畦田灌溉水流演进计算简化模型研究

在对水量平衡模型进行修改的基础上,结合零惯量运动方程,以水量平衡方程为基础,对畦灌水流演进模型的结构进行了研究。应用无因次系统模型,求得了模型的显式和隐式解。该模型可以用来计算畦灌水流演进距离。对山东省陈垓引黄灌区畦灌水流演进计算结果表明,该模型比以往使用的模型简单,计算精度与较复杂的零惯量模型的计算精度相当。模型计算不需编程,可以用手算完成全部计算过程,解决了传统的水量平衡模型无法解决的问题。     

畦田灌溉水流演进计算简化模型研

在对水量平衡模型进行修改的基础上，结合零惯量运动方程，以水量平衡方程为基础，对畦灌水流演进模型的结构进行了研究。应用无因次系统模型，求得了模型的显式和隐式解。该模型可以用来计算畦灌水流演进距离。对山东省陈垓引黄灌区畦灌水流演进计算结果表明，该模型比以往使用的模型简单，计算精度与较复杂的零惯量模型的计算精度相当。模型计算不需编程，可以用手算完成全部计算过程，解决了传统的水量平衡模型无法解决的问题。     

Dimensionless advance curves for infiltration families

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.     

Modeling and error analysis of kinematic-wave equations of furrow irrigation

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.     

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     

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     

Infiltration parameters from optimisation on furrow irrigation advance data

Knowledge of the soil infiltration parameters is necessary for efficient furrow irrigation. A method is proposed for the determination of the parameters in the Kostiakov-Lewis infiltration equation from measurements of the furrow irrigation advance and inflow. The method employs a volume balance model using optimisation to minimise the error between the predicted and measured advance and differs from existing approaches in that only advance data and inflow rates are required. The average cross sectional area of the furrow and the final infiltration rate are treated as fitted parameters and need not be measured. A simple but effective optimisation algorithm is developed which allows for the solution of the four parameters without user input. The speed and simplicity of the optimisation may lead to application in real-time control of furrow irrigation. Received: 16 August 1995     

Infiltration parameters from surface irrigation advance and run-off data

A computer model was developed to employ runoff data in the calculation of the infiltration parameters of the modified Kostiakov equation. The model (IPARM) uses a simple volume balance approach to estimate the parameters from commonly collected field data. Several data sets have been used to verify the procedure. Infiltration parameters were calculated using both advance and runoff data combined and advance data alone. Simulations of each example using SIRMOD were compared to the measured data to identify the possible benefits of the procedure. The inclusion of runoff did not compromise the ability to reproduce the advance curve however the simulations are more capable of reproducing the measured runoff rates and volumes and therefore offer better estimations of the total volume applied to the soil (in one case a reduction in error of the total infiltration from 22% to 1%). This procedure will be of most benefit where the infiltration parameters are expected to represent soil hydraulic characteristics for times greater than the completion of the advance phase. Further analysis has shown that the infiltration parameters are more sensitive to runoff than the advance highlighting the requirement for accurate field measurement and a weighting factor between the advance and runoff errors.     

Evaluation of various quick methods for estimating furrow and border infiltration parameters

For estimating infiltration properties of surface irrigation, some ‘quick’ and easy methods have been developed. The main objective of this study was to evaluate different ‘quick’ methods and to compare the obtained results with two new methods proposed based on the Shepard one-point approach. For this purpose, data sets measured in six borders and five furrows were used for evaluating different methods. Using the volume balance equation and estimated infiltration parameters, the total infiltrated volume and advance times were predicted to evaluate the accuracy of estimated infiltration parameters. The results showed that the modified Mailapalli and Elliott and Walker methods provided the lowest errors for both furrow and border irrigations. The Elliott and Walker method predicted advance times with highest accuracy. There was very small difference between the Shepard and new proposed one-point methods. The performance of the Elliott and Walker method was slightly better than the new proposed two-point method for the experimental furrows, while a minor difference was found for the experimental borders. The results also showed that the performance of the Elliot and Walker method would be improved using binomial approximation instead of Kiefer approximation.     

