Derivation of shape factors for border irrigation advance

Using a linear advance function, a derivation of shape factors for border irrigation advance is presented. Using the proposed derivation, irrigation advance length is predicted for two sets of data reported in the literature. A close agreement is found between observations and predictions. Results of this study are compared with those of others for the same data.     

An improved solution for the infiltration advance problem in irrigation hydraulics

The irrigation advance problem in irrigation hydraulics has been spread across the engineering and soil science literature over a number of decades. The Lewis–Milne framework has been used extensively, but one problem has been to find a suitable infiltration equation. The infiltration advance solutions of Philip and Farrell, and Collis-George and Freebairn are compared to a new solution based on the linear soil infiltration equation. It is shown that the linear soil solution is able to give similar results to the Philip and Farrell solution at early stages of infiltration when this is valid, and the Collis-George and Freebairn solution at longer times when this is valid. The linear soil infiltration advance solution presented here is the first using physically meaningful parameters which is able to give adequate infiltration and advance behaviour over all time scales. To further test the linear soil concept, we inversely fit irrigation advance data to get the sorptivity, saturated hydraulic conductivity and infiltration rate behaviour of the soil using all three infiltration equations. The linear soil is shown to give the best fit for the infiltration behaviour to the measured results with an average r ² of 0.98 compared to 0.84 for Philip and Farrell and 0.77 for Collis-George and Freebairn. The linear soil model was also the best fit using other statistical tests such as RMSE and RSR.     

Surface water storage independent equation for predicting furrow irrigation advance

 A simple equation is developed to predict the advance rate of flow in furrows. The proposed equation does not use as inputs the data required for estimating the surface storage. In previous surface storage independent models it is generally assumed that the surface storage volume is negligible (compared with infiltrated volume). The proposed equation is derived by eliminating the surface storage term from the original volume balance equation and its derivative. The suggested equation thus needs no assumption about the magnitude of the value of surface storage volume. Infiltration is described by the extended Kostiakov-Lewis formula. The suggested equation is compared with observed furrow data, with the numerical kinematic-wave model and with a recently developed numerical model that ignores surface storage. For furrows in which the surface storage is not significant (compared with infiltration) all models predict advance reasonably well. For furrows in which the surface storage is relatively important, the proposed equation predicts advance with good accuracy, whereas previous models ignoring the surface storage greatly overpredict the advance rate. Received: 20 October 1998     

Determination of infiltration rate from border irrigation advance and recession trajectories

A volume-balance technique utilizing irrigation advance and recession functions, numerical integration, and an optimization procedure was developed to determine infiltration parameters. The procedure is simple yet rational and accounts for spatial variability of soil characteristics. The required data are flow rate, the coefficients and exponents of the advance and recession functions, and inflow shut-off time. In a field experiment on a clay loam soil (typical of southern Alberta) at the Lethbridge Research Centre, infiltration rates estimated by this technique were similar and in close agreement with those measured with a ring infiltrometer. Except for two border strips, there were no significant mean differences between simulated (I_s) and measured (I_m) infiltration rates. In the two non-conforming border strips, field measured infiltration rates were higher than those simulated with the volume balance approach, most likely due mainly to spatial variability of soil characteristics and partly to lateral flow which occasionally occurs when measuring infiltration with a ring infiltrometer.     

An optimization technique for estimating infiltration characteristics in border irrigation

Because infiltration characteristics of soil vary spatially and temporally in a field, available methods for their estimation in border irrigation are either not suitable or have limitations for their field use. Here an optimization technique based on the volume balance approach is developed for estimating infiltration characteristics. Five different infiltration equations, viz, Kostiakov, modified Kostiakov, Philip, Horton, and Collis-George were employed. The method was applied to data obtained from experiments on border irrigation for five different soil types. All equations, except that of Philip, fitted the data satisfactorily. A possible explanation for this relates to assumptions inherent in its derivation and the spatial variability of infiltration in the field.     

Design procedure for border irrigation

An open-end graded border design procedure is presented. The proposed method based on the principle of mass conservation requires Kostiakov and Manning formulations for infiltration and roughness, respectively. The key assumption of the present design procedure is that the minimum infiltrated depth occurs at the lower border end and is equal to the required depth of infiltration. The philosophy behind the proposed design procedure is to select the appropriate flow rate q ₀ and cutoff time T _cof for given field conditions including the field geometry (field length and slope) and the soil characteristics (including the surface roughness coefficient and infiltration parameters). The results of two example border fields were in close agreement with those obtained from a zero-inertia model. Received: 23 December 1996     

Solution of the kinematic-wave equations for border irrigation

A method is developed to obtain solutions to the kinematic-wave equations for border irrigation. The accuracy of this method is assessed by comparing the results with the kinematic-wave train (KWT) method previously reported to be accurate. Experimental data on freely draining borders were utilized for comparison and evaluation of these methods. The prediction error for advance time resulting from the two methods was comparable: it was below 25% for three sets of data but as high as 50% for one set of data. The prediction error for recession time was also comparable: below 6% for the same three sets of data but 14.0% for one set.     

