Macias is president of the Tagus water basin, which stretches across central Spain southwest to Portugal, supplying Madrid's 6 million inhabitants on the way.

Two months of Atlantic storms in October and November have brought only partial relief and the two big reservoirs at the head of the Tagus are only 12 percent full.

"The storms and rain were very abnormal this year. In the lower parts of the river basin it rained quite a lot but in the upper part it rained very little," Macias said.

He is cautious about attributing the drought to climate change with only a few years data to go on, but says that the country's water authorities have to face up to climate change.

"It's probably going to give us totally different weather patterns, with less rain falling in less time and more violent storms," he says.

Most of Spain is naturally dry and suffers periodic cycles of drought, such as a five year one in the mid 1990s.

The year from October 2004 to September 2005 was the driest at least since records began in the 1940s. Rain in 2005/6 was 11 percent below average and 2006/7 is proving erratic.

The Tagus has to supply an urban population of 7 to 8 million people in Madrid and the surrounding area, provide irrigation for 300,000 hectares (750,000 acres) of maize and pasture and cool two nuclear power stations.

It then has to deliver a specified quantity and quality of water at the border with Portugal, as set out in a treaty on shared rivers.

Another complication is that the big reservoirs at the head of the Tagus periodically have to send water to the dry southeastern regions of Alicante and Murcia.

On Friday ministers approved the latest transfer of 22 cubic hectometres, half for urban use and half for irrigation. That means the Tagus is supplying a further 2 million people, at least until a batch of desalination plants along the Mediterranean coast is completed.

WATER SAVING MEASURES

Macias' team has limited scope to curb water consumption.

The Agriculture and Environment Ministries are modernising irrigation systems all over the country in a bid to reduce agricultural usage, which accounts for between 70 and 80 percent of the total.

Madrid's household consumption is relatively modest at 130 litres a day per person but industrial and public usage is almost twice that amount again.

Where the water authorities can act is by insisting golf courses and parks use recycled water for their green spaces and by closing some of the estimated 20,000 illegal wells tapping into the aquifer, which is the region's safety reserve.

The big wells and most of the 21 golf courses should be under control in a couple of years, Macias says.

So far, Madrid's taps have never run dry and Macias is confident that for the moment urban supplies are adequate.