Journal of Irrigation and Drainage Engineering

Quantitative information about the spatial and temporal patterns of compensatory root water uptake (RWU) in flood-irrigated pecan orchard is limited. We evaluated spatio-temporal compensated and uncompensated RWU patterns of mature pecan tree in a silty clay loam orchard using the HYDRUS (2D/3D) model. HYDRUS (2D/3D) simulations, which agreed well with measured water contents and temperatures at different soil depths and horizontal distances from the tree trunk, suggested that while both compensated and uncompensated RWU varied with soil depth they did not do so laterally because of similar spatial vertical distributions of root length density (RLD) for the under-canopy and the tree canopy dripline locations. Considering compensated RWU resulted in an increase in actual transpiration by 8%, and a decrease in evaporation and drainage by 5% and 50%, respectively, during a growing season. Simulated transpiration and relative transpiration (a ratio between actual and potential transpiration) values were correlated with measured transpiration and plant-based water stress indicators (stem and leaf water potentials), respectively. Overall, our results of the spatio-temporal compensatory RWU provide support to use HYDRUS (2D/3D) as a tool for managing efficient water use of pecan.

Overwetting and soil salinization processes are common in irrigated date palm orchards in Israel. Subsurface drainage systems are generally used to overcome soil salinity. Subsurface drainage models can contribute to the selection of a proper drainage system and its proper placement in the field. In this paper, the groundwater flow modeling program MODFLOW was used to simulate groundwater levels in a date palm orchard in Argaman, in the Jordan Valley, Israel. Using a three-layer groundwater flow model, the most efficient drainage system was a combination of 4.5-m depth primary drains and 3-m depth drains of different lengths installed at a different spacing between drains. Installation of this drainage system would cost approximately NIS$2.6 million, i.e., 30% less than the initially proposed project. Given certain input, a spatially distributed groundwater flow model such as MODFLOW can provide more reliable information than different analytical solutions for planning an effective subsurface drainage system.

Low impact development (LID) practices intercept storm-water runoff and infiltrate it through a range of media types and underlying soils. Hydrologic performance is typically evaluated by comparing inlet and underdrain outlet flows, but there is no standard practice for defining and measuring performance in LID structures designed without underdrains that infiltrate into the ground. Water content reflectometer (WCR) sensors were installed in the aggregate storage layer under permeable pavement and rain garden media to test their ability to measure the size and timing of the wetting front in infiltrating LID practices. WCR data were also used to monitor infiltration rates in the underlying soil beneath both practices. Bench-scale testing was performed to quantify the response of WCRs to saturated and unsaturated conditions and calibrate sensors to a range of water content values. Bench-scale testing revealed that WCRs installed in the aggregate were calibrated to volumetric water content (VWC) as the aggregate approached saturation. At partial saturation levels, however, mixing models did not accurately predict VWC; apparent permittivity is therefore the appropriate response metric to use under unsaturated flow conditions in the aggregate. WCR responses to a wide range of storm characteristics during the first 6 months of parking-lot and rain-garden monitoring are presented. These monitoring data demonstrated the effects of parking surface and rain-garden cell size on the maximum magnitude of WCR response, time lag from the onset of rain to WCR response, and degree of return to antecedent water content conditions following the end of the storm event. Spatial and temporal variability outweighed any effects of parking surface or cell size on wetting front rates in underlying soil. Methods to protect WCRs placed in the aggregate layer from construction activities of the permeable parking lot are also discussed.

Storing water in main irrigation canal reaches could be an influential strategy to improve the existing operational activities in the irrigation canals. However, the control of such a canal system will become much more complicated due to freeboards of the reaches temporarily decreasing. In this paper, Model Predictive Control (MPC) is applied to control the water level of an accurate model of a realistic main canal, which consists of 13 canal reaches, using an in-line storage operational strategy. Four different test scenarios are selected to cover a range of conventional to unconventional operational strategies by imposing limitations on the head-gate opening. Different target bands are created between the predefined allowed maximum and minimum water level for the canal reaches and the MPC is obliged to keep the water levels within these ranges. The results show that the in-line storage improves current operational performance of the canal system by compensating the existing delay times of flow traveling in the canal and gradual increasing and decreasing of the inflow that avoids large wave occurrences in the canal reaches.

Field experiments were conducted during kharif 2009 and 2010 at the Agricultural Research Station, Anantapur, located in the scarce rainfall zone of Andhra Pradesh in south India to assess the effect of dry spells or moisture stress at different crop growth stages on yield attributes, pod yield, and haulm yield of groundnut. The study was conducted in a 3-factor split-split plot design with conditions of (1) rainfed and irrigated as two main plots; (2) stress imposed during 30–50, 50–70, 70–90 days in 2009 and 50–90 days after sowing (DAS) in 2010 and “no stress” as four subplots; and (3) four varieties—ICGV-91114, K-6, TMV-2, and Narayani—as sub-subplots. Among varieties, Narayani gave significantly higher oil content compared with other varieties in both years. Among the stress conditions, significantly higher pod yield was attained under the no-stress condition compared with the stress that occurred during 70–90 DAS, but it was statistically at par with the stress that occurred during 30–50 and 50–70 DAS in 2009. In 2010, significantly higher pod yield was attained under the no-stress condition compared with the stress that occurred during 50–90 DAS. Among varieties, ICGV-91114 attained significantly higher pod yield compared with K-6 and TMV-2, but was at par with Narayani in 2009. However, the pod yields of varieties did not differ significantly in 2010. Among different growth stages of groundnut, maximum pod yield reduction was observed when the stress was imposed at the pod-to-kernel development stage, followed by the pod development stage (70–90 DAS) and the flowering stage (30–50 DAS) compared with no stress. Varieties ICGV-91114 and Narayani were drought resistant because of higher yield attributes, yield, and water use efficiency, and they could be recommended for cultivation under arid alfisols of southern India.