Evaluating infiltration for border irrigation models

The infiltration characteristics of a soil are important to the design, evaluation and management of border irrigation systems. The use and verification of border irrigation models also rely heavily on infiltration. This paper presents a technique for determining infiltration when detailed information is available on the total infiltrated volume during the irrigation which can be obtained from measurements of inflow, outflow, and water depths on the border strip. The method uses a volume balance at progressive times and is an extension of earlier work. Data from this method were used as input to the zone-inertia border irrigation model and good agreement was found between measured and computed values of advance, recession, runoff rates and volumes, and surface water depths.     

Evaluation of infiltration measurements for border irrigation

A number of methods are discussed for obtaining a reasonable estimate of the infiltration function for irrigation borders. Data from ring infiltrometers are fit to power functions for infiltration rate and cumulative infiltration rate versus time and to a branch function where the infiltration rate is not allowed to go below some value (called the final infiltration rate). A volume balance within the border is used to adjust the data to give a better indication of the “average” infiltration conditions over the border. The results of Bouwer's method, which uses a series of borders as infiltrometers, were compared to the results of ring data for actual field data. Bower's method was also analyzed by developing advance and recession curves with the zero-inertia border-irrigation model with a known infiltration rate. The zero-inertia model was also used to examine the effect of different infiltration functions for specific examples (resulting from different irrigations or different estimation methods) on the application of water by surface irrigation.     

A quasi-steady state integral model for border irrigation

Summary A quasi-steady state integral (QSSI) model was developed for irrigation on freely draining borders. A semi-analytical method was used for solving the governing equations. The model results compared favorably with experimental data from 13 experimental borders for advance and from 4 experimental borders for recession. The absolute average percent deviation (APD) between calculated and observed advance times varied between 13.1 and 26.6 for 4 data sets and between 9.2 and 18.8 for 9 data sets. The APD for recession times varied between 1.7 and 5.7 for 4 data sets. The calculated advance times were smaller than observed values for these borders. For constant infiltration parameters, the border bed roughness was found to be the single most important parameter affecting model results.     

A numerical kinematic wave model for border irrigation

Summary A numerical model is developed to solve kinematic wave equations of border irrigation. This model accommodates transient infiltration, which may be defined by any of the well known infiltration models. Test runs, performed using different incremental values of time and space, were found to give results within 5% of one another, thus showing the stability of the numerical model. The conservation of volume of water was satisfied within 1% error at different values of time and space. Three sample data sets from field experiments were used to analyze the numerical model.     

A quasi-steady state integral model for closed-end border irrigation

A quasi-steady state integral (QSSI) model was developed for irrigation on closed-end (CE) borders. A semi-analytical method was used for solving the governing equations. The model results compared favorably with experimental data from 18 experimental CE borders. The absolute average percent deviation (APD) between calculated and observed advance times varied between 5.3 and 28.5. The APD for recession times varied between 1.0 and 37.3. The calculated advance times were found to be consistently smaller than observed values for these borders. For constant infiltration parameters, the border bed roughness was found to be the single most important parameter affecting model results.     

畦灌灌水技术参数的多目标模糊优化模型

为了提高畦田灌水质量和高效用水,采用田间水利用系数的数值模拟模型求解田间水利用系数和灌水均匀度,以两者为目标建立了畦灌灌水技术参数的多目标优化数学模型.分析了该优化问题的模糊性,提出了模型的模糊解法.利用所建立的多目标模糊优化模型和计算方法,对试验畦田进行了灌水技术参数的优化计算.根据优化计算所确定的灌水技术参数,即单宽流量和灌水时间,进行田间灌水试验,测定和计算了田间水利用系数和灌水均匀度,并与优化计算的目标值进行了比较.结果表明,实测值与计算目标值有较好的一致性.因此,所提出的灌水技术参数优化模型及解法,可同时满足节水与保证灌水质量的要求.     

An approach to estimating the potential production benefits from improved irrigation water management for rice

Production benefits of improved allocation of irrigation water are often difficult to measure. In situations of irrigated wet rice cultivation, bothex post estimates of such benefits andex ante estimates of the maximum potential benefits of further improvements in allocation of a given water supply are possible using a conceptual framework which (1) functionally relates weekly water supplies to weekly measures of average water shortage on individual paddy fields; (2) aggregates the weekly water shortage measures into a seasonal water shortage index; and (3) relates, via a production function, the seasonal water shortage index to yields. An empirical application of this framework estimates the potential increase in production from further improvements in water allocation in one Philippine irrigation system to be negligible.     

