Why to design irrigation systems

The agriculture is the sector which uses the water resources of a country mostly (more than 70% in Italy).

Irrigation is the most important factor in agriculture because it ensures the greatest increase in quantity and quality in production, more of the same treatments adopted for the soil and plants. The design is the key to obtain an efficient irrigation system and maximize the productivity of the harvest.
The micro and sprinkler irrigation are the most spread technics of irrigation. Particularly the microirrigation is able to reach the greatest benefits in terms of efficiency, water saving and agricultural productivity.
2 - 4d.jpg
But this advanced technique has an Achilles' tendon: it needs careful and rigorous design for irrigation systems. In order to obtain the maximum benefit for irrigation, it’s absolutely necessary that the water reaches the plants uniformly. Today, too often, the irrigation systems have low quality and this brings the following consequences:

  • excess of water and fertilizers in some parts and lack in other ones
  • various growth conditions of crop, different for size, maturation and quality of fruits (with issues for harvesting)
  • under or over sizing of pipes.

Generally the farmer aims to meet plants’ needs, only where few water arrives, but he risks to irrigate too much other parts, waste water which runs over the surface or leach deeply, and consequently damage the cultivation and consume more energy for pumping.IIn an irrigation system that has 70% of efficiency, a third of water isn’t used by roots of plants.

3 - Grafico spreco.bmp
4 - Strumenti progetto.bmp
Generally the technicians haven’t the necessary tools to design and analyze the network in a correct and careful way. They rely a lot on drawing softwares which find out the path of the pipes, calculate the amount of pipes and emitters to use and don’t estimate the quality of irrigation. The hydraulic design has to be focused on maximum values of uniformity, the factor that most influences the crop yield response.To properly design a system and achieve the right quality of irrigation, it's necessary to obtain uniformity of distribution of 90%. Also, wanting to meet a more restrictive eligibility project, you must contain the change of discharge of all parts of the system in a range of 10% of the nominal discharge.

5 - autocompensante.jpg

Even if it uses pressure-compensated emitters the network has to be inside a pressure range in order to allow the correct working. In addition, these emitters have shorter service life than other ones, are more expensive and require more care.

When designing an irrigation system many variables come into play such as the size and ground slope to be irrigated, and the characteristics of the emitters used. All of these factors and design criteria have important consequences in the behavior of the system in which the only drawing can not answer. It is therefore necessary to use a tool capable of dealing with the hard task of a real design.