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1.
Basin irrigation design with longitudinal slope 总被引：1，自引：0，他引：1
César González Luis CerveraDavid Moret-Fernández 《Agricultural Water Management》2011,98(10):1516-1522
The aims of this paper are to analyze theoretically the influence of the longitudinal slope of a surface irrigation field on the uniformity of irrigation and to provide practical tools to design, analyze and manage surface irrigation systems with longitudinal slope and blocked end. An example is shown where a 20% savings in water is obtained by giving the field the optimal slope.In 1982, Clemmens and Dedrick published a practical set of dimensionless graphs to level-basin design and analysis (with no slope). This article generalizes those graphs taking account the existence of field slope. So, Clemmens and Dedrick's graphs are a particular case of obtained results.The analysis is based on solving one-dimensional free surface Saint-Venant equations including infiltration, applying the dimensional analysis to reduce the number of variables involved. Saint-Venant equations are solved with the finite differences method, applying the full hydrodynamic model and the zero-inertia model. Two computer programs are used: WinSRFR and POZAL (a specific software that calculates the optimal cutoff time).The result is a set of three-dimensional graphs that show the relationships of field slope, irrigation uniformity and the rest of the involved dimensionless variables, related to infiltration parameters, Manning roughness coefficient, cutoff time, inflow rate and field length and width. The graphs could be useful in practice to determine the optimal slope of a field, the inflow rate or the length and width of a field, achieving substantial savings of water in surface irrigation. 相似文献
2.
Several parameters that measure the irrigation performance were analyzed for their relation to surface-irrigation design variables and yield. Application efficiency (AE), requirement efficiency (RE), uniformity coefficient (UC), deficit efficiency distribution (DED) and requirement distribution efficiency (RDE) were examined with respect to surface irrigation design variables (inflow discharge, length of the run, and time of irrigation cutoff). RE, RDE and UC were correlated with relative yield. Surface-irrigation models were used to simulate furrow and border irrigation and to determine the value of the performance irrigation parameters. A linear crop-water-production function was used to estimate yield. The RE and RDE were very well correlated with the design variables in border and furrow irrigation, and they were the parameters best correlated with the relative yield. The UC was not correlated with the design variables and gave a poor correlation with the relative yield. The AE was well correlated with the design variables. 相似文献
3.
明渠正常水深的计算是排灌渠道设计中的一项重要工作.通过对典型渠道断面引入包含渠道糙率、底坡、断面几何要素和流量的一组量纲为一的参数,将目前文献中正常水深的显式计算公式进行量纲为一化的统一表达,使其更具有通用性并且方便进行相对误差评价;指出每种典型渠道断面量纲为一的参数在实际工程中的常用取值范围,在此范围内对各量纲为一的显式计算公式进行相对误差评价,作出相对误差全局分布图,比较各显式公式的最大相对误差和全局相对误差,并比较公式的简捷性,据此优选出梯形、圆形、弧底梯形、普通城门洞形、马蹄形等5种断面正常水深简捷、精度高、适用范围广的显式计算公式;应用最优一致逼近原理,提出标准城门洞形断面正常水深分段表示的显式计算公式.相对误差分析表明：推荐出的6种典型渠道断面正常水深的显式计算公式的最大相对误差均小于1%,可为典型断面排灌渠道的设计及水力计算提供有效的计算方法. 相似文献
4.
Empirical functions for dependent furrow irrigation variables. 总被引：1，自引：0，他引：1
A complete set of dependent furrow irrigation variables has been identified, for which empirical functions, of general applicability,
have been developed. A one-dimensional sensitivity analysis technique coupled with dimensional analysis was employed to reduce
the number of independent irrigation variables to a manageable size. Simulation experiments were carried out to generate the
data used in developing the pertinent functional relationships. Regression analysis was used to ascertain the specific form
of the equations. The predictive quality of the functions has been assessed by comparing their output with those of a zero-inertia
model, and was found to be satisfactory.
Received: 22 May 1996 相似文献
5.
典型断面渠道临界水深计算 总被引：2，自引：0，他引：2
系统总结了明渠特征水深研究领域的计算方法,评价了各方法的特点;为了优选出典型断面渠道临界水深简捷、通用、精度高、适用范围广的显式计算公式,通过定义包含典型断面几何要素及流量的量纲为一的参数,将目前成果中临界水深的显式计算公式用定义量纲为一的参数进行统一表达,并对其进行简捷性、精度及适用范围的综合评价比较,优选出梯形、圆形、弧底梯形、普通城门洞形、马蹄形等5种典型断面渠道临界水深的显式计算公式;对标准城门洞形断面的临界水深应用最优一致逼近原理,提出以幂函数形式分段表达的新显式计算公式．误差分析表明,在工程常用范围内,由推荐的显式公式所计算的6种典型断面的临界水深,其最大相对误差均小于1％,满足工程设计对精度的要求．该研究可为典型断面排灌渠道的设计及水力计算提供参考． 相似文献
6.
