Showing papers in "Journal of Irrigation and Drainage Engineering-asce in 1988"
TL;DR: In this paper, the authors present an alternative treatment that includes a spatially variable discharge function as part of the basic solution, which is based on a discharge that is uniform, although ramifications of the manufacturer's variability have been modeled based on the derived hydraulic profile.
Abstract: An important objective of any trickle system is a uniform distribution of water delivered through the emitters. Computation of flow distribution requires knowledge of the variables such as pressure, flow rate, length of lateral, characteristics of the orifices, and frictional loss in the system. Several studies have been reported that establish these relationships. In each study, the primary solution is based on a discharge that is uniform, although ramifications of the manufacturer's variability have been modeled based on the derived hydraulic profile. Herein, we present an alternative treatment that includes a spatially variable discharge function as part of the basic solution.
63 citations
TL;DR: In this paper, the characteristics of square-edge and round-nosed, rectangular, broad-crested weirs were studied under free-flow and submerged-flow conditions, and the effect of nonhydrostatic distribution of pressure was taken into account in the formulation of the momentum equation.
Abstract: The characteristics of square‐edged and round‐nosed, rectangular, broad‐crested weirs are studied under free‐flow and submergedflow conditions. The discharge coefficient, Cd, of a weir having height P and length L is found to be a function of the upstream head, H, causing flow and the radius, R, of the upstream top corner. For a given head, under free‐flow conditions, a semiempirical relationship between Cd, H/P, and R/P is derived using the momentum relationships. For the square‐edged weir, the effect of nonhydrostatic distribution of pressure is taken into account in the formulation of the momentum equation. In addition, for the round‐nosed weir, new relations are developed to supplement the existing results for square‐edged weirs. Experimental data are presented to validate the proposed dependence of Cd on H/P with R/P as the group parameter. Under drowned‐flow conditions, the submergence limit for a broad‐crested weir varies with the ratios H/P and R/P. The flow‐reduction factor for a given submergenc...
59 citations
TL;DR: In this paper, the authors describe a new analytical solution in system design based on the trickle lateral analysis described in the companion paper, which is used to illustrate applications of new analytical solutions.
Abstract: The trickle lateral analysis described in the companion paper is used to illustrate applications of a new analytical solution in system design. Examples are provided to point out the basic concepts and procedures based on this and related analytical solutions. Very simple and yet powerful design curves for different flow regimes are presented. Verification of the solution is also made by comparing the results with experimental measurements. The simplicity of the solution, coupled with the ease of including variable discharge, makes the analytical solution attractive for diversified uses in trickle system design.
51 citations
TL;DR: In this paper, a model is developed for simulating the vertical movement of water through a crop's root system, which is then coupled to a variably saturated flow model via a root extraction term that is a function of the water pressure gradient across the root-soil interface as well as soil and root parameters.
Abstract: A model is developed for simulating the vertical movement of water through a crop's root system The root‐water flow model is then coupled to a variably‐ saturated flow model via a root extraction term that is a function of the water pressure gradient across the root‐soil interface as well as soil and root parameters The resulting root‐soil water flow model is a coupled pair of partial differential equations that describe the macroscopic movement of water through a root‐soil system Rainfall, irrigation, and evaporation are treated as sources of potential soilsurface flux, and transpiration is treated as a source of potential root‐surface flux Solution of the model is accomplished by using a Galerkin finite element method The model is verified by comparing simulated and field measured soil‐water content levels The comparisons show a very good agreement between simulated and measured soil‐water contents The root extraction distribution, cumulative flow from an underlying water table, and sensitivity o
40 citations
TL;DR: In this article, a field experiment was conducted on a seasonally waterlogged, shallow loamy soil in Arrou, France, under temperate climate, where rainfall and drainage discharge were recorded on an hourly basis, as well as water tension profiles and water table levels at different distances from the trench.
