Journal of Irrigation and Drainage Engineering

Organic mulching and irrigation are considered to be important soil conservation and agricultural practices. However, the effectiveness of these practices on soil properties and potato production in the relatively cool, moist maritime region of Canada has not yet been well studied. In the growing seasons of 2000–2003, a field experiment was conducted at the Potato Research Centre, Agriculture and Agri-Food Canada, Fredericton, New Brunswick, to assess the benefits of hay mulching on a loamy sand soil under potato production. Treatments consisted of four levels of hay mulching: 0, 2.25, 4.5, and $9.0\mathrm{Mg}{\mathrm{ha}}^{-1}$ with four replicates under irrigation or nonirrigation. Results showed that hay mulching could help conserve soil moisture in nonirrigation treatments with an increase of mean soil moisture content by 5.7 to 9.5% under 2.25 to $9.0\mathrm{Mg}{\mathrm{ha}}^{-1}$ of hay mulch relative to a control. The greatest conservation effect on soil water in our region would be achieved with a mulch rate of $5.6\mathrm{Mg}{\mathrm{ha}}^{-1}$. Under irrigation, mulching slightly increased soil temperature. Without irrigation, soil temperature was affected both positively and negatively by mulching, depending on time of day and quantity of mulch applied. During periods of warmer weather, mulching reduced maximum soil temperature during daytime but increased minimum soil temperature during nighttime. While the magnitude of soil temperature change was slight, it varied linearly with mulch quantity. During periods of cold weather, mulching generally increased soil temperature. The soil organic carbon content in the year following mulching increased proportionally with the amount of mulch applied in the nonirrigated treatments. Thus, thicker mulching treatments resulted in a greater increase in soil organic matter accumulation. Irrigation was found to potentially induce organic matter loss for the lower mulching treatment ($2.25\mathrm{Mg}{\mathrm{ha}}^{-1}$) and control. No significant effects of hay mulching on total potato tuber yield under irrigation were found, but tuber yield under nonirrigation increased linearly with the amount of mulch applied.

This article reviews procedures for estimating surface storage in surface irrigation volume balance calculations. Those procedures are based on the assumption of a power law relationship for flow depth as a function of distance along the stream. The analysis uses zero-inertia simulation and a system of dimensionless variables to examine how the depth profile varies as a function of hydraulic conditions when infiltration is given by the empirical extended Kostiakov equation. Alternatives for approximating the exponent of the depth profile power law ($\beta$) are suggested. The magnitude of the resulting errors relative to zero-inertia model predictions is quantified. Results show that the range of variation for the parameter $\beta$ increases with field slope, with increasing advance length relative to the maximum advance distance, and when infiltration rates are relatively constant with time during the irrigation event. Estimating $\beta$ as a function of advance distance is most challenging under these conditions. Potentially large errors in the determination of $\beta$ do not undermine the proposed procedures when the surface volume represents only a small fraction of the applied volume. Users of volume balance procedures need to be aware of conditions in which uncertain surface volume calculations can lead to potentially large volume balance errors and, thus, in which results need to be interpreted carefully.

Volume-balance models of surface irrigation calculate the infiltrated volume at a given time as a product of the stream length, upstream infiltration, and shape factors. The best-known expression of this type was derived by combining the Lewis-Milne equation with empirical power-law expressions for infiltration and advance as functions of time. This expression results in systematic errors that are not well understood by users of volume-balance methods. This article examines those errors in furrow irrigation by comparison with infiltrated volumes computed with zero-inertia simulation. The potential for errors is greatest with light soils and where the bottom slope is large enough to produce kinematic flow conditions. An example is presented to show how these errors in a parameter-estimation problem based on a volume balance can be corrected iteratively with the help of zero-inertia simulation.

The purpose of this study was to develop an optimization model for the optimal placement of structural best management practices (BMPs) at the watershed scale for a reservoir. In this research, the authors considered three types of structural BMPs (i.e., a wet detention pond, a grass swale, and an infiltration trench). The complete model consists of three interacting submodels: a watershed water quality simulation model [the Hydrologic Simulation Program-FORTRAN (HSPF) model], a reservoir water quality model (the CE-QUAL-W2 model); and an optimization model that uses a well-developed genetic algorithm (GA) software. This research used the Feitsui Reservoir and its watershed in northern Taiwan as the area of application. For the optimization model, the objective function was to minimize the total annual cost of BMPs, within the constraints of achieving minimum water quality standards for the concentrations of phosphorus, ammonium, nitrate-nitrite and for the total suspended solids in the reservoir. The study first simulated the discharge and pollutant loads for the watershed in 2002–2003 by using HSPF. The reservoir model CE-QUAL-W2 was then used to simulate variations in pollutant concentrations in the reservoir on the basis of the input discharge and pollutant loads from HSPF. The optimization model was finally used to search for the near-optimal selection and placement of BMPs in the watershed. The results obtained from the completed model effectively demonstrate its viability in improving water quality in the reservoir by adopting optimal BMPs placement strategies.

