滚移式喷灌机压力对喷灌均匀性影响

为解决喷灌机械的喷灌均匀性差、移动不方便等问题,研制一种操控简单、适应性强的大型滚移式喷灌机,对其水量分布均匀系数和喷灌强度进行试验.试验采用单因素多重比较设计方法,选取距进水端距离分别为40,150,260 m处为测试处,喷灌压力分别为0.20,0.25,0.30,0.35,0.40 MPa,并运用Design-expert软件进行分析,研究各喷灌压力在各测试处对水量分布均匀系数和喷灌强度的影响.结果表明,各测试处的压力对水量分布均匀系数的影响均为显著性差异,且随喷灌压力上升,水量分布均匀系数升高.对喷灌强度的影响呈正相关性,但喷灌压力高于0.30 MPa时影响不显著.喷灌压力在0.40 MPa时,水量分布均匀系数平均可达88.75%,喷灌强度为12.3 mm/h,各处的水量分布均匀系数和喷灌强度能够保持均匀一致,并能够稳定作业,达到最优状态,完全满足大型滚移式喷灌机的性能要求.该项研究对于促进滚移式喷灌机推广和应用具有重要意义,为其深入研究提供了参考依据.     

射流式喷头水量分布动态仿真及试验

【目的】研究工作压力,喷头组合间距、组合斱式和旋转速度对射流式喷头及多喷头组合喷灌均匀性系数(CU)和分布均匀系数(DU)的影响。【斱法】采用不同工作条件下单喷头和多喷头组合喷灌水量分布的动态仿真代码,对射流式喷头开展了水力性能试验;研究了射流式喷头在不同工作压力及安装高度条件下对喷灌强度、水量分布的影响;建立了水量峰值强度与工作压力的回归关系式;模拟了单喷头在正斱形和三角形组合喷灌下的空间水量分布。【结果】喷头在1.5 m安装高度、100~300 kPa压力条件下,水量峰值集中在5 mm/h附近,标准偏差(STD)为0.23。喷头在100 kPa工作压力,安装高度为1.1、1.3 m的水量峰值强度分别可高达8.9、10.5mm/h。不同工作压力下的单喷头喷灌的DU和CU标准偏差分别为15.5%、9.3%,且DU对压力的变化相对更为敏感。【结论】在实际喷灌工程中正斱形组合喷灌的间距应小于8m,三角形组合喷头之间的间距应布置在8m附近,此时的喷灌均匀度最高,单个喷灌设备覆盖范围最广,成本最低。     

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.     

平移式喷灌机行走速度及喷灌均匀度试验研究

为研究低压喷灌下喷灌机行走速度合理取值以及喷灌均匀度对土壤含水率均匀度的影响,以自行研制的轻小型平移式喷灌机为研究对象,通过室内单喷头试验和田间喷灌试验,探究了特定灌水定额下喷灌机的工作压力与行走速度关系,并对其水量分布、喷灌均匀度以及土壤含水率均匀度随时间变化进行了分析.结果表明：通过确定灌水定额能够计算出平移式喷灌机的行走速度和工作压力：当灌水定额分别为10,15,20 mm时,40~120 kPa喷灌压力下喷灌机行走速度最小为17.27 m/h,最大为58.65 m/h;增大喷灌压力能小范围提高均匀度,40 kPa工作压力均匀度为0.696,60~120 kPa喷灌压力下均匀度变化范围为0.731~0.788,喷灌水在土壤中的二次分布均匀度明显高于地表喷灌均匀度,40 kPa喷灌压力下喷后6 h土壤含水率均匀度达到0.906,24 h后达到0.953,可相应降低喷灌均匀度设计值以降低运行成本,节约能耗.     

