Journal of Irrigation and Drainage Engineering

Long-term and continuous crop evapotranspiration ($E{T}_c$) and the crop coefficient ($K_c$) of jatropha (Jatropha curcas L.), which are needed to determine irrigation requirements, are lacking. The objective of this study was to measure jatropha $E{T}_c$ and $K_c$ over four growing years. Field experiments were conducted from March 2012 to August 2015, and three different irrigation treatments were evaluated. The $K_c$ values were determined for the irrigated treatments as the ratio between the $E{T}_c$ and grass-reference evapotranspiration ($E{T}_0$) (i.e., $K_c=E{T}_c/E{T}_0$). The $E{T}_c$ was determined using a directly weighing lysimeter, and agrometeorological parameters measured at a weather station were used to estimate the $E{T}_0$. Over the four growing years, the $E{T}_c$ values ranged from 0.7 to $8.3\mathrm{mm}{\mathrm{day}}^{-1}$ for center pivot irrigation, $0.6-7.4\mathrm{mm}{\mathrm{day}}^{-1}$ for drip irrigation, and $0.4-5.4\mathrm{mm}{\mathrm{day}}^{-1}$ for no irrigation (rainfed). In the first growing year, a $K_c$ average of 0.6 for all treatments was found. The highest $K_c$ values were obtained at midphase (from December to February), with values of 0.9 and 0.8 in the second growing year, respectively, for the center pivot and drip treatments. During the same growth phase for the third and fourth growing season, the $K_c$ for both irrigated treatments were averaged at 0.9.

The objective of this study was to develop an application for smartphones capable of providing Conilon coffee producers with information on when and how much to irrigate, thus making it possible to carry out irrigation management practices with a view to rationalizing water and electrical resources. The work was carried out in Santa Teresa, a mountainous region in the state of Espírito Santo, Brazil. To determine the reference evapotranspiration, the Hargreaves-Samani model was proposed in document research and, subsequently, the system design was created in data flow, with presentation of the system phases through diagramming. The application was developed in the Personal Home Page (PHP) language. A context and a data flow diagram were created for use in the application in question. An application for smartphones was developed to provide Conilon coffee producers with reliable information on when and how much to irrigate, thus enabling irrigation management. It is worth mentioning that future research must be conducted to validate the efficiency of the application in the culture of Conilon coffee, evaluating the production of coffee.

Drought is among the most hazardous climatic disasters that significantly influence various aspects of the environment and human life. Qualitative and reliable drought forecasting is important worldwide for effective planning and decision-making in disaster-prone regions. Data-driven models have been extensively used for drought forecasting, but due to the inadequacy of information on model performance, the selection of an appropriate forecasting model remains a challenge. This study concerns a comparative analysis of six machine learning (ML) techniques widely used for hydrological drought forecasting. The standardized runoff index (SRI) was calculated at a seasonal (3-month) time scale for the period 1973 to 2016 in four selected watersheds of the Han River basin in South Korea. The ML models employed were built-ins, using precipitation, temperature, and humidity as input variables and the SRI as the target variable. The results indicated that all the ML models were able to map the relationship for seasonal SRI using the applied input vectors. The decision tree (DT) technique outperformed in all the watersheds with an average mean absolute error $(\mathrm{MAE})=0.26$, root mean square error $(\mathrm{RMSE})=0.34$, Nash-Sutcliffe efficiency $(\mathrm{NSE})=0.87$, and coefficient of determination $(R^2)=0.89$. The performances of the support vector machine (SVM) and deep learning neural network (DLNN) were similar, whereas the fuzzy rule-based system (FRBS) performed very well compared to the artificial neural network (ANN) and the adaptive neuro-fuzzy inference system (ANFIS). The overall findings of this study indicate that, considering performance criteria and computation time, the DT was the most accurate ML technique for hydrological drought forecasting in the Han River basin.

