Journal of Irrigation and Drainage Engineering

Frequency domain reflectometry (FDR) downhole sensors have been increasingly used for soil moisture field monitoring because they allow measurement, even continuously, along a soil profile. Moreover, they can also be installed with minimal soil disturbance around the access tube. The objectives of the paper were to assess the field and laboratory calibration protocols for a FDR capacitance probe (Diviner 2000) for a range of soils characterized by different particle size distributions and shrink/swell potential and to propose a practical and effective protocol on the basis of undisturbed soil samples, accounting for soil shrinkage/swelling processes characterizing swelling clay soils. The experiments showed that on coarse-textured soils, field calibration under wet, moist, and dry conditions allows estimations of the volumetric soil water content, with root-mean-square error (RMSE) values always lower than $0.058{\mathrm{cm}}^3·{\mathrm{cm}}^{-3}$. On the contrary, the problems occurring in the field on finer-textured soils, which are characterized by a clay content ranging between 36.7 and 45.1% and moderate to high shrink/swell potential, did not permit identification of suitable calibration equations and then accurate estimations of the soil water content. For such soils, in fact, a great dispersion of the experimental data and consequently high error values associated with the site-specific calibration equations, i.e., up to $0.121{\mathrm{cm}}^3·{\mathrm{cm}}^{-3}$ for the soil characterized by the highest clay percentage, were observed. The laboratory experiments were carried out by using undisturbed soil monoliths which, compared with sieved soils, have the advantage of accounting for the natural soil structure surrounding the access tube and monitoring the soil shrinkage processes occurring in clay soils during sensor calibration experiments. The Diviner 2000 calibration equations obtained in the laboratory were characterized by error values generally lower than those obtained in the field and always smaller than $0.053{\mathrm{cm}}^3·{\mathrm{cm}}^{-3}$. Finally, in the range of a soil water content between approximately 10% and the maximum observed, the scaled frequency measured by the sensor was almost constant at a decreasing soil water content. This circumstance can be ascribed to the normal phase of the shrinkage process determining the compensative effects between the reduction of the volumetric soil water content and the increasing soil bulk density. The maximum variations of scaled frequency were observed in the range of the soil water content, for which the resulting soil bulk density was approximately constant. The knowledge of the soil shrinkage characteristic curve therefore assumes a key role when calibrating FDR sensors on shrinking/swelling clay soils.

The use of lay-flat polyethylene pipes to irrigate horticultural crops has been receiving widespread attention in the last decade, due to the significant improvements in their hydraulic performance, their potentially high application efficiency, and their limited installation costs. However, even if hydraulic design procedures for conventional microirrigation systems are fairly well established, there is still the need to know how different pipe-wall thicknesses of lay-flat pipes can affect the pipe geometry under different operating pressures as well as the related consequences on friction losses. This paper, after comparing two different procedures (caliper and photographic) to assess the geometry of lay-flat polyethylene pipes under different operating pressures, analyzes the friction losses per unit of pipe length, $J$, in order to identify and to assess a procedure for their evaluation. Hydrostatic tests, initially carried out on pipes with wall thicknesses of 6, 8, and 10 thousandth of an inch (mil), evidenced that the pipe dimensions measured with both methods are quite similar, despite the generally higher standard deviations characterizing caliper measurements when compared to photographic method. Tests allowed to verify that most of the changes in pipe dimensions occur within a range of pressure from 0 kPa to about 30 kPa, with pipe horizontal width and vertical height quite similar at higher pressures and pipes have a tendency to become circular. Additionally, due to the elasticity of the material, over a certain limit of water pressure, both the pipe dimensions tend to rise, with a trend depending on pipe thickness. According to the experimental data, the relationships between pipe effective diameter and water pressure were then determined for the three considered pipes. Moreover, based on measured friction losses and pipe effective diameters, it was confirmed that the relationship between the Darcy-Weisbach friction factor, $f$, and the Reynolds number, $\mathsf{R}$, can be described by a power equation in which, by assuming a value of $-0.25$ for the exponent, it results a coefficient $c=0.285$, lower than the theoretical. For the three investigated pipes the errors associated to estimated $J$ were finally evaluated by considering (1) the experimental relationships between friction factor and Reynolds number as well as between pipe diameter and operating pressure (Case A); (2) the same value of c, but pipe effective diameters of 16.20, 16.10, and 15.85 mm corresponding to $p=p_{\text{lim}}$ (Case B); (3) the standard procedure, with a value of $c=0.302$ and the pipe diameter equal to 16.10 mm, as suggested by the manufacturer. The results evidenced that suitable estimations of $J$ need to account for the variations of the pipe effective diameter with water pressure. On the other hand, incorrect values of pipe diameter combined with inexact values of the friction factor generate inaccurate estimations of friction losses, with unavoidable consequences in pipe design.

