Evaluation of surface irrigation system performance using System Dynamics (SD) approach

Various methods and criteria have been proposed and utilized for the evaluation of irrigation systems performance, which can be used for comparison of design conditions and irrigation systems performance. Surface irrigation systems should be paid more attention among all other irrigation systems due to their operation simplicity and high losses. In the present study, while describing main relationships of irrigation evaluation criteria of application efficiency, water requirement efficiency, Deep Percolation Ratio and Tail Water Ratio, a method based on SD will be introduced. Modeling of this approach has been done using VENSIM-DSS software. Model has been tested in a case study that included the modeling of a furrow in four irrigation status: current situation, full irrigation, deficit irrigation and finally deficit irrigation with optimized irrigation cutoff time and inflow into furrow. The results reveal the high capabilities of SD approach in modeling water resources and irrigation systems. Its user friendly and ability in transferring data to the data bank can introduce this approach and software as an applicable decision support system.     

A simulation study of comparison of the evaluation procedures for three irrigation methods

Standard evaluation procedures, based on field measurements and statistical, hydraulic models, have been developed for assessing irrigation systems performance. However, given the diverse nature of the irrigation methods, it is not possible to use a unique evaluation procedure. Ideally, variables would be measured at every point throughout the field under study, but that is clearly impractical. Instead, measurements are taken of selected samples, or irrigation models are used to predict field-wide distributions of the variables. In this paper, irrigation models for trickle, sprinkler and furrow irrigation are used to assess how well the irrigation performance indicators generated by standard procedures match those generated by whole-field simulations. Six performance indicators were used: distribution uniformity, uniformity coefficient of Christiansen, application efficiency, deep percolation ratio, tail water ratio and requirement efficiency. The analysis was applied to systems typical of cotton crops in Southern Spain. The results show that the procedure used to determine performance indicators in trickle irrigation provides good estimates of the whole field performance. The procedure used in sprinkler irrigation is also acceptable, but yields variable results. Finally, the standard procedure used for furrow irrigation produces biased, highly variable results and overestimates distribution uniformity.     

On-farm performance evaluation of improved traditional small-scale irrigation practices: A case study from Dire Dawa area, Ethiopia

Field evaluation of surface irrigation systems play a fundamental role to determine the efficiency of the system as it is being used and to identify management practices and system configurations that can be implemented to improve the irrigation efficiency. This study evaluated the performance of an ‘improved’ traditional small-scale irrigation practice at Adada, a representative small-scale irrigation practice in Dire Dawa Administrative Council, Eastern Ethiopia. In order to determine numerical values of performance measures, certain parameters were measured/observed before, during and after an irrigation event while farmers are performing their normal irrigation practice. These parameters include: irrigated crop, irrigation method, stream size, cutoff time, soil moisture deficiency, and field size, shape and spacing. The results showed that the irrigation water applied to a farmer's plot during an irrigation event/turn was generally higher than the required depth to be applied per event. Since the irrigation method used was end-dyked, the major cause of water loss was due to deep percolation. The deep percolation loss was 32% in sorghum, 57% in maize, and 70% in tomato and potato fields. The type of irrigation system used, the ridged irrigation practice and the poor irrigation scheduling in the study sites were the main problems identified in the management and operations of the schemes. The following corrective measures are recommended to improve the system: (1) farmers should regulate the depth of irrigation water they apply according to the type of crop and its growth stage, change the field irrigation system and/or configuration especially for shallow rooted row crops, to furrow system, (2) guidance and support to farmers in developing and introduction of appropriate irrigation scheduling, and (3) future development interventions towards improvement of traditional irrigation practices should also focus in improving the on farm irrigation systems in addition to improving physical infrastructure of the scheme.     

A one-dimensional complete hydrodynamic model of border irrigation based on a hybrid numerical method

A numerical model of border irrigation flow is a useful tool in the design and evaluation of surface irrigation systems. A one-dimensional complete hydrodynamic numerical model of border irrigation was established by using the time–space hybrid numerical method. Differences in stability, convergence, precision, and efficiency of the one-dimensional model were analyzed and compared between the hybrid numerical method proposed here and the Roe finite-volume method. At the same time, the computational performance and simulation effects were validated based on the results of typical border irrigation tests. The results show that the hybrid numerical method provides better numerical stability and convergence with little water quantity-balance and average relative errors than does the Roe finite-volume method. The computational efficiency is about two times higher under the same measurement circumstances. The proposed model of border irrigation can increase computational stability and convergence, can improve computational precision and efficiency, and can provide a good numerical simulation tool for the design and evaluation of border irrigation systems.     

