Irrigation
A.A. Khosravi; A. Parvaresh Rizi; R. Barati
Abstract
Introduction: In many cases, after a flood, some information is needed about the flood characteristics at the upstream of a specific location where there is no hydrometric station on the river or flow discharge, and water surface level was not measured at the time of the flood. In reverse flood routing, ...
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Introduction: In many cases, after a flood, some information is needed about the flood characteristics at the upstream of a specific location where there is no hydrometric station on the river or flow discharge, and water surface level was not measured at the time of the flood. In reverse flood routing, calculations are performed from the downstream section step by step to the upstream section of the river and inlet hydrograph is produced based on river hydraulic characteristics and downstream hydrograph. During floods in rivers, the volume of floods gradually decreases due to infiltration into the bed and sides. This reduction in flood volume, called transmission losses, is significant in arid areas. Therefore, developed models for flood routing in seasonal rivers in arid and semi-arid regions should provide an appropriate estimate of transmission losses. In the routing process, the governing equations are combined with an equation to account for infiltration or seepage losses into the riverbed or canal. Then, by routing the flood along the interval and examining the resulting hydrographs at different points, the amount of transmission losses is determined. In the present study, which deals with the reverse hydraulic routing of floods in arid areas, the infiltration losses along the river estimated by the Green-Ampt relationship was considered in numerical models so as to perform reverse flood routing with appropriate accuracy and under hydraulic conditions of ephemeral rivers. To the best of our knowledge, so far no study has analyzed transmission losses in reverse hydraulic flood routing.Materials and Methods: The equations governing gradual variable flows are known as the Saint-Venant equations, which include the continuity and the momentum equations. In hydraulic flow routing models, the complete form of the continuity equation is used, but the momentum equation is applied in various forms obtained by removing some components. The simplest hydraulic routing model is the kinematic wave model in which the components related to inertial forces and pressure force in the momentum equation are omitted. In the diffusion wave model, the components related to inertial forces are omitted, but the pressure force is taken into account and finally, in the dynamic wave model, the momentum equation is considered completely without simplification. In the present study, separate programs were prepared in MATLAB 2013 software for reverse hydraulic flood routing by Kinematic and dynamic wave methods. In these numerical models, by coupling the Green-Ampt infiltration equation with the continuity equation, the depth and flow rate in different places and times are calculated in the upstream direction of the flow.Results and Discussion: In order to validate the results of the developed numerical models and to evaluate its applicability, a set of measured data known as Lane hydrograph and Bambeichi hydrograph was used. The results showed that both reverse hydraulic flood routing models produced the upstream hydrograph with appropriate accuracy. The results of the Bambeichi hydrograph data were more accurate than the Lane hydrograph due to its shorter length of the interval between upstream and downstream sections. For example, the peak discharge of inlet hydrograph calculated by the dynamic wave method for the Lane hydrograph data had an error of 7% compared to the observed value, while the error obtained for Bambeichi hydrograph data was 2%. Therefore, the accuracy of inverse routing models in estimating the volume of upstream hydrograph and consequently the amount of transmission losses was desirable especially for the Bambeichi hydrograph data. The highest error in estimating losses was 25% for the reverse kinematic model and the data related to the Lane hydrograph.Between the two reverse hydraulic flood routing methods, the performance of the dynamic wave method was more accurate for the most numerical experiments, as the governing equations are completely solved in this method. This difference is more pronounced in the Lane hydrograph, which represents the actual conditions of an ephemeral river.Conclusion: The accuracy of the developed numerical models was 90% in estimating the peak flow rate of the upstream hydrograph, and between 85% and 97% in estimating the time related to this discharge. The volume of the upstream hydrograph, which indicates the model performance in estimating the infiltration in the flow path, was also modeled with 75 to 98% accuracy. These results show that the numerical models simulate reverse flood routing with acceptable accuracy in ephemeral rivers, where transmission or seepage losses are significant. Due to different approaches in calculating infiltration losses, these methods can make differences for the hydrograph output of numerical models.