Abstract: The subsurface drainage operation of shallow soils is characterized by sudden and brief peak flows followed by long‐lasting tail recessions. A field experiment was conducted on a seasonally waterlogged, shallow loamy soil in Arrou, France, under temperate climate. Rainfall and drainage discharge were recorded on an hourly basis, as well as water tension profiles and water‐table levels at different distances from the trench. Observed peak flows are related to sudden increases in the horizontal hydraulic gradients near the trench and to the stability of the water‐table shape. Using these results and extending Boussinesq's usual transient‐state approach, SIDRA, a theoretical model in which soil vertical heterogeneity is taken into account, has been elaborated and applied to simulate by finite differences hourly water‐table levels and drain flow rates. The paper compares observed and measured values of the winters of both 1980–81 and 1985–86.
39 citations
TL;DR: In this article, all friction headloss equations have an uncertainty in the estimation of pi, i.e., there is an unknown value of pi for each headloss equation, which affects pipe and pump sizing as well as the hydraulic balance of networks.
Abstract: Hydraulic friction loss in pipelines directly affects pipe and pump sizing, as well as the hydraulic balance of networks. All friction headloss equations have an uncertainty in the estimation of pi...
38 citations
TL;DR: In this article, the Laplace transformation, integral, and numerical solution methods to the Lewis and Milne surface irrigation volume balance equation are presented and discussed, and a simple and direct method based on the Kostiakov infiltration equation and the power advance equation is suggested for field use in determining infiltration from advance data and for calculations of irrigation efficiencies.
Abstract: Laplace transformation, integral, and numerical solution methods to the Lewis and Milne surface irrigation volume balance equation are presented and discussed. Six formulations of the volume balance equation are presented. These consist of combinations of one of three infiltration equation (Kostiakov, extended Kostiakov, or SCS) and one of two advance equations (power or SCS). A simple and direct method based on the Kostiakov infiltration equation and the power advance equation is suggested for field use in determining infiltration from advance data and for calculations of irrigation efficiencies. This method and formulation accurately predicted the field and laboratory runoff data analyzed in Part II of this paper.
36 citations
TL;DR: The effect of measurement uncertainty on infiltration measurements can be estimated so that the confidence interval of a mean or the actual infiltration variability level can be determined as mentioned in this paper. But, the effect of uncertainty on the accuracy of the inflow-outflow measurement is not discussed.
Abstract: Furrow infiltration and channel seepage are often measured with inflow-outflow measurements. Inaccuracy in the flow measurement will cause a larger uncertainty in the calculated infiltration. The infiltration rate determination uncertainty increases rapidly as the percent of the inflow that is infiltrated decreases. The effect of measurement uncertainty on infiltration measurements can be estimated so that the confidence interval of a mean or the actual infiltration variability level can be determined.
30 citations
TL;DR: In this article, three stochastic weather models are developed for use with nonpoint-source pollution simulation models that require sequences of daily precipitation and mean daily temperature, and two simple models have parameters that can be estimated from available secondary data.
Abstract: Three stochastic weather models are developed for use with nonpoint‐source pollution simulation models that require sequences of daily precipitation and mean daily temperature. Two simple models have parameters that can be estimated from available secondary data. Both generate temperature and precipitation independently. A third model represents a more sophisticated approach and requires primary data for parameter estimation. A model validation analysis was attempted using three U.S. weather stations. The first two models did not reproduce the higher‐order moments or the tail of the wet‐dry precipitation distribution. All models used normal temperature distributions which did not reproduce the higher‐order moments of the observed temperature distributions. Using historical and generated weather data as input to the Cornell Nutrient Simulation model, annual runoff and percolation, and dissolved nitrogen and phosphorus losses were compared. The third model gave output that was not statistically different fr...
29 citations
TL;DR: In this article, the LCH-ARTICLE-1988-007 Record created on 2007-04-24, modified on 2016-08-08, was used as a reference.
Abstract: Note: [82] Reference LCH-ARTICLE-1988-007 Record created on 2007-04-24, modified on 2016-08-08
28 citations
TL;DR: In this paper, records of short-duration rainfall (5 to 30 min. duration) from a dense network of recording rain gauges in southeastern Arizona indicate that flood peaks based on NOAA Atlas 2 for less frequent events (50-yr and 100-yr. frequencies) for small watersheds are underestimated.
