Abstract:
Limited by experimental conditions, the water distribution of sprinkler irrigation on sloping land is difficult to measure. In order to solve this problem, ballistic theory and the model for evaporation of droplets were used to calculate the trajectory of the spray water droplet. On the basis of the measured water distribution of one radial leg on flat ground, and using the translation of coordinates from three-dimensional space to two-dimensional space, a simulation model for calculating the water distribution of sprinkler in sloping field was proposed. A custom computer software script was developed using Eclipse software to implement the method to a case study. The software could calculate water distribution at different sloping lands when the operating environment and hydraulic parameters of the sprinkler were given. Three-dimension triangulation interpolation model was applied in order to get the grid data of single sprinkler water distribution, and the grid data were used to calculate the uniformity of different sprinkler spacing with square and triangular lattice configuration. Measured and simulated values were compared for the water distribution and spray distance to validate the accuracy of the software on 2.86°, 5.71° and 8.53° sloping land using Rainbird LF1200 sprinkler. The results revealed that the simulated and measured water distribution and jet distance had the maximum relative errors of 9% and 5.04%, indicating that the model could be well used to simulate the water distribution for sprinkler on sloping land. The model could be directly applied in the design of sprinkler irrigation system in sloping field. The effects of slopes, square and triangular sprinkler layout, sprinkler spacing and operating pressure on water application uniformity were analyzed for the Rainbird LF1200 sprinkler using the simulation model. Furthermore, effects of 4 factors(pressure, layout, spacing, and slope) on water uniformity were evaluated. The results showed that the sprinkler operating pressure greatly affected the uniformity, followed by sprinkler layout, sprinkler spacing, and slope with 95% confidence interval. If the Rainbird LF1200 sprinkler was used in the sprinkler irrigation system, the sprinklers must be operated at the working pressure range. Taking account of the cost, system and water uniformity into the design of the sprinkler irrigation system, we recommended that the sprinkler had spacing of 0.8 times as the spraying range on flat ground, and the square arrangement on slope less than 15°. The results here could provide useful information for design of spraying irrigation system on slope.