A full-prototype physical model was laboratory tested to determine a rating equation applicable to large Parshall flumes with supercritical flow. The experimental program was composed of a 1.5-m (5-ft.) Parshall flume configuration and included 11 tests with discharges up to $0.854{\mathrm{m}}^3/\mathrm{s}$ (30.15 cfs) and Froude numbers varying from 0.67–1.31. The resulting 1.5-m (5-ft) Parshall flume data were compared to existing rating equations for predicting discharge in a Parshall flume with subcritical and supercritical flow. A new rating equation specific to supercritical flow in large Parshall flumes was developed. Further, an analysis was conducted, which determined that varying regression coefficients on an existing supercritical flow-rating equation also produced an accurate rating equation for large Parshall flumes. A convergence ratio was defined and used to determine the flow regime within the flume where the 1.5-m (5-ft) Parshall flume data, combined with previously-published small Parshall flume data, indicated three convergence ratio zones: (1) subcritical, (2) transition, and (3) supercritical. Guidance was provided for rating equation selection based on the convergence ratio zone and flume size.

To design the off-stream detention basin by the sides of rivers or channels, flood-level reduction in main channels should be evaluated under unsteady flow. Flow discharge diverted to the side weir from the main stream can be calculated practically by the standard weir or lateral weir equations. In this study, experimental and numerical modeling with a side-weir detention basin was conducted for unsteady flow. The experimental results were compared with the numerical backwater profile calculation considering the water discharge overflowed into the basin from the channel. The overflowed discharge was estimated by the standard weir and lateral weir equations for various flow types at the side weir. The standard weir equation accurately predicted flow discharge diverted to the side weir for free overflow condition. The lateral weir equation calculated a precise flood level and time of peak flow for the condition modeled, especially when the various flows, including free and submerged overflows, were developed at the side weir.

Side weirs are hydraulic structures widely used in practice and extensively studied in the technical literature. The flow along a side weir is a classic example of spatially varied flow, the study of which is generally performed by means of a momentum or energy approach. The momentum approach is usually more accurate but requires the experimental estimation of correction coefficients leading to a formulation that is difficult to apply to a practical design. The energy approach, instead, is not as accurate when the flow depths on the side weir are significantly higher than the same weir crest. A novel, simplified theoretical model for the study of single side weir in a circular pipe, operating in supercritical flow, is proposed. The model originates from an experimental analysis of the flow power variation along the side weir. The proposed model has shown good performance in free surface representation and is capable of estimating the lateral outflow with good accuracy. The suggested formulation is compared with others of acknowledged value, showing comparable performance.

A micrometeorological approach based on the surface energy balance was adopted to estimate evapotranspiration fluxes and crop coefficient data from an irrigated cactus pear [Opuntia ficus-indica L. (Mill.)] orchard under Mediterranean climatic conditions. High-frequency temperature readings were taken above the canopy top to get sensible heat flux values ($H_{\mathrm{SR}}$) using the surface renewal technique. These values were compared against eddy covariance sensible heat fluxes ($H_{\mathrm{EC}}$) for calibration. Latent heat flux (or evapotranspiration, ET) was obtained by solving the daily energy balance equation. Measurements of soil hydraulic components were integrated with the analysis of the surface energy fluxes and crop development in terms of phenology and aboveground biomass accumulation. Microlysimeters were used to compute evaporation rates, allowing the separation of daily transpiration from ET data. Ecophysiological measurements were carried to estimate dry weight accumulation and partitioning. Cactus pear evapotranspired a total of approximately 286 and 252 mm of water during the two monitored growing seasons, respectively. Average daily values of crop (${\mathrm{ET}}_c$) and reference (${\mathrm{ET}}_0$) evapotranspiration were in the order of 2.5 and 5.0 mm, respectively, with a corresponding value of the mean crop coefficient of approximately 0.40. The annual dry mass fixed per single tree was $38.8\pm 1.3\mathrm{kg}$, with a total production of $12.9\mathrm{t}{\mathrm{ha}}^{-1}$, which is comparable to many $C_3$ and $C_4$ plants and resulted in a water use efficiency (WUE) of 4.6 and $4.4\mathrm{g}\mathrm{DM}\mathrm{kg}{\mathrm{H}}_2{\mathrm{O}}^{-1}$ in 2009 and 2010, respectively. The stem area index (SAI) was 3.5.

In this paper, the outflow process of an upstream inclined grid with longitudinal 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 and an exponent of the power equation depend on the slope angle and the void ratio. Finally, this new stage discharge is tested by using measurements obtained by laboratory runs conducted in this investigation.