introduce and evaluate two other sensitivity indicators: offtake sensitivity to downstream water depth, and check sensitivity to tertiary canal water depth.Application of the sensitivity indicators in the Doroodzan irrigation system showed the usefulness of developed sensitivity indicators. The average sensitivity indicators varied from 1.10 to 0.44 (m À1 ) for offtakes and 0.58 to 0.03 (m À1 ) for cross-regulators.

“…differentiating with respect to the h ds , Renault and Hemakumara (1999) defined an offtake sensitivity indicator: ''upward sensitivity for conveyance''. The equation they obtained is…”

Section: Resultsmentioning

confidence: 99%

“…MODELLING APPROACH Renault and Hemakumara (1999) used the following equations for the flow passing through the gated offtakes ( Figure 3): …”

Section: Description Of the Study Areamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Influence of lateral canal water depth on offtake and cross‐regulator discharge

Shahrokhnia¹,

Javan

Shahrokhnia

2008

“…As stated by Renault and Hemakumara (1999), the knowledge of sensitivity analysis for irrigation canals intends to address the following questions: What is the propensity of the system to be affected by perturbations? How could we develop more simplified operational procedures?…”

Section: Sensitivity Analysis Of Irrigation Distribution Systemsmentioning

confidence: 99%

Hydraulic sensitivity indicators for canal operation assessment

Kouchakzadeh

Montazar

2005

An open channel irrigation system is a physical infrastructure composed of canal reaches and numerous structures such as offtakes and cross-regulators, which conveys, regulates and distributes water for irrigation purposes. Each structure is meant to transform an input variable into an output one, and the flexibility of the output with respect to input variations can be expressed by a structure sensitivity indicator. The sensitivity analysis approach, applied to irrigation systems, might be considered an intermediary approach between steady and unsteady flow conditions for describing the flow behavior of irrigation canals. In this paper a preliminary analytical framework is developed to address the sensitivity of irrigation distribution systems. The development of hydraulic sensitivity indicators at local and reach levels is presented first. Then, by incorporating the time parameter in the analysis, a method for estimating a reach-time response to a perturbation is proposed. Also, a case study to evaluate the applicability of sensitivity indicators in assessing flow behavior in an irrigation canal was carried out. The results indicate that the proposed approach is capable of predicting the time required for damping a perturbation with a specified condition and provides the users with sufficient information to improve the management of water distribution in an irrigation network. Copyright

Perspective of Water Distribution Based on the Performance of Hydraulic Structures in the Varamin Irrigation Scheme (Iran)

Mohammadi

Rizi

Abbasi

2018

Despite the extensive application of check and offtake structures in irrigation canals, their periodic assessment is generally not included in water management plans, especially in Iran. This issue would be more important when there are many problems in water distribution in irrigation projects. In this study the performance and operating status of different hydraulic structures in the Varamin irrigation scheme were evaluated using a precise flowmeter. Results show that Neyrpic modules have an error in range of −8 to 83% and these structures, on average, delivered 22% more water. The discharge coefficient of duckbill weirs has changed considerably as well and they are not able to regulate the water level appropriately, because of ageing and physical destruction. The results showed that to achieve an acceptable performance of Neyrpic modules in this scheme it is essential to perform some physical modifications, such as cleaning and sealing the gates, removing sediment around the gates, replacing old gates and continuous inspection of infrastructure. A series of measurements to estimate water losses during the conveyance process show that the conveyance efficiency for each 1000 m length of main, secondary and tertiary canals are respectively 95.0, 91.5 and 89.3%. Consequently to achieve a suitable water distribution pattern, preventive maintenance should be considered. © 2018 John Wiley & Sons, Ltd.