基于WinSRFR软件的河套灌区水平畦田规格的优化

为了提升河套灌区的土地资源与灌水质量,以大田水平畦灌试验水流推进与消退实测数据为基础,采用数值模拟和分析方法,对河套灌区现状畦田规格进行优化设计.通过WinSRFR软件系统设计功能,基于田间各灌水要素,采用水量平衡法计算灌水质量指标并采用零惯量模拟率定.模拟出不同畦田规格组合的灌水质量指标等值线图,确定了满足灌水要求并具有较高灌水质量的灌溉系统的优化范围,考虑土地权属与畦田规格现状,提出了典型田块设计方案.方案1:合并田-毛渠-田,畦长为102 m、畦宽为65~95 m,畦田面积为6 670 ~10 005 m².方案2:合并田-毛渠-田-路-田,畦长为154 m、畦宽为65~110 m,畦田面积为10 005 ~16 675 m².     

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.     

Accounting for temporal inflow variation in the inverse solution for infiltration in surface irrigation

A simple modification of the volume balance equation of the IPARM model is presented to facilitate the use of variable inflow. Traditional approaches for estimating infiltration from advance and/or runoff have merely considered the constant or step inflow case. Whenever this assumption is violated, significant uncertainty is introduced into the estimated infiltration parameters. Evaluation of the procedure with a number of data sets has demonstrated significant improvements in the estimates of infiltration parameters. Furthermore, the technique has shown that a portion of the apparent variability in estimated soil intake rates between furrows in the same field is a consequence of the constant inflow assumption. Accounting for the variable inflow to estimate infiltration functions, both standardised the shape of the infiltration curve and reduced the magnitude of the variation between curves. The proposed technique remains restricted by limitations similar to that of other volume balance models but offers greater performance under typical inflow variations often experienced in practice.     

Furrow infiltration estimation from time to a single advance point

A simple and quick method to determine the Soil Conservation Service (SCS) intake function in furrow irrigation is presented. The time of advance at only one location of the field, inflow rate, and average flow area are the only field data required to estimate the two parameters of the SCS infiltration equation. The dependence of the two intake parameters, k and α, of the SCS intake function was expressed analytically and then the single unknown intake parameter of the SCS function, α, could be determined by applying a volume–balance (VB) equation using a power advance assumption. Estimates of infiltration by the proposed method were compared with measured furrow infiltration data and a recently developed one-point method which uses the two parameter Philip infiltration equation, but is restricted by an assumption that the advance trajectory follows the power function with the exponent of 1/2. It is shown that the proposed one-point method can give more accurate results than the previous one-point method.     

Infiltration in surface irrigated swelling soils

Infiltration characteristics for border strip irrigation at two sites with swelling clay soils were examined. Volume infiltrated was calculated from flow onto the field monitored with flow meters; depth of water in the soil estimated from soil samples taken before and after irrigation; and the advance profile which was used to calculate the volume infiltrated with time. Volume infiltrated was compared with volume of cracks before irrigation.Linear advance and observed crack closing supported the hypothesis that infiltration approached zero after about 10 min. Volume of cracks was less than 20% of the volume infiltrated. Wetting front was 3–10 times greater than depth of observed surface cracks. There was no significant correlation between intake opportunity time and depth of infiltration, but elevation irregularities were related to infiltration.     

Simulation of furrow irrigation practices (SOFIP): a field-scale modelling of water management and crop yield for furrow irrigation

Because of the spatial and temporal variabilities of the advance infiltration process, furrow irrigation investigations should not be limited to a single furrow irrigation event when using a modelling approach. The paper deals with the development and application of simulation of furrow irrigation practices (SOFIP), a model used to analyse furrow irrigation practices that take into account spatial and temporal variabilities of the advance infiltration process. SOFIP can be used to compare alternative furrow irrigation management strategies and find options that mitigate local deep-percolation risks while ensuring a crop yield level that is acceptable to the farmer. The model is comprised of three distinct modelling elements. The first element is RAIEOPT, a hydraulic model that predicts the advance infiltration process. Infiltration prediction in RAIEOPT depends on a soil moisture deficit parameter. PILOTE, a crop model, which is designed to simulate soil water balance and predict yield values, updates the soil moisture parameter. This parameter is an input of a parameter generator (PG), the third model component, which in turn provides RAIEOPT with the data required to simulate irrigation at the scale of an N-furrow set. The study of sources of variability and their impact on irrigation advance, based on field observations, allowed us to build a robust PG. Model applications show that irrigation practices must account for inter-furrow advance variability when optimising furrow irrigation systems. The impact of advance variability on deep percolation and crop yield losses depends on both climatic conditions and irrigation practices.     