Effect of field levelling quality on irrigation efficiency and crop yield

Proper land levelling in areas irrigated by canals is an essential pre-requisite for judicious use of scarce irrigation water. The concept of land levelling index, which is different from land uniformity coefficient used hitherto, has been adopted to evaluate quantitatively the precision or quality of land levelling work. Using this concept the quality of land levelling work being done in newly canal commanded areas has been assessed and it is demonstrated that the prevalent deficiency in levelling quality ranges from 21.4 to 42.2%. Field investigations have been carried out to assess quantitatively the effect of land levelling quality on irrigation and water-use efficiencies and crop yield. The study comprised five levelling indices viz., 1.2, 2.0, 2.5, 3.0 and 3.7 cm and two irrigation treatments, i.e., fixed depth and complete irrigation. The results show that irrigation application, distribution, and water-use efficiency are appreciably reduced with increase in levelling index or deterioration in levelling quality. The wheat grain yield is also similarly reduced and it is significantly less for levelling index values higher than 2.5 cm. The fixed irrigation depth treatment gives better results from the point of water economy than does the complete irrigation treatment. From this study, it can be inferred that to obtain reasonably high yield and judicious use of water at a reasonable cost the field levelling index should not have a value greater than 3.0 cm.     

Water Productivity from Integrated Basin Modeling

It is obvious that real water saving measures are only possible if the current water resources are clearly understood. For a basin in western Turkey, simulation modeling at three different scales, field, irrigation scheme and basin level was performed to obtain all terms of the water balance. These water balance numbers were used to calculate the Productivity of Water (PW) at the three levels. The four performance indicators considered were: PW_irrigated (yield / irrigation), PW_inflow (yield / net inflow), PW_depleted (productivity / depletion), and PW_process (productivity / process depletion), all expressed in kg yield per m³ water. For the two cotton fields considered at the field scale level, the more upstream field performed better than the field at the tail-end. This was partly a result of the difference in climatic condition, but was mainly due to the location of the two fields: upstream vs. downstream. At the irrigation scheme level PW_irrigated was higher than at the individual cotton field, since non-irrigated crops were also included. Other PW values were lower as crops more sensitive to drought were also found in the irrigated areas. Basin scale PWs are lower than those at the irrigation scheme, as large areas of the basin were covered with less productive land covers. It is concluded that performance indicators are useful ways of representing water dynamics with clearly understandable numbers, and that it is important to consider all the spatial scales at the appropriate level of detail.     

Errors in predicting furrow irrigation performance using single measures of infiltration

Commercial performance evaluations of surface irrigation are commonly conducted using infiltration functions obtained at a single inflow rate. However, evaluations of alternative irrigation management (e.g. flow rate, cut-off strategy) and design (e.g. field length) options using simulation models often rely on this single measured infiltration function, raising concerns over the accuracy of the predicted performance improvements. Measured field data obtained from 12 combinations of inflow rate and slope over two irrigations were used to investigate the accuracy of simulated surface irrigation performance due to changes in the infiltration. Substantial errors in performance prediction were identified due to (a) infiltration differences at various inflow rates and slopes and (b) the method of specifying the irrigation cut-off. Where the irrigation cut-off at various inflow rates was specified as a fixed time identified from simulations using the infiltration measured at a single inflow rate, then the predicted application efficiency was generally well correlated with the application efficiency measured under field conditions at the various inflow rates. However, the predictions of distribution uniformity (DU) were poor. Conversely, specifying the irrigation cut-off as a function of water advance distance resulted in adequate predictions of DU but poor predictions of application efficiency. Adjusting the infiltration function for the change in wetted perimeter at different inflow rates improved the accuracy of the performance predictions and substantially reduced the error in performance prediction associated with the cut-off recommendation strategy.     

