Journal of Irrigation and Drainage Engineering

New technologies could improve irrigation efficiency of turfgrass, promoting water conservation and reducing environmental impacts. The objectives of this research were to quantify irrigation water use and to evaluate turf quality differences between (1) time-based scheduling with and without a rain sensor (RS); (2) a time-based schedule compared to a soil moisture sensor (SMS)-based irrigation system; and (3) different commercially available SMS systems. The experimental area consisted of common bermudagrass [Cynodon dactylon (L.) Pers.] plots $(3.7\mathrm{m}\times 3.7\mathrm{m})$ , located in Gainesville, Fla. The monitoring period took place from July 20 to December 14, 2004, and from March 25 to August 31, 2005. SMS-based treatments consisted of irrigating one, two, or seven days a week, each with four different commercial SMS brands. Time-based treatments with or without RS and a nonirrigated treatment were also implemented. Significant differences in turfgrass quality among treatments were not detected due to the sustained wet weather conditions during the testing periods. The treatment with the rain sensor resulted in 34% less water applied than that without the rain sensor (2-WORS) treatment. Most SMS brands recorded irrigation water savings compared to 2-WORS, ranging from 69 to 92% for three of four SMSs tested, depending on the irrigation frequency. Therefore, SMS systems represent a promising technology because of the water savings that they can achieve during wet weather conditions while maintaining acceptable turfgrass quality.

This paper details a study performed by the Irrigation Training and Research Center to determine motor performances under varying speeds [induced by a variable frequency drives (VFD) controller] and loads. A further goal of the study was to provide sufficient information to designers so that they could estimate total pumping plant power usage with a VFD-controlled installation. Motors were tested with a VFD as well as across-the-line. On average, the relative efficiency of the electrical system with a VFD may be approximately 8% lower than the relative efficiency of a properly designed, full-load across-the-line system. If one considers actual field operating conditions this 8% is misleading because overall energy savings can be obtained with VFDs due to their ability to properly adjust speeds to meet actual field conditions.

A linear programming (LP) model is presented for optimal design of the pressurized irrigation system subunit. The objective function of the LP is to minimize the equivalent annual fixed cost of pipe network of the irrigation system and its annual operating energy cost. The hydraulic characteristics in the irrigation subunit are ensured by using the length, energy conservation, and pressure head constraints. The input data are the system layout, segment-wise cost and hydraulic gradients in all the alternative pipe diameters, and energy cost per unit head of pumping water through the pipeline network. The output data are: segment-wise lengths of different diameters, operating inlet pressure head, and equivalent annual cost of the pipeline network. The explicit optimal design is demonstrated with design examples on lateral and submain or manifold of pressurized irrigation systems. The effect of the equations for friction head loss calculation on optimization procedure is investigated through the design example for microirrigation manifold. The performance evaluation of the proposed model in comparison with the analytical methods, graphical methods, numerical solutions, and dynamic programming optimization model reveals the good performance of the proposed model. The verification of operating inlet pressure head obtained by the proposed model with accurate numerical step-by-step method suggested that it is mostly accurate.

