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.     

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.     

Effects of water infiltration and storage in cultivated soil on surface irrigation

Surface irrigation analysis and design require the knowledge of the variation of the cumulative infiltration water Z (L) (per unit area) into the soil as a function of the infiltration time t (T). The purpose of this study is to evaluate water infiltration and storage under surface irrigation in an alluvial clay soil cultivated with grape yield, and to determine if partially wetted furrow irrigation has more efficient water storage and infiltration than traditional border irrigation. The two irrigation components considered were wet (WT) and dry (DT) treatments, at which water applied when available soil water reached 65% and 50%, and the traditional border irrigation control. Empirical power form equations were obtained for measured advance and recession times along the furrow length during the irrigation stages of advance, storage, depletion and recession. The infiltration (cumulative depth, Z and rate, I) was functioned to opportunity time (t_o) in minute for WT and DT treatments as: Z_WT = 0.528 t_o^0.6, Z_DT = 1.2 t_o^0.501, I_WT = 19 t_o^−0.4, and I_DT = 36 t_o^−0.498. The irrigation efficiency and soil water distribution have been evaluated using linear distribution and relative schedule depth. Coefficient of variation (CV) was 5.2 and 9.5% for WT and DT under furrow irrigation system comparing with 7.8% in border, respectively. Water was deeply percolated as 11.88 and 19.2% for wet and dry furrow treatments, respectively, compared with 12.8% for control, with no deficit in the irrigated area. Partially wetted furrow irrigation had greater water-efficiency and grape yield than both dry furrow and traditional border irrigations, where application efficiency achieved as 88.1% for wet furrow irrigation that achieved high grape fruit yield (30.71 Mg/ha) and water use efficiency 11.9 kg/m³.     

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.     

Evaluation of surface irrigation as a function of water infiltration in cultivated soils in the Nile Delta

As sources of irrigation water are decreasing, efficient use of surface irrigation is essential. The purpose of this study is to determine if partially-wetted furrow irrigation has more efficient water storage and infiltration than traditional border irrigation in an alluvial clay soil under cultivated grape production. The two irrigation components considered were wet (WT) and dry (DT) treatments, at which water was applied when available soil water reached 65 % and 50 %, and the traditional border irrigation control. Empirical power form equations were obtained for measured advance and recession times along the furrow length during the irrigation stages of advance, storage, depletion and recession. Coefficient of variation (CV) was 5.2 and 9.5 % for WT and DT under furrow irrigation system comparing with 7.8 % in border, respectively. Water was deeply percolated as 11.9 and 19.2 % for wet and dry furrow treatments respectively, compared with 12.8 % for control, with no deficit in the irrigated area. Partially-wetted furrow irrigation had greater water-efficiency and grape yield than dry furrow and traditional border irrigation, where application efficiency achieved as 88.1 % for wet furrow irrigation that achieved high grape fruit yield (30.71 Mg /ha). The infiltration (cumulative depth, Z and rate, I) was functioned to opportunity time (t ₀ ) in minute for WT and DT treatments as: Z _WT ?=?0.528?t ₀ ^0.6, Z _DT ?=?1.2?t ₀ ^0.501, I _WT ?=?19?t ₀ ^?0.4, I _DT ?=?36?t ₀ ^?0.498. Empirical power form equations were obtained for measured advance and recession times along the furrow length during the irrigation stages of advance, storage, depletion and recession. The irrigation parameters and coefficients, and soil water distribution have been also evaluated.     

肥液浓度和生物质掺混量对微润灌溉入渗特性的影响

为了探明肥液质量浓度和生物质掺混质量比对微润灌溉土壤水分入渗特性的影响,采用室内土箱模拟试验的方法,设置3个肥液质量浓度水平(清水F₀:0 mg/L,低浓度F_L:200 mg/L,高浓度F_H:400 mg/L)和4个生物质掺混质量比水平(自然风干土B₀:0 g/kg,低掺混量B_L:15 g/kg,中掺混量B_M:30 g/kg,高掺混量B_H:45 g/kg),以发酵腐熟花生壳粉末为掺混生物质,研究微润灌溉的水分入渗速率、累积入渗量、湿润体体积以及湿润体质量含水率的分布特征.试验结果表明:肥液质量浓度和生物质掺混质量比对微润灌溉的初始入渗速率、稳定入渗速率、累积入渗量和湿润体质量含水率均值影响均具有统计学意义.与水平F₀B₀相比,增加肥液质量浓度和生物质掺混质量比可提高初始入渗速率13.02%~44.85%、稳定入渗速率13.50%~48.78%、累积入渗量5.65%~56.62%和湿润体质量含水率均值6.62%~30.09%;不同入渗时间内的累积入渗量符合Kostiakov模型;湿润体体积随肥液质量浓度和生物质掺混质量比增大而增大,且湿润体体积与入渗时间呈二次多项式关系;湿润体剖面面积和灌水均匀系数随肥液质量浓度和生物质掺混质量比增大而增大.     

