Journal of Irrigation and Drainage Engineering

Farmers continue to show great differences in irrigation water use, even for a given location and crop. Irrigation advisory services have narrowed the gap between scientific knowledge and on-farm scheduling, but their success has been limited. The performance of sprinkler irrigation is greatly affected by factors such as wind speed, whose short-time variability requires tactical adjustments of the irrigation schedule. Mounting energy costs often require the consideration of interday and intraday tariff evolution. Opportunities have arisen that allow these challenges to be addressed through irrigation controllers guided by irrigation and crop simulation models. Remote control systems are often installed in collective pressurized irrigation networks. Agrometeorological information networks are available in regions worldwide. Water users’ associations use specialized databases for water management. Different configurations of irrigation controllers based on simulation models can develop, continuously update, and execute irrigation schedules aiming at maximizing irrigation adequacy and water productivity. Bottlenecks requiring action in the fields of research, development, and innovation are analyzed, with the goal of establishing agendas leading to the implementation and commercial deployment of advanced controllers for solid-set irrigation.

The estimation of reference evapotranspiration ($E{T}_0$) is very important for the management of water resources and the determination of the water budget, especially under arid conditions. The applicability of simple forms of Penman equations that were recently developed by Valiantzas is investigated in this study. The new empirical equations are applied to daily climatic data from four stations located in the Mediterranean region of Turkey: Adana, Antalya, Isparta, and Mersin. The results are compared with the $E{T}_0$ values obtained by Food and Agricultural Organization 56 Penman-Monteith and the following empirical equations: Copais, Turc, Hargreaves-Samani, Hargreaves, Ritchie, and Irmak. Root mean square errors, mean absolute errors, and determination coefficient statistics are used for comparison of the empirical models. The results indicate that the Valiantzas equation with full weather data performs better than the other empirical methods at stations in Adana, Antalya, and Isparta. In the Mersin station, however, the Copais equation perform the best out of the nine methods. The worst estimates are generally obtained from the Turc method.

As the use of pervious concrete pavements increases, evaporation of storm water retained in the pervious concrete system becomes an important design parameter. This paper extends the knowledge of experimentally determined evaporation rates. The experimental setup consists of a column containing pervious concrete and coarse stone hanging in balance with a column of similar weight. The authors used a load cell to capture any changes in the weight between the two columns as the result of addition, drainage, and evaporation of water in the system. Results show the amount of water present in the system, cumulative evaporation, and evaporation rates calculated in terms of 24-h averages. The calculated evaporation rates start at a maximum of $0.02\mathrm{mm}/\mathrm{h}$ and decrease with time, reaching a plateau towards the end of the experiment when the column is considered dry. In addition, the decreasing slope of evaporation rate curves with respect to the decrease in the amount of water present in the experimental column indicates that evaporation is a nonlinear function of the amount of water present in the system.

The aim of this study was to investigate the effects of drainage processes on non-point-source pollution in a complex irrigation and drainage system. Field experiments were conducted to measure quality and quantity of leakage and irrigation-return water in field drains, lateral drains, and the main drain during paddy-growing periods for 2 years. Water-flow and chemical-transport processes from paddy fields to field drains were simulated numerically. A modified Muskingum method was proposed to calculate the processes of water flow and chemical transport in lateral and main drains. Results showed that the Muskingum method was applied successfully to calculate the drainage and chemical-transport processes, as well as to quantify the effect of drain storage on the processes. Results from the field experiments and simulations indicated that the fate of ammonium (${\mathrm{NH}}_4^{+}$), nitrate (${\mathrm{NO}}_3^{-}$), and chemical oxygen demand (COD) in the system was primarily controlled by the drainage processes. Mass of ${\mathrm{NH}}_4^{+}$ discharged from paddy fields to drains was mainly through subsurface flow (i.e., the leakage from paddy fields to field drains) and mass of ${\mathrm{NO}}_3^{-}$ mainly through deep leakage (i.e., the leakage from paddy fields to groundwater and finally to drains). The COD transportation was through irrigation-return water, subsurface flow, and deep leakage. Eighty-one percent of the discharged ${\mathrm{NH}}_4^{+}$ mass by leakage and 64% of the discharged ${\mathrm{NO}}_3^{-}$ mass were through subsurface flow and deep leakage, respectively. Approximately 15% of the applied nitrogen in the paddy field was lost through the drainage processes. Within the total discharged nitrogen in the main drain, 38% and 62% were from subsurface flow and deep leakage, respectively. The methods and results from this study should be useful to characterize non-point-source pollution in paddy-irrigation district.

