ABSTRACT
J. MONTERO, J.M. TARJUELO, F.T. HONRUBIA, J. ORTIZ, P. CARRION, J A. de JUAN and M. CALVO Centre Regional de Estudios del Agua, Institute de Desarrollo Regional, University of Castilla-La Mancha, Albacete, Spain
Abstract In the order to study the problems of water distribution when using centre pivot systems, 84 assessments have been carried out in Albacete (Spain), a region where these systems have been used for fifteen years and cover a surface over 40000 ha. The average size of the pilot plot ranges 10 to 150 ha and several kinds of sprayer or sprinkler nozzles are present (operating pressure: 50-350 kPa). Results show that, in general, water distribution may be considered as acceptable (average CU: 86.6%). A major problem is reducing evaporation and drift losses during the water application process. In this way, the height of emitter over the ground and the type o emitter are two main factors. The effects of equipment size, type of nozzle, operating pressure and even wind action on water distribution uniformity are not significant. There are significant differences according to the existence of several shallow waterlogged formations (possible run-off in slope zones), the shorter is the wetted width, and the closer the nozzle is located above ground. The best balance between evaporation and drift losses and uniformity may be achieved locating sprayer or sprinkler nozzles two meters high, with a value of wetted width around 15 m, with a operating pressure requirement ranging 150 to 200 kPa. Keywords: Centre pivot, evaporation losses, sprinkler irrigation, uniformity, wind drift losses.
