neda Sheikh Rezazadeh Nikou; Mohammad javad monem; A. Ziaei
Abstract
Introduction: Pivot weirs (sharp crested inclined weirs, Fig. 1-a) is frequently used for discharge measurement, controlling water surface and flow diversion. Some typical features of pivot weirs are: (a) overshot design for better water level control, (b) Their application as head gates, turnout or ...
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Introduction: Pivot weirs (sharp crested inclined weirs, Fig. 1-a) is frequently used for discharge measurement, controlling water surface and flow diversion. Some typical features of pivot weirs are: (a) overshot design for better water level control, (b) Their application as head gates, turnout or check structure which requiring low head loss and high accuracy, (c) ease of removing sediment deposit behind the weir, and (d) ability to manage and monitor on-site or operating remotely when connected to a supervisory control and data acquisition (SCADA) network. Kindsvater and Carter (8) derived a weir discharge equation based on energy and continuity equations. Hulsing (4) determined head-discharge relationship of inclined suppressed sharp crested weir with the slope of 3:3, 2:3 and 1:3 toward downstream and compared them with the equivalent normal sharp crested weir. In the USBR report on pivot weirs (regarding The Boulder Canyon Project,1948) the head discharge data of the suppressed pivot weir were presented in a channel with 5.5m length, 2.9m depth and 0.61m width. Some field experiments were also carried out in the IID (Imperial Irrigation District) on a trapezoidal cross-section (0.61 m bottom width) channel with pivot weir of 1.7m length, and two different widths of 1.63m. The flow rate (350-880 lit/s) was held constant and different angles (15-50°) calibrated instead of holding the angle constant and varying the flow rate. Some other laboratory tests were performed with Wahlin and Replogle (1994) on two pivot weirs with 1.2 m and 1.14 m width for the 0.61 m and 0.46 m length of blade and contraction factor of 0.925. RUBICON Company established an extensive operation on the application and automation of pivot weirs in irrigation channels in Australia (Www.rubicon.com). All previous studies concentrated on modifying the normal rectangular weir head-discharge equation so that it can be used for the pivot weirs. In this study, it is trying to derive a unique head-discharge equation for pivot weirs based on dimension analysis and critical discharge equation (implementing Ferro rule). This equation can be used for different inclined angles and side contractions. The obtained unique and simple discharge equation can be used in automation of this structure.
Material and Method: In this research, experimental data consist of experiments carried out in hydraulic research institute of Tehran, Iran and experiments of USBR on Pivot weir with side contraction in 0.925 in the canal with 1.14 m width and 0.46 m blade length (Wahlin and Replogle, 1994). Experiments of the water institute of Tehran were carried out in the concrete rectangular weir with 10.30m long, 1m wide and 1m depth (Fig.2). Experimental model was consisted of canals, water supply system, dampers (avoided of turbulent flow upstream of pivot weir), pivot weirs, sluice gate at the end of the channel (make different tail waters). With respect to laboratory equipment’s, three pivot weirs with of 80×65, 60×55 and 40×40 (cm×cm) respectively length of the blade and the width was built and set 5.5 m far from the first of the canal. Discharge was determined from the calibrated weir located at the upstream of pivot weir. A manual point gauge with ±0.01 mm sensitivity was used to measure water surface levels.
Extraction of discharge equation: Dimensional Analysis based on Ferro rule (2000 and 2001) is used to determine the discharge formula of pivot weirs. Since the h-Q function is usually exponential, the relation between dimensionless parameters could be defined as Ferro rule.
Results and Discussion: The rating curve of the pivot weirs with different side contractions is compared with the normal suppressed rectangular weir (equal weir height) in Fig. 3. The discharge of normal suppressed rectangular weir was calculated from the discharge equation of Kindsvater-Carter and discharge coefficient of Rehbock (1) for the equal weir height and head of pivot weirs. For a constant water head, the discharge of pivot weir with a side contraction of 0.925 is more than the normal suppressed weir. When the weir plate is inclined to the bottom of the canal, because of the stagnation area behind the weir plate, the streamlines approach the weir blade smoothly and the energy dissipation is lower than for the normal weirs. The vortex behind the weir plate increases as the inclined angle increases and subsequently the discharge coefficient decreases. Reduction of discharge for a constant water head in contract weirs is simply justified by decreasing of the weir width. The α and β coefficients were obtained based on all experimental data. Discharge equation obtained based on critical depth-discharge equation.
Conclusion: In this study, based on dimension analysis a unique head-discharge relation was obtained which could be used for different inclined angels and side contractions. This equation is more appropriate than previous formulas which are modifications to the normal weir head-discharge equation. The accuracy of this equation was evaluated by different data sets including different inclined angle, side contractions, weir heights and also a wide discharge range. This equation could be used in the automated irrigation network easily.
K. Shahverdi; M.J. Monem
Abstract
Introduction: Nowadays considering water shortage and weak management in agricultural water sector and for optimal uses of water, irrigation networks performance need to be improveed. Recently, intelligent management of water conveyance and delivery, and better control technologies have been considered ...