M. DelfanAzari; Atefeh parvaresh Rizi
Abstract
Introduction: The energy crisis has led the world toward the reduction of energy consumption. More than 70 percent of the energy in agriculture sector is used by pumps. In our country, there is no clear standard and guideline and also no adequate supervision for the design, selection, installation and ...
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Introduction: The energy crisis has led the world toward the reduction of energy consumption. More than 70 percent of the energy in agriculture sector is used by pumps. In our country, there is no clear standard and guideline and also no adequate supervision for the design, selection, installation and operation of pumping systems appropriate to the circumstances and needs. Consequently, these systems operate with low efficiency and high losses of energy. While more than 20 percent of the world's electricity is consumed by pumps, average pumping efficiency is less than 40%. So evaluation of pumping stations and providing some solutions to increase efficiency and pumping system’s life time and to reduce energy consumption can be an effective in optimization of energy consumption in the country. The main reasons for the low efficiency of pumping systems comparing to potential efficiency are using unsuitable techniques for flow control, hydraulic and physical changes of pumping system during the time, using pumps or motors with low efficiency and poor maintenance. Normally the amount of flow is not constant over the time in a pumping system and needed flow rate is changed at different times. Designing of pumping system should be responsible for peak requirements as well as it must suggest the suitable flow control method to achieve least energy losses for minimum flow requirements. Also one of the main capabilities to reduce energy consumption in pumping stations is improving the flow control method. Using the flow control valves and bypass line with high energy losses is very common. While the use of variable speed pumps (VSPs) that supply water requirement with sufficient pressure and minimum amount of energy, is limited due to lack of awareness of designers and (or) high initial costs.
Materials and Methods: In this study, the operation of the pumping stations under four scenarios (for discharge control) in a drip irrigation system was analyzed and evaluated: A) Pumping station equipped with VSPs, in this case it is possible to regulate energy consumption due to the required discharge and pressure for irrigation system , B) Pumping stations equipped with constant speed pumps (CSPs) and flow control valve maneuver in every decade of irrigation, C) Pumping stations equipped with CSPs without any flow control and D) Pumping stations equipped with CSPs and flow control valve maneuver per month of irrigation. Pumping stations equipped with CSPs was designed for a 100 hectares irrigation area for peach and apple trees in the South West of Isfahan province. The produced pressure under four types of flow control were determined. Then pump performance and energy consumption were evaluated under three operation scenarios (B, C and D) and afterward compared with the performance of VSP stations that was designed for this irrigation system.
Results and discussion: The most important point in the design of pumping stations is energy consumption, because the cost of energy supply is high and the operation should be able to save more energy. Using the output values of pressure and flow rate from developed model, the amount of energy consumption for each pump was calculated. It was observed that the energy consumed in pumping stations equipped with VSPs is significantly less than other stations. Regarding to the total energy consumption and the amount of energy that each scenario can save, the percentage of energy savings were calculated. The results show that the highest percentage of energy savings are belonging to scenario (a) (using VSPs).
Conclusion: The results of this study show that application of VSPs at pumping stations than commonly pumping stations with CPSs, depending on the type of CSP operation, saves 44 to 54 percent of energy. Using VSPs, which save a lot of energy compare to other methods, can be an important phase in optimizing energy consumption and minimizing the cost operation of the agriculture pumping station. So the type of operation that discussed in the present study and also the type of irrigation system, pump selection, cultivated area and irrigation scheduling are effective at saving energy during VSPs employment. In a recent case, reduction in energy cost should be independently calculated for each irrigation system and be considered in the lifetime costs of pumping system. Regarding the results of this research and also latest studies, it can be said that the study design and implementation of variable speed pumps in irrigation projects should be considered in national scale. Because development of pressurized irrigation schemes that inevitably need to pump, is the country's main policies for efficient use of water.