Abstract: Small watershed storm runoff in the southwestern United States is dominated by intense, short-duration convective rains of limited areal extent. Most commonly, flood peak estimates are based on rainfall predictions found in the National Oceanic and Atmospheric Administration (NOAA) Atlas 2, a precipitation-frequency atlas for the Western United States. Records of short-duration rainfall (5 to 30 min. duration) from a dense network of recording rain gauges in southeastern Arizona indicate that flood peaks based on NOAA Atlas 2 for less frequent events (50-yr. and 100-yr. frequencies) for small watersheds are underestimated.
TL;DR: In this paper, an adjusted F factor to compute pressure head loss in pipes having multiple, equally spaced outlets is derived for any given distance from the first outlet to the beginning of the pipe.
Abstract: An adjusted F factor to compute pressure head loss in pipes having multiple, equally spaced outlets is derived for any given distance from the first outlet to the beginning of the pipe. The proposed factor is dependent on the number of outlets and is expressed as a function of the Christiansen's F factor. It may be useful to irrigation engineers to estimate friction loss in sprinkle and trickle irrigation laterals and manifolds, as well as gated pipes.
TL;DR: In this article, the flow features of a Venturi flume, constricted with sharp-edged, thin-plated elements, are investigated. But the authors focused on the head discharge equation for various constriction rates, the limit submergence, and the internal flow mechanism.
Abstract: The flow features of a Venturi flume, constricted with sharp‐edged, thin‐plated elements are investigated. These elements, located at both side walls of a rectangular duct, as are usually found in large municipal sewers, are fixed at the bottom and at the ceiling by a simple device. Particular attention is paid to the head‐discharge equation for various constriction rates, the limit submergence, and the discussion of the internal flow mechanism. The theoretical approach accounts for the effects of fluid separation from the constriction elements and for the streamline curvature. Compared to the conventional discharge equation, the effects of the contraction geometry, and the relative energy head are thus included. The final result corresponds to an explicit equation for discharge once the contraction geometry is fixed and the upstream flow depth is recorded. Design curves allow a rapid and precise determination of discharge.
TL;DR: In this paper, a friction correction factor (FCPF) was derived for the estimation of friction loss in a center-pivot irrigation system lateral, and the results obtained using the FCP were compared with the result obtained with the conventional FCP.
Abstract: A friction correction factor (Fcp) for use in the estimation of friction loss in a center-pivot irrigation system lateral is derived. The results obtained using the Fcp are compared with the result...
TL;DR: In this paper, a kinematic-wave model with spatial variability of infiltration is developed to solve directly for advance times, and the model is solved implicitly for flow area and time step using the double-sweep technique.
Abstract: A kinematic-wave furrow model with spatial variability of infiltration is developed to solve directly for advance times. In addition, infiltration varies with wetted perimeter. During advance, the system of nonlinear equations is solved implicitly for flow area and time step using the double-sweep technique. During runoff and recession, flow area is found explicitly cell-by-cell at each specified time step. Including spatially varying infiltration as well as wetted perimeter effects improves furrow irrigation simulation when compared with the results of previous kinematic-wave models.
TL;DR: In this article, Laplace transformation, integral, and numerical solutions and six empirical formulations to the Lewis and Milne surface irrigation volume balance equation were evaluated using field and laboratory data, and the results indicated that simple and direct method of analysis based on the Kostiakov infiltration equation and the power advance equation satisfactorily predicted observed runoff volumes.
Abstract: Laplace transformation, integral, and numerical solutions and six empirical formulations to the Lewis and Milne surface irrigation volume balance equation were evaluated using field and laboratory data. These formulations and the proposed solution methods are presented in Part I of this paper. The field data were from published experiments, and the laboratory data were obtained from a 61‐m model border with a computer‐controlled infiltrating bed which could simulate a wide range of infiltration characteristics. The results indicated that a simple and direct method of analysis based on the Kostiakov infiltration equation and the power advance equation satisfactorily predicted observed runoff volumes. Furthermore, this method accurately determined the infiltration characteristics that were simulated by the model border.
