Optimizing the hydraulic designing of pressurized irrigation network on the lands of village Era by using the computerized model WaterGems

Transcription

1 Optimizing the hydraulic designing of pressurized irrigation network on the lands of village Era by using the computerized model WaterGems Ali Ghadami Firouzabadi 1 and Majid Arabfard 2 1. Ali Ghadami Firouzabadi,PHD Student, Department of Water Engineering Sari Agricultural Sciences and Natural Resources University Sari,Iran 2. Majid Arabfard, PHD Student, Department of Water Engineering Sari Agricultural Sciences and Natural Resources University Sari,Iran Corresponding author: majidarabfard@yahoo.com,aghadami@gmail.com ABSTRACT: Hydraulic control of network has special complexities in the pressurized irrigation plans especially in large projects with large area and non-uniform and irregular topography. This cannot be achieved simply through the manual computing and it needs the time-consuming processes although the control of calculation accuracy in this method needs to be discussed. In the pressurized irrigation network plan on the lands of Era village in Mazandaran province of Iran, the need to use a tool, which can be useful in further controlling of design accuracy, has been undeniable considering the extent approximately 50 Ha of lands and non-uniform topography of dales with a height difference about 50 meters in the project lands. Thus it has been tried to apply the available software such as WatNet and WaterGems in designing the water networks in this project. Software model, WaterGems, which has been prepared and provided for hydraulic design of water networks, can have an effective application in hydraulic design of pressurized irrigation network. In this software model, the network can be introduced to the model and the hydraulic simulation can be implemented or be utilized in qualitative modeling by introducing the map of project location as the background and by designing the configuration of network design and introducing the way of supplying the discharge and pressure, valves, facilities needed for the network such as central control, pressure relief valve and... Due to the high ability of software WaterGems in displaying the results obtained from the simulation and according to the irregular topography of target region, which has made the requirement for using this computerized model in designing the network undeniable, this computerized model has been used as one of the best hydraulic simulators of water networks in hydraulic design of pressurized irrigation network, and thus the hydraulic analysis of target network with specific topography has been simulated in a way that the design criteria in this network are met. The main and ultimate objective of applying this model on the lands of this particular project is to select the appropriate pipe diameter and required pressure for beginning of lines with regard to the non-uniform topography of Land. Keywords: hydraulic Simulation, pressurized irrigation in Mazandaran province, WaterGems Model, water network analysis INTRODUCTION Despite the appropriate average rainfall in Mazandaran province, the need for irrigating the crops especially in the high-consumption months (June, July, August, September) has been important because of poor time distribution; in line with achieving these objectives and with regard to the distribution and development of pressurized irrigation systems, Jihad Agriculture Organization in Mazandaran province has put the study of target projects on its agenda and the farmers' pressurized irrigation plan in Era village has been considered in this regard.

2 Studied lands are located in the district Chahar Dangeh, the behind-the- mountain village from Sari city and its original area has been about 50 hectares. Now, about 32 hectares of lands are planted and the rest of it is put on the agenda. Topographic of studied area is according to the map 1. Non-uniform topography of project region and the necessity for using the control tool at the time of hydraulic design are shown in this map. Several sources and references have been provided so far in order to design the pressurized irrigation networks; the publication 286 of President Deputy Strategic Planning and Control [1] can be noted in this regard. In this regard and especially in chapters 3 and 4 of this publication, the terms of designing the pressurized irrigation networks can be cited and the criteria and principles of this publication can be utilized. Map 1. Topography of lands in the project. Bently watergems is an applied software for creating or simulating the transmission lines and water distribution network and analysis of desired network; thus the hydraulic design of this project has been implemented and simulated by relying on this computerized model. In the software or computer programs such as WatNet, Epanet or programs, which were used for hydraulic design of pressurized irrigation network in the Excel software and etc, despite the fact that the accuracy of calculation was reliable, the model WaterGEMS was completely superior than the methods and programs, which were used before, due to the limit caused by the inability of program to display the network plan and other available limitations. Therefore, the use of this software and its application in pressurized irrigation networks are increasing day to day. Some of the features of this software are mentioned as follows: Ability to receive the detailed information about the types of pumps used in the network as the pump performance curve. Evaluating the speed in different directions and possibility to change the diameter of directions in order to eliminate the speed or pressure limits. Ability to calculate all hydraulic features of pipeline including: the speed and pressure across different sectors of network. Ability to receive different models of utilizing the network and hydraulic review of network under the different conditions of utilization and changes of discharge.

