Irrigation Master Planning

The first phase of any major development involves identifying the critical requirements for an irrigation system and the most appropriate approach. PSI has the experience and skills to evaluate a site and analyse the opportunities and constraints as it relates to the irrigation system. This includes identifying water sources, consumptive use estimates, pumping method(s), phasing, mainline pipe routing, conduit locations and schematic locations for critical components such as pump stations control components, weather stations etc. This is a critical phase for determining the scale of the irrigation system and initial budgets as well as the potential impacts for coordination with other trade disciplines.

Consumptive Use Estimates

PSI has been fortunate to work on projects in over two dozen countries around the world. We realize that different regions around the world can have drastically different climates and ecosystems. As such, it is critically important for an effective irrigation system to determine the specific watering needs that a project will require. This is necessary to reduce the overall cost of the system as well as to manage it properly over time. PSI is able to ascertain local weather data including evapo-transpiration (ET) rates, rainfall and also the proposed plant types to be irrigated. We use all this information to determine the daily, monthly and annual watering requirements expected for a project. PSI has the experience working throughout the globe to understand that a “one-size-fits-all” approach does not apply. Each project much be analysed independently to develop the appropriate water needs. These estimates directly impact major infrastructure costs including lake sizes, storage tanks and pump station and pipe sizes. As such, having an experienced consultant who is independent (not working for any manufacturers) who is capable of accurately estimating these requirements can save the client a tremendous amount of capital expense. It is very valuable to a client to have the irrigation consultant involved as early as possible to assist with these matters.

Detail Design and Documentation

Once the design criteria has been determined, PSI will develop the detail design documents for open competitive tender purposes. These documents typically include hydraulic layout include emitter device locations, hydraulic calculations, electrical requirements and control components and a full bill of quantities. Specifications and design details are supplied so that the client will have a complete set of documents able to be tendered to multiple contractors for competitive bids. It is during this phase that an experiences independent design consultant has tremendous value to the client as we are to determine which products and design methods are most appropriate for a project without bias to a given manufacturer or other party. As truly independent consultants, we look after the needs of our client as the top priority.

Construction Observation

It can be frustrating to spend the time and effort developing design documents, details, specifications and bill of quantities, identifying the critical steps and methodologies for the proper installation of an irrigation system, only to have a contractor with inadequate skills be selected who proceeds to make field changes that the owner is unaware of. This not only can lead to an ineffectual system which may appear to work initially, but it will create an on-going maintenance nightmare for an owner as well as costs them thousands and thousands of dollars in upkeep over future years to fix. These changes made in the field often do not take into account the peak demand requirements of the system which causes stress to the hydraulic and electrical network which reduces the lifecycle of the irrigation systems by many years (if not decades). To address this problem, PSI offers on-site observation services to verify that the contractor is installing the irrigation system per the design requirements. Any field changes that may be required due to design changes in the field can be interpreted by PSI and the proper adjustments made which will work within the design parameters of the system.


Most of the sophisticated irrigation systems these days will have a central computer which will operate the system. It is imperative that these computers are programmed properly so the irrigation system is operated in the most efficient way possible as designed. This is the one item that we see most often gets ignored which could easily increase the efficiency and reduce the on-going operational costs immensely. PSI is able to program the systems so that the electrical network and hydraulic network are managed properly. We take into account the hydraulic limitations as well as the different watering needs throughout the site taking into account plant species, sun-shade factors, soil types, slopes etc. The programming can become come complex and intricate which is why it is very good to have the designer of the system work with the irrigation manager to develop a program, or set of programs that meets the projects requirements in the most efficient manner possible.

Irrigation System Audits

For existing projects where an irrigation system has already been installed and the owner believes that it is not operating properly or could be managed better, PSI can be engaged to perform a system audit to analyse the existing conditions and develop a detailed report on the best methods to maximize the system, or we will recommend what changes can be made to make it function better. We will review the irrigation heads, spacings, precipitation rates, uniformity and arcs at various “sample” portions to get a firm understanding of how the system is operating. We will also review any as-builts to try to understand how the system is functioning as a whole. As this data can then allow us to recommend changes to hardware components as well as adjusting schedules to maximize efficiency and help eliminate wet and dry spots. These changes can allow the system to function more smoothly, extending the life of the system as a whole so the return on investment can be increased.

Hydraulic Modelling

PSI is one of the few firms that develops and interactive hydraulic model for all major projects to ensure that the irrigation design will function as required during peak demand for a project. This modelling takes into account the type of pipe, pipe sizing, flow rates, elevation changes, fitting losses and calculates the pressure losses throughout the site as well as verifies that the velocities in the system remain below accepted design standards. High flow velocities in the hydraulic network are a major problem which is a prime cause of fittings failures over the life of a project. If these can be managed, the return on investment will be maximized over the life of the system. This modelling is also very useful for when field changes are required as design solutions can be tailored knowing exactly how the adjustments will affect the project as a whole.

As-Builts and Post Installation Inspection

Once a project is successfully installed, PSI can coordinate the “as-built” drawings for the irrigation system to provide to the owner in CAD and hard copy format. These as-builts will reflect the installed components and PSI will then add the programming notes and details so the as-built can be used in conjunction with the day to day use of the system by the irrigation personnel. This can prove an invaluable tool for maintenance crews to locate components within the system for repair as well as for operating the system in an efficient manner. This also acts as another safeguard for the owner to verify that the system has been installed as per the design requirements. PSI can also visit a project site when the project is ready to hand over a system to the owner to inspect that the system is operating as intended. PSI can verify that the correct operation and maintenance manuals are supplied as well as the spare parts and training provided by the contractor as is often stipulated in the design documents.