More than half of the public water supply in the Maltese islands originates from reverse osmosis plants, the National Statistics Office said.

In a statement issued on the occasion of World Water Day, the NSO said that 55.8 per cent of water in Malta originated from RO plants while the remainder was extracted from the ground.

World Water Day this year is being celebrated on the theme of water and food security. It was chosen by the United Nations to raise awareness about the effects of food production on the quality and quantity of water resources.

In Malta, the production of food by the agricultural sector takes a significant toll on local freshwater resources which are primarily replenished by rainfall.

The annual rainfall between 2000 and 2011 ranged from a low of 341.4 mm in 2001 to a high of 907.7 mm in 2003. During this 12-year period, the average annual rainfall amounted to 545.3 mm, slightly less than Malta's rainfall climatic norm of 553.1 mm per year.

From September 2008 to August 2009 total rainfall amounted to 763 mm. In the following agricultural year, the total rainfall almost halved to 388 mm. In contrast, the area under irrigation in 2009/2010 increased by 21.2 per cent when compared to 2008/2009.

This increase, together with a decrease in rainfall, brought about a surge of 47.8 per cent in the volume of irrigation water.

On average, 46 per cent of irrigation water is used for 'fresh vegetables', followed by 'potatoes' with 29.8 per cent.

Over both agricultural years, the average irrigation water demand ranged from 374 m3 per hectare for 'other fruit trees' to 18,802 m3 per hectare for 'flowers/seeds'.

However, it should be noted that since the land area devoted to the growing of 'flowers/seeds' is comparatively small, the irrigation water consumed by this category averaged 2.8 per cent of the total irrigation water used over both agricultural years.

From 2008 to 2011, 55.8 per cent of the public water supply produced by the Water Services Corporation originated from reverse osmosis plants. The rest, averaging 13.1 million cubic metres per year was extracted from groundwater, which constitutes Malta's only freshwater resource.

Groundwater is tapped for irrigation purposes as well.

For both agricultural years, the amount of water used for irrigation purposes exceeded groundwater extraction for public water supply.

In the agricultural year 2009/2010, the amount of irrigation water used almost equalled the public water supply produced by the Water Services Corporation.