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.     

Accounting for slow drainage and hysteresis in irrigation scheduling

Summary Soils continue to drain for several days following irrigation. Water budgeting predictions can be improved by accounting for this, provided hysteresis is recognized in the field capacity condition. Uncertainty in this condition was evident in experiments comparing predicted soil water depletions with neutron probe measurements. Comparisons were made for potato, lettuce and calabrese crops, irrigated by hose-reel machine. Best agreement between measurements and predictions was obtained when excess water storage above a lower field capacity condition was allowed for; corresponding to minimum root mean square errors of 3.2 mm–6.2 mm. These were comparable to the practical limits of uncertainty associated with field depletion measurements.     

Real-time prediction of soil infiltration characteristics for the management of furrow irrigation

The spatial and temporal variations commonly found in the infiltration characteristic for surface-irrigated fields are a major physical constraint to achieve higher irrigation application efficiencies. Substantial work has been directed towards developing methods to estimate the infiltration characteristics of soil from irrigation advance data. However, none of the existing methods are entirely suitable for use in real-time control. The greatest limitation is that they are data intensive. A new method that uses a model infiltration curve (MIC) is proposed. In this method a scaling process is used to reduce the amount of data required to predict the infiltration characteristics for each furrow and each irrigation event for a whole field. Data from 44 furrow irrigation events from two different fields were used to evaluate the proposed method. Infiltration characteristics calculated using the proposed method were compared to values calculated from the full advance data using the INFILT computer model. The infiltration curves calculated by the proposed method were of similar shape to the INFILT curves and gave similar values for cumulative infiltration up to the irrigation advance time for each furrow. More importantly the statistical properties of the two sets of infiltration characteristics were similar. This suggests that they would return equivalent estimates of irrigation performance for the two fields and that the proposed method could be suitable for use in real-time control.     

Estimation of advance and infiltration equations in furrow irrigation for untested discharges

The exponents of the advance and infiltration power laws have been shown to remain practically constant for different furrow irrigation discharges. Under this hypothesis, a procedure to estimate the advance and infiltration equations corresponding to untested discharges was developed. The proposed procedure was validated with different field experiments, obtaining satisfactory results for non-erosive discharges. However, significant deviations were obtained when erosive discharges were used. This behavior corroborates the hypothesis presented by some authors that the erosion and sedimentation processes occurring in furrow irrigation as a consequence of high surface velocities can reduce—and even suppress—the effect of the wetted perimeter on the infiltration rate. Finally, an equation was derived to predict the effect of the wetted perimeter on the infiltration parameters.     

Dimensional analysis in surface irrigation

The surface-irrigation design process requires multiple analyses of surface irrigations to test tentative values of design parameters in the search for an optimum. Preparation of general design charts can aid the design process if the users' test cases fall within the scope of the charts. The large number of independent variables in surface irrigation preclude the generation of charts covering the practical range of all independent variables, when these are in dimensioned form. Dimensionless formulations allow significant reductions in the amount of data generated and presented, without loss of generality. Relationships pertinent to surface-irrigation analyses and design are reviewed in dimensionless terms. Dimensionless forms are developed primarily from an examination of the equations governing surface-irrigation phenomena. Additionally, dimensionless forms are derived from a study of the dimensions of the pertinent variables, without recourse to the governing equations. The Buckingham Pi Theorem is derived in the context of surface irrigation. Different choices for reference variables, leading to different meanings for the resulting dimensionless parameters, have advantages and disadvantages for analysis and design of surface irrigation systems. The different systems developed in the past for border irrigation are reviewed and their consequences noted; new systems with potential for future studies are suggested. Particular attention is devoted to those dimensionless representations useful in design.     

沟灌条件下灌水沟入渗特性研究

为探明沟灌时灌水沟的水分入渗规律,从沟灌二维入渗过程、入渗湿润锋运移特性、累计入渗水量变化过程、土壤含水量分布等方面研究了沟灌的入渗特征及其影响,研究表明：灌水沟中水深、沟底宽、湿周对沟灌入渗过程均有明显影响。沟中水深增大,有利于加大侧向入渗,垂向入渗减少,而水深减小,会加大垂向入渗,增加深层渗漏。灌水沟底宽不影响灌水沟的侧向入渗,仅影响垂向入渗,底宽减小,垂向入渗深度相应减小,且土壤表面以下40 cm深以内水平向入渗深度平均值与最大垂向入渗深度的比值在沟底宽小时均大于沟底宽大时。合理的断面形式和大小有利于减小垂向入渗,加大水平侧向入渗,灌水沟断面形式为梯形断面时,宽深比近似为2效果最优。研究结果可为改进沟灌灌水技术提供参考。     

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.     

