In this page it will be dealt with irrigation design software and other tools to design irrigation systems. Nowadays engineers involved in the design of irrigation systems make use of tools such as abacuses, graphs, tables provided by manufacturers of materials for irrigation in their catalogs. Are also developed spreadsheets and several companies offer software to design irrigation systems, but these are based on approximate algorithms. Typically, these software are created for small projects of irrigation systems for public parks and gardening, and make use of simplifying assumptions valid only for small plants for irrigation. Therefore, these instruments, and also the irrigation software proposed by third parties, are inadequate for professional use and for the design of irrigation systems of large dimensions. In summary, the design of irrigation systems is now based on:

Empirical methods, slow and laborious, which consist in testing, directly in the field, the material to be adopted in the irrigation system; Abacuses/graphs or tables provided by manufacturers of materials for irrigation in their catalogs; Tedious mathematical procedures that consider only standard and unrealistic through the use of simple or sophisticated spreadsheets; Irrigation design software, based on approximate algorithms, usually born for small projects of public green and gardening, which are supported by simplifying assumptions valid for small irrigation systems but less suitable for professional use and for the design of large sizes irrigation systems. These software, based on inaccurate calculation criteria, are more dedicated to the CAD drawing of irrigation systems, rather than a professional complete project equipped with a reliable hydraulic calculation.

There are other methods that combine the classical equations of hydraulics, but do not consider the characteristics of hydraulic functioning of the emitter resulting in inaccurate or too expensive in terms of IT resources and difficult to implement in software for irrigation.

The design of an irrigation system can be performed with the use of abacuses, graphs and tables, prepared directly by the firms producing material for irrigation, and which show, for the type of product which is considered (conducted and dispensers), the maximum allowable planimetric development under certain conditions of pressure, flow and slope. For example, for a laterals these catalogs show the maximum allowable development in length when using a certain diameter of the pipe and a certain emitter. They did not cover the different slopes (which are assumed horizontal or sub-horizontal), nor the interaction with the other parts that compose the irrigation system (which may have 5 as 200 lateralss). Furthermore, the results reported are valid only for a well-determined supply pressure. These assumptions entail negative consequences, both on the uniformity of distribution of the flow rates provided and on the efficiency of the irrigation system itself, produced by a functioning, during operation, of the irrigation system different from that expected in the design stage. Of course, you can take advantage of these sizing tools, only with reference to irrigation equipment manufactured by the same company. It then determines a situation of uncertainty for the professional who, in the design of an irrigation system, in making a comparison of the solutions proposed by different companies can not disentangle among various methods of sizing.

When using spreadsheets, the design of irrigation systems is performed or through simplified methods (and therefore approximate) or through stringent ones that are, in this case, very expensive in terms of human resources, time and applicable only on small to very small scale of irrigation systems. In fact, if one wanted to take account of all the mutual interactions between the various parts of the irrigation system would be necessary to construct the calculation tables too complex to implement and not manageable. These procedures also have never been automated, so the spreadsheet must be set each time you design a new irrigation system. For example, if you wanted to design a small irrigation system, designed to serve an area of one hectare extension where you plan to insert 10,000 emitters, the rigorous calculation with spreadsheet requires the writing of 30,000 equations, which would make this a difficult task even for the most scrupulous designers.

The most advanced software for irrigation on the market today are not very accessible to the general public, constituted by the majority of technicians who deal with the design of irrigation systems. Most of the time these are excessively expensive, with an interface very complicated and difficult to use. They typically have a laborious input handling, and provide impractical results in real installation management of the irrigation system. The majority of irrigation software study the approximate solution: considering only the equations of continuity and motion and not the third equation that characterizes the operation of the emitters. Moreover, these applications calculate only the continuous head losses (due to friction of the fluid against the walls of the pipes and which determine variations of pressure along the various constituent parts of the plant) and do not consider the localized head losses (which strongly affect the pressure variations along the laterals) determined by the presence of numerous emitters that cause continuous enlargements and constrictions of the passage section of the water.

Another component which is neglected is the kinetic energy possessed by the fluid in motion, which entails, especially when the flow rates conveyed in the pipes are high, the simplifications which further increase the level of approximation of the results. Still in the case of these software for irrigation the calculation is made by isolating the branch of pipe that we want to calculate from the rest of the irrigation network (which is not counted in its entirety), and then neglecting inopportunely the mutual interactions between the various parts of the irrigation network. The adoption of a series of simplifying assumptions determine substantive differences between the magnitudes (in terms of pressure and flow) calculated in the design stage and those obtained in the field during the functioning of the plant, resulting in obvious repercussions on the uniformity of the flow delivered and then the qualitative and quantitative yield of agricultural crops. The design software for irrigation systems currently on the market only allow the calculation of irrigation networks with a very limited number of nodes. In many applications, the convergence criteria used are based on the minimum cost and this does not ensure the uniformity of distribution of water. They use the equation of motion by imposing speed and do not consider the characteristic equation (which shows the characteristics of the used emitter). The criterion of the speed used often is based on the hypothesis not true that the speed remains constant throughout the development of the laterals and in all the pipes of the irrigation system, while in reality it is greatly variable along the direction in which moves the water, from a maximum value of a few meters per second to zero. The results of this approach are then approximated. Ultimately all these instruments involve various problems and limitations:

The risk of incorrect results; Higher costs and waste: we often tend to oversize for safety reasons, parts of a plant and the use of water resources is not efficient; Agricultural production limited by the unoptimized irrigation factor; Legal arguments, often occurring between the farm where it is installed the irrigation system and the professional or the company that operates the installation.