TL;DR: In this article, the authors present a method for describing and evaluating some of the major factors that cause nonuniformity in surface irrigation systems, including variations in opportunity times (e.g., caused by nonparallel advance and recession curves), variations in soil infiltration properties, variations in land grading, and variations in advance rates.
Abstract: This paper presents a method for describing and evaluating some of the major factors that cause nonuniformity in surface irrigation systems. Methods including the following are presented for statistically combining these effects: variations in opportunity times (e.g., caused by nonparallel advance and recession curves), variations in soil infiltration properties, variations in land grading, and variations in advance rates. A simulation model is used to test the derived equations for a typical example.
TL;DR: In this article, a power series approximation to a logarithmic term was used to directly calculate the accumulated infiltration for nonuniform soils, which can be used by engineers and hydrologists to predict the potential change in the depth of infiltration for discrete time steps.
Abstract: The solution for accumulated infiltration using the Green-Ampt equation requires an iterative solution. By using a power series approximtion to a logarithmic term, an equation has been developed to directly calculate the accumulated infiltration for nonuniform soils. A second equation developed primarily for computer models predicts the potential change in the depth of infiltration for discrete time steps. The expression is relatively simple and may be easily programmed for use in hydrologic models. The maximum error resulting from the power series approximation is 8% and will usually be much less. These solutions may be used by engineers and hydrologists to predict infiltration and runoff for vertically nonuniform soils without a time consuming iterative process.
TL;DR: Several methods for measuring the rate of infiltration in a volcanic ash soil are compared on the basis of field measurements as mentioned in this paper, and functional relationships among the infiltration rate equations are also obtained for each method of infiltration.
Abstract: Several methods for measuring the rate of infiltration in a volcanic ash soil are compared on the basis of field measurements. Methods that use stagnant water give lower values of soil infiltration rate than those that use flowing water. The performances of the Kostiakov and the modified Kostiakov infiltration equations are analyzed for seven methods. These equations closely match field data collected with each technique used. Functional relationships among the infiltration rate equations are also obtained for each method of infiltration.
TL;DR: In this article, the effect of changing the trajectory angle of a medium-sized irrigation sprinkler operating in windy conditions has been studied using a computersimulation model, which has been verified both in still air and under windy condition, and it has been shown that the optimal trajectory angle that maximizes distance of throw is a function of the wind velocity and varies from 29° to less than 5° in winds greater than 8 m/s.
Abstract: The effect of changing the trajectory angle of a medium‐sized irrigation sprinkler operating in windy conditions has been studied using a computersimulation model. The model, which has been verified both in still air and under windy conditions, shows that the trajectory angle that maximizes distance of throw is a function of the wind velocity and varies from 29° in still air to less than 5° in winds greater than 8 m/s. The advantage gained from trajectory angles greater than 25° in still air is quickly overcome by the disadvantages in range reduction and drift in relatively light winds. When choosing the appropriate trajectory angle, consideration should be given to the drop‐size distribution and the wind velocity, because wind drift and range both depend upon drop size and trajectory angle.
TL;DR: In this article, a two-stage programming approach is used to determine the optimal on-farm design and operation under different modes of volumetric equity and iso-efficiency, and a methodology to subdivide the project area into different distinct portions is developed.
Abstract: Project-scale optimal on-farm designs considering total water availability and also the variability in the on-farm parameters are obtained using a two-stage programming approach in a mode of maximizing the net benefits from the project area. This provides the basis for comparing the consequences of project-scale design and operation under modes of volumetric equity and iso-efficiency. A methodology to subdivide the project area into different distinct portions is developed. A sample application indicates that there could be a wide variation in flow requirements in all the three modes. Variations in net on-farm benefits under modes of project-scale optimality and volumetric equity are also large. The sample study indicates that the iso-efficiency design results in near-optimal project-scale returns with uniform unit benefits in the different areas.
TL;DR: In this article, the unsupervised classification technique of Earth Resources Laboratory Application Software (ELAS) was used to determine land use/land cover classifications using Landsat Multispectral Scanner System (MSS) data.