Differential pressure fertilization devices are applied widely in cultivated areas. The device suffers from local insufficient or excessive fertilization, which causes environmental pollution and decreases grain production. A flux control methodology is proposed to maintain optimum fertilization for the device based on fertilizer continuity equation. The fertigation flux is constant in the proposed methodology, and the target fertilizer concentration decreases linearly in the device to maintain the optimum fertilization from the fertigation system inlet. The methodology is applied directly for fertilizer in the case of a large dispersion coefficient when the mixture of water and fertilizer is immediate and uniform. An extra parameter is required, and a simple predictor-corrector method is suggested for fertilizer in case of small dispersion coefficient. A grade regulation method is suggested for convenient application of the methodology. A developed numerical model was applied to verify the methodology’s feasibility for optimum fertilization. The numerical model simulates the mixing of water and fertilizer fairly well for different fertilizer dispersion coefficients and indicates the applicability of the flux control methodology. The flux control methodology well simulates optimum fertilization, and both the simple predictor-corrector method and the grade regulation method have the potential to improve the performance of fertigation application based on differential pressure fertilization device.

Aiming to quantify the impacts of the center pivot irrigation technique on soil moisture dynamics and to improve irrigation crop water needs, a mathematical model was developed to estimate the water distribution pattern of a center pivot. The model is based on the ballistic theory modeling of a single sprinkler radial curve that simulates the trajectories of the droplets discharged by the sprinkler’s nozzle. Subsequently, a water distribution pattern of a sprinkler irrigation technique (and ultimately center pivot) can be accurately estimated. This paper describes the theoretical and mathematical approaches of the developed model and its application in the case study, which was Las Tiesas farm in the area of Barrax, Spain, because the model was expanded to take into account the presence of not only one center pivot but multiple ones. In the case study, several center pivots with different characteristics in terms of size and hourly irrigation rates are present. The model correctly estimates the water distribution as it takes into account the different spatial (different sizes of pixels) and temporal basis (hourly and daily basis) and correctly estimates the water distribution when compared with satellite data. The results are given by the model, which is strictly done in the following order: simulating droplets trajectories, water distribution radial curve of single sprinkler, overlapped sprinklers patterns, and center pivots water distribution radial curve and patterns. The mathematical model gives the water distribution pattern under a center pivot irrigation system on a daily and hourly basis. The model can be adjusted to give the results not only for one center pivot but for two or more as desired.

A comparison of water use and maintenance effort was made between traditional and Florida-Friendly Landscaping (FFL). Traditional Florida landscapes are generally turf dominated with minimal shrubbery, all indiscriminately irrigated using single-zone, large-rotor sprinklers. Conversely, FFL landscapes feature reduced turf cover, substantial areas with mulched ornamental beds, and zoned irrigation that includes microirrigation and smart controllers. This study used three identically sized landscape replicates (each $455{\mathrm{m}}^2$; $\mathrm{4,900}{\mathrm{ft}}^2$), with half of each landscaped in a traditional Florida manner using 75% turf, and the other half using an FFL landscape that reduced turf extent to 25% but incorporated groundcovers and mulched beds. During a 12-month establishment period, the FFL landscape used 69.7% less irrigation water than the traditional landscape, and 83.9% less water in a 34-month postestablishment period. Substantial postestablishment water savings were realized by simply turning off the microirrigation to the ornamental beds and visually inspecting for drought stress. After establishment, the average maintenance labor was similar in both landscape types; however, the time spent mowing or hand weeding between the two landscape types was nearly reciprocal.

Evaluating the adequacy and efficiency of irrigation practices and identifying potential irrigation management improvements in agricultural watersheds require accurate estimates of water fluxes under actual management conditions. Such estimates are also beneficial for other applications, such as simulating physiological and hydrologic processes at field and basin scales. A three-year study was conducted at an agricultural watershed in west-central Oklahoma to quantify water fluxes and to compare the actual fluxes with those calculated assuming well-watered conditions. Measured applied irrigation data revealed that almost all studied fields were under-irrigated, with an average amount that was only 30% of what should have been applied to maintain well-watered (no stress) conditions. Other water fluxes, namely crop evapotranspiration (ET), runoff (RO), and deep percolation (DP), were estimated using two models with different levels of complexity: the root zone soil water balance (SWB) and the HYDRUS models. The outputs of the two models were close (normalized root mean square difference of 5% and 3% under actual and well-watered conditions, respectively) and showed that the common under-irrigation practices lead to a reduction in all fluxes compared to the hypothetical well-watered conditions. According to the HYDRUS model results, the average actual ET, RO, and DP fluxes were 82%, 50%, and 33% of what would have been experienced under well-watered conditions. The soil water content simulations of HYDRUS under the actual scenario were similar to readings of in-situ sensors installed at four depths at each study site with an overall root mean square difference of $0.06{\mathrm{cm}}^3{\mathrm{cm}}^{-3}$. The findings of this study demonstrate that differences between actual fluxes and those calculated based on no water stress assumptions could be notable, leading to major errors if well-watered fluxes are used in crop growth models, hydrologic simulations, irrigation energy use and emission models, and other applications.