3 Ability to display hydraulic calculation results on the plan of project or in separate tables. Ability to filter the hydraulic results and determining the high or low pressure points of networks. Given the above cases and thanks to the high abilities of this software, this computerized model has been used in analyzing the pressurized irrigation network of mentioned project (for more information about the way of working with program see the references [3], [4] and [5]. In this software, the application of different units of drip irrigation in a network can be modeled and the high or even low pressure points of network can be identified. This model has allocated a special position in modeling the pressurized irrigation networks due to the high graphic capabilities and ability of display and hydraulic analysis of different situations of irrigation network performance. MATERIALS AND METHODS Region Meteorology Table 1 summarizes the results of meteorological parameters in project region according to the meteorological statistics of Kiasar station. Average annual rainfall (mm) 330 Relative humidity (Percent) 22 Table 1. Meteorological factors of region Sunshine Hours Freezing Annual (Hour per year) days evaporation (Mm) Average Temperature (C) 80 average wind speed ( m / sec ) 9 Initial design factors Table 2 shows the initial factors needed for apple trees. Water Resources Water resources of apple garden, called the instrumentation fallow, contain two wells and a spring with a total water discharge 15 liters per second and due to the distribution of their position, the water storage pond in the northwest region has been built with sufficient capacity in order to pumped the required water into the drip irrigation system after collecting and transporting the water from the mentioned resources to the storage pool. Interpretation of test results conducted on the applied water in this plan is in accordance with the following description: This water has very low EC, thus it has no limitation in this regard. It is put into the group 1 in terms of salinity and these kinds of water have very low salinity. Moreover, this water is put in group 1 in terms of classified sodium and has low amount of sodium and can be consumed for watering the sensitive plants. Carbonate of this water has no limitation and the amount of its bicarbonate is medium. In terms of Sulfate, this water is without limitation and the total calcium and magnesium is in the acceptable range. This water has no limitation in terms of SAR. No Table 2. Initial parameters of designing the apple trees in project region Describing the required factors Value Unit Spacing between the row of trees Space of trees on the row 6 5 Meter Meter Maximum surface of tree shadow 42 Percent Maximum daily evapotranspiration 3.9 Mm per day Effective deep by root Water storage capacity into the soil Meter Mm per m Percentage of allowable soil moisture discharge 50 Percent Soil Resources General factors related to the features of studied region soil, which has loamy structure, are indicated in Table 3: Infiltration rate mm/h 13 Porosity % 47 Table 3. General features of project region soil Specific weight Field capacity Water plant uptake gr/cm 3 % % Available water mm/m 170 Required Water

4 The methods recommended by the World Food and Agriculture Organization in the Journals FAO24 and FAO56 and the data related to the evapotranspiration and effective rainfall and also the results of meteorological studies have been used in order to estimate the water requirement of under cultivation crop. Designing has been performed for supplying the water required for Apple with 5 6 m intervals. Maximum water requirement of this crop is equal to 3.9 mm per day in July based on the data of Table 4. Table 4. Evapotranspiration of consumption-peak month based on the meteorological information in Kiasar station Hydraulic principles and calculation of pipelines In this plan, polyethylene PE 80 6 pipes have been used in the pressurized irrigation network according to the extent of parts, requirements of plan, flow discharge, diameter of required pipes, and also sustainable pressure, price, accessibility, technical and economic studies as well as the topography of lands. Hydraulic calculations of pipelines in pressurized irrigation network are among the most important parts of designing the water transmission and distribution systems. All hydraulic calculations in this plan have been based on Hazen-Williams equation and the important hydraulic parameters in designing the pipelines including the flow discharge, speed and pressure. Selection of Hazen-Williams coefficient In Hazen-Williams equation, the coefficient C is an important parameter which is expressed as the coefficient of roughness. Changes of this coefficient depend on the pipe material, water quality and hydraulic conditions of fluid flow in the pipe. Value of coefficient C in new pipes, which are determined by the laboratory, will be changed gradually, so that the value of coefficient is reduced during the utilizing years and this will lead to too increased pressure drop. Therefore, the roughness coefficient is chosen according to the average period of utilizing and other effective factors. In this plan, the coefficient C has been considered equal to 135 for Polyethylene pipes. Estimated water requirement Not full wetting of field surface in drip irrigation is among the major cause of creating the difference in estimating the water requirement of plants in this method compared to other methods of irrigation. Based on the relevant calculations, the amount of water requirement at the time of maximum growth has been estimated equal to 2 mm per a day. Drip irrigation efficiency Irrigation efficiency represents a gross amount percentage of ground irrigated water which provides the plant required water, leaching requirement and the losses. In this project, the total efficiency has been considered equal to 85%. Dropper Designing The aim of designing the dropper is to select the appropriate dropper according to soil structure, plant type and to determine the number of required dropper for each tree based on the plants intervals and to select its pressure and discharge. This choice depends on the technical conditions as well as economic and cultural conditions. Table (5) represents the properties of selected dropper.

