Model to Forecast Maximum Flows in On-Demand Irrigation Distribution Networks

A model is developed using data from an on-demand pressurized water distribution network located in sector VIII of the Genil-Cabra irrigation district of Santaella, Córdoba (southern Spain), to simulate an irrigation season and calculate the flows that circulate in the system at any given time during the irrigation day. Using the results obtained by the model, water demand frequencies can be estimated. These results are compared to those attained by Clément’s and Mavropoulos’s formulas. This procedure enables us to determine to what extent it is possible to adjust statistical distributions to the demand obtained by both models and to verify if the hypotheses upon which these models are based are, in fact, fulfilled. Moreover, we are able to study which periods are the most appropriate for determining peak demand. Our results show that the statistical methods slightly underestimate demand because demand tends to be concentrated at two peak times during the day: one at mid-morning and another in the late afternoon. Nonetheless, the design flow obtained by the models is valid for designing the system. After studying the demand frequencies, we concluded that a better fit is achieved when a more flexible distribution such as the gamma distribution is used.     

Optimal Design of Pressurized Irrigation Subunit

A linear programming (LP) model is presented for optimal design of the pressurized irrigation system subunit. The objective function of the LP is to minimize the equivalent annual fixed cost of pipe network of the irrigation system and its annual operating energy cost. The hydraulic characteristics in the irrigation subunit are ensured by using the length, energy conservation, and pressure head constraints. The input data are the system layout, segment-wise cost and hydraulic gradients in all the alternative pipe diameters, and energy cost per unit head of pumping water through the pipeline network. The output data are: segment-wise lengths of different diameters, operating inlet pressure head, and equivalent annual cost of the pipeline network. The explicit optimal design is demonstrated with design examples on lateral and submain or manifold of pressurized irrigation systems. The effect of the equations for friction head loss calculation on optimization procedure is investigated through the design example for microirrigation manifold. The performance evaluation of the proposed model in comparison with the analytical methods, graphical methods, numerical solutions, and dynamic programming optimization model reveals the good performance of the proposed model. The verification of operating inlet pressure head obtained by the proposed model with accurate numerical step-by-step method suggested that it is mostly accurate.     

Pumping Selection and Regulation for Water-Distribution Networks

Because of the increasing importance of on-demand irrigation systems, a support system for general use has been developed to aid in selecting and regulating pumping stations. This innovation will improve the balance between total costs (project and energy) and operation quality. The procedure first determines the maximum and minimum system head curves, followed by the evolution of demand curves to obtain the maximum discharge needed. Once this discharge is determined, it is possible to carry out the dimensioning and regulation of the pumping station. An easy tool to select the number of variable and fixed speed pumps has also been developed Excel and Visual Basic can be used. The results demonstrate the importance of selecting pumps that are best adapted to the system head curve. The minimum total cost solution has been obtained by using one variable-speed pump in conjunction with another operating at fixed speed.     

Use of Genetic Algorithm in Optimization of Irrigation Pumping Stations

Energy costs constitute the largest expenditure for nearly all water utilities worldwide and can consume up to 65% of a water utility’s annual operating budget. One of the greatest potential areas for energy cost savings is in the scheduling of pump operations. This paper presents a new management model, WAPIRRA Scheduler, for the optimal design and operation of water distribution systems. The model makes use of the latest advances in genetic algorithm (GA) optimization to automatically determine annually the least cost of pumping stations while satisfying target hydraulic performance requirements. Optimal design and operation refers to selecting pump type, capacity, and number of units as well as scheduling the operation of irrigation pumps that results in minimum design and operating cost for a given set of demand curves. The optimization process consists of three main steps: (1) generating randomly an initial set of pump combinations to start the optimization process for a given demand-duration curve; (2) minimizing the total annual cost, which consists of operation and maintenance costs and depreciation cost of the initial investment, by changing the set and discharge of pump sets based on the provided model; and (3) achieving the final criterion to stop the optimization process and reporting the optimized results of the model. Computational analysis is based upon one major objective function and solving it by means of a computer program that is developed following the GA approach to find the optimized solution of generated equations. Application of the model to a real-world project shows considerable savings in cost and energy.     