基于指数平滑预测的高效变量喷灌方法

针对现有灌溉系统只能实现大田经验均一灌溉、缺乏决策指导的问题,基于田间ZigBee无线网络实时采集的田间预埋水分传感器信息,提出一种基于二次平滑预测算法的变量灌溉指导数据处理方法,根据理论设定值自行调整平滑权重,使其预测数据达到最优,得到变量作业处方图;研制了基于PLC的喷灌机变量控制系统,通过模拟百分率计时器对喷灌机逐跨调节,并实时调整行走步长与速度,实现变量灌溉。田间对比试验结果表明,变量灌溉效率及节水方面均优于传统灌溉。     

I. A decision support system to improve planning and management in large irrigation schemes

This paper describes a decision support system (DSS) that was developed to improve planning and management for the large irrigation schemes in the Alentejo region of Portugal. The system was designed to help in the analysis and evaluation of the crops and crop systems that can potentially be cultivated, together with identification of limitations affecting crop selection and crop yields. It integrates socio-economic and biophysical data at the field level to analyse the performance of an irrigation scheme in terms of the adoption of irrigation by farmers and farmers’ incomes. The final output is given in the form of specific actions and policies for the irrigated areas. The DSS was designed initially to be used in the Alqueva project, a large irrigation scheme that is under construction in Alentejo. Nevertheless, the final framework is generic in nature, being suitable for planning and policy evaluation in other large irrigation schemes.     

熵权模糊物元模型在节水灌溉综合效益评价的应用

针对以往节水灌溉综合效益评价中多采用简单的多指标综合评价的不足,运用熵权法来确定评价指标的权重,建立基于熵权的物元可拓模型对灌区节水灌溉综合效益进行评价,分别从节水灌溉的社会效益、经济效益和生态效益3个方面入手,构建评价指标综合体系.并以吉安市的田南灌区、谷口灌区、银湾桥灌区和南车灌区共4个灌区为实例进行评价,结果显示:银湾桥灌区的节水灌溉综合效益级别为“一般”,田南灌区的节水灌溉综合效益级别向“一般”级别转化,谷口灌区的节水灌溉综合效益级别向“较好”级别转化,而南车灌区的节水灌溉综合效益级别向“好”级别转化,采用灵敏度分析方法进一步验证评价结果的稳定,所得评价结果科学可靠.说明熵权物元分析法在节水灌溉综合效益评价中具有一定的应用价值.     

Usefulness and limitations of decision support systems for improving irrigation scheme management

SIMIS (the FAO Scheme Irrigation Management Information System) is a decision support system that integrates tools and performance indicators to facilitate the planning and management of irrigation schemes. The authors used SIMIS to compute performance indicators in an irrigation scheme in Southern Spain that were used to identify distribution system constraints affecting the flexibility of water deliveries and to identify scheme sectors where deliveries could not meet the predicted crop water demands. Applying SIMIS, the authors and the irrigation scheme manager evaluated measures to overcome the constraints for future irrigation campaigns, and to refine the water orders made every 2 weeks to the basin authority. On the other hand, SIMIS presented limitations to the evaluation of on-demand delivery schedules. To overcome these limitations, an external model, developed outside SIMIS, showed that the current distribution network of the scheme has the capacity to deliver water on-demand only if a slight water deficit is accepted during the peak demand period. The analysis showed that by relaxing the stringency of the quality of operation of on-demand systems, rotation systems may be transformed into on-demand systems without changing their structures. This analysis could also be done using Clément's hypothesis, but doing so resulted in overestimates of the quality of operation and of the relative irrigation supply.     

Performance assessment of Doroodzan irrigation network by steady state hydraulic modeling

There is a need for improvement in the operation and management of many irrigation and drainage systems worldwide. Computer models are used widely for better management. One of such models is HEC-RAS that was applied to Ordibehesht Canal at the Doroodzan irrigation network, northwest of Fars province in the southern Iran. The model was calibrated and validated for two irrigation seasons during 2001 and 2002. The present gate opening rules used to control the offtakes were simulated by the model and the discharge reductions were evaluated. Discharge reduction of offtakes due to discharge reductions at system source were evaluated by the model. Results show that the present rule is not appropriate for the present system. Fluctuations of discharge at the beginning of canal show considerable and nonuniform changes in discharge of offtakes along the Ordibehesht Canal. The head offtakes show more reductions in the water delivered than middle and tail offtakes. A new sensitivity indicator was defined and used to show the response of offtakes due to discharge changes at system source. The study also shows that HEC-RAS model can be used successfully for a large and complex irrigation system for evaluation of its performance in the absence of observed flow data and improvement of irrigation management plans.     