Abstract: Landsat Multispectral Scanner System (MSS) data in conjunction with the unsupervised classification technique of Earth Resources Laboratory Application Software (ELAS) were used to determine land use/land cover classifications. The Landsat computer compatible tapes (CCT) for February 9, 1976 were analyzed to spectrally classify unique land use/land cover conditions within the Econlockhatchee (Econ) River basin, Florida. The results showed that the scatter diagrams of Band 4 (0.5-0.6μm)‐Band 7 (0.8-1.1μm) and Band 4‐Band 6 (0.7-0.8μm) can be utilized as well as the traditional Band 5 (0.6-0.7μm)‐Band 7 scatter diagram approach for classifying land use/land cover. Both the zoom transfer scope and the geographic information system have been demonstrated to be very useful tools for land use/land cover classification of Landsat data. The Landsat data can be successfully used to monitor the USGS land use/land cover Level I, and the cost and time requirements for the Landsat approach are much less than for the c...
TL;DR: The sensitivity of flow measurement uncertainty to head or time reading uncertainty is proportional to the ratio of the device discharge equation exponent to the reading as discussed by the authors, i.e., the sensitivity of the reading uncertainty to the flow measurement error.
Abstract: The primary source of error in properly calibrated, constructed, and installed flow measurement devices is due to reading error or uncertainty. Head reading uncertainty in small V-notch flumes and submerged orifices is measured in the field as ±\N3mm with no consistent variation with reading. Elapsed time measurement uncertainty for volumetric measurements increases with the square root of the time. The sensitivity of flow measurement uncertainty to head or time reading uncertainty is proportional to the ratio of the device discharge equation exponent to the reading. Furrow flow measurement uncertainty varies with the device and flow rate, but generally exceeds ±\N5% and often exceeds ±\N10%. Maintaining uncertainty below ±\N10% requires flume measurements in the upper 50% of their range, orifice measurements with head readings greater than 30mm, and volumetric measurement elapsed times greater than 4 seconds.
TL;DR: In this paper, the authors used stepwise regression analysis to determine four annual flow statistics: the mean; the standard deviation; the skew coefficient; and first-order serial correlation coefficient, with two sets of equations for northcentral and southern Idaho providing the best predictive results.
Abstract: Annual streamflow records for 124 stream gages in and near Idaho are examined to determine four annual flow statistics: the mean; the standard deviation; the skew coefficient; and first‐order serial correlation coefficient. Using step‐wise regression analysis, the mean and standard deviation are related to the basin characteristics of drainage area, mean annual precipitation, and percent forest cover, with the data regionalized geographically. Two sets of equations for north‐central and southern Idaho provide the best predictive results, with the equations for north‐central Idaho yielding multiple correlation coefficients in excess of 0.97. For the skew and serial correlation coefficients, maps of generalized regional values are prepared by the application of kriging theory, with the resulting maps illustrating the spatial variability of these statistics. The developed equations and maps can be used to estimate annual flow statistics at ungaged locations throughout the state.
TL;DR: In this article, a new concept in surface irrigation efficiency, termed deficit/excess efficiency, is presented; it has potential for use as an objective function for optimization purposes in the design and operation of on-farm irrigation systems.
Abstract: A new concept in surface irrigation efficiency, termed deficit/excess efficiency, is presented; it has potential for use as an objective function for optimization purposes in the design and operation of on‐farm irrigation systems. This concept, which yields a unimodal function of the volume of water applied, combines selected characteristics of application efficiency, storage efficiency, and Christiansen's uniformity coefficient. Under normal conditions, small applications of water produce high application efficiency, but a low uniformity coefficient and storage efficiency; conversely, large applications produce a high uniformity coefficient and storage efficiency, but low application efficiency. Thus, none of these latter terms are unimodal functions of the volume of water applied. The proposed deficit/excess efficiency can be modified according to management criteria to assign a benefit or penalty to the amount of runoff, deep percolation, and under irrigation in the irrigated field. Algebraic relations...
TL;DR: In this article, a hydrologic balance model was developed that employs neutron probe readings for soil moisture content coupled with measured amounts of precipitation and irrigation to estimate evapotranspiration over time periods corresponding to the frequency of neutron probes readings.
