Journal of Irrigation and Drainage Engineering

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Over the last few decades, groundwater resources in many regions have been depleted at a higher rate than the underlying aquifers have been replenished. This imbalance has led water management agencies to consider managed aquifer recharge networks, in which infiltration basins are used to replenish the aquifers using previously uncaptured stormwater runoff. In this work, optimization methods were used to select parameter values to minimize the cost associated with constructing such a network while ensuring the network has the ability to supplement demands placed on the aquifer. The objective function considered incorporates land and construction costs, along with rewards for effective aquifer recharge, and constraints were incorporated to enforce capture of a minimum volume of stormwater runoff. Two hybridized global search algorithms were considered, one based on particle swarm optimization and the other on a genetic algorithm approach. Both methods returned solutions that were close in terms of minimal cost but varied in terms of individual basin sizes. Thus, the algorithms are able to aid decision makers by providing several cost-competitive solutions that can then be used to support a community dialogue.

Deep percolation from an irrigated field has received little attention in research studies although it contributes to significant loss of fresh water in a given region. Deep percolation is often estimated as a residual in a water balance equation. Several methods have been used to estimate deep percolation from a cropped area ranging from empirical relations to physically based models. However, there are limited studies available concerning deep percolation from water-intensive crop fields such as rice and berseem under unpuddled field conditions. This study deals with the estimation and field verification of deep percolation from water-intensive crop fields. Deep percolation was estimated using both water balance and physically based models. Field observation of deep percolation was carried out using drainage-type lysimeters. Field experiments showed that deep percolation accounted for approximately 85% of the input water in Rice Season 1 and 79% of input water in Rice Season 2. Conversely, about 65% of input water in Berseem Season 1 and nearly 49% of input water in Berseem Season 2 was accounted as deep percolation. The vertical fluxes simulated using the physically based Hydrus-1D model matched the observed data well on a daily time basis, unlike the simple water balance model. Both models performed better on lumped time steps. A simple water balance model could be a preferable choice for lumped time steps, while a process-based model may be advantageous for shorter temporal resolution. Comparatively, the performance of the physically based model is better in the wet season than the dry season, which is attributed to the pronounced development of macropores in the dry season.

Soil salinization is a major and long-standing environmental problem worldwide. Leaching through subsurface drainage systems under ponding conditions has been widely adopted to ameliorate saline soils in coastal areas with shallow groundwater tables. Because the seepage rate decreases by orders of magnitude from the near-drain area to midway between subsurface drains, to achieve a uniform leaching outcome requires a large amount of freshwater. This paper introduces a new method for improving the leaching efficiency by setting up a low-permeability soil layer over the subsurface drain. Numerical simulations of the water flow and solute transport in soils quantify the improved leaching efficiency provided by the new method. The results show that for the subsurface drainage system under the condition of complete and continuous ponding, an introduced low-permeability soil layer of a certain length can reduce the surface water infiltration rate near the subsurface drain but increase it in the midway area. This leads to a relatively uniform salt leaching condition in the upper soil layer. Based on the removal of salt over the top 0.6-m soil leaching depth, the new method is found to save water by 82 and 52% for homogeneous and layered (a silt loam layer overlying a sandy loam layer) soils, respectively. This study sheds light on physical processes in coastal subsurface drainage systems and provides guidance for future optimal designs of soil amelioration schemes.

Standard box-culvert designs are similar to ancient designs. The acknowledgment of the ecological impact of culverts and road crossings on rivers has led to changes in culvert design guidelines. A small triangular corner baffle system was tested to assist upstream passage of small body-mass fish in box-culvert structures on a flat bed slope. The study was conducted in a near full–scale physical facility, which had a width of 0.5 m and a length of 12 m. The investigation presented a detailed characterization of the flow field. Tests showed that small-bodied fish preferred to swim in slow-velocity regions (i.e., in the baffles’ corner). The most effective baffles had heights comparable to fish length. A key outcome of the study is the adverse impact of strong flow reversal on small-bodied fish, because strong flow reversal may confuse small-bodied fish attempting upstream culvert passage. A remedial measure is the ventilation of baffles, tested successfully herein.

If the flow in a pipeline is maintained by creating a pressure head by pumping, it is called a pumping main. On the other hand, the flow in a canal is maintained through an elevation difference. Being gravity sustained, open-channel flow is preferred in comparison to pipe flow that is sustained by pumping. Furthermore, in the absence of moving parts, open-channel flow has greater reliability. For a gently sloping topography, the gravitational system involves large canal sections. In comparison to a pumping main such a small sloped canal may be uneconomical. A review of the literature has indicated that there is no guideline available for adoption of a canal for such a flat terrain. In this investigation, the optimal cost function of pumping main has been compared with the cost of various canal section shapes to find a criterion for adoption of canal flow.

The effect of angled baffle blocks for improving hydraulic jump characteristics in a gradually diverging stilling basin with an adverse bed slope was investigated experimentally. Baffle blocks with different angles of placement were used in diverging stilling basins. The different geometric characteristics of the stilling basin, including bed slopes (0–0.075) and wall angles (3–9°), were also used for each arrangement of blocks. The results indicated that baffle blocks affect the sequent depth ratio significantly, although they also considerably decrease the length of the jump when compared with a diverging basin without blocks. Comparison of two arrangements of blocks showed that the use of baffle blocks in a converging arrangement improves the characteristics of the hydraulic jump. The most effective convergence angle (i.e., the angle between baffle longitudinal axis and flow direction) of the blocks was found to be 30°, which reduced the length and depth ratios of the hydraulic jump by up to 35 and 16%, respectively.

A recently developed rotating spray plate sprinkler (RSPS) with a six-grooved plate (R 3000) is evaluated in this paper. A set of nozzles numbered $15/128\mathrm{in.}$ (2.98 mm), $17/128\mathrm{in.}$ (3.37 mm), and $19/128\mathrm{in.}$ (3.77 mm) was tested with a nozzle elevation of 1.2 m using working pressures of 100, 200, and 300 kPa. The individual water distribution patterns, including the discharge–pressure relationship, wetted radius, sprinkler rotation speed, and water application rate, were evaluated under indoor experimental conditions. The results show that the discharge coefficient was mainly dependent on the nozzle diameter, which had a good value of more than 0.9 for all conditions. The wetted radius increased with the nozzle size as well as the operating pressure, and an empirical equation for those relationships was developed in this study. The sprinkler rotation time decreased with increasing operating pressure because an increase of the operating pressure resulted in an impact force from the nozzle to the plate sufficiently large to overcome the plate’s resistance. The sprinkler head produced quite similar water application parabola-shaped profiles at different nozzle sizes, and equations of the water application rate with regard to the distance from the sprinklers are provided. The average coefficients of determination for $d=2.98$, 3.37, and 3.77 mm were 88.2, 81.3, and 90.1%, respectively.