A short-term real-time operation model with fuzzy state variables is developed for irrigation of multiple crops based on earlier work on long-term steady-state policy. The features of the model that distinguish it from the earlier work are (1) apart from inclusion of fuzziness in reservoir storage and in soil moisture of crops, spatial variations in rainfall and soil moisture of crops are included in the real-time operation model by considering gridded command area with a grid size of 0.5° latitude by 0.5° longitude; (2) the water allocation model and soil moisture balance equations are integrated with the real-time operation model with consideration of ponding water depth for Paddy crop; the model solution specifies reservoir releases for irrigation in a 10-day time period and allocations among the crops on a daily basis at each grid by maintaining soil moisture balance at the end of the day; and (3) the release policy is developed using forecasted daily rainfall data of each grid and is implemented for the current time period using actual 10-day inflow and actual daily rainfall of each grid. The real-time operation model is applied to Bhadra Reservoir in Karnataka, India. The results obtained using the real-time operation model are compared with those of the standard operating policy model. Inclusion of fuzziness in reservoir storage and soil moisture of crops captures hydrologic uncertainties in real time. Considerations of irrigation decisions on a daily basis and the gridded command area result in variations in allocating water to the crops, variations in actual crop evapotranspiration, and variations in soil moisture of the crops on a daily basis for each grid of the command area.

Side weirs are water intake or discharge structures that discharge water from, e.g., a dam, an open channel to external environment for using flow control, or irrigation system. In this paper, to examine how the sill placed in different locations of the main channel effects a side-weir discharge performance, a three-dimensional (3D) computational fluid dynamics (CFD) model together with experimental results were used. In the numerical simulations, $k\text{-}\epsilon$ turbulence model and volume of fluid (VOF) method were used. The hydrodynamics properties of flow on the sill were determined and effects on the discharge were discussed. It is seen that the using a sill located in a suitable place considerably increases outflow discharge of the side weir.

The ability to optimize an artificial neural network (ANN) and adaptive neuro-fuzzy inference system (ANFIS) in reference evapotranspiration (${\mathrm{ET}}_0$) estimation using the cuckoo search algorithm (CSA) is studied in this paper. The monthly series of climatic data (minimum and maximum air temperatures, actual vapor pressure, sunshine hours, and wind speed at height of 2.0 m) from twelve meteorological stations in Serbia during the period 1983–2010 were used as inputs to the soft computing models. As the reference ${\mathrm{ET}}_0$ equation, the FAO-56 Penman-Monteith equation was selected. Statistical indicators such as the root-mean-square error (RMSE), mean absolute error (MAE), and coefficient of determination ($R^2$) were used as comparing criteria for the evaluation of the models’ performances. The obtained results show that the proposed $\mathrm{ANFIS}+\mathrm{CSA}$ model can be used for ${\mathrm{ET}}_0$ estimation with high reliability ($\mathrm{RMSE}=0.2650\mathrm{mm}{\mathrm{day}}^{-1}$, $\mathrm{MAE}=0.1843$ and $R^2=0.9695$). The selected soft computing models were compared with the results of two empirical models (adjusted Hargreaves and Priestley-Taylor) and their calibrated versions. Priestley-Taylor method had the highest RMSE ($0.5420\mathrm{mm}{\mathrm{day}}^{-1}$). The lowest RMSE of $0.1883\mathrm{mm}{\mathrm{day}}^{-1}$ has the ANN model. The calibrated adjusted Hargreaves model performs better than the calibrated Priestley-Taylor model. The $\mathrm{ANN}+\mathrm{CSA}$, ANFIS, and $\mathrm{ANFIS}+\mathrm{CSA}$ had better characteristics than the two estimated empirical equations and their calibrated versions.