Alfalfa-reference evapotranspiration $\left({\mathrm{ET}}_r\right)$ values sometimes need to be converted to grass-reference ET $\left({\mathrm{ET}}_o\right)$ , or vice versa, to enable crop coefficients developed for one reference surface to be used with the other. However, guidelines to make these conversions are lacking. The objectives of this study were to: (1) develop ${\mathrm{ET}}_r$ to ${\mathrm{ET}}_o$ ratios ( $K_r$ values) for different climatic regions for the growing season and nongrowing (dormant) seasons; and (2) determine the seasonal behavior of $K_r$ values between the locations and in the same location for different seasons. Monthly average $K_r$ values from daily values were developed for Bushland, (Tex.), Clay Center, (Neb.), Davis, (Calif.), Gainesville, (Fla.), Phoenix (Ariz.), and Rockport, (Mo.) for the calendar year and for the growing season (May–September). ${\mathrm{ET}}_r$ and ${\mathrm{ET}}_o$ values that were used to determine $K_r$ values were calculated by several methods. Methods included the standardized American Society of Civil Engineers Penman–Monteith (ASCE-PM), Food and Agriculture Organization Paper 56 (FAO56) equation (68), 1972 and 1982 Kimberly-Penman, 1963 Jensen-Haise, and the High Plains Regional Climate Center (HPRCC) Penman. The $K_r$ values determined by the same and different methods exhibited substantial variations among locations. For example, the $K_r$ values developed with the ASCE-PM method in July were 1.38, 1.27, 1.32, 1.11, 1.28, and 1.19, for Bushland, Clay Center, Davis, Gainesville, Phoenix, and Rockport, respectively. The variability in the $K_r$ values among locations justifies the need for developing local $K_r$ values because the values did not appear to be transferable among locations. In general, variations in $K_r$ values were less for the growing season than for the calendar year. Average standard deviation between years was maximum 0.13 for the calendar year and maximum 0.10 for the growing season. The ASCE-PM $K_r$ values had less variability among locations than those obtained with other methods. The FAO56 procedure $K_r$ values had higher variability among locations, especially for areas with low relative humidity and high wind speed. The 1972 Kim-Pen method resulted in the closest $K_r$ values compared with the ASCE-PM method at all locations. Some of the methods, including the ASCE-PM, produced potentially unrealistically high $K_r$ values (e.g., 1.78, 1.80) during the nongrowing season, which could be due to instabilities and uncertainties that exist when estimating ${\mathrm{ET}}_r$ and ${\mathrm{ET}}_o$ in dormant season since the hypothetical reference conditions are usually not met during this period in most locations. Because simultaneous and direct measurements of the ${\mathrm{ET}}_r$ and ${\mathrm{ET}}_o$ values rarely exist, it appears that the approach of ${\mathrm{ET}}_r$ to ${\mathrm{ET}}_o$ ratios calculated with the ASCE-PM method is currently the best approach available to derive $K_r$ values for locations where these measurements are not available. The $K_r$ values developed in this study can be useful for making conversions from ${\mathrm{ET}}_r$ to ${\mathrm{ET}}_o$ , or vice versa, to enable using crop coefficients developed for one reference surface with the other to determine actual crop water use for locations, with similar climatic characteristics of this study, when locally measured $K_r$ values are not available.

The effects of irrigation water salinity on growth, yield, and water consumption of okra was investigated with a pot experiment. For this purpose, five irrigation water salinity levels with electrical conductivities of 1.5, 2.5, 3.5, 5.0, and $7.0\mathrm{dS}∕\mathrm{m}$ and tap water as a control treatment were used in a randomized design with five replications. Irrigation practices were realized by considering the weight of each pot. Threshold soil salinity and slope values of the yield response to soil salinity level were determined to be $3.48\mathrm{dS}∕\mathrm{m}$ and 4.2%, respectively, for fruit yield, $4.24\mathrm{dS}∕\mathrm{m}$ and 7.0% for vegetative dry weight, and $6.0\mathrm{dS}∕\mathrm{m}$ and 7.9% for root dry weight. The results revealed that okra was moderately tolerant to salinity. Increasing soil salinity levels caused significant decreases in plant water consumption. Plant water consumption decreased by 2.43% per unit increase in soil salinity. Plant coefficient $\left(K_y\right)$ was 1.26. Saline irrigation water treatments altered Cl, Mg, Ca, and Na accumulations in leaves, whereas only Na accumulation in fruits was observed.

A small body of knowledge exists on the root water uptake (RWU) and evapotranspiration in humid environments having a mixture of natural vegetative cover. In this paper, we assess the impacts of atmospheric conditions and land cover on RWU from a natural vegetative cover. An intensive field investigation was carried out to monitor water table fluctuations along two flow transects comprising an upland grass area and a lowland riparian zone. Calibration and validation of the soil hydraulic parameters using the two-dimensional variably saturated ground water flow model, HYDRUS-2D, confirms the reliability of the model to simulate satisfactorily the large-scale daily fluctuation of RWU. Simulation results revealed that the actual RWU during the wet season is about 40% higher than RWU in the dry season due to high water table levels and temperatures prevailing throughout the wet season. Simulation results using HYDRUS-2D, which was modified to accommodate variable surface boundary conditions and heterogeneous root distribution, showed that the RWU from the riparian zone was 38 and 56% higher than RWU from the pasture land during the dry and wet seasons, respectively.