5 Description Type of Dropper Install method Table 5. Properties of selected dropper explanation Pressure regulator and self washer on line Operating pressure (m) Dropper Discharge (liters per hour) 4 Dropper arrangement 3 droppers as the loop with the intervals 0.75 m from each other for 0 to 6 years of ages and 6 ones for after from 6 years of age Drip irrigation network properties Based on the relevant calculations, the maximum amount of required water in this plan is 18.5 liters per second and it is expected that it will be provided within 16 hours of a day. Main network of drip irrigation based on the topography of region has been divided into six irrigation shifts. Irrigation shifts become active and inactive by opening and closing the valves provided for them. In each shift, the target valve should be opened and other valves should be closed. Pumping capacity in this project is calculated based on the maximum daily water requirement in water-consumed month. It should be explained that the pumps always pump with design discharge (maximum capacity) and the required capacity of lands is provided during various months by setting the work hours of pumps. Application of model WaterGems in hydraulic simulation of project lands As mentioned, the particular topography of region according to the dales of lands has forced the necessity of using a tool to control the network hydraulic calculation. In the hydraulic simulation of pressurized irrigation networks by using the model WaterGems, the first step in hydraulic analysis of water network is to introduce the layout of target network and route location of pipes, nodes and pumping station (or supply source of discharge- pressure). In order to achieve this goal, it is better to define the network layout on the topographic map and perform the initial hydraulic calculations including the pipe diameter, pressure of nodes, etc in order to do the relevant simulation based on the initial calculations and obtain the precise results. These initial calculations can be designed by excel files and be done for this purpose or by other existing software such as WatNet and so on. Although the initial design of network can be done through this model (WaterGEMS), it is recommended that the hydraulic computations to be performed and the network be finalized by the model WaterGEMS in order to achieve more desired result, also the other models should be used for controlling the calculations. For this purpose, after determining the network configuration and depicting it on the regional map (according to the map 2), which is better to have the topographic information of region (Alignment lines or height points), this map is introduced as the background to the program WaterGEMS and the nodes (intersection of pipelines or other needed points) and the route of pipes and the way for supplying the pressure and discharge (through the pump or storage pond, etc.) are depicted. At this stage of introducing the network, the following measures should be taken: 1. Introducing the map of regional plan and network configuration: The plan of region and initial configuration of network should be introduced to the program in order to develop the designer's vision and as a graphical tool. For this purpose, the desired map is saved in the AutoCAD environment and in the format dxf and this file is introduced to the program as one of the backgrounds. 2. Introducing the height points of network: At this stage, the regional alignment lines or distributed height points can be introduced to the program as the initial available information in order to be known for the network as the height layer and the height of each point introduced to the network can be defined for the program by this way. These height layers are introduced to the program in the format dxf. 3. Introducing the way for supplying the pressure and discharge required for the network: Given the layout of pumping station (a set of used series or parallel pumps) the e way for supplying the pressure and discharge required for the network is introduced to the program in order to evaluate the performance of network in various conditions. Different situation means that if the discharge required for the network is different in various time steps, the pump changes the supply pressure according to the consumed discharge of network in order to be compatible with the discharge-pressure curve. This can be

6 achieved through introducing the discharge-pressure curve of pump(s) used in the network and is known as one of the priorities of this simulation model (Figure 1). Despite the fact that the reservoir is necessary for using the pumping station, sometimes the storage with static head is used due to the plan conditions or the storage pool with the height head as the method of providing the discharge-pressure is used in order to simplify the network analysis. This case can be introduced to the model by defining the Reservoir.. Map 2. Selected appropriate layout for the plan Figure 1. Introducing the pumping and central control station of drip irrigation system in the WaterGEMS model [2]