Peatland drainage and peat extraction result in runoff water rich in humus, sediments, and nutrients that requires simple purification methods to prevent pollution of surface waters. Chemical treatment of drainage water has been suggested as best management practice. However, good chemical purification results require flocculators to achieve efficient particle aggregation. This study evaluated gravity-driven hydraulic flocculators using full-scale three-dimensional (3D) computational fluid dynamic (CFD) turbulence models to simulate hydraulics, combined with data obtained in jar tests to estimate optimal mixing conditions for coagulation [velocity gradient ($G$-values)]. The CFD model was first run for several barrier configurations. The optimal structure was then tested for different ratios of distance between barriers [or opening slot width ($B$)] and flocculator width ($W$). The relationship between distribution of $G$-values and the target value of $40–60{\mathrm{s}}^{-1}$ was determined for different designs. The best $B/W$ ratio was found to be $1/4$. For this ratio, the flow depth was the only variable parameter that needed to be optimized by the CFD model to achieve target $G$-values.

This study investigated methods for predicting and managing surface water spread and depth on porous pavement bike lanes adjacent to impervious traffic lanes. Results are presented from a theoretical and experimental study into the hydraulic performance of porous pavement bike lanes. Analysis of the Saint-Venant equations was used to show that the distance required for water running onto a porous pavement to fully infiltrate into the pavement is linearly proportional to the width of the adjacent impervious traffic lanes and the rainfall intensity. It is inversely proportional to the sum of the rainfall intensity and pavement hydraulic conductivity. This result was validated by a series of large-scale laboratory experiments. A second model is presented for calculating the spacing of curb opening inlets along the side of a porous pavement that is relatively flat in the longitudinal direction. A graphical analysis of the runoff hydrograph that flows into the porous pavement was used to predict the peak discharge per unit length of pavement that must be handled by a curb opening inlet. This peak flow, combined with a local regulatory limit on the spread, leads to a simple algebraic expression for the required length of curb opening inlet per unit length of bike lane. Examples of how both these results can be used in preliminary design calculations are presented.

Using perlite substrates over several growing seasons is widely done in greenhouse production; its successful application depends on substrate modification and growing practices. The goal of this research was to characterize the evolution of the physical, hydraulic, and aeration properties of perlite with time within two parts of the pot, where the effect of solarization was also determined. New perlite and perlite that had been used one to four times as growing media were analyzed, and the induced modifications were measured in terms of the hydraulic retention, permeability at saturation, porosity, bulk density, water-holding capacity, and particle size distribution. The study showed that reuse influences the perlite particle size and reduces the hydraulic conductivity of the medium; the aeration properties and easily available water were improved by reuse, which supports crop growth. However, the variations found in this study from the reused substrates’ hydraulic features would not significantly modify the irrigation regime of the growing media inside a greenhouse. The solarization did not substantially alter the primary physical and hydraulic properties of the medium.

The International Network of Irrigation Testing Laboratories (INITL) undertook a sprinkler intercomparison testing exercise to generate data for an objective comparison of the performances of the different facilities and identify opportunities for further improvements. Three impact sprinklers were tested in four laboratories in accordance with established standards. The plots of flow rate-pressure profiles were found to be consistent, and correlated to those obtained from previous studies. Although there were slight variations in the measured flow rate data, the mean flow rates at each pressure level were the same for the three sprinklers, and the shapes of the radial distribution profiles were similar. The deviations of reconstituted flow rates (from the measured) of at least two tests in each facility were found to exceed the recommended limit. The sprinkler software developed by INITL was found to have a good correlation with a related commercial software program.

