Dynamic model for water application using centre pivot irrigation

The application pattern for single, stationary spray sprinklers exposed to the wind was modelled to simulate water application in a centre pivot-irrigated field. In the model, a dynamic square grid of cells for water application and a static square grid of cells for water collection were defined. The dynamic grid contained the information on the water application pattern of an isolated spray sprinkler, and this followed the motion of the centre pivot lateral. The static grid represented the entire field, and received water from the dynamic grid at fixed time intervals. Model outputs included the applied water distribution pattern and measures of irrigation uniformity (radial, travelling path and global). A series of experiments using pivoted and single spray sprinklers were conducted simultaneously. The results from the model compared well with field observations. The resulting root mean square errors for the Heermann and Hein uniformity coefficient and the average applied water depth were 0.02% and 0.08 mm, respectively. Model simulations were carried out to illustrate the effect of wind on irrigation uniformity.