The regions of Valencia and Murcia have threatened to complain to the Constitutional Court about a controversial 180 million euro pipeline from the river Ebro delta, due to supply Barcelona from October.
"It's an emergency measure to give drinking water to five million people who might not have it in a few months," said Spain's Deputy Prime Minister Maria Fernandez de la Vega.
A longer-term answer will be a desalination plant, billed as the biggest in the European Union, under construction on the outskirts of Barcelona and due on stream in May 2009.
The plant is just one of several planned or being built in Spain, which will be needed to offset the impact of global warming in coming years in the Mediterranean region, water experts say.
"It was already very important when it was planned but now, with the urgent drought, it has become indispensable," said Tomas Azurra, chief engineer at the plant at the estuary of the Llobregat river.
The plant, which is 75-percent funded by the EU, is being built by a consortium including water firm Agbar and Dragados, part of construction firm FCC. It will supply 20 percent of Barcelona's water.
MORE EFFICIENT
Stephanie Blenckner of the Stockholm International Water Institute said desalination plants were costly but affordable to European countries, and preferable to permanently diverting water from rivers such as the Ebro.
She added that countries like Spain needed to capture more rainwater in future, as climate change would exacerbate alternating periods of drought and heavy rain.
"The rain is the biggest resource we have and we can dispose of it all year round if we have sensible storage opportunities," Blenckner said.
She also predicted increasing tensions due to demand for water from the tourism industry, which accounts for about 11 per cent of Spain's economy.
"Water will be essential for tourism and that will sharpen up social consequences, as it already has done in places like Morocco and Egypt," Blenckner said.
The World Bank said in April declining water quality has already knocked around 1 per cent off gross domestic product in Morocco, Algeria and Egypt and almost 3 per cent in Iran.
