Evaluation of variable speed pumps in pressurized water distribution systems

Because of its simplicity, a constant speed pump is frequently employed in pressured water distribution systems. Constant-speed pumps, on the other hand, struggle to cope with fluctuating water flow needs. When the discharge demand differs from the design discharge, the needed demand (discharge and head) can be fulfilled by simply altering the pump speed without making any other system changes. In this study, the efficiency of stations equipped with variable speed pumps under all operating conditions exceeds that of stations equipped with fixed speed pumps. The use of variable speed pumps not only increases efficiency but also aids in meeting water needs. In this study, the application of variable speed pumps in pressurized irrigation systems is investigated. The chosen pump station contains an actual sprinkler irrigation system with three lateral lines and a 600-meter main pipe near Tabriz, Iran. The primary pipes are 8 and 6 inches in diameter. The use of a variable speed pump enhances average pump efficiency by 18.7%, according to the findings. In addition, as compared to a fixed speed pump, the variable speed pump system saves 57.6% on electricity. As a result, variable speed pumps should be used in pressurised systems. This research contributes step-by-step calculations for sprinkler irrigation system design. Engineers who are unfamiliar with the commutation procedure will benefit from this knowledge.

Variable water demands in growing season, spatial altitude difference in hydrant points, incompatibility in irrigation time, crop pattern alternation and the other environmental factors are among the most important dynamic factors affecting the operation of pumping stations in an irrigation system. Pumping stations could be effectively operated using a dynamic or time-dependent approach. In this study, the performance of an agricultural pumping station, which will be equipped with variable speed pumps, was analyzed. The station is located in an agricultural area in Qazvin Province, northern Iran. The dynamic model of the pumping station was developed for simulating five defined operation scenarios. The results showed that using variable speed pumps is capable of reducing energy consumption up to 67 %, in comparison with current constant speed modes. The ratio of energy consumption for pumped water was determined equal to 0.37 kwh/m3 in variable speed mode, implying up to 45% reduction in comparison with use constant speed pumps.

Low efficiencies of irrigation pumping stations usually stem from their improper designing, operation, and maintenance of such systems. In the present study, the water and energy losses and the pressure variations of a pressurized irrigation system were investigated through analysing the characteristic curves of the pumps and assessing the discharge and pressure heads needed by the system during the irrigation season (i.e. the system demand curves). Variable-speed pumps can be adjusted to the system demand, making them more efficient than constant-speed pumps while bringing down water and energy consumption. Given this assumption, the suitability of variable-speed pumps to save water and energy in a 100 hectares apple and peach orchard, located in Isfahan Province, central Iran, was investigated. The pressure head, the pump efficiency, and the water and energy losses of the orchard’s irrigation system designed based on variable-speed pumps were calculated and compared with those of common constant-speed systems. The results showed that using variable-speed technology in designing pumping stations not only increases the efficiency and reduces unnecessary pressures but also can result in optimal water use and, depending on operational condition, 44–54% reduction in energy consumption can be achieved, which is significant in national scale.

A computer model was developed to simulate pressure and flow rate distribution along pipes and laterals of pressurized irrigation systems in operation. The software runs in a Windows environment and is capable of simulating irrigation systems having multiple pump stations combined in series and/or in parallel, booster pump stations, parallel pipes and looping pipes. Hand-move, wheel line and center pivot laterals with pressure regulators, one or two drop pipes per outlet and booster pump can be simulated. Leakage can be included in the main pipe network or along the laterals. Lateral inlet pressure can be set to an upper limit to simulate valve closure. Practically any type of nozzle and pump can be simulated since cubic spline functions are used to interpolate values from head-flow rate sets of data. To accomplish these capabilities, algorithms were developed and adapted to convert laterals into a set of head-flow rate data so that a simplified algorithm could be adapted to solve the entire pipe network. A user-friendly interface was designed to allow data for pumps, nozzle and pressure regulators to be interactively entered, edited and analyzed prior to the simulation run. The layout of the irrigation system can be drawn on screen using the mouse. Data can be independently entered and edited for each irrigation system component already drawn in the screen, at any time and in any order. Data for the entire irrigation system are verified at many levels before the simulation is run, to make the model less susceptible to crash. The model proved to be a practical tool for upgrading and designing pressurized irrigation systems.