关中灌区管理体制改革成效的综合评价

对关中灌区监测指标体系进行了层次分析。通过一些定性指标的量化,利用层次分析法(AHP),建立了综合考虑灌区改制的政策评价、灌溉效果评价、工程项目实施评价和社会评价的指标体系及其综合评价模型,对各灌区的改制成效和历年综合改制成效进行了目标评价值计算,其结果可以比较客观、全面地反映灌区改制的成效。     

轻小型喷灌机组评价指标及评价方法现状

轻小型喷灌机组是应用比较广泛的一种喷灌机具,经过40多年的发展,轻小型喷灌机组已经具有多种机组形式,可满足各种地形条件、投资水平及劳动力状况等不同场合应用。总结了轻小型喷灌机组不同配置形式的优缺点,详细分析了国内外轻小型喷灌机组的评价指标。针对不同评价指标提出,应研究轻小型喷灌机组形式的设计和管道水力计算,通过合理的能耗评价指标,优化机组配置,以降低系统能耗。还应研究室外试验条件下机组配置参数、管道布置情况及运行条件、环境因素等因素及其交互作用对喷灌系统喷洒均匀性的影响,研究适用于轻小型移动式喷灌机组的一套综合评价理论与方法。最后提出将灰色关联法应用于轻小型喷灌机组的多因素多目标评价中,为喷灌机组比选及机组性能综合分析提供了一种有效工具。     

基于博弈论法确定灌区运行状况综合评价指标的权重

为了确定综合评价过程中的指标权重系数是否合理,考虑评价结果的合理性和科学性.通过运用博弈论思想将主观的层次分析法(analytic hierarchy process,AHP)和客观的变异系数法(variation coefficient method, CVM)确定的权重系数集成得到最终的权重结果,并以“驱动力-状态-响应”(DSR)模型为基础,建立了一套大型灌区运行状况综合评价指标体系,将得到的主观权重、客观权重和综合权重分别运用到灌区运行状况的综合评价中进行实证分析,研究结果表明:基于博弈论确定的综合权重对灌区进行评价的结果既能体现决策者的主观要求,又能符合灌区实际运行状况.该方法过程简洁,结果科学、客观,具有较好的通用性.     

Identifying a new paradigm for assessing irrigation system performance

There are many definitions of irrigation system efficiency that are applied over a range of scales. Many traditional definitions considered only the water diverted as the water volume of concern. Considering also the water consumed in defining effective irrigation efficiency is a shift from the classical definition of system efficiency. In this paper, equations are derived for calculating the following system performance measures: the irrigation consumptive use coefficient, irrigation system efficiency, irrigation water and soil salinities, relative yield, and productivity of consumed, diverted and beneficially used water. The expressions are based on quite general assumptions and are valid for systems with a single water source and layouts composed of (or simplified to) irrigation units arranged in a row. The aim of these expressions is to illustrate how system performance is affected by the reuse of water which depends on the system’s hydraulic connections and the irrigation unit performance. Illustrations of the model are provided for systems in series and in parallel. Testing and refinement by removing some of the general assumptions underlying the model will be needed to develop practical applications that can be more confidently applied for comparison and improvement of irrigation systems.     

A systems approach for the estimation of the effects of land consolidation projects (LCPs): a model and its application

Land consolidation projects (LCPs) are costly rural development actions that are often questioned. Integrated LCPs are geographically confined Land Rural Development Actions and their ex ante evaluation involves interdisciplinary research, in order to predict changes in farmers' behaviour, patterns of land use and in crops and technologies used. A model that incorporates methods for the evaluation of the performance of the agricultural system before and after the transformations proposed in the project is presented. It is argued that the systems approach is the appropriate method to integrate each particular change and evaluate the global impact of every action included in the project. The model was applied to the Valença-LCP in 1989, before project execution (Coelho, 1992 Análise de Projectos de Emparcelamento Rural. O caso de Valença do Minho. PhD thesis, UTL, ISA, Lisboa.). It evaluates each effect of the project (land, irrigation and drainage and road reconstruction) on a technical and social basis and estimates its economic impacts. The observed results used to evaluate model performance were obtained in 1995, after project implementation. The results from the comparison of model predictions (ex ante evaluation) with observations after LCP implementation (ex post evaluation) suggest that a multidisciplinary approach such as the one proposed here, supported by robust models, can be used as a reliable basis for the evaluation and decision-making process of LCPs.     