Probability of Pressure Deficit in On-Demand Branched Networks and Incorporation into Design Decisions

This technical paper presents analytical expressions to estimate the probability function of head losses in any path of an on-demand branched irrigation network. They are developed for estimating the probability of pressure deficit of a given magnitude at any hydrant. They are also useful for examining the probability of a power deficit at a pumping station designed to guarantee service to a hydrant, as well as the head characteristic curve of the distribution system linked to a definite probability. All this quantified information is useful for decision making on network design and performance. The probabilities calculated with the developed expressions can be taken as complementary or alternative concepts to Clément’s classical design flow method, which is taken here as a benchmark for comparisons. Illustrative examples of network designs are presented to validate the proposed expressions. The least cost design solutions using Clément’s design flows are compared with design solutions here obtained to get the same probability of pressure deficit at the most unfavorable hydrants. The new solutions are less expensive because the flow constraint can be avoided.     

Optimal Design and Operation of Irrigation Pumping Stations

A methodology based on solving a large-scale nonlinear programming problem is presented for the optimal design and operation of pumping stations. Optimum design and operation refers to the selection of pump type, capacity, and number of units as well as scheduling the operation of irrigation pumps that results in minimum design and operating cost for a given set of demand curves. The design criteria for such pumping stations are based fundamentally on some important and critical parameters, such as pump capacity, number of units, types of pumps, and civil works. The optimization process consists of three main steps: (1) determination of minimum yearly consumed energy; (2) minimization of the total cost for all sets of pumping stations; and (3) selection of the least-cost set among the feasible sets of pumping stations, recognizing a combination of the cited criteria. The computational analysis is based upon one major objective function and a computer program, which is developed to solve the generated equations. Application of the model to the Farabi Agricultural and Industrial Project, Iran, shows considerable savings, about 25% in total annual cost of the pumping station.     

Optimum Design of Microirrigation Systems in Sloping Lands

When an area to be irrigated has a high slope gradient in the manifold line direction, an option is to use a tapered pipeline to economize on pipe costs and to keep pressure head variations within desired limits. The objective of this paper is to develop a linear optimization model to design a microirrigation system with tapered, downhill manifold lines, minimizing the equivalent annual cost of the hydraulic network and the annual pumping cost, and maximizing the emission uniformity previously established to the subunit. The input data are irrigation system layout, cost of all hydraulic network components, and electricity price. The output data are equivalent annual cost, pipeline diameter in each line of the system, pressure head in each node, and total operating pressure head. To illustrate its capability, the model is applied in a citrus orchard in S?o Paulo State, Brazil, considering slopes of 3, 6, and 9%. The model proved to be efficient in the design of the irrigation system in terms of the emission uniformity desired.     

Model for the Simulation of Water Flows in Irrigation Districts. I: Description

Significant improvements in the profitability and sustainability of irrigated areas can be obtained by the application of new technologies. In this work, a model for the simulation of water flows in irrigation districts is presented. The model is based on the combination of a number of modules specialized on surface irrigation, open channel distribution networks, crop growth modeling, irrigation decision making, and hydrosaline balances. These modules are executed in parallel, and are connected by a series of variables. The surface irrigation module is based on a numerical hydrodynamic routine solving the Saint Venant equations, including the heterogeneity of soil physical properties. The simulation of water conveyance is performed on the basis of the capacity of the elements of the conveyance network. Crop growth is simulated using a scheme derived from the well-known model CropWat. The irrigation decision making module satisfies water orders considering water stress, yield sensitivity to stress, multiple water sources, and the network capacity. Finally, the hydrosaline module is based on a steady state approach, and provides estimations of the volume and salinity of the irrigation return flows for the whole irrigation season. The application of the model to district irrigation management and modernization studies may be limited by the volume of data required. In a companion paper, the model is calibrated, validated, and applied to a real irrigation district.     

