Journal of Irrigation and Drainage Engineering

Rain gardens use natural processes, such as infiltration and evapotranspiration, to control runoff from rain events. Although prior research has shown that rain gardens are effective at controlling the volume of runoff and pollutants associated with runoff, the extent of groundwater mounding under rain gardens remains a concern for landowners, practitioners, and regulators. A rain garden on Villanova University’s campus was instrumented with monitoring wells to observe the influence of the rain garden on the water table. This rain garden receives the runoff from approximately 0.52 ha that consists of grassy areas as well as parking lots. This paper investigates vertical and lateral behavior of localized mounding caused by infiltration in a rain garden subsequent to a storm event. The data used for the analysis were selected from 1.5 years of continuous monitoring at the site. A statistical model was developed, describing event-based peak groundwater rise as a function of radial distance from the rain garden’s center and infiltrated water depth. Statistical analysis was performed to demonstrate significance of the model parameters. Analyses of time to peak and time to return to prestorm levels (dissipate) were performed. The system exhibited a very pronounced dissipation behavior in peak rise, normalized to infiltrated depth of water, with an increase in radial distance. Temporal lag in mounding peak and dissipation was investigated with respect to radial distance. In light of the observed behavior, a methodology for estimating site-specific vertical and lateral impacts was proposed. The methodology was applied to the rain garden, and the results reviewed in the context of geospecific design storms. The paper concludes with a discussion on the expected effects of localized mounding from the rain garden on foundations of adjacent buildings.

Centralized model predictive controllers are common in water systems. The control action variable can be the discharge, and the subsystems (canal pools) are modeled separately. This paper focuses on short canal pools where the interactions are stronger between canal pools. Could this procedure be better if gate openings were used as control action variables and the interconnected system were modeled for the controller? Model predictive controllers (MPCs) were developed using the discharge and the gate opening as control action variable and tested experimentally using the laboratory canal of the Technical University of Catalonia. It was found that for centralized MPCs for short canal pools, the use of gate opening as control action variable is more beneficial than discharge. Another additional advantage is that in this way it is possible to put constraints on the gate opening and the change of gate opening, which are important to the limitations of the physical system.

Studies have shown minimal impact by smart irrigation controllers when installed indiscriminately, but targeting overirrigators increases the water conservation potential. The objective was to evaluate different methodologies defining residential overirrigators. Two independent smart controller studies were conducted by utilities in Hillsborough County [Hillsborough County Water Resource Services (HCWRS)] and Orange County [Orange County Utilities (OCU)], Florida. In HCWRS, the cooperators qualified when irrigation was in the top 50th percentile of potable water users in the county. Additionally, the 21 cooperators were located in three cities determined as having high water use relative to other cities in the same area. In OCU, 132 cooperators received smart controllers when frequently irrigating more than 1.5 times the gross irrigation requirement (GIR). Actual ratios of historical average irrigation to the GIR ranged from 1.45 to 2.37 in HCWRS and 6.04–8.33 in OCU. As a result, cooperators in OCU showed significant reductions in irrigation with a return on investment of 4–14 months compared to HCWRS with a payback period of 17–27 months despite higher water rates and larger irrigated areas in HCWRS. Using the GIR as a benchmark proved to be a better method than using utility-wide percentile ranges of irrigation application to target homeowners for smart controllers to ensure irrigation reductions. Smart controllers are recommended for homeowners who average two times the monthly GIR for at least three months per year over at least three years when implemented in conjunction with relatively well-maintained irrigation systems. Water savings were guaranteed when ratios averaged more than six using the same frequency standards. Additional requirements for successful implementation include site-specific programming and providing basic knowledge to the homeowner.

Jamaica’s water resources are under increasing risk of degradation and depletion, especially in light of increasing population growth, urbanization, and climate change. In this study, the soil and water assessment tool (SWAT) was used to simulate the hydrologic characteristics of the Rio Nuevo watershed in Jamaica to assess streamflow availability for irrigation supply during dry periods. Approximately 85% of the watershed consists of aquiclude rock material, thus resulting in low potential for interaction between surface and groundwater. Historical climatic data (precipitation and temperature) were obtained for the watershed, and streamflow data were obtained for the Rio Nuevo, which drains the watershed. The model was calibrated over the period 2002–2004, and validated using the period 2005–2007. This paper outlines the parameterization of SWAT for the Rio Nuevo watershed and describes the potential for its use in agricultural water scarcity management in Jamaica. A Nash-Sutcliffe efficiency (NSE) coefficient of 0.76 was obtained for calibration, whereas a coefficient of 0.50 was obtained for validation. Results indicate that in drought periods, the stream cannot supply the necessary water needed for the agricultural areas.

Irrigation channels need expansions to provide a cross-sectional transition. Expansions often cause flow separation, turbulent eddy motions, channel erosion, and flow energy dissipation. The purpose of this paper is to investigate the effectiveness of fitting a hump at the expansion’s bottom in reducing flow separation and energy loss. This paper reports analytical solutions to the problem of flow transition and associated energy head loss, by using the momentum and energy concepts complementarily, as well as experimental results for verifying the solutions. The use of a triangular hump can effectively reduce head loss; the head loss coefficient drops by a factor of up to 4. The mechanism at work is that the presence of a hump forces the flow to accelerate, neutralizes the decelerating effects of expanding width, and creates favorable pressure gradients working against flow separation. Humps with a crest height of 5–9% of the depth of approach flow are recommended, with a good potential to save a substantial amount of flow energy. Researchers can easily incorporate such humps into existing expansions.

Estimation of excess storm water is among the most basic hydrological challenges for hydrologists and engineers. The initial abstraction ratio $\lambda$ (= 0.2) assumed in the original U.S. Soil Conservation Service curve number (SCS-CN) is ambiguous and must be calibrated from rainfall-runoff measurements for better runoff estimation. Eight different models including the original SCS-CN model, modified models inspired by it, and three newly proposed models were investigated to assess the accuracy of runoff estimation using rainfall-runoff measurements from 15 watersheds in South Korea. Different methods for CN determination were evaluated to see the effect of CN and $\lambda$ on runoff estimation. The optimized $\lambda$ and CN exhibited better results than fixed values as in the original SCS-CN model. Using three different goodness-of-fit statistics to assess the accuracy of the estimates, our proposed models outperformed in all watersheds in the study area when compared with the original SCS-CN model and some of its modified models.

Sharp-crested weirs are widely applied in agricultural and hydraulic engineering for measuring and regulating flow. The various shapes of weirs give rise to their special characteristics. This study introduces a novel sharp-crested weir design with a sinusoidal notch, and investigates physical models of sinusoidal sharp-crested weirs of different widths and heights. The analysis aims to establish the head-discharge relationship and to inspect the three-dimensional velocity distribution and the hydrodynamic characteristics of flow in the vicinity of the weir plate. The hydraulic behavior of sinusoidal weirs is also compared with that of rectangular sharp-crested weirs. The results show that the secondary currents and the turbulence intensity in the vicinity of the sinusoidal weirs are stronger than those of rectangular weirs. Therefore, this type of weir can provide an efficient passage for floating debris and sediment.