灌区运行状况综合评价权重系数的确定

由于主观赋权法确定的权重系数与评价者的知识结构及偏好有关,它存在较浓的主观色彩,为了避免这种弊端,利用客观赋权法拉开档次法来确定权重系数,并用于灌区运行状况的综合评价。"拉开档次"法直接利用评价对象评价指标的实际观测值来确定权重系数,这种方法在整个评价过程中无人为的干扰,这将更能体现评价结果的真实性、可靠性与合理性。通过某灌区实例分析可知该方法可靠、分析结果合理,可为灌区运行评价提供科学依据。     

贵州大型灌区续建配套与节水改造综合效益指标体系构建研究

研究适合贵州大型灌区续建配套与节水改造项目综合效益评价体系。根据系统学理论,采用专家咨询法,划分灌区续改建项目的效益指标结构,运用AHP法、熵值法,基于博弈论的综合集成赋权法,对指标权重赋权,并运用MATLAB等软件计算。研究得出续改建项目的综合效益指标体系,以及指标的主观权重、客观权重、综合集成权重,并且基于博弈论的综合集成赋权法,较好的平衡了主客观的差异,较为合理的体现贵州灌区的现状。贵州灌区建设需要一套科学合理的综合效益评价体系,指导今后的项目评价,总结前期工作经验,为灌区实现现代化农业明确方向。     

Analysis of surface irrigation systems with WinSRFR—Example application

WinSRFR is an integrated software package for analyzing surface irrigation systems. Software functionalities and technical features are described in a companion article. This article documents an example application. The analyzed field is a graded basin (close-ended border) irrigation system. The event analysis tools of WinSRFR are used first to evaluate performance of the irrigation system and estimate its infiltration and hydraulic roughness properties. Performance contours in the Operations Analysis World are then used to optimize irrigation system inflow rate and cutoff time. The adequacy of the existing design is examined with the performance contours provided in the Physical Design World. Hydraulic and practical constraints are considered in finding an optimal operation or design solution. Finally, sensitivity analyses are used to demonstrate the robustness of the solutions.     

Characterizing microtopographical effects on level-basin irrigation performance

Microtopography has long been recognized as one of the key variables in level-basin irrigation performance, although little effort has been devoted to establish its relevance. In this work, experimental data are used to quantify the influence of microtopography on irrigation performance. An irrigation evaluation was performed on a small level-basin (256 m²) LASER levelled to zero slope. Irrigation depth was gravimetrically measured and estimated at the 49 nodes of a regular network. Data from the irrigation evaluation and a two-dimensional flat-bed model were used to estimate irrigation depth. Irrigation times, soil surface elevation and distance to the inlet were estimated at the same nodes, and a correlation matrix was computed. Results showed that soil surface elevation was highly and significantly correlated with the times of advance (0.725⁷¹), recession ( −0.815⁷¹) and opportunity ( −0.852⁷¹), and with the measured irrigation depth ( −0.583⁷¹). Distribution uniformity using soil water measurements was 71.0%. Estimates from the irrigation evaluation and the two-dimensional model were 85.3% and 94.9%, respectively. The irrigation evaluation procedure could explain 30⁷¹% of the measured variability in irrigation depth. A large part of the unexplained variance in measured irrigation depth seems to be due to the spatial variation of infiltration properties. Predictions by the two-dimensional model were not significantly related to the measured values. A simple method was devised to estimate microtopography-adjusted irrigation performance from the results of a flat bed model and the standard deviation of elevation. Microtopography can have an important effect on level-basin irrigation performance. Models not considering this variable may incur large errors when simulating irrigation performance.     

基于组合权重的灌区输水系统适宜性模糊物元模型

阐述了灌区输水系统适宜性的内涵,初探灌区输水系统的适宜性。以黑龙江省农垦红兴隆管理局蛤蟆通灌区、江川灌区及依兰县倭肯河灌区为研究对象,运用基于AHP-熵权法的模糊物元模型进行灌区输水系统适宜性评价。构建了灌区输水系统适宜性评价指标体系,采用层次分析法和熵权法相结合的方法确定各评价指标的权重。结果表明:输水渠道衬砌率是影响灌区输水系统适宜性的主要因素,进一步分析表明蛤蟆通灌区输水系统的适宜性为Ⅱ级,倭肯河灌区和江川灌区输水系统的适宜性为Ⅲ级。研究结果对今后灌区的建设以及节水改造具有重要的指导意义。     

灌溉宏观经济分析与决策系统的建立和应用

运用市场经济理论研究灌溉行业与经济运行规律,提出了灌溉宏观经济评价的方法与准则;对典型省区多年来灌溉经济的运作结果进行了分析评价;在此基础上运用人工神经网络理论,建立了通用的灌溉宏观经济评价人工神经网络模型;分析了政府对市场机制的调控原则与管理策略,提出了统一的灌溉宏观经济分析与决策系统。用此系统对山东省灌溉行业的情况进行了实例分析,诊断了现存问题,提出了改进建议,其研究方法与成果对灌溉行业宏观管理与当前正在进行的灌溉经营管理体制改革具有十分重要的指导意义。