Set Sprinkler Irrigation and Its Cost

In this study, annual water application costs per unit area (ha) have been analyzed at the level of irrigation subunit in set sprinkler irrigation systems designed with pipes of different materials. In the cost, investment (pumping, pipes, sprinklers, ditches), energy, labor, maintenance, and water costs have been considered. Four systems were studied: one with buried pipes, in a permanent solid-set system, using: (a) polyvinyl chloride with buried pipes (PVCb), and three with pipes on the surface in surface solid-set systems, using (b) polyvinyl chloride pipes, (c) polyethylene pipes, and (d) aluminum pipes. The correct selection of the irrigation subunit size and shape can lead to a significant decrease in cost. The most economic irrigation subunits, among the four systems studied, were those formed by four laterals and a number of sprinklers per lateral of 10, 9, and 6 at 12?m×12?m, 12?m×18?m, and 18?m×18?m spacing, respectively. The most influential factor on the annual water application cost was spacing. Considering total annual cost, water cost was the most important, followed by investment and energy. Among the analyzed systems, the permanent system using PVCb produced the lowest annual water application cost per unit area.     

Optimum Design and Management of Pressurized Branched Irrigation Networks

The scarcity of water resources is the driving force behind modernizing irrigation systems in order to guarantee equal rights to all beneficiaries and to save water. Traditional distribution systems have the common shortcoming that water must be distributed through some rotational criteria. This type of distribution is necessary to spread the benefits of scarce resources. Irrigation systems based on on-demand delivery scheduling offer flexibility to farmers and greater potential profit than other types of irrigation schedules. However, in this type of irrigation system, the network design has to be adequate for delivering the demand during the peak period whilst satisfying minimum pressure constraints along with minimum and maximum velocity constraints at the farm delivery points (hydrants) and in the pipes, respectively. In this paper, optimum design and management of pressurized irrigation systems are considered to be based on rotation and on-demand delivery scheduling using a genetic algorithm. Comparison is made between the two scheduling techniques by application to two real irrigation systems. Performance criteria are formulated for the optimum design of a new irrigation system and better management of an existing irrigation system. The design and management problems are highly constrained optimization problems. Special operators are developed for handling the large number of constraints in the representation and fitness evaluation stages of the genetic algorithm. The performance of the developed genetic algorithm is assessed in comparison to traditional optimization techniques. It is shown that the methodology developed performs better than the linear programming method and that solutions generated by the modified genetic algorithm show an improvement in capital cost. The method is also shown to perform better in satisfying the constraints. Comparison between on-demand and rotation delivery scheduling shows that a greater than 50% saving can be achieved in total cost at the cost of reducing flexibility in the irrigation time. Finally, it is shown that minimizing standard deviation of flow in pipes does not result in the best distribution, and therefore minimum cost, neither for systems with uniform flows or those with large variations in discharge at hydrants.     

Development of a Hydro-Salinity Simulation Model for Colorado’s Arkansas Valley

A model to calculate the quantity and quality of river flows by simulating hydro-chemical processes in soil and the spatial/temporal distribution of irrigation return flows is introduced. By simulating the hydro-chemical processes, the quantity and quality of the deep percolating water can be predicted. The spatial and temporal distribution of the deep percolating water is simulated by constructing a groundwater flow path and calculating the groundwater travel time using response functions. A probabilistic approach was developed to calculate the groundwater travel time taking into account the fact that some irrigated fields have subsurface drainage which shortens travel times. All related hydrological components are integrated into the computation of river flow quantity and quality including groundwater return flow, irrigation tail water, tributary inflow, river diversion, phreatophyte consumption, river channel losses, and river depletion due to pumping. An illustrative example is included to demonstrate the capabilities of the model. The results of this example show that river salinity is lower during the irrigation season and higher during the off season. Due to salts carried by return flows, downstream reaches have higher salinity levels than upstream reaches.     

