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Mon 7 Jul 2008 04:00 AM

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Water works

The need to reduce water consumption has never been greater. COD takes a look at how landscaping irrigation can become more efficient.

The need to reduce water consumption has never been greater. COD takes a look at how landscaping irrigation can become more efficient.

Sustainable landscaping is the latest trend in the region right now and of the various ways that landscaping can be made more sustainable, nothing is more important than saving water.

There is a huge shortage of natural water in the region, creating an acute need to watch water consumption, and as one of the biggest users of water the landscaping industry is under particular pressure to increase water efficiency.

Over-watering in the Middle East region is a common problem, more so than under-watering.

According to Rehbein Environmental Solutions International, Dubai currently uses around 150 million gallons of water a day on irrigation - equivalent to 68% of the Emirate's total water usage.

New guidelines such as the Estidama introduced by Abu Dhabi's Urban Planning Council last month, underline the importance of water efficient landscaping in sustainable landscaping, but at the same time, vast stretches of greenery continue to top developers' wish-lists for new projects. How is the outdoor design professional meant to reconcile two such conflicting demands?

Concept control

The first step is to minimise the water requirements at the design stage, says Rajan Dewan, director in charge of irrigation, horticulture and site supervision at regional landscape practice Cracknell.

"We need to start with the landscape design," he says. "We can play with the design and introduce some hard elements that are not visible, areas where you don't need irrigation. It is all [about] your skill as to how you design your landscape because when you drive along the road, you will still see a green effect, but you will [also] see some of the areas have been hidden and covered with pebbles."

Spacing of trees on highways, for example, can be played with to give the effect of a tree-lined route without vast numbers of trees, he says.

Spatial planning is key to reducing water requirements, says Jim Haynes, general manager, irrigation division at Fitco, a supplier of a range of landscape irrigation products.

"Avoid large square or rectangular (football shape) turf areas in preference to small irregular (for example, kidney) shapes. This will reduce the surface area of grass used while at the same time giving the impression that there is a lot more grassed area than there actually is," he advises.

Landscape architects need to work with horticulturalists and irrigation designers to come up with the most water efficient designs, he adds. "Designs may look great on a computer screen but in practice may contain difficult areas to irrigate and maintain. This can often be easily avoided with the interface of practical irrigation knowledge and plant selection and layout at the design stage," he says.

Turn off the tap

The second point is an obvious one: stop using potable water. Most of the public parks and large-scale green areas are now irrigated with treated sewage effluent (TSE), a combination of grey water (wastewater from basins and showers) and black water (water from toilets), but residential properties and some of the smaller hotels still mostly use potable water, the most precious form of water in a region where rainfall is a rarity.

While there are no regulations at present on water consumption, the government is pushing people towards using non-potable water for irrigation by initiatives such as raising the price of water.Credits are awarded under the LEED and Estidama guidelines for the reduction of potable water use.

Computer control

The major means of reducing the quantity of water used comes down to how it is applied, however, and it is here where landscaping irrigation tends to come in for criticism.

The biggest progress in irrigation has been the control of each sprinkler and the control of checking how much water we are actually putting on the ground.

Poor practices tend to include sprinklers running mid-afternoon when evaporation losses are at their highest, irrigation systems that do a better job of watering the nearby pavement than turf, and - particularly for residential developments - persistent use of hoses rather than computer controlled systems.

"Over-watering in the Middle East region is a common problem, more so than under-watering," says Haynes. "Many of these problems evolve from the labour force's inability to fully utilise the capabilities of the products selected by the designer. Generally, the simpler the system is to install, operate and maintain the more successful it shall be in the long term."

Sophisticated technologies now mean that just switching from manual to automatic irrigation methods can significantly reduce water consumption.

Advanced control systems include weather based irrigation controllers that adapt water requirements to match climate conditions, and moisture sensors programmed to make sure water is applied only where it is needed, particularly useful for podium landscapes.

"Low flow concepts, pressure regulation and automatic irrigation control systems combined with weather based controllers will help preserve water and energy by ensuring that irrigation networks are efficiently and uniformly distributing water," comments Ziad Amine, sales and marketing manager at irrigation solution provider Middle East Agriculture Company (MEAC).