A mathematical model for border irrigation III. Evaluation of Models

Summary This paper, the concluding one of a series of three, evaluates 9 border irrigation models (3 for advance, 3 for vertical recession and 3 for horizontal recession) which have closed-form solutions. Experimental data from 10 vegetated and nonvegetated borders are used to compare these models with the proposed (Singh-Yu or SY) model derived in Parts I and II. The proposed model is found to be superior in terms of accuracy, ease of application, and physical basis of parameters.     

Prediction of the advancing wetting front in border strip irrigation

Summary Four methods of predicting the advance of the water front in border irrigation are compared for nine sets of experimental data reported in the literature. The water balance method (Bishop et al., 1967), the method of Katopodes and Strelkoff (1977) based on zero inertia hydraulics and the method of Michael (1978) enable the distances that the wetting front advances to be calculated for various advance times. A new method presented in this paper, although less accurate than that of Katopodes and Strelkoff, and particularly for nearly flat border strips, enables the coefficients of exponential advance equations to be simply calculated. The dependence of all four methods on reliable infiltration characteristics and on the accurate prediction of the Manning roughness coefficient is emphasized.Lecturer and Visiting Senior Lecturer, respectively     

灌溉渠道生态化设计研究进展

针对灌区硬质化渠道导致生物栖息环境退化和水陆生物通道阻隔的问题,主要从生态护坡技术、营造生境条件、构建生物通道等方面,总结分析了国内外关于灌溉渠道生态化设计的方法和实践.研究表明,现有研究主要集中在渠道材质自然化、表面多孔粗糙化、流况多样化、断面和地形多样化、植栽绿美化、生物通道与生态保育等方面,中国的相关研究与实践尚处于起步阶段.在阐述生态型渠道概念与作用的基础上,归纳分析了生态衬砌形式、新型生态护坡材料和植被工程护坡等生态护坡技术,渠道坡面生态孔洞、渠底多样化和多孔质空间等生境条件构建方法,以及硬质护坡坡面生态改造和边坡植被生态修复等生物通道构建方法,并对其特点和适用性进行了对比分析,总结提出了中国灌溉渠道生态化设计研究的热点问题和发展方向.     

Evaluation on the potential of improving border irrigation performance through border dimensions optimization: a case study on the irrigation districts along the lower Yellow River

In the Yucheng region along the lower reach of the Yellow River, current border irrigation systems in all three irrigation districts have low irrigation performances with the applied depth per irrigation event >150 mm, and application efficiency <65 %. It is often difficult to change irrigation practices, and rates of adoption are usually slow for China’s small-scale farmers. This study emphasizes the feasibility of optimizing border dimensions in border irrigation taking into consideration the existing irrigation conditions and farmers’ methods of irrigation practice. The performances of current border irrigation systems and improved systems were evaluated using agricultural irrigation survey data, field experimental data, and a simulation model. The irrigation conditions, that is, inflow rate, border dimensions, and relative cutoff distance, in the irrigation districts were found to be diverse. However, after border dimensions were optimized through simulation and field testing, it was determined that the applied depth per irrigation event could be decreased by an average of 49 mm, and the application efficiency could be increased on average by 26.7 % in the three irrigation districts. The annual potential amount of water savings among the three districts was calculated to be approximately 5,551 × 10⁴ m³ in the Yucheng region. Optimizing border dimensions is a practical technology for small-scale farming practices in the irrigation districts along the lower Yellow River.     

Application of kinematic wave equations to border irrigation design

Accuracy of the kinematic wave (KW) approximation was tested on 31 experimental irrigation borders by computing the KW number and its modified version. In a majority of cases, this approximation was found to be sufficiently accurate. A KW model, reported previously, was used to derive dimensionless advance and recession curves for application to border irrigation design. These curves can be developed for a wide range of design variables and parameters for ready practical use. A step by step design procedure, based on this model is presented. Its validity was tested by comparing observed irrigation efficiencies with those computed by the model. A close agreement between computed and observed efficiencies suggests that the KW model is reasonably accurate. Its simplicity and physical basis may justify its large-scale field application.     

不同畦面结构下地面灌溉效果的对比分析

为研究畦面结构变化对地面灌溉效果的影响,在4种不同畦面结构的大田灌溉试验基础上,用WinSRFR3.1模型对平作畦灌、细沟灌、畦作浅沟灌和微垄沟灌的田面土壤特性参数和灌水效果进行估算和模拟,比较了不同灌溉方式由于畦面结构改变引起的田面土壤特性和灌水效果差异,并提出不同畦面结构的适宜畦田规格。研究认为,不同畦面结构的田面糙率系数和土壤入渗特性差异明显,微垄沟灌糙率系数最大而平作畦灌糙率系数最小,平作畦灌入渗速率最快而畦作浅沟灌入渗速率最慢;对长畦田来说,畦作浅沟灌灌水效果最好,微垄沟灌次之,平作畦灌最差;在