Evaluation of Water and Energy Use in Pressurized Irrigation Networks in Southern Spain

A procedure for evaluating water and energy use in pressurized irrigation networks was developed. Performance indicators were derived from the International Program for Technology and Research in Irrigation and Drainage (IPTRID) and the Institute for Diversification and Energy Savings (IDAE) in Spain and applied to ten representative irrigation districts with on-demand pressurized networks during the 2006–2007 irrigation season. The results confirm the high energy requirements needed for operating these irrigation schemes. To apply an average depth of 2,589??m3/ha, the energy required was estimated to be 1,000??kW???h/ha. Power requirements per unit of irrigated area were 1.56??kW/ha and the pumping energy (PE) efficiency was 58%.     

Assessing Pressure Changes in an On-Demand Water Distribution System on Drip Irrigation Performance—Case Study in Italy

The hydrant pressure head in an on-demand water distribution system can be subject to high fluctuation depending on the discharge flowing inside the pipes, with consequent impacts on the performance of on-farm irrigation systems. In this work, an Italian water distribution system was analyzed using the AKLA model at upstream discharges of 1,200 and 600?L?s?1 to estimate the range of hydrant pressure variation. A computer model was developed, calibrated, and used to evaluate the performance of a drip irrigation system by relating the on-farm network with the hydrant characteristic curve at a certain operating status. The flow regulator within the hydrant played an important role in stabilizing the performance of the network at hydrant pressures higher than 27 m. At lower hydrant pressures, to apply the same amount of water, irrigation time must be extended by 17 and 95% for pressure heads of 20 and 12 m, respectively. These approaches described have great utility to ensure adequate irrigation management when water is delivered by pressurized on-demand systems.     

Economic Viability of Water Pumping Systems Supplied by Wind Energy Conversion and Diesel Generator Systems in North Central Anatolia, Turkey

In this study, a comparison of the economic viability of wind turbine and diesel water pumping systems (WPSs) is presented for five different sites located in the north central Anatolia region of Turkey. A water pumping system was considered for water usage. The wind energy potential was investigated by using the time-series wind data taken from the Turkish State Meteorological Service (TSMS). Data were processed using FORTRAN computer code. The wind power and the amount of water to be pumped was evaluated using various wind energy conversion systems (WECSs), and unit energy and water cost were measured using life the cycle cost (LCC) method for these WECSs. Moreover, the cost of water to be delivered utilizing WPS with diesel generator (DG) was compared with the cost of water delivered viaWPS with WECS. Sinop had reasonable wind potential to produce electrical energy using WECS and the minimum cost of energy output and cost of water to be delivered were $0.24/kWh and $3.70/m3 in this observation station, respectively. In addition, if the water demand is lower than 1,000??m3 in Sinop, such as the water consumption of a household and farm, the WPS with WECS (for Turbines?1, 2, and 4) will be more plausible than the WPS with DG system. If a medium-scale WECS were set up in Sinop, it could supply both the annual electrical demand and water consumption of a household and farm. Finally, Sinop is going to be a marginal area for cost-effective electrical energy generation as the costs of WECSs are lowered.     

Stochastic Study of Windpumps with Reservoir in Southern High Plains

Hourly wind-speed data for 11 years (1983–1993), historical ground-water table data, and performance test results under varying conditions for two mechanical windpumps and one electrical windpump were used at Bushland, Tex., to evolve major recommendations pertaining to wind-powered irrigation management. Stochastic analysis of hourly wind-speed data showed that the average daily wind speed lies most frequently in the range of 5.5–6 m∕s, with the upper and lower limits being 16 and 4.5 m∕s, respectively. This is conducive to most of the wind energy conversion systems manufactured today. The discharge of the electrical windpump was more than four times higher than the mechanical windpumps at high wind speeds. The performance of the electrical windpump was also much better at a high operating head (60 m) than at low operating heads under high wind regimes, showing its suitability for ground-water pumping in the Southern High Plains. Stochastic estimation of daily windpump discharge revealed that pumping rates are high in the spring and autumn seasons, favoring irrigation of a winter wheat crop. The trend of variation in unit reservoir capacity, under different levels of daily demand and risk, shows that wind-powered irrigation systems with high risk can be adopted under higher economic return conditions. Though the results obtained in this study are applicable mainly to the Southern High Plains of the United States, the methodology developed will have general applicability.     