This paper presents an economic framework of all potential benefits and costs arising from present activities and implementation of policies; including crop production costs, capital and operating costs of development projects, environmental costs, pumping costs, and costs imposed by reduced crop production. The methodology was applied for a water resource system of Rafsanjan Plain, in the central part of Iran. The water supply and demand system of the region was simulated into two different models. The former was a decision support system (DSS)-based model, and the latter was a system dynamics-based model. Despite some minor differences, the principal characteristics of the region was similarly simulated in both models. Then, management scenarios were generated considering different strategies including the interbasin water transfer, improvements in irrigation techniques, limiting future expansion of cultivated area, and restricting withdrawal from groundwater. By combining these strategies, various scenarios could be generated. To evaluate the scenarios, the net present value (NPV) factor, and a multi criteria decision making (MCDM) model are used to evaluate the scenarios. The entropy information theory is also used to calculate the weights of different criteria in ranking different scenarios. This study demonstrates how combining multiple tools and techniques along with an economic framework could effectively assist decision makers to understand the consequences of a taken strategy in a specific region. The results show that despite the shortage of water resources in this area, interbasin water transfer is not viable.

Free surface flow in open-channel transitions is characterized by distributions of velocity and pressure that deviate from uniform and hydrostatic conditions, respectively. Under such circumstances the widely used expressions in textbooks [e.g., $E=h+U^2/(2g)$ and $h_c={(q^2/g)}^{1/3}$] are not valid to investigate the changes in velocity and depth. A depth-averaged form of the Bernoulli equation for ideal fluid flows introduces correction coefficients to account for the real velocity and pressure distributions into the specific energy equation. The behavior of these coefficients in curvilinear motion at and in the neighbourhood of control sections was not documented in the literature. Herein detailed two-dimensional ideal fluid flow computations are used to characterize the entire velocity and pressure fields in typical channel controls involving transcritical flow, namely the round-crested weir, the transition from mild to steep slope and the free overfall. The detailed two-dimensional ideal fluid flow solution is used to study the behavior of the depth-averaged coefficients, and a novel generalized specific energy diagram is introduced using universal coordinates. The development is used to pursue a simplified critical flow theory for curved flow, relevant to water discharge measurement with circular weirs.

