Irrigation systems can slash water use

Farms and forests in Abu Dhabi could in future be irrigated by less than half the water used today, under systems on trial in the emirate. Two new technologies that supply water to plants' roots, rather than pouring it on surface soil where it evaporates, are being tested by the Environment Agency Abu Dhabi (EAD). The systems could bring substantial savings to the farming and forestry sectors in Abu Dhabi, which account for more than half of water demand in the emirate.

Majid al Mansouri, EAD's secretary general, said the new systems would ensure that no water was lost due to evaporation. As a result, soils would not be damaged from the build-up of salts left over from the process. In above-surface systems, a proportion of the sprayed water evaporates in the desert heat. In time, this process deposits large amounts of salt in the topsoil, turning it barren. The first method uses semi-permeable underground pipes that "leak" water when pressure is applied and is expected to use up to 60 per cent less water than current systems. The pipes have been laid 30cm underground on a 440 hectare area in Bainuna, in Abu Dhabi's Western Region, for tests.

Dr Mohammed Dawoud, manager of the water resources department at EAD, said the tests would analyse water use and salt deposits for comparison with other means of irrigation. Mr Dawoud said underground pipes, made from recycled car tyres, would also need replacing only after 25 years. In contrast, aboveground irrigation pipes need to be replaced every two years. "We expect it will save a lot of money," he said.

In addition, the test irrigation site at Bainuna is being used to restore the houbara bustard to its natural habitat. The second project at Bu Arta, near Al Ain, irrigates three lines of trees using salt water through underground pipes. The plants "suck" out the water from the pipes themselves, with no external pressure required. The pipes also act as membranes, Mr Dawoud said, allowing only fresh water through and leaving brine in the pipes. The pipes are rinsed out on occasion, and the soil remains in good condition.

Dr Dawoud said all the trees were alive even though the water entering the network had a high salinity."We are now trying with field crops such as maize and vegetables," he said. The experiment will take place at a five-hectare site in Umm Zomol, near the border with Saudi Arabia, where the use of water with a salinity of 52,000 ppm will be tested. Pipe laying is expected to begin at the end of this month with results expected within a year, he said.

The systems are being tested as Abu Dhabi, like many countries in the region, tries to conserve its limited supplies of fresh water. Cutting water use by the agriculture and forestry sectors is a main goal for the Abu Dhabi water masterplan, a document which will assess the emirate's water needs until 2025. [e-mail]