A model for modifying the canal delivery schedule during the dry season has been formulated to overcome the problem of low irrigation efficiency in a major irrigation project in India. Phulnakhara Distributary of the Puri main canal system (a run-of-the-river scheme) in the state of Orissa was chosen for this study. The model adopts a procedure of daily water balance simulation in paddy field and daily moisture balance simulation in nonpaddy crops field in the crop root zone. The historical canal flow data show that the prevailing delivery schedule is continuous. In addition to prevailing a continuous delivery schedule, five alternative rotational (variable discharge, constant duration, and constant frequency) schedules were considered. The alternatives considered are: 7 days canal operation followed by 7 days canal closure (7_7); 10 days canal operation followed by 10 days canal closure (10_10); 15 days canal operation followed by 15 days canal closure (15_15); 10 days canal operation followed by 7 days canal closure (10_7); and 15 days canal operation followed by 7 days canal closure (15_7). Considering both paddy and nonpaddy crops to be grown in the command during the dry season, 7 days canal operation followed by 7 days canal closure rotational schedule were found to be the best alternative. The alternative schedule 7_7 has registered weighted average seasonal evapotranspiraton (ET) of 354 mm in comparison to 347, 342, and 352 mm in 10_10, 15_15, and 10_7 schedules, respectively. In the paddy field, schedule 7_7 registered maximum of 4 days of disappearance of water as compared to 5 days and 6 days for 15_7 and 10_7 schedule, respectively. Besides creating a favorable water regime and better crop ET, this schedule saves about 10.31% of water over prevailing (actual) water supplies.

Manning’s roughness coefficient is one of the input parameters in many surface irrigation simulation models. It affects the velocity of flow and thereby its variation with time and distance along the field length influence water application. In this study, variation of Manning’s roughness coefficient was studied for a furrow plot consisting of three 40 m long free drained furrows of parabolic shape and having a top width of 0.30 m, a depth of 0.15 m and a slope of 0.5%. The irrigation experiments were carried out with the inflow rates of 0.2, 0.3, 0.4, and $0.5\text{L}{\text{s}}^1$ ; and 0.3, 0.4, 0.5, 0.6, and $0.7\text{L}{\text{s}}^{-1}$ under bare; and cropped field conditions, respectively. Furrow cross-section data were collected before each irrigation event at 0.5, 13, 26 and 39.5 m from the head end along the center furrow using a profilometer. During the irrigation event, water depth and velocity of flow were measured at these locations at an interval of 15 min using point gauge and color dye, respectively. The furrow cross-section data were fitted into a second-degree polynomial equation to determine the furrow shape parameters that were used along with the flow depth data for determining the wetted area and wetted perimeter. The wetted area, wetted perimeter, and the velocity data were used to estimate Manning’s roughness coefficient spatially and temporally. It is found that for both bare and cropped field conditions, Manning’s roughness coefficient was more at second and last quarter of the furrow due to soil erosion at these locations. Manning’s roughness coefficient at these locations varied from 0.019 to 0.022 and 0.015 to 0.018 for bare field whereas from 0.02 to 0.024, and 0.019 to 0.022 for cropped field, respectively. The temporal variation of Manning’s roughness coefficient for both bare and cropped furrow conditions decreased with the elapsed time. However, these decreasing trends were observed more for lower inflow rates. Further, the average Manning’s roughness coefficient for the subsequent irrigations was varied from 0.018 to 0.02 and from 0.019 to 0.0245 for bare and cropped conditions, respectively. Thus, the values of Manning’s roughness coefficients were more for cropped furrow conditions than for bare furrow.

The concept of low impact development (LID) is to apply decentralized on-site runoff source control to preserve the watershed hydrologic and ecological functions. An integrated layout using bioretention and vegetated landscape can decrease the developed runoff volume and peak flow. One of the key factors in urban hydrology is the imperviousness in the watershed. The conventional approach is to weight the imperviousness by the subareas in the watershed. Obviously, the area-weighted method has become inadequate when coping with LID because LID takes the flow path into consideration. When an impervious area directly drains onto a pervious area, the area-weighted method fails to count for the additional soil infiltration loss. In this study, the conventional area-weighted method is modified with a paved area reduction factor that converts the area-weighted imperviousness to its effective imperviousness. A family of curves was also developed for engineering applications. When a cascading process is introduced to the runoff flow path, the paved area reduction factor can be determined using the impervious to pervious area ratio and the infiltration to rainfall intensity ratio.