Check dams with grids upgrading upstream are often used in mountain rivers, where intense sediment transport and steep slopes occur. In some cases, sloping grids are used in the construction of debris flow breakers. In this paper, the outflow process of an upstream-inclined grid with transversal bars is studied by using the dimensional analysis and the incomplete self-similarity theory. Next, the theoretical analysis shows that a power equation can be used for establishing the stage-discharge equation. The coefficient of the power equation depends on both the slope angle and the void ratio, whereas the exponent depends only on the slope angle. Finally, this deduced stage–discharge relationship is tested by laboratory measurements obtained using a sloping grid with transversal bars having different values of the slope angle and the void ratio.

Construction activities require contractors to install, continuously monitor, and maintain controls to minimize erosion and sediment transport. Construction sites discharge up to 100 times more sediment per acre than agriculture land activities because of mechanized compaction of bare soils that decreases infiltration capacity, increases runoff volumes, and increases erosion potential. Silt fence perimeter controls are widely used by the construction industry to intercept and impound stormwater runoff sheet flow, forming large impoundment areas ideal for sedimentation. Ditch checks are often used to minimize channel erosion and promote sedimentation in conveyance channels through runoff impoundment. Structural failures of silt fence have caused many state agencies to exclude their use in concentrated flows. Researchers at the Auburn University-Erosion and Sediment Control Testing Facility (AU-ESCTF) have evaluated the use of wire backed, nonwoven geotextile silt fence as ditch checks using large-scale testing techniques. This research has shown that silt fence, properly installed, can be used as a ditch check successfully. A longevity test of an enhanced silt fence ditch check installation resulted in sediment retention of 91.2% by volume.

A design storm definition procedure for the sizing of channels within mixed urban and lowland rice drainage systems is developed, with reference to the Northern Delta in Vietnam. By analyzing a 20-years-long time series of rainfall observations recorded at Hanoi monitoring station, typical storm events were identified and a set of suitable design storms was determined and recommended for the optimal design storm selection. A procedure to select an optimal design hyetograph is then defined, based on a combination of the design storm method and continuous simulation. A set of simulation experiments on a fictitious basin was finally carried out to support the choice of the storm temporal pattern providing the best performance in terms of reproduction of runoff peaks.

In this work, the probability distribution of peak discharge at the hillslope bottom is determined hypothesizing a prevalent Hortonian mechanism of runoff production for a given rainfall duration. As is well known, the probability distribution of peak discharge depends on the probability of both the rainfall event as well as that of the antecedent soil moisture conditions. In particular, the probability of the rainfall event is calculated according to the familiar rainfall duration–intensity–frequency approach, whereas the ecohydrological method from the literature is used here to define the probability of the antecedent soil moisture conditions. The latter depends on a set of parameters describing the dynamic interactions between average climate, soil and vegetation. By using the Monte Carlo procedure, the peak discharge is derived for a given rainfall duration and for each antecedent moisture condition/rainfall intensity pair from a physical-based model from the literature, by coupling the analytical solution of the overland flow equations over a hillslope with an established model that accounts for the infiltration process. Thus, the probability of peak discharge is evaluated via the typical multivariate probability distribution procedure. The methodology proposed was applied to three soil classes, i.e., silty clay loam (SCL), silty clay (SC), and silty loam (SL), for three climatically diverse Sicilian localities, namely Acireale (eastern Sicily, along the Ionian coast), Enna (central mountainous region), and Trapani (westernmost coast). For each of these places, precipitation and temperature data sets are widely available.