Design strategies that enhance modern irrigation practices, reduce energy consumption, and improve water use efficiency and crop yields are fundamental for sustainability. Although microirrigation is currently a widely applied method, center-pivot irrigation systems have become very popular on large farms, thanks to their automation, wide-coverage, and reliability. Different design procedures have been proposed, even though some aspects have not been solved yet. This paper presents a simple design procedure for center-pivot systems using a gradually decreasing sprinkler spacing along with a pivot lateral, which makes it possible to set favorable and uniformly distributed water application rates. The sprinkler spacing distribution along the radial direction is derived by considering just one dimensionless group accounting for the geometric and hydraulic input parameters. According to this outcome, the results showed that the suggested procedure made it possible to select the sprinkler characteristics and the pipe diameter based on the desired input parameters, i.e., the uniform water application rate and the lateral length. For assigned input parameters, the lateral length is delimited by a threshold value, indicating that lateral lengths longer than that threshold value require the modifications of a sprinkler flow rate or pipe diameter. Finally, applications based on the proposed hydraulic design procedure were performed and discussed for two different cases.

Land disturbing construction activities can become nonpoint sources of pollution, particularly due to suspended sediment, if erosion and sediment control measures are ineffective. Wattles have become popular practices among many governing agencies and contractors because of the variety of wattle materials available and their vast array of applications, such as ditch checks, inlet protection practices, and perimeter controls. As technologies continue to emerge, quantifying wattle performance can be a difficult and daunting task. To better understand hydraulic performance, flume experiments were conducted on eight manufactured wattles using a testing regime that used four inflow rates of 0.007, 0.021, 0.035, and $0.057{\mathrm{m}}^3/\mathrm{s}$ (0.25, 0.75, 1.25, and $2.00{\mathrm{ft}}^3/\mathrm{s}$) and three longitudinal channel slopes of 3.50%, 4.25%, and 5.00%. Hydraulic measurements to assess wattle performance were taken for each trial after flow stabilization. Six different fill materials (excelsior wood fiber, wheat straw, coconut coir, recycled synthetic fiber, chipped wood, and miscanthus fiber) and four containment systems (natural netting, synthetic netting, synthetic socking, and polyester socking) were evaluated. Test results indicated that wattles fall into one of four developed classes based on correlations between hydraulic depth ratios and subcritical length ratios identified in the study. Class 1 wattles are considered the least hydraulically favorable, and Class 4 wattles are considered the most favorable at reducing supercritical flows when compared to the performance of an impervious weir control test. Two-way (flow rate and channel slope) ANOVA analyses were conducted to evaluate the degree of wattle performance variations for each wattle type, and a multiple linear regression model was developed to quantify performance characteristics based on fill material, slope, and flow rate from a base case (i.e., impervious weir) scenario. The ANOVA analyses indicated that synthetic fiber and miscanthus filled wattles had superior hydraulic performance capabilities when subjected to various flow rates and longitudinal slopes based on no statistical difference across flow rates and slopes. The multiple linear regression model suggested that excelsior fiber was the least effective fill material for establishing flow velocities favorable for soil particle settlement, while miscanthus fiber created the most favorable conditions. Lastly, water absorption evaluations suggest that saturated wattle density, as opposed to dry density, can be used to link the wattle fill type to hydraulic performance.