灌区灌溉用水时空优化配置方法

将传统的灌溉水量在作物间的优化分配模型和建立的渠系工作制度多目标优化模型与地理信息系统相集成,提出了基于空间决策支持系统的灌区灌溉用水优化配置的新方法.综合考虑了灌区内作物、土壤、气象站点、渠系布置的空间差异、年季间气象以及作物不同生育阶段对应参数的时间差异.与传统优化方法相比,该方法可根据管理者对优化精度的要求,灵活选择优化尺度,同时,简化了求解时空优化配水问题的繁琐程度,结果表现形式更加丰富.在此基础上建立的空间决策支持系统界面友好,运行效率高,可移植性和通用性强.经实例验证,优化后的配水方案与原配水方案相比较,灌溉总用水量减少296％,产量增加243％,水分生产率提高05 kg／m3,灌溉净效益增加168％.优化后配水方案具有将有限的水资源向经济价值较高作物转移的趋势.该方法为灌区灌溉用水优化配置提供了新思路.     

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.     

Choosing optimal design depth for surface irrigation systems

The surface irrigation system design was formulated as a mathematical programming problem. The minimum cost of a furrow irrigation system for a hypothetical case was calculated for different design depths (25, 51, 76, 102 and 127 mm). The crop yields and net returns were simulated for the given design depths. A design (depletion) depth of 51 mm was found optimal under the given conditions.     

Distribution and storage characterization of soil solution for drip irrigation

The increased use of marginal quality water with drip irrigation requires sound fertigation practices that reconcile environmental concerns with viable crop production objectives. We conducted experiments to characterize dynamics and patterns of soil solution within wet bulb formed by drip irrigation. Time-domain reflectometry probes were used to monitor the distribution of potassium nitrate (KNO₃) and water distribution from drippers discharging at constant flow rates of 2, 4 and 8 L h⁻¹ in soil-filled containers. Considering results from different profiles, we observed greater solute storage near the dripper decreasing gradually towards the wetting front. About half of the applied KNO₃ solution (48%) was stored in the first layer (0–0.10 m) for all experiments, 29% was stored in the next layer (0.10–0.20 m). Comparing different dripper flow rates, we observed higher solution storage for 4 L h⁻¹, with 45, 53 and 47% of applied KNO₃ solution accumulating in the first layer (0–0.10 m) for dripper flow rates of 2, 4 and 8 L h⁻¹, respectively. The results suggest that based on the volume and frequency used in this experiment, it would be advantageous to apply small amounts of solution at more frequent intervals to reduce deep percolation losses of applied water and solutes.     

第二讲现代地面灌溉机械设备(二)

3平地机械 土地是否平整,可显著影响灌溉水的利用率,一般进入田间的灌水量有1/3由于深层渗漏、积水、跑水等原因而浪费掉,即田间水利用系数只有0.6～0.7,其主要原因就是土地不平整.所以,平整土地是实施地面灌溉的先决条件.     

Application of the optimization method for estimating infiltration characteristics in furrow irrigation and its comparison with other methods

The infiltration characteristics of a soil vary spatially and temporally, and due to this the available methods for estimating the characteristics in furrow irrigation are either not suitable or have restrictions for their field use. An optimization method based on the volume balance approach, originally developed for estimating infiltration parameters in border irrigation, and using multiple observations of arrival time of the wetting front was modified for furrow irrigation. The method was applied to 13 irrigation events on furrows monitored on a farm in northern New South Wales, Australia. The soil type at the experimental site has a high clay content (up to 67%) and develops cracks when dry. In addition to the optimization method, one-point and two-point methods using observations of arrival time reported in the literature were also used. The accuracy of different methods was evaluated by comparing the calculated total volume of water infiltrated into the furrow with that observed in the field. The optimization method was the most accurate and the one-point and the two-point were the least accurate among three methods considered in the present study. A possible explanation for a poor performance of the one-point and two-point methods might be related to the assumptions made in the derivation of the methods and the unsuitability of the Philip and the Kostiakov infiltration equations used for the field condition in the present study.     

实用节水灌溉机械(设备)讲座第二讲现代地面灌溉机械设备(四)

5 低压输水管道 以管道替代土渠进行输水是世界各国认同的发展趋势.低压管道输水可以采用各种管材、管径的管道将水从水泵一直输送到田间进行地面灌溉,输水管道几乎全埋在地下.它所具有的优点主要是水的有效利用率高(约95%,比土渠提高30%～40%);工作压力低(≤0.02～0.2MPa,可节能20%～25%);节约土地(1%～3%);省工(40%);运行费用低;受外界干扰少(如气候、地形、经营体制、作物分区、灌水时间等);灌水快(管内流速快,流量集中),灌水周期短,节省农时;技术简单易学等.缺点主要是投资较大,但目前随着新管材、新工艺的出现,投资在日益下降.