J. Mohan Reddy 《Irrigation Science》1994,15(2-3):123-136
The design problem of furrow irrigation systems considering runoff and drainage water quality was formulated as an optimization problem, with maximization of net benefits as the objective. A power advance function with an empirically derived relationship between the furrow irrigation design variables and relative crop yield were used in the formulation. The generalized geometric programming technique was used to solve for the optimal values for the design variables that maximized the net benefits from a furrow irrigation system. The optimal efficiency for which the system must be designed under a given set of soil, crop, and economic conditions is not known in advance. In the design, the application efficiency was not specified a priori. It was an output from the optimal design. The analysis suggested that it might not be economical to design surface irrigation systems to achieve a high application efficiency that is specified a priori. In the absence of environmental degradation problems from irrigation, it may sometimes be profitable to design surface irrigation systems to operate at less than the standard application efficiency (55%–90%) that is routinely used in the design. Formulation of the design problem as an optimization problem would yield the optimal application efficiency that would maximize the net benefits to the farmer under any given set of conditions. 相似文献
7.
《Agricultural Water Management》1999,41(2):115-131
Dimensionless advance curves of border irrigation have been developed for Soil Conservation Service (SCS) infiltration families. The volume balance equation was nondimensionally formulated and then used to plot a dimensionless advance curve for each infiltration family that is a function of the exponent a in the infiltration power function and the dimensionless time t*. Initially, the SCS infiltration formula was fitted into a power function. The equivalent parameters for each SCS infiltration family were obtained through a nonlinear regression analysis. The dimensionless curves for a given inflow rate, slope, and roughness coefficient can be used to determine either advance distance at a particular time or time of advance for a certain distance through a few simple steps. The curves also allow reviewing the advance trend of each infiltration family for a sufficiently wide range of dimensionless time covering any condition of dimensioned input parameters. It is anticipated that the curves will help in designing, evaluating, and managing irrigation borders. The more complex zero inertia model has also been used to enhance results of obtained dimensionless advance curves and of fitted SCS infiltration parameters. 相似文献
8.
A mathematical model based on the complete hydrodynamic equations describing open-channel flow is developed for simulation of a complete irrigation in a surface irrigation system. An explicit two-step numerical scheme has been employed for the solution of the flow equations. The total infiltrated water depth at each location along the field is determined. From this intermediate result three performance parameters, expressing the merits of the irrigation as affected by the magnitude of each of the various independent physical or management variables involved in the process, are evaluated. Through an analysis of these effects the selection of the proper size or magnitude of a number of the major parameters becomes possible and thus an optimum combination of the main design or operation parameters in a surface irrigation system can be obtained. Two examples of the proposed technique are included as well as some typical graphs of standardized solution. 相似文献
9.
Water scarcity and the high consumption of water resources in agriculture have strengthened the need to manage and optimize
irrigation systems. Among surface irrigation systems, furrow irrigation with cutback is commonly used because of its potentially
higher irrigation efficiency, lower costs and relative simplicity. The performance of this system is affected by various management
and design variables, and hence different management scenarios should be evaluated before it is applied in practice. For this
purpose, empirical functions for the performance evaluation indices are useful. This paper employs sensitivity, dimensional
and regression analyses in the development of empirical functions for application efficiency, deep percolation, runoff and
distribution uniformity. The proposed functions were evaluated using a numerical zero-inertia model and field measured data.
Coefficients of determination for E
a, D
r, R
r and U
cc were calculated to be 0.90, 0.91, 0.90 and 0.84, respectively. These values indicate that the proposed functions enable the
performance indices to be predicted satisfactorily. Values for the indices calculated using the developed dimensionless functions
showed a very good agreement with both the outputs of the zero-inertia model and values calculated from measured field data.
As the functions were general (not site and irrigation specific) and explicit, they could prove to be of practical significance
in both conventional and optimal design and management of free-draining, graded furrow irrigation systems with cutback flows.
相似文献
| M. NavabianEmail: |
10.