The cost and time involved in frequent field observations pertaining to quantification of nitrate leaching below the crop root zone leads to the use of simulation models, which is a more plausible approach. Nitrate leaching below the root zone of a maize–wheat cropping system under surface irrigation was assessed. The model’s predicted results pertaining to water percolation and nitrate leaching were in line with the observed data, with root mean square error (RMSE) values close to zero, and index of agreement values close to 1. The seasonal percolation of water below 120 cm soil depth in maize and wheat were 36.5 and 27.5% of applied water, respectively. Similarly, nitrate leaching below 120 cm soil depth was 18.1 and 14.3% of the applied nitrogenous fertilizer in maize and wheat, respectively. Under similar conditions, the nitrate leaching under a maize–wheat cropping system was $6.8\mathrm{kg}{\mathrm{NO}}_3{\mathrm{ha}}^{-1}$ less than in a rice–wheat cropping system. Furthermore, nitrate leaching below the crop root zone under different fertilizer application rates was estimated and best-fit second-order polynomial equations were developed. The equations can be used for estimation of nitrate leaching under different fertilizer input scenarios of maize-grown and wheat-grown areas under similar hydro-agro-climatic regions.

Microirrigation plants, if properly designed, allow water use efficiency to be optimized and quite high values of emission uniformity to be obtained in the field. It is known that disposing paired laterals, in which two distribution pipes extend in opposite directions from a common manifold, contribute to increasing water use efficiency. Recently, an analytical procedure has been proposed to optimally design paired drip laterals on uniform slopes under the assumption of neglect: (1) the variations of the emitters’ flow rate along the lateral, and (2) the local losses due to the emitters’ insertions. However, this procedure is not readily usable for every geometric and hydraulic characteristic of the lateral and slope fields because it requires solving a system of implicit equations. This study derives simple explicit relationships, reproducing the proposed approach, allowing derivation of the design variables that are required for the optimal design. Moreover, an easy method to determine the best position of the manifold associated to the optimal lateral length on uniform slopes is proposed, making evident a very moderate influence of the geometric and hydraulic characteristics of the lateral. The proposed procedure was successful compared with that derived by the analytical solution. Applications of the proposed relationships, considering different design parameters, are presented and discussed.

This study introduces the weed optimization algorithm (WOA) to optimal reservoir operation. The WOA is a metaheuristic optimization method inspired by weeds’ life cycle. The effectiveness of the WOA is demonstrated with the optimization of mathematical functions and reservoir systems. The WOA is applied in continuous-time and discrete-time formulations of reservoir-operation optimization and its results are compared with global optimal solutions obtained with nonlinear programming (NLP), linear programming (LP), and the genetic algorithm (GA). The results show the WOA’s fast convergence to solutions that are very near the global optimal solutions of the reservoir optimization problems.

This study proposes a factorial two-stage irrigation system optimization model (FTIM) for supporting agricultural irrigation water-resource management under uncertainty. The FTIM incorporates fractional factorial design, two-stage stochastic programming (TSP), interval linear programming (ILP), and interval probability and is applied to agricultural water allocation. The FTIM can take full advantage of conventional two-stage optimization approaches to tackle uncertainties presented as intervals, to investigate potential interactions among input parameters and their influences on system performance, and to enhance applicability to dual uncertainties expressed as interval probabilities. The proposed FTIM approach is for the first time applied to a hypothetical case study of water resource allocation in an agricultural irrigation problem. The results indicate that the effects of parameters on the objective function are evaluated quantitatively, which can help decision makers screen out significant parameters, analyze their interactions in model response, and identify possible schemes with maximized net system benefit. Especially for the study problem, the most positive significant factor affecting total net benefits is water quality at a medium flow; penalties resulting from undelivered water and benefit rates of onion farms in both periods have negative effects.

For landslide mitigation purposes, a system of two screen dams was created along the main channel of the Capreria River in Sicily. The de facto constructed wetlands occasioned behind the flow-path barriers produced, for several years, an appreciable reduction of organic load of the upstream municipal wastewaters from the nearby town of Riesi, Italy. This coincidence inspires the prospect of promoting a multifunctional role for these slope-stabilization works, thereby allowing them to be viewed from an intriguing and innovative planning perspective.

