Journal of Irrigation and Drainage Engineering

Increasing municipal water demand has led to new innovations in water-saving technology. Evapotranspiration-based irrigation controllers, also known as weather-based irrigation controllers, are a technology that use evapotranspiration (ET) estimates to schedule irrigation. Although real-time on-site data collection could help improve data quality, limited data parameters collected or simplified reference evapotranspiration (${\mathrm{ET}}_{\mathrm{o}}$) estimation methods from an on-site sensor could potentially have an impact on estimated ${\mathrm{ET}}_{\mathrm{o}}$ values for stand-alone controllers. Conversely, collection of data from off-site weather stations that are not representative of the local conditions could lead to inaccurate ${\mathrm{ET}}_{\mathrm{o}}$ estimations for local irrigation sites. The Weathermatic SL1600 and Toro Intelli-sense controllers were selected for testing because of the different methods of data collection and ${\mathrm{ET}}_{\mathrm{o}}$ estimation. This study was conducted in two locations: Wimauma and Gainesville, Florida. In Wimauma the Weathermatic controller significantly overestimated ${\mathrm{ET}}_{\mathrm{o}}$ compared to on-site ${\mathrm{ET}}_{\mathrm{o}}$ estimates using the ASCE-EWRI standardized method (${\mathrm{ET}}_{\mathrm{o}}$) by 9–15% for the duration of the study, while ${\mathrm{ET}}_{\mathrm{o}}$ sent to the Toro controllers was similar to on-site ${\mathrm{ET}}_{\mathrm{o}}$ estimations (1–3%) for the duration of the study. However, the Weathermatic controller overestimated ${\mathrm{ET}}_{\mathrm{o}}$ for every season (fall: 5–8%; winter: 6–8%; spring: 11–16%; summer: 22–25%), and the Toro controller overestimated ${\mathrm{ET}}_{\mathrm{o}}$ in the summer seasons (12%) and underestimated ${\mathrm{ET}}_o$ in the winter seasons (17%). In Gainesville, the Weathermatic and Toro controllers both overestimated ${\mathrm{ET}}_{\mathrm{o}}$ compared to on-site ${\mathrm{ET}}_{\mathrm{os}}$ (30 and 10%, respectively). However, when compared to ${\mathrm{ET}}_{\mathrm{os}}$ using data from the Gainesville National Oceanic and Atmospheric Administration (NOAA) weather station, the ${\mathrm{ET}}_{\mathrm{o}}$ of the Toro controller was consistent with the equation and location of the weather data that were likely used by the weather service to calculate ${\mathrm{ET}}_{\mathrm{o}}$, indicating that this was likely the data source for the ${\mathrm{ET}}_{\mathrm{o}}$ sent to the Toro controller. Overall, ${\mathrm{ET}}_{\mathrm{o}}$ sent to and used by the Toro Intelli-sense controllers was closer to on-site ${\mathrm{ET}}_{\mathrm{o}}$ estimations than that which was estimated by the Weathermatic SL1600 controllers on site.

The mechanical and drainage properties of graded aggregate base (GAB) materials used in mechanistic pavement design are the level one inputs. Several highway agencies need an evaluation of the stiffness and drainage characteristics of GAB stone delivered at highly variable gradations to construction sites. To fulfill the current need, the mechanical and drainage properties of seven GAB materials with varying petrography and physical properties were evaluated in the laboratory and field. The resilient modulus and hydraulic conductivity test results obtained in the laboratory were compared with the field measurements. The summary resilient moduli at optimum moisture content (OMC) were generally lower than those at OMC–2%; however, permanent deformations increased with the addition of moisture content. The correlation between the mean laboratory and field stiffness/modulus values was fair to acceptable ($R^2=0.65$ to 0.94), and additional measurements may yield a stronger correlation. An increase in base thickness from 6 to 60 cm resulted in a 1.7 to 2.4 times decrease in drainage time depending on the analytical method used. The material cost decreased 1.6 times with a change in the drainage quality from poor to excellent or time-to-drain from 10 to 0.08 days. Similarly, a 2.4 times decrease in cost was noticeable with a layer coefficient increase from 0.08 to 0.14. The resilient modulus, permanent deformation, and hydraulic conductivity of GAB materials should be evaluated to design a highway base with adequate stiffness and drainage performance.

Low-level outlet works through dams are typically used to provide irrigation, reservoir sediment flushing, reservoir draw down, and/or minimum downstream flows to meet biological needs. To reduce the likelihood of negative pressure development downstream of the control gate, which may lead to cavitation noise, vibration, and damage, air vents are typically installed downstream of the gate. Undersized air vents may allow vapor pressure and cavitation to occur; oversized air vents have a negative economic impact. Air demand design criteria have been developed for vertical control gates (common to larger dams). The guidance for sizing air vents for an inclined slide gate, which are common for small-to-medium-sized embankment dam geometries, however, is limited. This study compares laboratory-scale and prototype-scale air-demand data. The influences of conduit slope, hydraulic jump presence, and air delivery system geometry on air demand were found to influence air demand. A method for estimating the required air vent diameter for a low-level outlet with an inclined slide gate at the inlet is presented.

Pervious concrete systems can reduce storm water runoff, minimize non-point-source pollution, and increase groundwater recharge. However, pervious concrete has the potential to clog, reducing its infiltration rate enough to eliminate these benefits. Pervious concrete clogs when sediment builds up at the surface or within the pervious concrete void matrix, blocking the flow path through the void matrix, thus reducing the infiltration rate. This study measured the effect of sediment accumulation on the hydraulic conductivity of pervious concrete. The resulting data were used to develop a model that predicts the hydraulic conductivity of pervious concrete based on the initial hydraulic conductivity and the amount and type of accumulated sediment.