7 4. Introducing the central control station with the decrease amount appropriate to the network capacity: Given the necessity of using the central control station in most of the pressurized irrigation projects (especially in drip irrigation projects), this facilities can be introduced to the model through installing the valves GPV in the network including the pumping station or valves PRV in the network with storage pool. In this case, these facilities can be used in the model according to the Figure 1 by the definition of appropriate decrease in filtration. In this project, the valve GPV has been used in order to introduce the central control. 5. Introducing the applied nodes and valves and depicting the route of pipes: After introducing the background map and the method of determining the discharge-pressure of network and also defining the central control station with the expected amount of decreased pressure, first the location of nodes required type of valves (such as the pressure relief valve) is introduced to the model and then the route of pipes is depicted. In introducing the nodes and valves, first the height of points (and valve diameter) should be defined and in introducing the route of pipes the diameter and length of pipes need to be defined. If the schematic method is used in this step, it is necessary to introduce the length of routes and height of nodes to the program. If the scale map is used as the basis of calculations, the length of routes or height of points (nodes) can be got from the relevant file and in this case there is no need to enter the information manually. In this plan, the second method (using a scale map) has been used for introducing the network plan. 6. Introducing the area of irrigation units and displaying the performance of these units in different time steps : According to the shifted irrigation units, the flow routes (pipes in which the water is flowing) can be displayed in color and or the thickness of flow routes can be increased in order to make the way of displaying the network more appropriate (Figure 2). Therefore, the amount of flowing discharge towards them and the model of function (working time and functional arrangement of units) are defined while defining the nodes. After introducing the covered manifolds of each unit (by introducing the functional model of each node) the discharge required for each part and the performance of selected pump (discharge and pressure) can be assessed at the time of network operation. Thus the network performance can be simulated while each shift is working and the discharge of pipelines and pressure of nodes can be assessed, the low-high pressure points identified and the necessary measures be taken in the network in this regard. These measures can contain changing the diameter of pipe, using the pressure relief valve or changing the pressure of main pipe beginning. Given the irregular topography of this project, using this feature of model has been extremely effective in optimizing the hydraulic design. Figure 2. Displaying the units working in drip irrigation system with changing the thickness and color [2] CONCLUSION According to the above description, it can be stated that the main input data required to run this computerized model in drip irrigation network of target lands has been classified as follows:

8 Depicting the network layout including the introduction of way of supplying the pressure and discharge and depicting the routes of pipelines based on the map of network arrangement which has been introduced as the background. Introducing the default units of measurement for all parts, for instance the unit of length (meter or ), diameter (millimeter or...), pressure, velocity and... Determining the diameter of pipes and length of their routes. Here, it is important to note that the internal diameter of pipes should be introduced to the program. Introducing the height of nodes through the lines of rate curve or mapped height points as the background to the network in order to read the height of points according to the available information or manual entering the height of points. Introducing the rate of discharge flowed through each manifold of drip irrigation. Given the existence of varied discharge along the route of drip irrigation manifold, no facilities have been considered in this model for this special case and a user with specific measures should manage this matter. It is suggested to consider this case in network configuration and determining the diameter of routes and to perform the relevant simulation since the multiple-drop pipes are used in these cases. Introducing the properties of discharge and pressure of used pumps or the head and height of resource or pool for supplying the pressure. Introducing the location of pipes and routes of irrigation parts (network segmentation) in a drip irrigation network. After introducing the network, the desired simulated hydraulic design can be implemented and the necessary changes such as changing the pipe diameter and changing in the pressure of network beginning or the pressure of each node can be applied in order to achieve the best result. RESULTS AND DISCUSSION As mentioned, the existence of non-uniform topography (dales) has caused that using the tool, which is able to overcome the existing limitations in designing, to become essential. This matter in this project has been able to reduce the existing complexity in designing and provide more assurance about the accuracy of calculations for the designing team; therefore, by referring to the capabilities of model WaterGems this model can be used in order to do the hydraulic calculations and control the results. This usage includes controlling the flow rate and pressure of each node in each of the irrigation routes while different parts are operating time in different shifts and it is so useful and important according to the topography of lands. In this regard, it is noted that two series of pumps have been inevitably used due to the complexity in the topography of lands and location of water resource (at the end of northwest of lands) and this capability is also a reason for superiority of model because selecting the pump is usually based on the discharge and pressure of critical part (Critical shift) and different conditions in function of irrigation components is usually not effective in selecting this important case. However, in this project the limitations of network discharge and pressure have been better identified and two series of pumps have been proposed for the lands due to the possibility of function graphic display of each of the parts by the computerized model, although this case can be utilize at the time of operating the network and also two models of pump can be used by special measures while repairing a series of pumps. Therefore, given the mentioned features, this model has been widely used in the hydraulic analysis of drip irrigation network in Era village lands in Sari city and the capabilities or limitations of network has been investigated after introducing the network layout, determining the suitable diameter of each route, and using other required features such as pressure relief valve and filtration. Hence, the graphical capability of this software has been among the advantages and priorities of this software model and has been used in determining the limitations of network and evaluating their solutions. REFERENCES Ab Dasht Saman Consulting Engineers, technical report of local irrigation project in farmers' lands in Era village by agency of Mr. Hassan Shafiei and partners, 2010 Bentley WaterGEMS V8i User' s Guide (WaterGEMS V8i User's Guide.pdf ) Meysami H. et al. applied education of software Bentley WaterGEMS V8i & V8 XM and Software accessories ArcGIS, Micro Station and Google Earth. President Deputy Strategic Planning and Control Publications, publication No. 286, Technical terms and criteria of pressurized irrigation (designing), 2004 WATERGEMS FOR GIS USER' S GUIDE