Pond Water Source for Irrigation on Steep Slopes

Existing technologies have been tailored to deliver cost-effective irrigation on a railway embankment and excavated steep slopes (referred to as batters) within a semiarid environment. Irrigation is to aid the establishment of 100% grass cover within a few weeks to mitigate soil erosion problems. It is based on water sourced from a temporary excavated pond plus the use of a solar powered pump and a drip irrigation system. Railway batter erosion remediation is timed for the wet summer season when irrigation can be used to supplement natural rainfall. For a given irrigation demand and catchment area, critical (minimum) pond volume is estimated from regional charts developed for ungauged catchments. About 20% of the critical volume is added to account for evaporation losses and dead storage. Also, seepage losses need to be considered if the soil is medium to coarse textured and if the pond is not lined with an impermeable material. Initial results are very encouraging with a cost estimate of AU$2.74/m2 of batter area treated (irrigated). Irrigation unit cost is expected to decrease with a larger scale irrigated batter area and the refinement of technologies and installation procedures. Although irrigation methodologies were developed for railway embankments and excavated slopes, they can also be used for erosion control on steep slopes such as road embankments or excavated slopes and earth dam side slopes.     

钢铁企业轧制计划与能源调度协同优化

钢铁企业物质流网络与能量流网络的协同优化是实现钢铁行业高层次系统节能的关键。钢铁企业在不同工况下煤气的富余量以及蒸汽和电力需求量不同,轧制工序(含加热炉)作为电力和煤气消耗大户,轧制计划的改变会影响能量流网络中能源介质的分配和调度。提出了钢铁流程物质流与能量流协同优化方法,在分时电价的条件下,利用启发式规则调度方法对一天内的轧制单元进行合理的排程,然后用线性规划方法以系统运行能源成本最小为目标函数,建立钢铁企业煤气 蒸汽 电力系统不同工况下的耦合优化调度模型。通过LINGO求解出模型的最优解,得到了轧制单元的最优排程以及不同工况下煤气、蒸汽、电力的最优实时生产调度方案,用于指导实际生产。利用S钢厂实际数据进行实例分析,得出的调度方案可实现煤气 蒸汽 电力系统的最优化分配,系统运行的能源成本降低8.54%,验证了模型的有效性。     

水泵机组流量优化分配的节能效果浅析

本文依据离心泵流量功率特性曲线，应用微增率法，求出水泵机组间最优负荷分配，即流量优化分配，从而使水泵机组的运行达到节能目的。经算例表明，运用这一流量优化分配方法可使水泵站获得一定的节能效果。     

Water Distribution Network Design Using Heuristics-Based Algorithm

Water distribution network that includes supply reservoirs, overhead tanks, consumer demand nodes, interconnecting pipes, lifting pumps, and control valves is the main mode of water supply for majority of the communities especially in urban areas. Supply of required quantity of water and at right time is the primary objective of water distribution network analysis. The analysis of water distribution networks can be broadly classified into design and operation problems and both problems have been the focus of many researchers over the past three decades. In the water distribution network design problems, the target is attaining the cost effective configuration that satisfies the minimum hydraulic head requirement at the demand nodes. In this paper, a new algorithm for design of water distribution network namely “heuristics-based algorithm” which completely utilizes the implicit information associated with the water distribution network to be designed has been proposed and validated with two water distribution networks. It is found that the proposed algorithm performs well for the least-cost design of water distribution networks.