A new set of dimensionless rainfall hyetographs has been developed for the state of South Carolina. The new hyetographs show trends similar to those developed recently in other states and in general have milder intensities and lower peak rainfall than the Soil Conservation Service (SCS) rainfall hyetographs. This paper evaluates the impact the new hyetographs have on rainfall runoff and detention pond design and compares the results with those using the SCS hyetographs. Peak discharges for basin runoff were reduced up to approximately 20% of the predicted peak runoff rate using the current SCS hyetographs. Detention pond peak stage was also reduced by 25–50% of the predicted SCS stage. This analysis suggests that design hyetographs should be regularly updated to incorporate recent rainfall data.

The time of concentration $\left(T_c\right)$ for a watershed is a widely used time parameter to estimate peak discharges in hydrologic designs. In this study, $T_c$ is estimated for 96 Texas watersheds using five empirical equations: Williams, Kirpich, Johnstone–Cross, Haktanir–Sezen, and Simas–Hawkins methods. The drainage areas of watersheds studied are approximately $0.88–440.3{\mathrm{km}}^2$ . Watershed parameters used to estimate $T_c$ were developed by researchers at three institutions using three different methods: the automated method using digital elevation models and geographic information system software, the manual method with watershed delineation, and the manual method without watershed delineation. $T_c$ estimated from five empirical equations using three sets of watershed parameters is compared and analyzed. $T_c$ estimated using watershed parameters developed by the three methods is qualitatively similar and has average relative differences ranging from 6.4 to $-16.9\%$ . Differences between manual and automatic-based watershed characteristics are considered minor sources of error in relation to other uncertainties inherent in time parameter estimation. Average relative differences of $T_c$ estimated using different empirical equations with the same set of watershed parameters range from $-38$ to 207% (absolute average differences range from $-3.0$ to $2.8\mathrm{h}$ ) and are much larger than differences estimated using three sets of watershed parameters. Kirpich and Haktanir–Sezen methods provide reliable estimates of mean values of $T_c$ variations.

Characterization of hydrologic processes of a watershed requires estimation of the specific time-response characteristics of the watershed. In the absence of observations these characteristics are estimated from watershed physical characteristics. An exploratory assessment of a particle-tracking approach for parametrizing unit hydrographs from topographic information for applicable Texas watersheds is presented. The study examined 126 watersheds in Texas, for which rainfall and runoff data were available with drainage areas ranging approximately from 0.65 to $388\mathrm{km}$ , main channel lengths ranging approximately from 1.1 to $80\mathrm{km}$ , and dimensionless main channel slopes ranging approximately from 0.0002 to 0.02. Unit hydrographs based on entirely on topographic information were generated and used to simulate direct runoff hydrographs from observed rainfall events. These simulated results are compared to observed results to assess method performance. Unit hydrographs were also generated by a conventional analysis (of the observed data) approach to provide additional performance comparison. The results demonstrate that the procedure is a reasonable approach to estimate unit hydrograph parameters from a relatively minimal description of watershed properties, in this case elevation and a binary development classification. The method produced unit hydrographs comparable to those determined by conventional analysis and thus is a useful synthetic hydrograph approach.

Groundwater is the most widely used water resource in the Afram Plains area, Ghana. The objective of this study was to determine the distribution of fluoride, sodium adsorption ratio (SAR), and salinity (EC) in groundwater from the different aquifers in the Afram Plains area. The distribution of these parameters would enable a determination of the quality of groundwater from the different aquifer units for use in households and irrigation purposes. The inverse distance weighting, interpolator with a power of 2 was applied to 143 data points of each parameter to generate prediction maps for fluoride, SAR, and EC in the area. The distribution maps from this study show that the shale aquifers that underlie the southwestern sections of the area have the highest levels of fluoride, SAR, and EC. A narrow strip of the shale aquifer in the southwestern region produces groundwater whose fluoride level $(2.2\mathrm{mg}∕\mathrm{L})$ is higher than the World Health Organization minimum allowable fluoride concentration of $1.5\mathrm{mg}∕\mathrm{L}$ in drinking water. The feldsparthic sandstone, arkose, siltstone, and mudstone aquifers in the northeastern sections of the area produce groundwater with fluoride concentration in the range of $0.0–0.3\mathrm{mg}∕\mathrm{L}$ , which fall outside the minimum range of $0.7–1.2\mathrm{mg}∕\mathrm{L}$ required in drinking water for normal bone and dental health. The highest SAR and EC are also associated with the shale aquifers to the southwestern section of the area. Using the World Food and Agriculture Organization’s guidelines for irrigation water quality, it was determined that groundwater from the Afram Plains area will generally have a mild to moderate effect on the hydraulic properties of soils when used as irrigation water.

