The Grand Avignon Metropolitan Area and the town of Cavaillon, located in the south of France with a Mediterranean climate, have recently been equipped with a centralised irrigation management system.
Being different in terms of size and the number of inhabitants, they both had major problems insofar as their irrigation system consumed far too much water and was difficult to manage. The technicians in charge of the green spaces have told us that in the course of these years, they would irrigate without taking note of the meteorological conditions, type of soil, rainfall and wind. These problems induced these two metropolitan areas to carry out a diagnosis of their irrigation systems and led them to consider the possibility of setting up a centralised irrigation management system, a network that would be very flexible and adaptable to all types of green spaces. These centralised management systems allow for the scarce water resource to be protected, as well as reducing maintenance costs, and thus an irrigation system would be installed that could be adapted to the actual requirements of the green spaces.
From the theoretical aspect to putting it into practice, we are going to allow you to discover, on the following pages, all of the advantages that can be obtained from such systems.
From the theoretical aspect: an illustrative example taken from the Grand Avignon Metropolitan Area
In order to reduce running costs and also conserve water, the Grand Avignon Metropolitan Area has installed an entirely self-sufficient Rain Bird meteorological station which allows for the irrigation system to be controlled in a centralised and sustainable manner. Seven sites have been fitted out so far, enabling substantial savings to be made in terms of energy and water consumption. The city of Avignon wishes to extend the use of this device to the majority of its public green spaces over the coming years.
Irrigating according to requirements.
This weather station allows for the plants’ evepotranspiration to be calculated, i.e. the actual water losses evaporated from the soil and transpired by the plants in the course of a day. “Too much irrigation is just as harmful as not providing enough water” explains Mr Juan, technician at Grand Avignon. This system, already installed in a large number of golf courses, allows for water savings of around 25 to 45% per year. Apart from the conservation of the water resource, this equipment also allows for less energy to be used (with the recently installed pumps that consume 25% less energy), and a reduction in operating costs. Therefore, when the slightest anomaly or malfunction appears in the network, the computer identifies the affected sector and an intervention is programmed.
There are considerable advantages.
Irrigation is scheduled for the night when evapotranspiration is lowest. Without this tool, it would have been impossible to know exactly how much water was required by the green spaces from one day to the next.
“The potential consequences would be: inappropriate irrigation leading to the wastage of water resources, vulnerability to diseases, soil compaction and the overuse of pumping stations, which would also result in too much energy being consumed” explains Jean-Michel Juan. Nowadays, thanks to centralised irrigation management, the Grand Avignon area has reduced its budget for operating and maintaining the system, mowing the grass, the use of plant health products and energy bills. Furthermore, Grand Avignon can now monitor its irrigation system in real time. The Grand Avignon technicians are now well aware of the number of plants that exist in the green spaces, which allows them to calculate the ETP (Potential Evapotranspiration) with absolute precision. Each solenoid valve has been identified with an exact diagnosis of the equipment, sprinklers, spray heads or drip system. The rainfall is calculated for each station, and the parameters linked to the soil, infiltration rate and soil water retention capacity were adjusted accordingly.
Nowadays, it is possible to refine the calculations of the precipitation rate for each station, solenoid valve by solenoid valve, by differentiating between the sectors in the shade from those fully exposed to the sun and wind, using a crop coefficient.
The operation of the centralised irrigation management system.
A Rain Bird Maxicom2 centralised management system allows the green spaces to be irrigated from a central point. The computerised irrigation programme can communicate with all the components of the irrigation system, satellite programmers, leak detectors, pumps and meteorological stations, in order to determine the required irrigation time and the amount to be applied. This system greatly enhances the efficiency and quality of the water distribution, while providing the opportunity to reschedule the Rain Bird EPS-Site satellite controller, in order to start or close down the irrigation network. Furthermore, it will immediately provide information about the quantity of water leaking out of the system or other anomalies in the irrigation system.
The meteorological station.
A meteorological station, self-sufficient because it is powered from a solar panel, records six parameters, namely: wind speed, wind direction, solar radiation, humidity, rainfall and temperature. This information is sent daily to a computer, which calculates the ETP, or Potential Evapotranspiration, which is now expressed in mm. of water, and not in irrigation time, i.e. it now calculates the actual water losses evaporated by the soil and transpired by the plants. The computer connects with the remote communication interfaces, in order to send the irrigation schedules. The computer receives information each morning about the events actually taking place in the field and records any malfunctions. The actual running times are compared with the calculated running times and any anomalies are analysed.
In actual practice: an illustrative example taken from the town of Cavaillon
The town of Cavaillon has recently installed a centralised control system for irrigating its green spaces. Four sites have been fitted out so far, enabling significant savings to be made on water and energy consumption. The town wishes to extend the use of this device to all of its green spaces.
On a beautiful autumn afternoon, I set off for the Green Spaces department of the city of Cavaillon, accompanied by Francis Manuel, from the company Hunter. We were welcomed by Pierre Verger, head of the department, Nicolas Charreton, his colleague, Emilien Estre, from the irrigation section and Damien Gros, the IT specialist. We headed towards the greenhouses: “We have just taken delivery of the biennials. They have been placed in this greenhouse for the time being, until we get around to planting them. The greenhouse is also used for carrying out the experiments”, explained Mr. Verger. The green spaces department has three large greenhouses (900 m2, in total), housing the bedding plants, flowerbeds and demonstration plants. “We have between 16,000 and 20,000 plants in rotation”, added M. Verger. “At this moment in time, we are irrigating twice a week, but during hot periods, we water every day”, explained Mr. Charreton.