Agricultural activities are considered the leading cause of surface water quality degradation in the United States. While agricultural production in the state of Alabama is mainly rain-fed, irrigation is currently being promoted to reduce drought vulnerability associated with the El Niño Southern Oscillation (ENSO). It is not clear, however, how increased irrigation and ENSO-induced seasonal to interannual climate variability will affect the transport of pollutants [mainly nitrogen (N) and phosphorus (P)] to surface water bodies. The objective of this study was to quantify the effect of irrigation and ENSO on nutrient transport. A standard model to assess soil and water was applied in the Big Creek watershed of southwest Alabama to address this objective. The hydrologic and water quality parameters of the model were calibrated and validated by comparing model predictions with 15 years of observed data, and the effect of irrigation was evaluated. Model simulations were performed for 59 years (1950–2008) to quantify the effect of ENSO on nutrient transport. Results show that total nitrogen (TN) and total phosphorus (TP) loads increased by 4 and 3%, respectively, when irrigation was applied to cropland subwatersheds. The increase in TN load was significant at 90% confidence level ($\alpha =0.10$), while the increase in the TP load was nonsignificant at $\alpha =0.1$, indicating that TN transport is more sensitive to irrigation. Further, results suggest that El Niño generates higher nutrient loads in November, January, February, May, and July as compared to La Niña. Overall, irrigation increased nutrient transport (especially TN) within the watershed; this increase was affected by ENSO, with the El Niño phase generating greater loads than the La Niña and Neutral phases. However, inappropriate management of nutrient application can lead to greater negative impacts on water quality than irrigation. Although, the study only examined one coastal plain watershed, the results are expected to be applicable to much of the ENSO-affected coastal plain area of the southeast United States.

A few risks restrict the sustainable development of wastewater land application including potential nitrogen contamination to groundwater. One important component is nitrogen loss caused by denitrification in a nitrogen mass balance to control nitrogen leaching. Few field studies have been specifically conducted to investigate denitrification in wastewater land application systems. The objective of this study was to quantify denitrification at a wastewater land application site located in a semiarid area. The denitrification rate was measured within three soils at the City of Lubbock Land Application Site in three different months. One-way ANOVA and a t-test were used to compare the differences of averages of many groups of data and of two groups of data at the $p<0.05$ level, respectively. If ANOVA or the t-test is not applicable, the Kruskal-Wallis one-way analysis of variance on ranks and the Mann-Whitney rank sum test were employed to compare the differences of medians of many groups of data and of two groups of data at the $p<0.05$ level, respectively. The denitrification rate in January was as high as 210 g ${\mathrm{N}}_2\mathrm{O}\text{-}\mathrm{N}/\mathrm{ha}/\mathrm{day}$, while soil moisture was 19.4%. The denitrification rate ranged from 0.5 to 2,229.2 g ${\mathrm{N}}_2\mathrm{O}\text{-}\mathrm{N}/\mathrm{ha}/\mathrm{day}$, which were the results of combined effects of environmental variables. Further and more detailed field investigation and quantification of denitrification are required in order for advanced nitrogen mass balance and sustainable nitrogen management at a wastewater land application site.

Evaporation is one of the sources of water loss from artificial reservoirs used by the agricultural sector. Current methods of covering artificial reservoirs are too costly to be used by poor, small-scale farmers. This paper presents a method for using waste polyethylene terephthalate (PET) bottles to reduce the evaporative losses from open tanks. This water-conservation method was tested using eight evaporation pans with daily water level measurements to record evaporation rate. Four pans were used as controls, two were covered with empty waste PET bottles, and two were covered with bottles partially filled with soil. The experiment showed an average reduction in evaporation by 40% with the PET bottle treatment, with a 90% confidence of reducing evaporation by at least 18%. The addition of soil did not affect the degree of evaporation reduction. Given the local economics of the region surrounding Pune, India, it was found that this intervention can save water at a cost of $\mathrm{US}\$0.09/{\mathrm{m}}^3$.