Introduction: Importance of a good outline and important design factors

Having a proper irrigation design process outline is a key element in the overall success of an irrigation design and subsequently a well irrigated landscape. A well planned irrigation design process will ensure that the proper factors are addressed and that important factors will not be forgotten. Successful implementation of a well thought out design process will result in a successful overall design. All of the important major factors of irrigation design must be examined in a systematic way to ensure the desired results. These factors include: Size of project, budget, type of landscape, availability and source of water, needed flow rate and pressure, sprinkler selection and layout, lateral layout, and controller selection.

Starting Point: Landscape size, type, and available budget

When first taking on an irrigation design there are some important major factors that have to be considered first. These are the size and type of landscape that need irrigation, and the available budget for the irrigation system. The size and type of landscape will determine what type of system is necessary. A project that is 100 acres with 85 percent turf will have much different irrigation requirements than a residence. A proper set of plans for the job also needs to be either obtained or created to ensure accuracy in planning and installation of the system. The available budget for the project plays a key role in the design process. Obviously, better irrigation hardware can be used in a project with a large budget. The available budget will also determine what available solutions there are to various problems or obstacles that occur when laying out the site's irrigation design. If a project had poor water pressure, and a large budget, a pump might be a feasible solution; whereas this option might not be viable in a project with more stringent fiscal restrictions.

Determining how much water is needed and water source:

These two factors are also going to have a large impact on the rest of the irrigation design process. They will determine how the water is distributed throughout the system, (sub-main and lateral layout) and what the available water pressure there is to work with. A good projection of the amount of water needed for the project will also be essential in determining how much the project is going to cost. A series of factors need to be taken into account when considering the amount of water needed. The climate and average temperature of the site has a large effect on water usage. In addition plant evapotranspiration is another major factor that will determine water use. Other factors such as soil type, existing vegetation, solar aspect, topography and any other influential site factors are also important factors in determining overall water usage. Water source is a pivotal factor that will determine available pressure and flow rate. Proper steps need to be taken to note the water source and the means of connection to the main line for the irrigation system. Water meter and service line size need to be taken into account and static pressure needs to be measured to determine what available pressure there is to work with in the system. This will have a pivotal effect on sprinkler and pipe choice later in the process.

Sprinkler and lateral layout:

Once all the necessary information has been determined and accounted for, the actual design process can begin. Based on available pressure, sprinklers must be selected that operate and cover the best under available conditions. Selection of sprinklers will also have a major effect on lateral layout and spacing. Coverage areas and precipitation rates need to be taken into account with the amount of water the landscape will require to ensure proper water allocation through the irrigation system. The available budget for the project may also have an effect on the type of equipment that can be installed, as overall cost may be a limiting factor in sprinkler selection. Overall efficiency of the system is another important factor that may have a profound effect on sprinkler choice. It is best to have a sprinkler that works best and that also works at the highest possible efficiency. As the sprinklers are being selected and laid out the layout of the laterals and the type of laterals need to be considered. One very important issue that needs to be taken into account at this point is necessary pressure and desired flow rate for the sprinklers. Lateral layout and pipe selection will have an important effect on pressure losses due to friction. As the design is being laid out it is very important to make all necessary calculations to ensure that the system in hydraulically sound. The system must have adequate pressure for all the sprinklers throughout the entire system. To ensure this proper measurements and calculations need to be made to ensure that the system will operate effectively once installed. This aspect can be the most complicated and technical of aspect of the whole design process, but it is absolutely pivotal to ensure that system runs as conceptually planned.

Irrigation Controller Selection:

An irrigation system is only as good as the people and irrigation controller that run and manage it. Selection of a good controller will ensure that the correct amount of water is applied and applied when it needs to be. It is important to take into account the size and needs of the site when selecting a controller. The controller should meet the needs of the site, but should not go beyond what the site needs. It would be a waste to install a commercial grade controller in a small residence that only needed a more basic device. Proper selection of the controller will cut down on maintenance and ensure that the irrigation system does its job.

Overview:

This is only a conceptual outline of the design process, there are many other factors and intermediate steps that have to be taken into account to ensure a good, functional irrigation design. This outline serves as starting point for the design process. Following these steps will ensure that important factors are not overlooked. Proper execution in regard to these factors will ensure a successful irrigation system design.