The implementation of roughened channels with cross beams (RCCB) in drainage systems reduces the negative effects of high kinetic energy on flood flows, such as the increased erosion of infrastructures or of the ground. This paper aims to highlight the importance of using RCCB in drainage systems and to contribute to a better knowledge of flow characteristics in RCCB. The performance of RCCB was studied under diverse conditions through the use of a physical model in which several cross beams were installed with different thickness, longitudinal spacing between them, and at different heights. Results of free-surface profile, pressure head, and velocity measurements for different arrangements of slopes, cross-beam dimensions, and spacing were compared with the scarce data available in literature and put together to form empirical relations to predict flow characteristics in the engineering practice dealing with RCCB design, such as discharge limit, maximum flow, water depth, and friction factor. In particular, it shows that energy dissipation in roughened channels with cross beams increases approximately 30% in relation to channels where cross beams are not used.

The interaction of nappes from adjacent weir walls near an upstream apex can cause local submergence, which reduces labyrinth weir discharge efficiency. Local submergence effects can cause the head-discharge relationships for labyrinth weirs of equivalent lengths but different cycle numbers to differ. Empirical labyrinth weir discharge coefficients implicitly account for apex effects and local submergence; however, the uncertainty associated with applying hydraulic design data developed from specific weir geometries to comparable but different labyrinth weir geometries is not well understood. This study investigates the concept of labyrinth weir nappe interference and identifies labyrinth weir flow characteristics that decrease discharge efficiency, including local submergence. Parametric methods for quantifying nappe interference region size as a function of weir geometry (e.g., sidewall angle and crest shape) and flow conditions (e.g., headwater and nappe aeration) are presented. A comparison between empirical methods found in the literature for determining the size of the nappe interference region and laboratory-scale experimental data showed a limited correlation. The data presented in this study are recommended as a more accurate alternative to predict the extent of the nappe interference region.

This paper details a new design for labyrinth side weirs, which has been tested and analyzed. The proposed geometry for this labyrinth side weir differs from a triangular labyrinth side weir, in that it is asymmetric in plan. The hydraulic behavior of the present labyrinth side weir, with a constant opening length, different weir heights and asymmetric labyrinth side weir included angles has been experimentally investigated in the subcritical situation. Based on the analysis of more than 180 experimental data, an equation for discharge coefficient of the asymmetric triangular labyrinth side weir has been presented. The results show that the discharge coefficient of the asymmetric labyrinth side weir is up to 1.6 and 2.35 times more efficient than a symmetric labyrinth and rectangular side, respectively.

The piano key (PK) weir is a relatively new nonlinear weir geometry that can be used to increase spillway discharge capacity over linear weir geometries, particularly when the weir footprint area is restricted (e.g., spillways on the crest of a concrete dam). The majority of the published PK weir research (e.g., head-discharge curves) has been based on channelized applications (sectional PK weir models in laboratory flumes). The head-discharge characteristics of crest-of-dam PK weir applications are influenced by the approach flow conditions. Using a laboratory-scale physical model, the hydraulic efficiency of a PK weir design was tested with varying approach flow depths, upstream apron slopes, and abutment details. In general, discharge efficiency increased with increasing approach flow depth, steeper approach aprons, and improved abutment geometries that reduced the effects of flow separation.

Furrow irrigation is one of the oldest methods of irrigation in which the soil surface is used to convey and infiltrate water. The most important problem in the path of improving furrow irrigation performance is the difficulty of estimating the infiltration function. In this study, the multilevel calibration method and the volume balance approach were used for estimating the Kostiakov-Lewis infiltration equation parameters and roughness coefficient for the constant and cutback inflow hydrograph shapes for furrow irrigation using field data. The multilevel calibration method predicts the total volume of runoff and infiltration with less relative error than the volume balance approach. The results of this study indicate that the simple volume balance approach and the multilevel calibration method predicted infiltration equation parameters and roughness coefficient with nearly the same accuracy, but the volume balance approach involved shorter execution times and required less iteration through the simulation algorithms than the multilevel calibration method.