Sprinkler water distributions as affected by winter wheat canopy

Sprinkler uniformity is often used to evaluate irrigation system performance. The measurement of uniformity is generally made from one test when no crop is present. However, a developing crop canopy has significant potential to modify the distribution of water applied during irrigation. This study was conducted to evaluate the influence of a winter wheat canopy on sprinkler uniformity and on canopy-intercepted water by measuring water distributions above and below the canopy. The Christiansen uniformity coefficient (CU) was calculated on both a daily and a cumulative basis. The CU was higher below the canopy than above the canopy. Canopy-intercepted water, which is here defined as the sum of canopy storage and stemflow, increased with increasing water application depth. Sprinkler uniformity had no significant effect on the mean amount of water interception by the canopy. The ratio of water interception to total water application depth for the whole irrigation season was between 0.24 and 0.28. The CUs calculated from the cumulative depth caught above and below the canopy are larger than the averages of individual CU values during the irrigation season. Measurement of individual CUs during the irrigation season therefore underestimates the cumulative CU. Experimental results also demonstrated that sprinkler uniformity in this study had little effect on crop yield. Received: 1 February 2000     

基于"节水增粮行动"取用水合理性分析及补偿措施建议

通过对凌海市节水增粮建设规模、取用水方案及取水合理性分析,其水资源开发利用通过采取管灌、膜下滴灌等工程,可以提高项目区水土资源利用效率,从而达到合理开发利用水资源的目的.本文并对取水的影响与补偿措施提出合理化建议.该项目的实施有利于提高农业综合生产力,保障粮食增产增收.     

畦灌灌水技术要素组合优化

以杨凌区进行的畦灌大田试验为基础,采用WinSRFR软件对各试验点的灌水质量进行了模拟,并分析了畦长、田面坡度、入畦单宽流量和改口成数对灌水效率Ea、灌水均匀度Ed和储水效率Es的影响;在此基础上,结合均匀试验设计与多元回归分析的方法,构建了包含灌水效率Ea、灌水均匀度Ed和储水效率Es在内的单目标优化模型,以入畦单宽流量和灌水时间为变量,采用遗传算法对模型进行求解,提出了试验点不同计划灌水深度条件下畦灌灌水技术要素的优化组合,结果表明其可获得高的灌水质量,达到常规畦灌节水的目的。     

GIS user-interface based irrigation delivery performance assessment: a case study for Tanjung Karang rice irrigation scheme in Malaysia

Various indicators are used for evaluating the performance of different aspects of an irrigation system, and assessments also differ in terms of the types of performance indicators used. This paper describes a GIS-based assessment system which utilizes a new concept and evaluated the inadequacy of a widely used Relative Water Supply (RWS) concept to characterize the irrigation delivery performance for a rice irrigation system as the season advances. Development of this GIS-based assessment system resulted in the creation of new indicators, viz., the Rice Relative Water Supply (RRWS), Cumulative Rice Relative Water Supply (CRRWS) and Ponding Water Index (PWI). These indicators were determined from field tests and evaluated in a Malaysian Tanjung Karang Rice Irrigation Scheme (TAKRIS). The RWS concept was found to be inaccurate for characterizing the oversupply condition on irrigation deliveries for rice irrigation; and difficult to correctly quantify the oversupply condition for irrigation supplies. Besides, it was found that the RRWS indicator can distinctly characterize the oversupply condition for RRWS > 1.0 and undersupply condition for RRWS < 1.0 on irrigation delivery for any given period. A value of 1.0 for RRWS indicates an irrigation delivery that matches perfectly the actual field water demand. This study presents a cumulative RRWS plot that provides important information on irrigation supplies for any given time interval for management decisions. An increasing slope in the actual CRRWS curve with CRRWS = 1.0, means that irrigation supply can be slightly curtailed in the next period. On the other hand, if the slope is negative, supply has to be increased. If a computed CRRWS line follows the CRRWS = 1.0 line, it means that irrigation deliveries are perfectly matched with the field water demand. A graphical user-interface was developed for structuring the assessment tool within an ArcGIS platform. The system can instantly provide information on the uniformity of water distribution and the shortfall or excess, and provides vital information in terms of decisions that need to be made for the next period. The system helps to maintain continuous updating of input and output databases on real field conditions. Results are displayed on the computer screen together with color-coded maps, graphs and tables in a comprehensible form. The system is likely to be adopted for evaluating various water allocation scenarios and water management options. It can also be used as an analytical and operational tool for irrigation managers.     