Rapid pipe filling or emptying of water mains and sewer systems is accompanied by transitions between free surface and pressurized flow regimes and subatmospheric unsteady flows, leading to the propagation of pressurized/depressurized wavefronts along the pipe. The occurrence of these phenomena is often more common when the flow becomes transient. The modeling of such flows is complex, and it requires the inclusion of several types of propagating wavefront to better figure out the effective transient phenomena and to apply the appropriate equations. When simulating mixed flows in closed conduits such as tunnels, sewers, and water mains with shock fitting models, the wavefront is determined by continuity, momentum, and energy equations. To better manage the application of these equations, experimental investigation was conducted on different depressurizing wavefront shapes. The behaviors, velocities, and effects of included air pockets are analyzed according to a series of pipe slopes and reservoir water levels. The flow behavior presents particular differences according to the pipe slope and the pipe upstream end status. When the upstream end of a pressurized pipe is closed, water remains immobile in the full sectional area at any location along the pipe length. Flow occurs in the pressurized zone only after the passage of the depressurized wavefront (DWF). Results show that the transition from pressurized flow to free-surface flow is accompanied by a negative wavefront illustrated by three physical shapes. First, the wavefront takes a pronounced concave shape followed by a 0.8D flow depth zone for low pipe slope values (less than 1.0%). Second, as the pipe slope value becomes larger (1.8–5.5%), the wavefront head becomes sharper. A third and more complex shape, which is an intermediate between the previous two, is observed for pipe slope values of around 1.0–1.8%. Comparison between experimental and numerical results also shows some limitations in the simplified form of actual numerical solutions of the continuity, energy, and momentum equations due to the negation of variables such as energy loss and forces due to friction, gravity, viscosity, and surface tension. Balancing these equations indicates that only the continuity equation applied around the propagating wavefront matches well with the experimental results. The difference between measured and calculated values by the used energy and momentum equations can reach 10.4% of the diameter and 18.4% of the hydrostatic force in pressurized zones, respectively. Finally, the results show that the combination of the continuity and the energy equations gives the best findings, but with an overestimation of 14.4%. Incorporating the continuity and momentum equations, the wavefront celerity is overestimated by as much as 24.3%. The combination of the momentum and the energy equations presents the worst findings, with a celerity value overestimated at by much as 69.4% and a water velocity value in the free surface underestimated by as little as $-8.6\%$. These results show the limits in applying the simplified form of the momentum and energy equations when wavefronts are examined. Taking into account parameters such as surface tension can balance the equations to obtain better results. Also, the obtained analytical forms may be applied easily by engineers who need simple formulas to estimate hydraulic parameters instead of using complex modeling.

This study was conducted to determine the spatial distribution of soil moisture and fine roots (white, diameter $<2\mathrm{mm}$) growth under water storage pit (WSP) irrigation of apple trees in an experimental apple orchard. Three irrigation treatments have been used since 2009—${\mathrm{WSP}}_{60}$ (water storage pit irrigation, pit depth 60 cm), ${\mathrm{WSP}}_{40}$ (water storage pit irrigation, pit depth 40 cm), and CK (border irrigation)—in controlled trials. In the considered soil profile of a 0–2 m depth, the soil moisture was mostly distributed in the middle-deep soil layer (40–150 cm) of the rhizosphere of apple trees, yet this was lower at a depth of 0–40 cm under WSP (${\mathrm{WSP}}_{60}$ or ${\mathrm{WSP}}_{40}$) irrigation. For CK, the soil moisture was mainly concentrated within a depth of 0–60 cm of the rhizosphere of apple trees. Compared with CK, the fine root length density (FRLD) in the surface soil (0–40 cm) was reduced by 7.52–7.56% under WSP (${\mathrm{WSP}}_{60}$ and ${\mathrm{WSP}}_{40}$) irrigation, whereas in the middle-deep soil layer (40–110 cm), it increased by 10.32–11.70%. The total amount of FRLD in a 0–2 m soil profile under WSP irrigation was 1.19–1.10 times that under CK. The FRLD increased, and the location of the highest concentration of fine roots deepened under WSP (${\mathrm{WSP}}_{60}$ and ${\mathrm{WSP}}_{40}$) irrigation. Thus, this method benefited roots by allowing them to absorb water in a wider area and improving drought resistance. The results obtained provide a theoretical basis for application of the WSP irrigation method.

Based on Section 438 of the Energy Independence and Security Act of 2007, the U.S. Environmental Protection Agency (USEPA) published a report providing technical guidance that recommends using the 95th percentile rainfall event for federal development or redevelopment projects to preserve or restore predevelopment hydrology of the site. In this study, the 95th percentile rainfall depths using daily rainfall data were computed following the USEPA guidelines from 18 selected weather stations. The purpose of this study is to investigate whether the 95th percentile daily rainfall depths truly represent the 95th percentile event rainfall depths. For analysis, the 95th percentile event rainfall depths were computed using hourly rainfall data for storm events separated by minimum interevent dry periods of 6, 8, 12, 18, 24, 48, and 72-h and compared with the 95th percentile daily rainfall depths. The 95th percentile event rainfall depths calculated using minimum interevent dry periods of 6–72 h are on average 11–100% greater than the 95th percentile daily rainfall depths recorded at 18 selected weather stations.