The flow based minor irrigation systems are common in the plateau areas of eastern India. However due to rolling topography and coarse soil texture, the irrigation efficiency is quite poor. With rolling topography, a scope exists to shift from surface irrigation to hybrid application system comprising gravity fed pipe conveyance and surface irrigation for rice in monsoon season and pumped pressurized irrigation system for post-monsoon crops. A system comprising an adjunct reservoir, a common mainline with option of sprinkler and drip at desirable location was designed for one outlet of a minor irrigation system and was evaluated for its hydraulics and irrigation efficiency. The system reduced the turbidity of the canal water from 11-16 NTU to 2-3 NTU in three stages i.e. adjunct reservoir, catchwell and filtration unit. It was found that the irrigation efficiency of sprinkler and drip irrigation systems were 77.2% and 90.19% respectively in comparison to 46.14% in case of surface irrigation system. The uniformity coefficients of sprinkler irrigation system and emission uniformity of drip irrigation system were 81.4% and 94.2% respectively. Thus the above system can be successfully used in minor irrigation commands, for increasing irrigation efficiency as well as yields. The economic analysis of the system indicated that if the cost of hybrid drip and sprinkler irrigation system is less than Rs. 38,000.00 /ha, then saving water through this system will be more economical.

As the main challenge to water resource management, the impacts of irrigation method improvement need to be addressed in regional hydrological processes. This study investigates the hydrological impacts of developing pressurized irrigation systems at the basin scale using the WEAP–WA (water evaluation and planning system–water accounting) coupling approach. Regarding the development of pressurized irrigation systems since 2006, two separate periods can be mentioned for surface irrigation (1998–2006) and for pressurized irrigation development (2006–2013) in the intermediate basin of Ahar‐Chai in Iran. All major water resource elements of the region were found and constructed in WEAP as predefined object‐oriented elements. The simplified soil moisture method was adopted to model the rainfall‐runoff process in irrigated areas. This model was calibrated and validated using PEST (parameter estimation tool) with acceptable statistical criteria. To understand water balance components, the water accounting framework (WAF) was employed, and the results indicated that modernizing the irrigation system increased water depletion and usage. The results indicate an increase of 26% in actual evapotranspiration in pressurized irrigation compared with surface irrigation (50% of the irrigated area). Actual evapotranspiration and nonbeneficial evapotranspiration per unit area also followed the same trend. However, pressurized systems have higher crop productivity and denser crop patterns. In contrast, the basin runoff during pressurized irrigation was 42% less than that during surface irrigation, which is due to fewer return flows caused by pressurized irrigation. Therefore, the basin surface runoff can be influenced by the type of irrigation. The results obtained by this study suggest an adverse effect of altering the surface irrigation methods in pressurized systems.

A comparative study of irrigation techniques for energy flow and greenhouse gas (GHG) emissions in wheat agroecosystems under contrasting environments in south of Iran

At present, constant speed pumps and variable speed pumps always run in parallel in pump stations of most water supply companies in China. Research on the frequency control characteristic for the mixed-pump station based on the two-stage optimal operation is performed. Firstly, the ratio of the variable speed pump is calculated inversely according to the outlet pressure of the pump station, and then the speed range can be determined dynamically, so that the variable speed pump can play the role of energy saving as far as possible in safe and rational running status. Secondly, the two-stage optimal operation model for mixed-pump stations of multi-source is established, which is of the operating-mode adaptability, and it is solved by the intelligent genetic algorithm. Furthermore, when the operation mode of multi-source pump stations is transformed, the optimal dispatching of water distribution system in corresponding operation mode can be realized through adjusting the variable parameters in the model. At last, the utility and superiority of the optimal operation method for mixed-pump stations of multiple resources is verified by means of the application in certain urban in China.

The effects of land consolidation projects on pressurized irrigation system design and the cost: A case study from Türkiye

Site selection of different irrigation systems can lead to higher water productivity in drought conditions. The present study intends to evaluate suitable regions along the Izeh plain (Iran) for different pressurized and gravitational irrigation systems using Analytical Hierarchy Process (AHP) based on Geographic Information System (GIS). To that end, a variety of inputs such as climate, topography, skilled labor and system costs, etc. were identified and classified into two main categories of socio-economic and environmental criteria. Each criterion was subdivided into several criteria to make the site selection more specific. A matrix of the pair-wise comparison was, in turn, used to compare these criteria and sub-criteria, and to evaluate them based on their relative importance based on the region’s suitability for different irrigation system alternatives. Geographical layers were then obtained for each sub-criterion to select the most suitable sites for different irrigation systems in the study area. Pressurized irrigation systems including wheel move irrigation system, drip irrigation system and solid-set sprinkler irrigation system, together with gravitational irrigation systems consisting of surface irrigation system, and low-pressure irrigation system were considered as irrigation system alternatives during the site selection process in this study. The result map of site selection for different alternatives showed that surface irrigation, drip irrigation and low pressure systems were the best irrigation system alternatives for the region studied.