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Introduction: Nowadays considering water shortage and weak management in agricultural water sector and for optimal uses of water, irrigation networks performance need to be improveed. Recently, intelligent management of water conveyance and delivery, and better control technologies have been considered for improving the performance of irrigation networks and their operation. For this affair, providing of mathematical model of automatic control system and related structures, which connected with hydrodynamic models, is necessary. The main objective of this research, is development of mathematical model of RL upstream control algorithm inside ICSS hydrodynamic model as a subroutine.
Materials and Methods: In the learning systems, a set of state-action rules called classifiers compete to control the system based on the system's receipt from the environment. One could be identified five main elements of the RL: an agent, an environment, a policy, a reward function, and a simulator. The learner (decision-maker) is called the agent. The thing it interacts with, comprising everything outside the agent, is called the environment. The agent selects an action based on existing state in the environment. When the agent takes an action and performs on environment, the environment goes new state and reward is assigned based on it. The agent and the environment continually interact to maximize the reward. The policy is a set of state-action pair, which have higher rewards. It defines the agent's behavior and says which action must be taken in which state. The reward function defines the goal in a RL problem. The reward function defines what the good and bad events are for the agent. The higher the reward, the better the action. The simulator provides environment information. In irrigation canals, the agent is the check structures. The action and state are the check structures adjustment and the water depth, respectively. The environment comprises the hydraulic information existing in the canal. Policy is a map of water depth-check structure pairs. Reward function is defined based on the difference between water depth and target depth, and the simulator is a hydrodynamic model which, in the present study, was Irrigation Conveyance System Simulation (ICSS). In the developed RL, the RL begins with required initializations, and then the canal structures are operated. While the maximum reward is reached at the time step of t, the agent receives some representation of the state of the environment and, on that basis, selects an action. The simulator performs the action and provides information on the state of the new environment by simulating the canal system. Finally, the reward is assigned. Maximizing the reward, the RL goes on to the next time step. This process is continued until the final simulation time step is reached. The learning process is similar for all operations. The ICSS hydrodynamic model was used to simulate the canal system and provide the environmental information. Input to the ICSS was the new selected action. The ICSS performed the action and simulated the canal system. The output from the ICSS was information on the new environment for use in the next time step. Two scenarios of flow increase and decrease with initial flow of 25 l/s were simulated. MAE (Maximum Absolute Error), IAE (Integral of Absolute magnitude of Error) and SRT (System Response Time) indicators have been used to assess developed model. For flow decrease scenario, the indicators value are obtained zero.
Results and Discussion: Results were obtained from the performed scenarios. In the flow increase scenario, water depth variations were inside the dead band, therefore, SRT indicator was obtained zero. The MAE and IAE indicators were obtained 3.5% and 2.57%, respectively, which showed the water depth deviations from target depth was very low. In the flow decrease scenario, the all indicators values were obtained zero. At time zero in two scenarios, 1000 populations were generated and tested. As the RL controlled the water depth, it generated new populations, too. The reason for this is that the RL generates a new population if there is no classifier with maximum reward in the population. There are no new generation after 0.03 hr and 0.16 hr in flow increase and flow decrease scenarios, respectively. Considering the results, it could be concluded that the developed control system is a powerful technique in terms of accuracy and response time for water depth control.
Conclusion: In this research, the RL upstream control system was developed and connected with ICSS hydrodynamic model and evaluated in two scenarios of flow increase and flow decrease. The results showed an ability to control of deviations, short response time and accurate performance of the developed RL control system, which could be used for further study in irrigation canals.
N. Ganji Khorramdel; K. Mohammadi; M.J. Monem
Abstract
Abstract
An estimate of the groundwater budget at the aquifer scale is particularly important for the sustainable management of available water resources. Water resources are generally subjected to over-exploitation for agricultural and domestic purposes in agrarian economies like Iran. Using water ...
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Abstract
An estimate of the groundwater budget at the aquifer scale is particularly important for the sustainable management of available water resources. Water resources are generally subjected to over-exploitation for agricultural and domestic purposes in agrarian economies like Iran. Using water table fluctuations in dry and wet seasons of a hydrological year is a reliable method for calculating the water budget. In this method, the existence of a piezometric network with careful monitoring and measurements is essential. The objective of this study was to develop a methodology for optimizing the piezometric network so that the groundwater budget could be estimated accurately. In this method the priority of each well and its effects on estimation of water budget was determined by using geostatistics. Using this analysis an optimal network could be determined. In order to demonstrate the applicability of proposed methodology, the Astane-Koochesfahan aquifer with an area of about 1173 km2 in north of Iran was selected. Fifty seven observation wells were analyzed using geostatistical methods and results showed that spherical variogram model had the best performance. It was recognized that such an optimized network provides far fewer measurement points, i.e. 33 wells, without considerably changing the conclusions regarding groundwater budget.
Key words: Groundwater balance, Guilan, water table monitoring network, Optimization, Geostatistics
