Journal of Irrigation and Drainage Engineering

As drip irrigation develops rapidly worldwide, the need for a standardized method to evaluate emitters’ clogging sensitivity is reinforced. Methodologies for evaluating the sensitivity of emitters to clogging enable identification of trends in the change in performance of emitters operated under clogging risk, selection of emitter designs with higher performance for a given set of water characteristics, and recommendation of a consistent filtration method and maintenance routines. In this study, a clogging test protocol for evaluating the sensitivity of emitters to clogging caused by suspended solid particles was assessed to improve the reliability of test results and analyze the impact of sample size (number of emitters) on clogging result accuracy. Two models of integrated non-pressure-compensating emitters were tested in three replications. The $160\text{-}\mathrm{h}$ clogging test procedure consisted of four $40\text{-}\mathrm{h}$ stages that varied in size and concentration of solid suspended particles. The results enabled accurate assessment of the combination of size and concentration of particles that caused clogging in each emitter model, thereby revealing trends in the sensitivity of emitters to clogging, which were not dependent on emitter sample size. Recommendations for an international standardized clogging test protocol are proposed.

Drainage ditches are effective agricultural facilities because they can drain excess water from the field, and an eco-friendly drainage ditch can also eliminate agricultural nonpoint source pollution effectively. Field work has been conducted in four types of drainage ditches with different revetment techniques, i.e., a two-stage ditch with a woodpile bank, a single trapezoidal ditch with a geotextile bag, a hollow hexagonal brick, and a reinforced vegetative bank revetment. The corresponding retention capacity of phosphorus in these ditches has been investigated. Results show that two-stage ditches can retain dissolved phosphorus (DP) more effectively compared to the other three single trapezoidal drainage ditches, and the retention efficiency is as high as 60%. The concentration of total suspended sediment (TSS) is positively correlated with that of total phosphorus (TP), and the retention capacity of drainage ditches on phosphorus will decrease as discharge increases. Current work proves that a well-designed two-stage section ditch can effectively eliminate the nonpoint source pollution during practical agriculture drainage application.

A solute transport model has been added to the WinSRFR surface irrigation software package. The model uses advective-dispersive principles to predict the flow of solute with the irrigation stream and its final longitudinal distribution along the field based on water flow predictions generated by the simulation engine. Computations are based on the fractional stepping method: advection is computed using the method of characteristics from the velocity field computed by the simulation engine water flow calculations, and dispersion is calculated from the advection results using a centered-difference finite-difference scheme. The Akima interpolation scheme was used to build the method-of-characteristics solution. The computations are robust and execute in little time. The accuracy of the model was evaluated with numerical tests and by comparison with field measurements. Results suggest that the model can generate useful predictions under typical irrigation conditions.

This paper presents the derivation of an analytical method for identifying the stability of uniform flow in three open channel sections (rectangular, parabolic, and circular). Using a dimensionless relative slope factor, a general equation for the prediction of stability thresholds for the occurrence of roll waves for each cross-section shape was developed, enabling the flow stability zones to be classified. The derivation is predicated based on a combination of the Vedernikov number and the logarithmic law of resistance, which involves significant resistance parameters. The proposed method was verified using a numerical example and actual measurements. It is hoped that the presented method, which provides a direct solution for the stability criteria of uniform flow, will be useful in open channel design.