TECHNICAL REPORT 8059 tso Published 1986-07-15 Irrigation equipment - Automatic irrigation systems : Hydraulic control Materiel d'irrigation -- Systemes d'irrigation automatiques - Regulation hydraulique ISo (International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through Iso technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with Iso also take part in the work. The main task of isO technical committees is to prepare International Standards. In exceptional circumstances a technical committee type 1, when the necessary support within the technical committee cannot be obtained for the publication of an International Standard, despite repeated efforts ; type 2, when the subject is still under technical development requiring wider exposure; type 3, when a technical committee has collected data of a different kind from that which is normally published as an International Standard ("state of the art", for example). necessarily have to be reviewed until the data they provide is considered no longer valid or useful. ISO/TR 8059 was prepared by Technical Committee ISO/TC 23, Tractors and machinery for agriculture and forestry. The reasons which led to the decision to publish this document in the form of a Technical Report type 3 are expliained in the Introduction. Introduction Automatic irrigation systems are a relatively new concept that began to develop in the second half of the 20th century. A brief review of the background of this development is therefore in order. world population. Available resources of water that can be used by agriculture are limited. Consequently, they have become a restrictingfactorwhichdemandsthatnewwaterresourcesbedevelopedandthatstrictcontrolbeexercisedoverexistingresources An in-depthstudy ofplant growth requirements has repeatedly shownthat improved and increased plant yieldsarenotnecessarily water is applied in a scientific and controlled way. ISO/TR 8059-1986 (E) UDC 631.67 Ref.No. ISO/TR 8059-1986 (E) International Organization for Standardization, 1986 Printed in Switzerland Price based on 7 pages ISO/TR 8059-1986 (E) devoted to supervising water application systems. The operator's responsibilities increase proportionately, and these factors make it difficult to fill the requirements of suitable and competent manpower. The solution to these problems can be summarized in two words : control and automation. Since irrigation operations are performed during specific periods of time, it may be reasonably assumed that irrigation control could be achieved through time control. This concept was used for a short time during the early stages of the development of automatic con trol devices, but was discarded later. The attempt to apply the time concept for quantitative control is an indirect approach based on two assumptions : a)the rate of flow is known; b) the rate of flow is constant. Assumption a) is based on data supplied by the manufacturers of other system components, such as : sprinklers, drippers, pipes, valves.Thesedatamostlypresentflowratesasafunctionofwaterpressureandpressureloss,whicharethenusedasabasisfor hydraulic design. Assumption b) is in fact a combination of two separate and independent assumptions, namely : 1)supply pressure is constant; 2) the system features do not change with time These assumptions are not borne out by modern irrigation systems. The flow of water at any given moment depends on the supply pressure and the resistance of the irrigation system. Changes in these factors have a great effect on the rate of flow of the water. As a result, the deviations in the quantities of water supplied may reach highpercentages,whencontrolisbasedonmeasuringtheduratio