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Savings on water: auditing an irrigation system

 

The audit of an irrigation system is carried out following a tried and tested method intended to optimise the use of the water resources within automatic irrigation systems, such as golf courses, public parks and gardens and sports grounds

During the audit of an irrigation system, it is advisable to assess the existing installation according to two distinct but complementary aspects: i.e. the technical and human aspect. In fact, an outstanding irrigation system used by poorly trained or untrained people will not be very effective. On the other hand, an energetic team which is well trained with the equipment can get the best out of ill-suited or obsolescent equipment.

 

Technical evaluation:

 

The technical evaluation aims to assess the technical performance of an irrigation system in terms of water management. This tool will enable you to determine the potential water savings that the user is entitled to expect in the installations by resolving the technical problems. The first stage of an audit is to validate the uniformity of distribution of the sprinklers. The efficiency of the nozzles is essential but not sufficient. The sprinklers must be chosen according to the size of the area to be irrigated and positioned step by step, using a square or triangular grid layout for optimum precipitation rate. The rate itself is unimportant. In order to make savings on water, the essential factor is that it must be uniform. The evaluation technique can be broken down into:

 

A field stage, which allows for a complete inventory of the equipment to be drawn up, together with a report on its condition (technical audit). There is a lot of information to be gathered in the field, such as:

 

  • The model of the sprinklers/nozzles.
  • The spacing of the sprinklers/nozzles and the layout.
  • The operating pressure of the sprinklers when in operation.
  • The precipitation rate recorded on the site at different points.
  • The condition of the spray heads or bodies and their installation (vertical or otherwise?)
  • The size of the nozzles and their uniformity.
  • The actual or designed diameters of the main pipes.

 

In fact, networks that are too extensive, unnoticed differences in height levels or simply too high a pressure in the system can disrupt the uniformity of distribution. Using small containers placed in a regular grid pattern in the field, the auditor measures the actual precipitation rate on site and the uniformity can thus be assessed. When the uniformity is poor, dry areas appear. In order to limit this phenomenon, the gardener has no other option but to increase the duration of irrigation, leading to an over-consumption of water and the unnecessary irrigation of areas already sufficiently watered.

 

Apart from the sprinklers, checks are made on:

 

  • The cables of the electrical system, their protection and their operating condition.
  • The status and suitability of the water resources and the pumping station, given the quantity and quality of water available.

 

During the technical audit, it must also be checked that the current installations conform to sanitary and regulatory standards (water charter for golf courses, hydraulic protection of the networks with backflow preventers, etc.).

 

The follow-up data analysis carried out by a design and planning consultant allows for an exact diagnosis of the irrigation system to be established in terms of water consumption. There are a number of methods available:

  • The most precise of these consists of taking water meter readings in order to assess the real consumption. However, this is not always possible because there may not be a local or main meter installed (irrigation, sanitary, water conveyance…).
  • The second method is theoretical and consists of taking the theoretical flow-rate of each spray head, then multiplying by the total number of spray heads and then multiplying by the daily operating time in order to obtain an estimate of the consumption.

 

This technical assessment will allow for a diagnosis to be established and suitable solutions to be proposed. With precise information on the flow-rates, pressures and programming, the auditor is able to simulate consumption and carry out a projection of what could happen after the various factors detected as being problematic have been adjusted. The ideal case is, naturally, to have available the actual consumption figures of previous years, but they cannot often be obtained. The user is aware most of the time of over-consumption, without actually knowing how much is being used.

 

 

Assessment of the irrigation practices

 

The human aspect is vital. The review of the irrigation practices is a tool that allows an overview to be provided of the current irrigation scheduling practices and any possible problems to be detected. It also allows for the professional water management skills of the personnel in charge of irrigation to be defined and clarified.

 

During the audit, the auditor will check, in particular, how broken sprinklers are replaced (according to the flow-rate, nozzle selection), how valves and inspection chambers are maintained and, of course, the programming of the control devices. Now, at that point, it is often observed that the users are familiar with good irrigation practices but have forgotten the original purpose. By clarifying why it is important to check the flow-rate of nozzles or even to “think through” their programming, the vast majority of users will suddenly remember techniques that they had forgotten. Furthermore, technical solutions have developed very rapidly of recent years and many users are unaware of the solutions that could be implemented.

 

Finally a new irrigation programme can be constructed from this objective information.

 

This, therefore, can be used as a basis for reflection with regard to future training requirements. The irrigation practices review is a decision-making support tool for choosing the level of professional training, in terms of content and priorities, both individually and collectively (the effect of “working as a team” and “skill sharing”).

 

 

Rational irrigation practices ?

 

The success of a well thought-out rational irrigation scheme depends on three factors:

 

  • A technical aspect, providing the solution to problems in the field and the introduction of new technologies. The problem is often resolved by installing nozzles that provide a very good uniformity of distribution by having a lower spray trajectory for better wind resistance (e.g.: the MP rotator from Hunter, R-Van rotary nozzles from Rain Bird). If it is difficult to change the positioning of sprinklers (which, nevertheless, can sometimes be necessary), small low-cost adjustments can sometimes be very effective. Amongst these, manufacturers offer anti-drain systems possibly linked to optional pressure-regulating devices on the sprinklers. Finally, the latest generations of programmers allow for the system to react automatically in the event of the over-consumption of water and moisture sensors allow an irrigation system to be transformed very easily, at minimal cost, into a “smart” technology.

 

  • An economic aspect, with savings on water being achieved and the planning of interventions based on the returns on the reasonable and sensible investments. For example, the calculation of the required “real” irrigation times. This stage is only possible after “optimising” the precipitation rate of the spray heads. In fact, a programme is only effective if the distribution of water is homogeneous over the entire area of the garden.

 

  • A human aspect, with the implementation of training programmes, credit given to acquired knowledge, the promotion of personal experiences, and finally, enhancing the prestige of the irrigation profession. As far as new products are concerned, particularly programmers and sensors, the users have to be trained. Training can be conducted on site when the installation intended for people using these new products is being installed and started up. In that case, it is a matter of building a training programme customised for a company or group using specific equipment for their individual needs. Manufacturers also organise training sessions in their own offices throughout the year according to a pre-established schedule. In that case, the training for the product is rather theoretical.

 

Obviously, we then arrive at the question of central control irrigation management systems. Contrary to what is often said, it is not a miracle cure!

It is the “icing on the cake” which “crownsl” a series of measures taken to reduce water consumption:

  • Carrying out a technical audit and a complete inventory of the installations, with the implementation of the necessary work considered essential for the proper operation of the systems in the field (sprinklers, valves, etc.),
  • Solving problems in the field and introduction of new technologies,
  • Auditing the irrigation practices,
  • Training of personnel,
  • The acquisition of a CMS [centralised management system] adapted to the user’s requirements and not one that is imposed by a manufacturer. With a modest budget, the user can be equipped with the basic components of a centralised management system and then refine the system requirements over the years by adding additional modules.
  • Support and follow-up of the implementation of this CMS.

 

However, a CMS can only prove to be effective when all technical problems are resolved, with the establishment of adapted irrigation practices and the implementation of a user-support system.

In the next few editions of Irrigazette, we will be developing the theme of saving water from the point of view of the sprinklers and the programming.

 

 

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