S. M. Seyedmousavi; A. parvaresh Rizi; S. Isapour
Abstract
Introduction: The use of automatic control system for managing the conveyance and distribution of water in surface irrigation systems, as a means of improving the management and performance of these systems is essential. Automating networks using the programmable controller provide the implementation ...
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Introduction: The use of automatic control system for managing the conveyance and distribution of water in surface irrigation systems, as a means of improving the management and performance of these systems is essential. Automating networks using the programmable controller provide the implementation of a number of control ways according to different water delivery scenarios. Also the implementation of these systems using sensors and recording water levels by hydraulic devices can supply an accurate data collection of water distribution networks in the long term and can influence the decisions to manage the network. Control systems in irrigation canals include two parts: calculation for adjustment the structures (algorithms or control system software) and application the calculated settings on structures (hardware of control systems). The success of these parts is depending on the ability of control algorithm to determine the control parameters.
Materials and Methods: Doosti irrigation network in the plains of Sarakhs is located in the northeast of Iran. In the end of the main canal, two canals has branched which named EPC and WPC2. This study was performed on the EPC canal with the discharge and length of 4.43 m3/s and 18.7 km respectively. There are 15 duck-bill check structures along the EPC. Also 14 intake structures and secondary canals are responsible for water distribution between local water users. In this study, the performance of system identification process, SI, in estimation of coefficients of proportional-integral controller and improvement of adjusting the control algorithm was compared with trial and error process. This proportional-integral control algorithm was designed for EPC canal. The efficiency of algorithm was evaluated using the simulation results of several different choices of operating systems with SOBEK hydrodynamic model and computing evaluation indices of control systems. This model can simulate all kinds of structures in water conveyance and distribution networks. In addition to the integrity of this software, two proprietary approach of the model are ability to design the control algorithms for smart irrigation systems and the ability to integrate each of its modules with each other and increase compliance with real systems. Evaluation of designed control algorithm was done using the pattern of the one-month operation, with extreme daily variation to cover the most intense perturbations in canal. To evaluate the performance of the designed control algorithm for investigated scenarios in the canal, the performance evaluation indices of control systems were used.
Results and Discussion: The results of SI process show that the delay time for the longest reach is greater than the other. Also the values of delay time show that the smaller discharges produce more delay time. By comparing the storage area for applied discharges for SI process, it was concluded that the amount of storage area for low flows is higher. Because for low flows with fixed target level in upstream the check structures, the length of backwater curve is more and consequently the amount of storage area would be higher. By comparing the amount of resonance frequency and maximum resonance for the potential of 10%, 50% and 80% of the design flow for various scenarios, it is indicated that in low flows the resonant behavior has significant effects on canal reach. The results show that the adjusted control algorithm using identification process, rather than trial and error, has considerable accuracy and high potential to flow control and to damp the perturbation of hydraulic disturbances. Also this algorithm provides the on-demand distribution and promotes the efficiency of water control and distribution systems.
Conclusion: Although using automated control systems faced with the problem of high initial investment but as an effective tool, it improves the performance of water delivery and provides the optimal usage of irrigation network capacity. For this reason, it is recommended to custodians of irrigation networks to design and employment of these controllers in irrigation networks with more attention. In present control system IP controller was used. This controller requires the calculation of adjustment coefficients of control algorithm. For comparison between the calculation of these coefficients by trial and error and the identification system, the IP controller for EPC canal of Doosti Irrigation was designed. Then its performance was studied based on the method of canal operation and standard indices. The results indicated that the tuned algorithm control using SI has considerable accuracy and potential to control the flow and to damp the perturbations concluding from structural and hydraulic disturbances. Also this algorithm provides demand oriented distribution and performance promotion of water distribution system. Since in this study a relatively long canal includes multiple reaches and structures such as inverted siphon was studied, the capability of PI and SI process is also confirmed in these situations.