Diagnosing irrigation performance and water productivity through satellite remote sensing and secondary data in a large irrigation system of Pakistan

Irrigation policy makers and managers need information on the irrigation performance and productivity of water at various scales to devise appropriate water management strategies, in particular considering dwindling water availability, further threats from climate change, and continually rising population and food demand. In practice it is often difficult to access sufficient water supply and use data to determine crop water consumption and irrigation performance. Energy balance techniques using remote sensing data have been developed by various researchers over the last 20 years, and can be used as a tool to directly estimate actual evapotranspiration, i.e., water consumption. This study demonstrates how remote sensing-based estimates of water consumption and water stress combined with secondary agricultural production data can provide better estimates of irrigation performance, including water productivity, at a variety of scales than alternative options. A principle benefit of the described approach is that it allows identification of areas where agricultural performance is less than potential, thereby providing insights into where and how irrigation systems can be managed to improve overall performance and increase water productivity in a sustainable manner. To demonstrate the advantages, the approach was applied in Rechna Doab irrigation system of Pakistan’s Punjab Province. Remote sensing-based indicators reflecting equity, adequacy, reliability and water productivity were estimated. Inter- and intra-irrigation subdivision level variability in irrigation performance, associated factors and improvement possibilities are discussed.     

Performance assessment of irrigation water management of heterogeneous irrigation schemes: 2. A case study

The non-uniformity of soils, weather, fields, cropping pattern and canal systems in most surface irrigation schemes makes irrigation water management complex, but optimum performance is important particularly in irrigation schemes with limited water supply. This paper focuses on the performance of irrigation water management during the area and water allocation with a case study of an irrigation scheme in the semi-arid region of India. Often the irrigation managers or authorities of these heterogeneous irrigation schemes also need to deal with different allocation rules. The allocation plans and the corresponding water delivery schedules during the allocation process were estimated with the help of a simulation–optimisation model for different allocation rules based on cropping distributions (free and fixed), water distributions (free and fixed-area proportionate), irrigation depth (full, fixed depth and variable depth irrigation) and irrigation interval (from 14 to 35 days). The performance measures of productivity (in terms of net benefits and area irrigated), equity (in water distribution), adequacy and excess were assessed for these different allocation plans and schedules. These were further compared with the performance measures of the existing rule (fixed depth irrigation at a fixed interval). The analysis revealed that these performance measures are in some cases complimentary and in other cases conflicting with each other. Therefore, it would be appropriate for the irrigation managers to understand fully the nature of the variation in performance measures for different allocation rules prior to deciding the allocation plans for the irrigation scheme.     

Irrigation uniformity as related to optimum crop production — additional research is needed

Summary The fact that uniformity of infiltrated water has significant effects on crop yield and optimum water application has been well documented. However procedures for obtaining quantitative data on infiltrated water uniformity on a field scale which can appropriately be combined with crop-water production functions to quantify and establish optimum irrigation management have not been adequately developed and verified and justify further research. Matching the scale of measurement to root zone scale is conceptually important but has not been properly verified. Data on infiltration rates measured in the field which have been reported in the literature were combined with crop water production functions to illustrate that the effects of uniformity on yields can be large.     

Review of irrigation system performance with respect to initial objectives

This paper presents the results of assessment studies of the performance of gravity irrigation projects, in six countries in different climate and social environments, with respect to their original objectives in terms of water availability, water use efficiencies, equity of water distribution, cropping intensity and crop yields, and project economic rates of return.An important lesson is the need for more realistic assumptions in the adoption of design standards, especially irrigation efficiency which affect the cropping intensity, the overall productivity of the project and its economic viability. This comparative method of performance assessment applied to a variety of projects has also provided some useful insights into the relative value of the different approaches to design of gravity irrigation systems.The views expressed in this paper are those of the author and are not presented as official views of the World Bank.     