Performance evaluation of irrigation has been an important area of research for better management of water resources. The present study was carried out to evaluate the performance of pressurized irrigation systems by using the previous researches conducted by our team in the Konya Basin of Turkey. The uniformity coefficient, UC and distribution uniformity, DU, as a performance parameter were analyzed. The average UC and DU values for drip irrigated areas were 80.9% and 68.9%, respectively. These values for sprinkler irrigated lands were 86.8% and 79.9%, respectively. The overall result showed that both UC and DU values were lower in drip irrigation than sprinkler irrigation. In general, sprinkler irrigation system has been applied for a long time while drip irrigation system has been used only recent years in Konya Closed Basin so low uniformity in drip irrigation system might be attributed to the poor experience of farmers especially about management and maintenance. It can be concluded that pressurized irrigation systems are efficient irrigation methods and should be widely used in agriculture especially in arid and semi-arid regions of the world under good management for sustainable water resources use.

The Australian Government is currently addressing the challenge of increasing water scarcity through significant on-farm infrastructure investment to facilitate the adoption of new water-efficient pressurized irrigation systems. However, it is highly likely that conversion to these systems will increase on-farm energy consumption and greenhouse gas (GHG) emissions, suggesting potential conflicts in terms of mitigation and adaptation policies. This study explored the trade-offs associated with the adoption of more water efficient but energy-intensive irrigation technologies by developing an integrated assessment framework. Integrated analysis of five case studies revealed trade-offs between water security and environmental security when conversion to pressurized irrigation systems was evaluated in terms of fuel and energy-related emissions, except in cases where older hand-shift sprinkler irrigation systems were replaced. These results suggest that priority should be given, in implementing on-farm infrastructure investment policy, to replacing inefficient and energy-intensive sprinkler irrigation systems such as hand-shift and roll-line. The results indicated that associated changes in the use of agricultural machinery and agrochemicals may also be important. The findings of this study support the use of an integrated approach to avoid possible conflicts in designing national climate change mitigation and adaptation policies, both of which are being developed in Australia.

To analyze a system of maintaining a fixed hydraulic head at a location for delivering adequate water supply with little or no storage, a conventional hydraulic model could be applied with constant speed pumps. However, modelers would need to iteratively adjust pump speed for each variable speed pump (VSP) to identify the appropriate speed factors at each time step. No doubt, this is a time consuming task, specially, when there are multiple VSPs installed in a system. This paper presents a technically enhanced approach that extends the hydraulic network model to automatically calculate the pump speed that is to deliver a prescribed hydraulic head. The improvement allows engineer to model not only a single VSP without rule-based control, but also multiple VSPs with simple and logic controls. The desired control head can be specified at any location in a system. This feature offers great flexibilities and modeling capabilities for engineers to efficiently analyze a variety of scenarios for the systems where VSPs are installed.

Severe water shortage and stress in pistachio farming areas of Iran have made pressurized irrigation systems unavoidable. Despite extensive subsidies, the adoption rate of these systems remains below 10% in pistachio orchards in Iran. This study employs logit, OLS and analysis of variance models to investigate the barriers to adopting pressurized irrigation systems in pistachio orchards in Kerman Province, Iran. Accordingly, all factors affecting the acceptance of pressurized irrigation systems were identified using research theory and the results of past studies. This study was accompanied by two innovations: first, analyzing both significant and non-significant influential factors in the logit model, and second, finding the roots of this influence. The results indicate that small-scale pistachio orchards, non-scientific horticulture systems, high-density planting, poor water quality and low farmers’ knowledge about irrigation systems are among the obstacles hindering the acceptance of pressurized irrigation systems. Additionally, energy subsidies for cheap water extraction, unclear and complex land ownership laws, water use permits, prohibition of transfer and trade of water, and lack of water market have been significant barriers to the adoption of new irrigation systems in pistachio orchards. Therefore, the Iranian government should reform the anti-technology structure of the agricultural sector, clarify water laws and regulations and modify water policies to incentivize the adoption of water-saving technologies.

Pressurized irrigation systems are widespread among other alternatives in Mediterranean countries. Since the initial investment costs of pressurized irrigation systems are quite high, it is crucial to determine design parameters such as pipe diameter. Most of the current optimization techniques for pipe diameter selection are based on linear, non-linear, and dynamic programming models. The ultimate aim of these techniques is to produce solutions to problems with less cost and computation time. In this study, a novel approach for determining pipe diameter was proposedusing Artificial Neural Networks (ANN) as an alternative to existing models. For this purpose, three pressurized irrigation systems were investigated. Different ANN architectures were created and tested using hydrant level parameters of the irrigation systems, such as irrigated area per hydrant, hydrant discharge, pipe length, and hydrant elevation. Different training algorithms, transfer functions, and hidden neuron numbers were tried to determine the best ANN model for each irrigation system. Using multilayer feed-forward ANN architecture, the highest coefficients of determination were found to be 0.97, 0.93, and 0.83 for irrigation systems investigated. It was concluded that pipe diameters could be determined by using artificial neural networks in the planning of pressurized irrigation systems.