The green spaces department employs 21 people in total and manages 40 hectares of green spaces (30 hectares in the town, in addition to the 10 hectares in the Grenouillet botanical garden). Over the last three years, a site has been specially devoted to the irrigation aspect, with a storage section, a workshop section and an office. “In the storage area we have all sizes of couplings, sprinklers, programmers, electro valves and solenoids”, explained Emilien Estre. In the office, he showed me a computer equipped with centralised management software. On the screen, it was possible to visualise each site, with its water consumption in real time. The software compares, on a permanent basis, the actual flow-rate compared with the parameter flow-rate. In the event of the flow rate being exceeded or if it drops off significantly, the solenoid valve in question is suspended and an alarm is triggered to facilitate the repair. This software is linked to the interfaces (or programmers), which are situated in the field, equipped with a modem and a GSM card reader (Another option: it is also possible to have wired telephone communication and a system with an IP). The user can also set in motion, stop or reconfigure the irrigation system from his/her computer or smart phone.
Four sites with a centralised control system.
At present, Cavaillon has four sites equipped with a centralised management system.
We headed for avenue Charles de Gaulle, the first site to be linked up in 2007. At the time, the town council was carrying out major works in the avenue in order to connect up the pressurised raw water system from the Saint Julien canal,with a budget of several tens of thousands of euros. The green spaces department took the opportunity to put forward the idea of a centralised irrigation management system, but it proved to be difficult for such a project to be included in the traditional budget of a small town. There are two programmers on this site, which control 30 stations; although 15 extra new ones will soon be added to these. We entered a site along the side of the avenue where there was a filter, electro-valves and two programmers. At the present time, 80% of the green spaces are irrigated with untreated water from the Saint-Julien canal, only the downtown area is now being irrigated with potable water. The raw or untreated water must be filtered before it can be used for irrigation. This network also allows for the towns allotments or vegetable plots to be watered.
Two ACC Hunter programmers control the 30 stations of the site: the 890-meter avenue, municipal police department, cemetery area, the cités (housing estates), the community and arts centre and the school. These are traditional programmers with multi-wiring; they are of the mixed kind; the interface only has to be changed to have a decoder system. One of the two programmers is equipped with a telephone modem, linked by a cable connection “if a sprinkler is stolen or deteriorates, then irrigation will stop because the higher flow rate will be detected by suitable sensors, neutralising the station concerned, enabling the user to replace the affected part”, explained Mr. Charreton. This feature is very useful in this part of the neighbourhood where vandalism is quite common. If it should rain, then irrigation will be stopped by the meteorological station, which is linked to the programmers. The information will be relayed to other programmers in the system, which, in turn, will cut out after communication with a central computer. During the 2008 fiscal year, the new installation allowed for irrigation costs to be reduced by 27%. The first tranche of work paid for itself within only two and a half years. Nicolas Charreton continued: “We will soon be adding a meteorological station to the system. It will measure the relative humidity, solar radiation, rainfall, wind and the irrigation parameters relating to all these elements”.
Emilien Estre and Damien Gros start up the irrigation system from their computer. We set off for the lawns that border the avenue Charles de Gaulle. Some of these are irrigated with traditional sprinklers
(Rain Bird), while others have a drip irrigation system (Netafim).
The subsurface drip irrigation network is laid out on a bed of sand, at a depth of 8 and 10 cm and the pipes are spaced 33.5 cm apart.
Being shorter, denser and more even, the turf irrigated by subsurface drip irrigation appears to be of a better quality. “Every year, a strip is renovated with subsurface drip irrigation”, explained Mr. Charreton. A little way further down the avenue, the freshly moved soil is ready to be converted into a flower bed. “We are only left with the flowerbeds on the outskirts of town. In the town centre, the tendency is still to use mineralisation. The flower beds are being taken up and replaced by plant holders”.
Theme-based roundabouts.
At the end of the avenue, a roundabout with a lawn, mulberry bushes, giant silkworm cocoons and water wheels conjures up memories of Cavaillon’s historical heritage. It is completely irrigated by subsurface drip irrigation. A new controller will soon be supplying the roundabout, at the beginning of avenue du Générale de Gaulle and avenue Mendes France. These 15 new stations allow for water to be taken from the town’s mains system to supply the gardens of the cite.
A little further on, a second roundabout decorated with lawns and Judas, apple and giant pear trees, the speciality of the region, should soon be linked to the centralised management system. The roundabout used to be irrigated with three old sprinklers, but in view of the scant amount of water supplied compared with the surface area irrigated, it was impossible to replace the sprinklers with other spray heads. The town, therefore, opted for the MP Rotator from Hunter, which allows for a uniform system to be achieved in terms of precipitation rate (10 to 12 mm/h). For seven or eight months now this roundabout has also been irrigated with untreated water because the canal passes nearby. The water is filtered and sent into the network via a regulator valve. On this site, a programmer controls 7 stations, and allows for the roundabout and gardens in the development area behind it also to be irrigated. By the roadside, the central reservations are put down to turf or left fallow. These annual flowerbeds (Cosmos, Carnations) are reseeded each spring and they die off at the beginning of winter. Mr. Verger explained: “This winter we are going to sow mustard; we will cut it, and then bury it, and this will provide the organic fertiliser required for planting the annuals the following spring”.
In the Ratacans district, a play area for children in a development area is irrigated with a centralised management system. “For the time being, our role is to make the area green again, but our aim is to build a herb garden for the children to explore.” A 2-wire decoder /programmer with a pedestal (because there is no electricity) allows for the irrigation management of the site.
Today, in Cavaillon, 57 stations in total are linked to the centralised management system. This new system allows for a number of stand-alone programmers to be removed and the installations to be grouped together so that they can be centralise. TThe aim is to have 89 by the end of the year and 100 stations by 2013.