A series of experimental and numerical studies were conducted to investigate the hydrodynamics of weir-culverts with a downstream ramp in submerged-flow condition. A comparison of the numerical and experimental results with the selected turbulent model indicated that the numerical model is capable of simulating weir-culverts with a downstream ramp with 5% error. Water surface profiles of the proposed weir-culvert models were observed in transition from free to fully submerged flow, and four flow regimes of impinging jet regime (IJR), surface jet regime (SJR), surface wave regime (SWR), and deeply submerged regime (DSR) were identified. The proposed flow regimes were classified based on the ratio of surface flow to mean downstream velocities and the ratio of tail water to headwater depths. For proper design and erosion protection of irrigation canals, hydrodynamic characteristics of the identified flow regimes such as streamwise velocity, velocity path lines, and turbulent kinetic energy ($k$) were extracted from experimental and numerical results. The results showed that the position of maximum $k$ moved from the toe of the weir-culvert to the water surface as the tail water level increased. This indicated a significant reduction of energy dissipation rate due to turbulence, which necessitates proper bed protection far downstream of the structure. A comparison of weir-culverts with different weir lengths in a DSR showed higher surface jet energy dissipation and contraction coefficient of weir-culverts with larger length. The eye of the rollers and the boundaries between vortices were extracted from numerical simulations, and it was found that the stagnation points and surface jet thickness profiles moved toward the downstream side of the weir-culvert as the weir length increased.

Surface water impoundment in an unlined triangular ditch during a single managed aquifer recharge (MAR) infiltration pulse lasts for time $T_e$, after which all initially disposed water seeps into a homogenous isotropic coarse soil. In ditches with initial water $W_0$ with depth $H_0$ and length $L$, the dyad $(W_0,H_0)$ vanishes at $t\to T_e$. The ditch slope that minimizes an objective function involving a linear combination of $T_e$, $W_0$, and $H_0$ with arbitrary cost coefficients was found. The analytical expression for $T_e$ as a function of the bank slope and the sand’s porosity is for soils without capillarity and mild bank slopes. An isoperimetric constraint in optimization is the volume of the water pulse released into the ditch. A global unique minimum exists if the coefficients factoring $W_0$ and $H_0$ are not identically zero. A numerical solution to a two-dimensional infiltration problem was obtained using HYDRUS 2D/3D and its reservoir boundary condition option for arbitrary soils and bank slopes. Optimal slopes of triangular ditches were found for an initially dry loam. The analytical and numerical optimal shapes were not sensitive to mild variations of the ditch slope.

Calibration studies typically relate the curve number to the rainfall amount; however, this dependence is neglected in the standard application of the curve-number method. This neglect causes an underestimation of the calculated runoff, which is of concern to engineers. This study quantifies the magnitude of the underestimation of runoff, and identifies the minimum rainfall amounts required for the standard curve-number method to yield runoff estimates with nominal errors less than 10%. These minimum rainfall amounts are shown to be in the range $13–0\mathrm{cm}$ for curve numbers in the range 40–100. The results also show that a reduced standard initial abstraction ratio below the current standard of 0.2 likely would lead to lower rainfall thresholds for the 10% error.

Enhancing water use efficiency is essential in irrigated agriculture owing to declining water resources, increasing population, growing water needs, and greater competition among water users. If properly designed and managed, with good operation and maintenance, a center-pivot irrigation system can have high water-application efficiency. One of the design factors for a center-pivot irrigation system is the hydraulic loss in the lateral pipe. In this study, an analytical relationship is presented as a series for calculating the hydraulic loss in the lateral pipe of a center-pivot irrigation system. Given the difficulty and complexity of using a mathematical series, the equation presented in this study and the equation developed by Anwar turn out to be general and asymptotic relations. The final relationships have 0.6% and 0.4% errors, respectively, relative to the series relationships. Due to the high accuracy and ease of use of the asymptotic relationship presented to calculate the hydraulic loss in the lateral pipe, it is recommended for use in designing center-pivot irrigation systems.

One of the general problems encountered in the design of open channels is the computation of normal depth, head loss, and discharge. A wide rectangular section is commonly used in natural streams and surface/sheet flow in watersheds and the triangular section is commonly used for irrigation and roadside channels. The normal depth or head loss is traditionally solved using a trial (iterative) procedure. This paper develops two direct solutions for the head loss and normal depth for the wide rectangular and triangular open channel sections. The explicit equations for the normal depths are developed in terms of fast converging power series. The maximum errors of the proposed explicit formulas are 0.65% and 2% for triangular and wide rectangular channels, respectively, compared with 5% and 8% for the existing methods.