《Agricultural Water Management》2005,76(3):139-159
Wind drift and evaporation losses (WDEL) represent a relevant water sink in sprinkler irrigation, particularly in areas with strong winds and high evaporative demand. The objectives of this paper include: (1) characterize WDEL under day and night operation conditions for solid-set and moving lateral configurations; (2) propose adequate predictive equations; and (3) prospect the effect of sprinkler irrigation on the meteorological variables and on the estimates of reference evapotranspiration. A total of 89 catch can irrigation evaluations were performed in both irrigation systems and under day and night conditions. Different predictive equations of WDEL were proposed for combinations of the two irrigation systems and the two operation times. The equations were selected based on their capability to explain and predict WDEL. Most equations use wind speed alone as an independent variable, although some use relative humidity or combinations of both variables plus air temperature. In the semi-arid meteorological conditions of Zaragoza (Spain), the average WDEL for the solid-set were 15.4 and 8.5% during day and night irrigations, respectively. For the experimental moving lateral, losses amounted to 9.8% during the day and 5.0% during the night. The effect of sprinkler irrigation on the meteorological variables was moderate, with small increases in relative humidity (3.9%) and decreases in air temperature (0.5 °C) during the irrigation event and a few minutes afterwards. Consequently, reference evapotranspiration, estimated by the Penman-Monteith method, decreased during the irrigation event by 0.023 mm h−1 on the average. This decrease represents 2.1% of WDEL, suggesting that the WDEL do not significantly contribute to satisfy crop water requirements, and therefore constitute a consumptive water loss. 相似文献
11.
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. 相似文献
12.
《Agricultural Water Management》2004,68(1):33-46
The paper examines the method of using project irrigation requirements (PIR) in the design and rehabilitation of small-scale smallholder irrigation systems within multi-sector and dynamic river basins. This procedure, which employs equations that determine irrigation and crop water requirements, is found embedded in irrigation thinking and planning methodologies throughout the irrigation world. The paper argues that if the PIR equations are used formally and conventionally without sufficiently accounting for changing demands for water in semi-arid river basins, they can lead to irrigation designs that over-prioritise water for individual irrigation systems and as such be labelled ‘irrigation-centred’. Although other adjustments and attempts at re-allocating water might be undertaken, basin managers are often unable to recognise, accommodate or transcend the irrigation focus that this approach generates thus curtailing the efficacy of re-allocation efforts. This argument is made on the basis of observations in the Usangu Plains of Tanzania of farmer-originated irrigation and donor attempts at rehabilitation and modernisation. Features of a modified planning and design methodology are suggested, which considers irrigation alongside other water sectors, and focuses on the river basin rather than on the individual system; an alternative which, it is proposed, is more flexible and ‘water-resource-centred’. The implications of this dualism in approaches (irrigation-centred or resource-centred) for basin management, livelihoods, conflict mediation and formal irrigation rehabilitation projects are explored. 相似文献
13.
Higher performance through combined improvements in irrigation methods and scheduling: a discussion 总被引：2，自引：0，他引：2
Luis S. Pereira 《Agricultural Water Management》1999,40(2-3):153-169
Prior to the discussion on approaches to combine irrigation scheduling and water application practices, several farm irrigation performance indicators are defined and analysed. These indicators concern the uniformity of water distribution along an irrigated field and the efficiency of on-farm water application. Then, the analysis focus is on three main irrigation systems: surface, sprinkler and microirrigation. For each of these systems, the analysis concerns the main characteristics and constraints of the systems, more relevant aspects influencing irrigation performances, and approaches which could lead to a more appropriate coupling of irrigation scheduling and water application methods. Conclusions point out on the need for combined improvements in irrigation scheduling and methods, for expanding field evaluation of irrigation in farmers fields, for improved design of on-farm systems, and for quality control of irrigation equipments and design. 相似文献
14.
Pedro Le o de Sousa Luí s L. Silva Ricardo P. Serralheiro 《Agricultural Water Management》1999,40(2-3):341-351
Traditional irrigation systems still cover a large area of irrigated lands in Portugal. The needs for competitiveness leads to the gradual abandon of traditional systems, resulting in social and economic impacts. Pressurised on-farm irrigation systems provide labour savings but imply important investments. Surface irrigation does not require expensive equipment and is low energy and low labour consuming, if modern systems are implemented. Flexible-pipe, gated-pipe, surge-flow valve and cablegation are the main equipment issues available to Portuguese farmers for modern surface irrigation practice. Conditions for application of these systems have been studied relative to different soil and topographic conditions. Plane land, either horizontal or sloped and undulated fields can be irrigated by surface systems, if a convenient design is accomplished. The adequacy of the irrigation systems has been evaluated and a cost-benefit study was carried out. A case study of a situation with undulated land, representative of South Portugal, is presented in this paper, comparing surface irrigation issues and a sprinkler system. Conclusions show a particular economic interest on adopting surge-valve, gated-pipe and cablegation. 相似文献
15.