安装高度和工作压力对育苗喷头水力性能影响的试验研究

[目的]探究安装高度及工作压力对育苗喷头水力性能的影响,得到育苗喷头适宜工作条件,优化育苗喷头喷洒水力性能.[方法]选取育苗喷头的安装高度为0.5、0.6、0.7 m,分别测试其在200、250、300、350 kPa工作压力下单喷头的水量分布.基于水量平衡原理,建立移动喷洒水量分布计算模型,将单喷头定喷水量分布转换为...     

Why invest in minor projects in sub-Saharan Africa? An exploration of the scale economy and diseconomy of irrigation projects

It is well-known that major irrigation projects have a strong scale economy, handicapping irrigation development in sub-Saharan Africa (SSA) because of the difficulty in formulating large-scale projects. Using project-level investment cost and performance data of major and minor irrigation projects, this paper examines the causes of the economy of scale phenomenon. We find that strong scale economy exists not only for major but also for minor projects, i.e., small- and micro-scale, projects. This is largely because of the existence of indivisible overhead costs such as high-opportunity-cost human resources for planning, designing and engineering management and supervision. We also find that large differences between major and minor projects in the absolute level of overhead as well as construction costs creates a strong scale diseconomy and results in better performance of minor projects. The advantage of minor projects holds even when their higher risk associated with the water source is taken into consideration. We argue that there is an urgent need to promote irrigation development in SSA through developing minor projects, and to reduce the heavy burden of overhead costs by developing the capacity of human resources at the national, local and farmer levels in the fields of irrigation engineering, irrigation agronomy, institutional development, and micro water management technologies.     

压力对低压喷头水量分布模型影响的试验研究

为研究喷头压力对水量分布模型的影响,以低压喷头为例,对其进行水力性能试验.通过计算矩形组合下不同压力的喷灌组合均匀系数C_u和组合分布均匀系数D_u,探索喷头压力对水量分布模型的影响.结果表明:对于低压喷头,喷灌强度随压力增大先逐渐增大,达到一定值后基本保持不变.在距喷头不同距离时,不同压力下的喷灌强度变化情况不同.在低压范围内,压力对喷灌组合均匀系数和组合分布均匀系数的影响较明显.在100~200 kPa范围下,C_u和D_u均随着压力的增大而增大.在200~300 kPa范围下,C_u与D_u均变化不大.最终提出二者的函数关系式,为多因素下水量分布模型的建立提供理论依据.     

Effects of alternative water distribution rules on irrigation system performance: a simulation analysis

Based on a simulation model reflecting physical and economic conditions typically found in rice irrigation systems in Asia, the irrigation performance implications of alternative water distribution rules for dry season irrigation are evaluated under varying degrees of water shortage. The rules examined reflect differing water distribution strategies designed either to maximize conveyance efficiency, economic efficiency, or equity; or to achieve a balance between efficiency and equity objectives. Irrigation performance is evaluated using several efficiency measures reflecting the physical, agronomic and economic productivity of water, and one measure of equity. Economic efficiency and equity among farmers within the portion of the irrigation system that is on in any given season are shown to be complementary, and not competing objectives. Economic efficiency and equity among all farmers within the command area of the irrigation system are largely complementary strategies at the lower levels of water shortage, but with increasing shortage, significant tradeoffs develop between these objectives. An operational rule for water distribution under a goal of maximizing economic efficiency is developed, and the data requirements for its implementation are shown to be modest. Under the model's assumed conditions of dry season rice production dependent solely on surface irrigation for water, the distribution strategy designed to maximize conveyance efficiency results in only modestly lower levels of economic efficiency and equity than could be achieved by the strategy designed to maximize economic efficiency.