并联光电跟踪平台建模与工作空间闭环控制

针对某小型浮式并联光电跟踪平台体积小、负载惯量大的特点,提出了一种以少自由度并联机构为基础的改进型并联机构。推导了平台的系统雅可比矩阵,基于拉格朗日方法得到了平台的动力学模型。针对并联平台的内部耦合、参数不确定和干扰的问题,基于工作空间提出了一种带有干扰观测器的复合滑模控制策略。利用干扰观测器观测系统干扰,减小干扰上界,基于反步法设计了滑模控制器跟踪目标轨迹并进一步抑制未观测出的干扰。仿真和实验结果表明,提出的数学模型和控制策略使平台跟踪误差减小到±0.08°,为PID控制误差的14.5%,特别适用于并联平台等内部耦合及干扰较显著的场合。     

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.     

膜孔灌溉田面综合糙率系数的确定

根据膜孔灌溉田面水流运动特性 ,建立了膜孔灌溉田面水流运动零惯性量数学模型 ,并将其与优化理论相结合 ,提出了确定膜孔灌溉田面综合糙率系数的优化模型。实例计算与方法验证表明 ,该方法能够简单而有效地确定膜孔灌溉田面综合糙率系数。该研究成果为膜孔灌溉理论与技术的进一步研究奠定了基础     

二维撒施畦灌地表水流溶质运移模型：II验证

基于撒施施肥方式下畦灌试验数据,从传统平均相对误差和马尔科夫随机过程两个角度,对二维撒施畦灌地表水流溶质运移模型进行了验证．基于传统平均相对误差的结果表明,模型模拟的水流推进与消退的平均相对误差分剐为4．98％和9．37％,水量平衡误差为0．28％,模拟各测点的溶质质量浓度变化过程平均相对误差为8．64％-14．22％,溶质平衡误差O．58％,构建的模型不仅具有较好的模拟二维撒施畦灌地表水流运动和溶质质量浓度变化过程的能力,还具备较佳的水量与溶质质量守恒性．基于马尔科夫随机过程的计算结果表明,地形项的随机性对模拟效果的影响为88．68％-96．21％,而畦面土壤物理属性等模型未能考虑因素的随机性对各测点溶质质量浓度变化的影响为3．79％-11．32％,因此仅考虑畦面微地形分布随机性的模型,具备优良的二维撒施畦灌地表水流和溶质运移过程的模拟性能．构建的模型为评价撒施施肥方式下的畦灌施肥系统性能,提供了合理完备的实用性数值模拟工具．     

A spreadsheet model to evaluate sloping furrow irrigation accounting for infiltration variability

A spreadsheet model was developed to evaluate the performance of furrow irrigation that accounts for soil variability and requires few field measurements. The model adjusts an advance trajectory to three (advance distance, advance time) points and, similarly, it adjusts a recession trajectory to three (recession distance, recession time) points. The head of the furrow (distance = 0) is one of the points used to adjust both trajectories. It then calculates the parameters of the infiltration equation using the two-point method (based on the volume balance equation with assumed surface shape parameters). The model gives the option to enter an estimate of the soil infiltration variability in order to account for this variation when calculating irrigation performance indicators. The combination of variance technique was used for this purpose. A set of irrigation performance indicators (distribution uniformity, application efficiency, tail water ratio, deep percolation ratio and deficit coefficient) is calculated, assuming that the infiltrated water follows a normal frequency distribution. To illustrate the evaluation method, it was applied to three irrigation events conducted on a sunflower field, with 234 m long furrows spaced 0.75 m apart. The evaluations were performed in two 3-furrow sets. The application efficiency was satisfactory in the first irrigation, but low in the other two. Uniformity was high in all three irrigations. The performance indicator that was most affected by soil variability was distribution uniformity. Considering soil spatial variability was important for more realistic determination of the infiltrated water distribution, and therefore of the deep percolation, but it had less importance for the determination of the application efficiency, due to the relevance of runoff in our field application.