When it comes to irrigation, one of the factors that cannot be underestimated is certainly the water flow rate. To better understand this topic, it is necessary to start from the definition of flow rate: “In fluid dynamics, flow rate is the amount of substance that crosses a section of area A in a unit of time”. Applied to the world of irrigation, this general definition becomes: certain water quantity that a water source is able to supply constantly is such as to satisfy the crop’s need. This parameter considered together with the overall system consumption, leads us to the diameter of the mainline pipes and a suggestion for a possible division into sections. The flow rate is measured either in liters per minute or in cubic meters per hour. (It is essential to know that the smaller the diameter of the pipe is, the lower the flow rate will be. Therefore, the amount of water distributed to the plants during equal time will be less.) The Working flow rate is the amount of water that an emitter can distribute by working at a certain pressure. It is measured in liters/minute or in mc/ hour.
How to calculate the flow rate of your irrigation system
Knowing the flow rate will allow you to better design your micro-irrigation system. There can be two types of water flow detection methods:
• using a measuring instrument, such as a flow meter or volumetric meter;
• using an empirical method, i.e. taking a container of known capacity, and detecting how much time, expressed in seconds, it is needed to fill it. The formula is: flow rate = 60 * LitersContainer/Second needed = Liters/minute
Irrigation pipes measurement
The diameter of the irrigation pipes often creates confusion, as it may refer to the external or internal diameter. Furthermore, the measurement can be expressed either in millimeters or inches. To avoid further confusion, remember that one inch is equivalent to 25.4 mm, and our advice is to refer to the external diameter. Other factors that influence water flow rate may be its viscosity and density, as well as the friction of the liquid against the pipe wall. Flow rate measurement is really an essential factor for the correct design of the irrigation system, as well as for its optimal functioning; it also permits to avoid liquid dispersion or low irrigation capacity.