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Mon 5 Nov 2007 12:32 PM

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Flush out the problems

Martin Saker, limnologist in Emaar's facilities management department, explains the problems and solutions associated with artificial lakes.

Flush out the problems

In most cases, artificial lakes have two functions. Firstly, to receive drainage run-off in the event of rain and secondly, to be aesthetically pleasing to the eye.

There have been a few problems with the region's lakes, with the major ones being related to the growth of algae, high nutrients, stagnant water and dead fish. These are ongoing problems that need addressing.

How are you going to rectify the problems?

We just finished a three month project aimed at identifying the major problems. It involved a comprehensive study of the water's physical and chemical characteristics and hydrologists from Jordan were involved to look at water movement through the system and other hydrologic issues.

Many contractors are dumping sewage and construction waste into the lake.

Restricted water flow from one lake to another and through the entire system has been identified as a major cause. The basic functioning of an artificial lake involves groundwater (sea water) being pumped to the surface and then into the lake. The water is then circulated through the interconnected lakes.

The groundwater contains high concentrations of nutrients and this leads to the growth of algae.

Emaar is determined to build more lakes so I'm involved in planning for future lake developments. Learning from our past mistakes, we are planning to design lakes to avoid many of the problems that have occurred in the past.

Lakes are very different to water features, which generally involve strong chemical treatments to ensure a constant level of water clarity. In contrast to chemically treated water features, we want to encourage fish, have plants growing around the edges and have lakes that appear as natural looking as possible.

Another maintenance problem is the salt water. It won't erode the pipes, but it is highly corrosive and at high concentrations can precipitate from solution to cause the blockage of interconnecting pipes between the lakes. We can tell if there's a blockage by the different levels of water in the lakes. If one is building up and the other one is staying the same, we know there's a blockage somewhere.

Does the interlinking of lakes allow bacteria to flow freely?

Yes. In these cases we have to increase the rate in which we are pumping the water through and flush it out or isolate the lake and treat the water. From past experience, the biggest problems are during the summer when temperatures are highest and bacteria multiply much faster. There's more evaporation and water quality in general is lower.

What can be done during the summmer months?

Pump the water through the system at a faster rate and as a back up, maintain chemical treatments on hand. So far we haven't had to use chemical treatments for improving water quality.

How often should they be maintained?

Continue monitoring the water quality on a monthly basis and take active control of the activities that go on around the lake such as irrigation and landscaping.

Many contractors are dumping sewage and construction waste into the lake. This represents a lack of awareness and care over the issues we face in maintaining the lakes. Since the lakes are so close to the residents we need to consider public health issues.

I spend much of my time visiting the lakes and identifying problems. We have several contractors we use to clean the lakes. I work in close collaboration with landscaping because a lot of landscaping practices, such as irrigation and the use of fertilisers, have a direct affect on the quality of water. Irrigation system maintenance is very important for maintenance.

What technology will you use?

Using pumps with different capacities can control the rate of water replacement. It is imperative that pump systems for inflow/outflow from natural lakes are adequate for providing an acceptable level of water exchange. This is the preferred option of Emaar.

Controlling the quality of water that enters the lake systems is more costly, although there are various chemical, bacteriological treatments and technologies that could be applied to remove phosphorus and nitrogen from water to slow the growth of algae.

Treatments such as reverse osmosis or desalination plants can convert poor quality salt/polluted water to the standard of drinking, however, they are costly and consume large amounts of energy.

In addition, there are various technologies available for lake restoration. For example, devices that mix the water to cause natural oxygenation may improve habitats for fish and prevent odour problems.

We have trialled several of these devices in our lakes and have not been happy with the results. In general, they do not work well where there are high concentrations of nutrients.

We are attempting to solve the problems by focusing on improving circulation patterns to prevent algae from growing, rather than applying treatments to kill them.

We recently finished the construction of a lake in The Greens. We prepared the lake, filled it with water and within three days, it was green. We had some complaints from residents and we're considering using chemicals, but we really don't want to.

When we're creating artificial environments, we want to do our best to produce something that is sustainable. We don't want to dump chlorine, copper sulphates or alum - there's plenty of different chemicals we could use to end up with crystal clear water. But we want to try and develop something sustainable and as natural as possible.

Emaar has 70 lakes in Emirates Living, Arabian Ranges and The Greens. In addition, it has new lakes under construction at Umm Al Quwain Marina and the Burj Dubai.

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