Journal of Irrigation and Drainage Engineering

Grate inlets collect surface runoff from the roadway and other land surfaces and connect to a drainage network. Surface runoff that does not discharge to a drainage system because of insufficient inlet capacity can cause flooding and excessive hazards to pedestrians and motorists, as well as diminished roadway durability, safety, and efficiency. To minimize these risks, this paper suggested a new drainage inlet by surrounding the conventional grate inlet with porous asphalt referred to as an efficient grate inlet. Testing was performed on a $1:1$ scale road model with simulated runoff of various inflows. Various geometrical parameters were simulated, such as discharge rate, longitudinal slope, cross slope, and the dimensions of porous asphalt. This paper investigates the drainage efficiency of the efficient grate inlet (EGI) and comparing it to that of the conventional grate inlet (CGI). An empirical relationship is proposed for the inlet efficiency as a function of the width of porous asphalt and roadway flow characteristics.

To achieve efficient simulation for surface shallow-water flows in large-scale basin irrigation, a semi-Lagrangian numerical solution for two-dimensional shallow-water equations in unstructured spatial cells was developed. In this numerical solution, all state variables were defined at the finite-volume cells and presented piecewise constant distribution. A redistribution method of the state variable values for the inner node of a spatial cell was developed and can strictly preserve mass conservation. Then, a simple displacement formula along a characteristic-line was applied to connect the variable values between a unknown and its adjacently known time steps of the semi-Lagrangian form of two-dimensional shallow-water equations. The water level gradient term was specially treated to accurately balance the water level distribution at the wet or wet–dry spatial cell interface. Simultaneously, an existing finite-volume method with a fully implicit temporal solution for the Eulerian form of two-dimensional shallow-water equations in a triangular spatial cell was selected as a comparative model. Finally, a performance comparison between the semi-Lagrangian and Eulerian numerical solutions was analyzed based on three basin irrigation experiments. The results show that the semi-Lagrangian and Eulerian numerical solutions presented similar average relative errors between the observed and simulated data. The semi-Lagrangian numerical solution exhibited lower mass conservation ability, but its water quantity balance errors were less than 0.3% for three experiments. The semi-Lagrangian numerical solution was six times more computationally efficient than the Eulerian numerical solution in central processing unit (CPU) time. Thus, the semi-Lagrangian numerical solution is more suitable to simulate shallow-water flows in basin irrigation.

A study to assess soil water redistribution under mobile drip irrigation (MDI), low-energy precision application (LEPA), and low-elevation spray application (LESA) was conducted under a center-pivot irrigation system. Water application devices included MDI (${\mathrm{MDI}}_1$ and ${\mathrm{MDI}}_2$ flow rates of 3.7 and $7.6\mathrm{L}/\mathrm{h}$, respectively), LEPA bubbler, and LESA spray. Measured soil water content was used to calibrate HYDRUS (2D/3D) version 2.05.0270, which was then used to simulate water redistribution within the soil profile after irrigation by MDI, LESA, and LEPA. Results showed that for all the devices, the effect of irrigation was mostly limited to the top 60 cm of the soil profile 72 h after irrigation. MDI driplines and LEPA showed the highest lateral soil water redistribution. The mean soil water contents for ${\mathrm{MDI}}_1$, ${\mathrm{MDI}}_2$, LEPA, and LESA at a depth of 30 cm were 0.31, 0.31, 0.31, and $0.33\mathrm{cm}·{\mathrm{cm}}^{-3}$ respectively; at a depth of 60 cm the corresponding values were 0.28, 0.28, 0.26, and $0.28\mathrm{cm}·{\mathrm{cm}}^{-3}$, respectively. The interquartile range of soil water content at 30 cm for ${\mathrm{MDI}}_1$ and ${\mathrm{MDI}}_2$ was $0.04\mathrm{cm}·{\mathrm{cm}}^{-3}$; the value for LEPA was $0.02\mathrm{cm}·{\mathrm{cm}}^{-3}$. The results indicated greater nonuniformity under MDI than under LESA. The results also showed that the MDI water redistribution pattern was similar to that of LEPA, but horizontal uniformity was less than with LESA. MDI had 48% and 19% less runoff potential compared with LEPA and LESA, respectively. Although soil water redistribution uniformity under MDI was less than under LESA and LEPA, it enabled better infiltration and lessened runoff potential.

Water dependencies and agricultural expansion have led to a remarkable increase in water demand. Proper management of water supply and demand is a crucial challenge in planning for sustainable development. Because the prevailing water allocation system in developing countries is based on low tariffs, particularly in the agricultural sector, a robust accounting cannot be implemented. The objective of this paper is to investigate the economic value of a change from gravity to drip irrigation using groundwater resources. It is implemented in the Rafsanjan plain, in central Iran, where the irrigation practices lead to unsustainable use of groundwater. In this area, the allocator (water authority board) is a governmental agency that can receive funding from other governmental agencies to affect water use policies. Considering the benefits accrued to the allocator and farmers (benefit for all agricultural water uses), the optimal investment in converting gravity irrigation systems to drip irrigation is determined. An economic framework is proposed with two simulation models [Water Evaluation and Planning (WEAP) and Vensim] to evaluate the dynamics of the water use benefits. According to the results, with expenditures of $65 million/year over a 25-year horizon, the discounted benefit to allocator and farmers in the year 2011 would be $60.48 and $911.9 million, respectively. The framework outlined can provide a mechanism to allocate water in a more precise way as well as to determine the economic value of water in the agricultural sector. The proposed methodology can be applied to other geographic settings.

This investigation deals with the mechanics of movement of singular quartz gravel and coarse sand riverbed particles upstream and over the inlet key of three Type A piano key weir (PKW) models, which were recorded with a high-speed camera. Acoustic Doppler velocimeter was used to obtain the upstream bed shear stress. The sediment threshold and regime over the upstream bed were compared with the previous investigations and found to be within the ranges. Generally, a sediment particle decelerates as it approaches the inlet key, but accelerates over it due to flow contraction and an increase in shear stress. Rolling and saltation regimes were observed over the key. The maximum particle velocity at the key end was highest in the 1-cycle model, then the 2-cycle model, then the 3-cycle model. Computational fluid dynamics (CFD) simulation shows a rapid increase in shear stress at the key end. For the used models, PKW required $17\%–43\%$ of additional shear stress on the upstream bed to pass sediment over the key. This study is useful for the in-channel application of PKW and sediment flushing over it.

The preservation of limited aquifer resources in the US Great Plains has driven the innovation and deployment of more efficient sprinkler packages for center pivot irrigation systems. One of the more efficient sprinkler packages available are in-canopy sprinkler packages, which hang low in the canopy. Although effective, they have the potential to become entangled in crop biomass and detach from the center pivot. Such detachments impact the efficiency and uniformity of the system, resulting in disrupted flow and pressure conditions, ultimately decreasing crop yield. Therefore, it is crucial that producers detect and replace missing in-canopy sprinklers immediately. A novel prototype monitoring system was designed using low-cost, publicly available technologies to monitor in-canopy sprinklers on a center pivot irrigation system and alert the user when and where an in-canopy sprinkler has become detached from the center pivot span. Later design revisions of the monitoring system introduced the ability of the monitoring system to also detect when a sprinkler became clogged. Experimental trials verified that the monitoring system operates efficiently and accurately; however, minor changes need to be made before large-scale implementation is possible.