The discharges flowing through rural drainage networks depend not only on the local climatic and hydrologic characteristics, but also on the geometric characteristics of the channels constituting the network. For this reason, the evaluation of the design discharges should be accomplished during the search of the optimal network. This leads to time-consuming optimization procedures, and it is desirable to devise efficient numerical alternatives. Two novel models, EGA and EGA-f, are proposed in order to increase the numerical efficiency of genetic algorithms (GAs) for the solution of the optimal rural drainage network problem. Both EGA and EGA-f procedures are based on the use of the nodal excavation depths at the channel ends as decision variables. Moreover, the EGA-f procedure improves EGA by freezing temporarily the design discharges during the optimization process in the case where uniform flows through the channels can be assumed. The application of the two models is demonstrated by means of numerical experiments, confirming their superiority over existing GAs for the optimization of rural drainage networks.

Laboratory experiments are conducted to measure the free-surface profile and the velocity field of an open channel flow over a semicylinder weir. The streamwise velocities of the flow are measured using a laser Doppler anemometer. The numerical simulation of the flow case having similar conditions with the experiment is performed. The basic equations of the problem are solved using the finite-volume method. A grid convergence analysis is applied to ensure the discretization error keeping within an acceptable limit for the predicted velocities. In the numerical modeling, the volume of fluid method is used to compute the free surface of the flow that interacts with the semicylindrical structure. In the numerical analysis, standard $k\text{-}\epsilon$, renormalization group $k\text{-}\epsilon$, realizable $k\text{-}\epsilon$, modified $k\text{-}\omega$, shear stress transport, and Reynolds stress turbulence closure models are employed. The computed results for the velocity field and free-surface profile of the flow are compared with the experimental data. The comparisons of the experimental and numerical results show that the numerical simulation using the Reynolds stress turbulence model provides better predictions for the horizontal velocities than the other turbulence models used herein.

In the past, several research experiments have focused on the hydraulic characterization of traditional drip irrigation systems, and different design methodologies have been proposed with the aim of achieving very high emitter discharge uniformity (EU). The increasing use of low-pressure lay-flat drip laterals, characterized by a thin-walled polyethylene pipe, makes necessary a specific determination of their hydraulic properties, aimed to a correct design of such systems. Here, the validity of an empirical local losses estimation model was assessed for five different commercial lay-flat drip tapes. Moreover, the errors in the maximum lateral lengths obtained for a fixed emitter uniformity, when the local losses are neglected or empirically estimated, were evaluated. The step by step (SBS) procedure was then implemented to model the hydraulic behavior of each tested lateral with values of the upstream pressure head different than those investigated. The experiments demonstrated that under the examined flow conditions, local losses represent a percentage variable between 2.0 and 11.4% of the friction losses measured in the laterals. Due to the limited contraction of flow streamlines produced by the emitters, the resulting values of the kinetic head coefficient, $\alpha$, were generally small and variable in the range between 0.020 and 0.060. The SBS procedure indicated that in lay-flat drip laterals, only when emitter spacing results are lower than 50 cm should it be necessary to take into account local losses, as the errors of ignoring such losses are negligible in the other cases. The results finally evidenced that the empirical local losses estimation model, valid for thick-walled laterals, generally overestimates $\alpha$, allowing a more conservative evaluation of the lateral lengths when a fixed EU is desired.

A new elliptical sharp-crested weir was developed to address discharge, pollution, and maintenance concerns associated with detention ponds. The elliptical weir was specifically designed to decrease the time and cost associated with clearing debris following storm events. A $2:1$ Froude-scale physical model was constructed and stage-discharge data were collected to analyze the stage-discharge relationship of the new weir. A total of 45 steady-state tests were conducted encompassing nine unique weir geometric configurations. The ellipse ratio varied from 12 to 16, and the gap width varied from 1.5 to 9.1 mm (0.005 to 0.030 ft). Empirical power-regression coefficients were determined for each of the configurations. Also, a theoretical rating equation was derived for the elliptical weir and a discharge coefficient of 0.642 was determined from analyzing the physical-model data. Trapezoidal integral approximation was used to develop an explicit approximate solution for the theoretical rating equation. By using the trapezoidal integral approximation, measured discharges were predicted with a mean absolute percent error of 3.55% for the data set, excluding discharges lower than $2.83\mathrm{L}/\mathrm{s}$ (0.10 cfs).

In this study, an integrated interval nonlinear programming model based on Jensen’s water production function is proposed for the optimal allocation of water resources under uncertainty in agricultural irrigation. The model provides an effective approach to solve the problems for crop irrigation schedules and to successfully deal with the inconsistencies in crop water requirements and rain capacity. The model can allocate the limited water to different growth stages of crops based on Jensen’s crop water production function, which further improves water use efficiency. The method provides the means to promote the development of water-saving irrigation and further improves the economic value of water resources. Two major advantages make the model unique in comparison to the other optimization techniques. First, it can solve the uncertainties of the agricultural water resources system, and the results are given in the form of intervals, which can provide more leeway for decision makers. Second, the rainfall was divided into 18 stages with 10 days per stage in this paper (each of the crop growth stages were matched with different stages); then, the limited water resources were optimally allocated to different crops in different growth stages based on Jensen’s model. The model not only increases the output per unit of water but also improves water use efficiency. In this paper, the Yongchang irrigation district in Wuwei was taken as an example to demonstrate the feasibility of the proposed model. The results are helpful for water resources managers in making decisions about water allocation and striking a balance between environmental and economic objectives.