Companies can expect to save between 25-30% on the amount of water consumed by using computer controlled irrigation techniques, according to industry sources.

Computer control is particularly useful for monitoring large-scale projects, providing an overview of operations, notes Omid Mohamadi, a manager at regional irrigation and landscaping company Mirak.

Whilst the efficacy of computerised irrigation is not in question, however, some companies are still holding back from investing in them due to the higher costs involved.  Investment is a must, however, say suppliers.

"We need to use the latest technologies that help preserve water and energy and at the same time reduce the overall cost of the system. Yes, in irrigation it is possible to enhance the efficiency and at the same time reduce the cost but we need to use the latest technologies and the latest products.  We cannot be efficient and conserve water and energy with concepts and products that are 20 years old," says Amine.

Micro management

Localised irrigation can particularly help make water efficient landscaping become more efficient, experts say.

"The biggest progess in irrigation has been the control of each sprinkler and the control of checking how much water we are actually putting on the ground and adding a bit or decreasing it via computers, via satellites. The green keeper can see how much water he's giving on any particular area now," says Peter Harradine, managing director of Orient Irrigation Services, a Dubai-based firm, which offers irrigation products and services through its design and contracting departments.Matching water requirements to those of a specific plant is particularly important, says Basem Taha, irrigation engineer at landscape contractor Blakedown Landscapes.

"Each plant around the world has its own water requirements so if we just program our central computers to fit the requirements of plans that would save a lot more water."

Micro irrigation is key, states Haynes. "With micro irrigation our aim is to accurately match the application rate of water applied with the soil type and root zone absorption potential of the plant. This aim not only applies to all tree, shrub and ground cover areas but should also be considered as equally important with sprinklers for lawn areas," he says.

"If we apply water too fast much of it will percolate past the root zone into the lower layers of the soil and be lost. Alternatively it may collect on the soil surface and be evaporated or run off onto hardscape areas. The better we equate our water application (through correct irrigation component selection and operation) with the plants root zone, soil type and climatic conditions the healthier the plant and the less water used," he adds.

Soil additives

Arriving at more water efficient landscaping isn't just a question of changing bad habits, however, but also controlling other elements such as selecting plants with low water requirements, and using soil additives to toughen up the local sandy soil.

Soil additives help increase the structure and water holding capacity of soil meaning that less water is leached out.

Manufacturers claim that such products can result in savings of as much as 50%, although no independent studies on the efficacy of soil amendment products have been produced to date.

Whichever way it's done, there is no doubt that the need for the amount of water to be reduced in the region has never been greater.

To meet regional water consumption reduction goals - the government in Abu Dhabi has pledged to cut the water consumption rate per head by half over the next five years - the region must find ways to stop wasting water.

While the buck doesn't stop with the landscape designer, it is clear that he, together with his counterpart contractor and supplier, is in a position to make a difference.

Watching water usage

Estidama

Under the new Estidama regulations by Abu Dhabi's Urban Planning Council, as many as 30 credits are related to water usage with five credits attainable for water efficient landscaping. Certification begins at 35 points.

Credits are awarded for reducing the quantity of potable water used for irrigation by 50% from a calculated mid-summer baseline case. Reductions are awarded for: plant species factor, irrigation efficiency, use of captured rainwater, use of recycled wastewater.

LEED

Under the LEED green building rating system developed by the US Green Building Council, two points can be awarded for water efficient landscaping.

One point is awarded for the reduction of potable water consumption for irrigation by 50% from a calculated mid-summer baseline case, with reductions attributed to a combination of: plant species factor, irrigation efficiency, use of captured rainwater, use of recycled wastewater, use of water treated and conveyed by a public agency specifically for non-potable uses.

A second point is awarded for the elimination of the use of potable water for landscape irrigation.

The credit requires use of only captured rainwater, recycled wastewater, recycled grey water, or treated water, or for the installation of landscaping not requiring permanent irrigation systems.

Certification under the LEED rating starts at 26 points.

RELATED LINK:Turning off the tap

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