Abstract: A hydrologic balance model has been developed that employs neutron probe readings for soil moisture content coupled with measured amounts of precipitation and irrigation. The major objective of the model is to estimate evapotranspiration over time periods corresponding to the frequency of neutron probe readings. Earlier versions of the model were successfully applied to determine differentials of evapotranspiration over limited horizontal distances in crop water production function field experiments. The current version of the model was specifically developed for application in a regional evapotranspiration experiment requiring model flexibility to respond to a wide range of hydrologic conditions. Example output from the model applied to the regional evapotranspiration experiment is indicated. A scheme for testing parameterization of various components of the hydrologic cycle using the model is presented.
TL;DR: In this article, the general problem of advance and recession of irrigation water on an initially dry surface is formulated using the kinematic wave theory, and analytical solutions for the advance and contraction are used to derive expressions for volumes in surface storage and cumulative volumes of infiltration and runoff during all phases of one irrigation cycle.
Abstract: The general problem of advance and recession of irrigation water on an initially dry surface is formulated using the kinematic‐wave theory. In this part of the study, the infiltration rate is assumed constant in time and space. Analytical solutions for the advance and recession are used to derive expressions for volumes in surface storage and cumulative volumes of infiltration and runoff during all phases of one irrigation cycle. This comprehensive analytical model is then tested using field data. Its usefulness and limitations are discussed.
TL;DR: In this article, the authors analyzed the performance of an irrigation water delivery system in the Bhakra Canal Command in India and found that a high degree of mismatch existed between water demand and supply.
Abstract: The temporal distribution of an irrigation water delivery and demand ratio was used to analyze the performance of an irrigation water delivery system in the Bhakra Canal Command in India. A high degree of mismatch was found to exist between water demand and supply. Based on historical canal deliveries, agroclimatic data, and crop production with dated inputs, yields of wheat, a major irrigated crop of the region, were simulated over a period of 20 years. It was found that crop production was constrained by 34% (20-year average) due to unfavorable water delivery characteristics. An evaluation was made of introducing auxiliary storage at the farm outlet level to modify the water delivery schedule. Based on the increase in crop yield due to improved distribution of water supply delivery and the cost of auxiliary storage (including the cost of pumping), it was found that auxiliary storage could be used to considerable economic advantage.
TL;DR: In this paper, the applicabilities and limitations of various models for approximating the solution of the Saint-Venant equations were discussed in the Al-Hassa irrigation system, which consists mainly of open concrete canals with different shapes and sizes, due to the presence of features such as gates, bottom falls and junctions.
Abstract: The Al‐Hassa irrigation system, which consists mainly of open concrete canals with different shapes and sizes, is complex in nature due to the presence of features such as gates, bottom falls, and junctions. The distribution of water through such a network is more complicated due to time‐dependent inflow from the springs and reservoirs into the system. In order to decide gate‐operating policies for irrigation scheduling purposes, the unsteady flow phenomenon used throughout the system to simulate depth and discharge at various reaches with time was studied. The applicabilities and limitations of various models for approximating the solution of Saint‐Venant equations were discussed. The applicabilities and limitations of various unsteady flow packages were also reviewed considering Al‐Hassa network configurations. Among all the available packages, the dynamic wave operational (DWOPER) model developed by the National Weather Service was updated, and hydraulic equations on features such as junctions with dis...
TL;DR: In this article, a procedure has been developed to increase irrigation efficiency by estimating probabilistic irrigation requirements for lowland rice cultivation for the Kalawewa irrigation scheme in Sri Lanka.
Abstract: A procedure has been developed to increase irrigation efficiency by estimating probabilistic irrigation requirements for lowland rice cultivation. The procedure uses a water balance equation with random components to maintain minimum desired water levels in paddy fields at the end of each irrigation period. The procedure estimates weekly pan evaporation and rainfall at different probability levels, which are then used to estimate weekly irrigation requirements through the water balance relationship. The method has been applied to the Kalawewa irrigation scheme in Sri Lanka. Different statistical transformations were used to normalize observed weekly rainfall and evaporation data and to describe their variations. The power transformation was best able to transform the weekly data to normality. Comparison of the use of the model and current system practices shows that a significant amount of water can be saved even when the system is operated at high probability levels.