A simple semianalytical model is proposed for calculating the drawdown due to pumping a well tapping two aquifers. The new model can take into account the transient pumping discharge and cross flow between the aquifers. The transient contributions of the aquifers to the pumped discharge can also be implicitly obtained using the model.

In this paper the stage–discharge relationship of a new flume named SMBF (Samani, Magallanex, Baiamonte, Ferro), originally proposed by Samani and Magallanez and tested by Baiamonte and Ferro, for measuring flow discharge in open channels is reviewed. The flume is obtained inserting two semicylinders in a rectangular cross section. The results of some experimental runs carried out using horizontal flumes characterized by different values of the contraction ratio (ranging from 0.17 to 0.81) are used for determining the two coefficients of the power stage–discharge equation. The stage–discharge equation is tested using flow measurements carried out in the period between December 2004 and March 2006 in the Sicilian experimental SPA1 basin. Field testing of the SMBF flume is developed using discharge measurements carried out by a Khafagi–Venturi flume placed in the field measurement channel.

This is a pioneer study that presents genetic programming (GP) as a new tool for prediction of local scour downstream of grade-control structures. The objective of this study is to provide an alternative formulation to conventional regression based equations and verify the superiority of GP over regression analysis. The training and testing patterns of the proposed GP formulation are based on well established and widely dispersed experimental results from the literature. Linear and nonlinear regression-based equations were derived throughout regression analysis on dimensionless parameters obtained from dimensional analysis. The GP-based formulation results are compared with experimental results and other equations and found to be more accurate.

This study investigates the feasibility of using turbidity $\left(T\right)$ as a surrogate for suspended sediment concentration $\left(C\right)$ in an irrigation-dominated watershed in southeastern California. A nonlinear $T–C$ relationship was developed and evaluated using two independent sets of data obtained by physical sampling and laboratory turbidimeter. The relationship was interpreted in terms of the heterogeneous particle size distribution in the samples. The effects of spatial and temporal variation of particle sizes and water colors on the relationship were examined. Further, possible effects of laboratory procedures on the relationship such as time delay of sample measurement and calibration of $T$ for $C$ using lab-prepared samples were analyzed. The study showed that the variation of particle size distribution is the key factor controlling the $T–C$ relationship. Water color and time delay for sample analysis did not significantly affect the turbidity values, whereas laboratory procedures may mislead the $T–C$ relationship. It is concluded that turbidity may be a surrogate for suspended sediment concentration in such irrigation-dominated watersheds in arid regions, though the $T–C$ relationship has to be established with care.

Polynomial weirs can be applied in agricultural and municipal engineering to produce a wide range of head-discharge behavior, including the proportional (linear) characteristics of the Sutro weir. This note describes a method to determine the head-discharge equations of sharp-crested weirs with openings defined by polynomials of any order $n$ . Examples of behavior of fourth-order polynomial weirs are discussed.

According to the Federal Highway Administration’s Hydraulic Design of Highway Culverts (HDS-5) Manual and the Hydrologic Engineering Center River Analysis System (HEC-RAS) Reference Manual, the exit loss associated with a culvert discharging into a downstream channel is equal to the change in culvert and channel velocity heads or a loss coefficient multiplied by the culvert velocity head. For a short culvert, the calculated exit loss often represents the largest single system energy loss component. To investigate the apparent dominance of exit loss in outlet control culvert hydraulics, a laboratory culvert exit loss study was conducted using prototype-scale culverts, with projecting end treatments, discharging into a downstream channel where all of the channel discharge was supplied by the culvert. The experimentally determined exit losses were compared with predicted exit loss values using traditional exit loss equations and the Borda–Carnot minor loss expression, which is traditionally used to quantify energy loss at sudden expansions in pressurized pipe flow. The Borda–Carnot expression proved to be significantly more accurate, relative to traditional methods, for the conditions tested.