A moving control volume approach was used to model the advance phase of a furrow irrigation system whereas a fixed control volume was used to model the nearly stationary phase and the runoff rate. The resulting finite-difference equations of the kinematic-wave model were linearized and explicit algebraic expressions were obtained for computation of advance and runoff rate. The solutions for the advance increment and the runoff rate were compared with the nonlinear scheme, the zero-inertia model, and a set of field data. A close agreement was found between the models and the field data. Assuming a constant infiltration rate, a differential equation was derived to estimate the error between the kinematic-wave model and the zero-inertia model in predicting the flow cross-sectional area along the field length. The differential equation and two dimensionless terms were used to define the limits for use of the kinematic-wave model in furrow irrigation. 相似文献
16.
Luciano Mateos 《Irrigation Science》2008,27(1):25-34
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. 相似文献
17.
我国温室产业近年来发展迅猛,由于面积、种植结构与密度等与大田差异较大,沿用大田滴灌系统的设计方法已不适宜,需要根据温室的具体条件确定设计方法。根据我国普通单栋温室情况,通过室内试验研究分析了入口压力、支管长度、毛管间距3个因素对滴灌系统中支管沿程压力分布的影响。结果表明:支管沿程压力分布的均匀性随支管长度的增加、毛管间距和首部压力的减小而降低。结合滴头的水力特性参数得出支管上的最大允许压力偏差为30.85%。毛管间距0.6、0.9和1.2m条件下,满足水力偏差要求的单栋温室支管最大铺设长度分别为20、40和60m。运用量纲分析方法将影响支管水头损失的基本量导出为3个无量纲量υd/ν、υ2/(g d)和L d/s2,通过多元回归建立支管水头损失的经验预测模型(R2=92.4%)。分析了支管能坡曲线的函数形式,回归得到了支管水头损失比和沿程压力分布模型。以上模型预测值与实测数据拟合效果良好,可用于温室滴灌系统水力计算及规划设计。 相似文献
18.
Dimensional analysis approach to estimate local head losses in microirrigation connectors 总被引：1，自引：0，他引：1
Danieli Bariviera Zitterell Jose Antonio Frizzone Osvaldo Rettore Neto 《Irrigation Science》2014,32(3):169-179
Local losses, which affect the uniformity of water application, are often ignored in the design of irrigation systems. Some accessories have no simple, efficient equations to estimate these losses. The main objective of this work was to develop an equation to estimate the local head loss in lateral passage connectors. Fifteen connector/pipe combinations were tested. The connectors were characterized by their internal diameters and dimensions. The local head loss was determined by subtracting the head loss on the connector and pipe from the head loss on the pipe. The parameters affecting the local head loss were defined as dimensionless terms using Buckingham’s theorem. A mathematical model was developed that presented a determination coefficient of 93.31 %. Elements such as the inner diameter of the connector, pipe length, connector, water flow velocity, Reynolds number and Froude number influenced the local head loss in the connectors. The model was compared with the observed data and presented excellent performance. It can be used to calculate the local head loss in lateral passage connectors. 相似文献
19.
传统畦灌模型多是基于非恒定渐变流方程建立的,在模拟变流量畦灌水流运动时的精度难以保障。本文综合分析了变流量畦灌过程中田面水流的运动状况,将其按照边界条件的不同划分为恒定流量进水阶段、变流量进水阶段、畦首消退阶段、田面消退第1阶段、田面消退第2阶段等5个阶段,基于非恒定渐变流方程和非恒定急变流方程构建了适用于变流量畦灌系统的渐变流-急变流数值模型,通过2组恒定流量畦灌、4组变流量畦灌的田间试验以及2组文献资料中的畦灌试验数据对模型进行了验证。结果表明,渐变流-急变流畦灌模型模拟值与现场实测结果吻合较好,模拟推进时间决定系数R2均大于0.96、模拟消退时间R2大于0.90。与目前常用的WinSRFR模型相比,渐变流-急变流畦灌数值模型在模拟恒定流量畦灌方面具有相似的精度,且在模拟变流量畦灌方面精度更高。渐变流-急变流畦灌模型可以较精准地模拟变流量畦灌的水流运动状况,可为分析变流量畦灌系统、优化变流量畦灌方案提供支撑。 相似文献
20.
Basin irrigation systems were designed for a constant flow rate. The operation of the designed system was simulated using the zero-inertia model of surface irrigation. The performance of the system was obtained for modified design flow rates. Three patterns of flow variation — sinusoidal, initially low then high, and initially high then low — were studied. The average of a variable flow rate in a given simulation equalled, was less than and greater than the design flow rates. The flow rate variations did not lower the performance of the system when the average flow rate during irrigation was greater than or equal to the design flow rate. Significant reductions in system performance occurred when the average flow rate was equal to 50% of the design. Basin irrigation systems should be designed for the average of the variable flow rate available at the field outlet. 相似文献