The tourism boom around one of the world's most popular summer holiday destinations, the Mediterranean Sea, is endangering freshwater supplies and tourists in the area must cut their consumption, the environmental group WWF said Thursday.
Each holiday-maker uses 50 percent to four times more water than that consumed by a regular inhabitant of a Spanish town, according to a report by WWF on the impact of tourism on freshwater resources in the region.
The report also criticised the widespread construction of golf courses and swimming pools that increase the demand for water where it is already scarce during summer.
"The tourism industry's growing demand for water-guzzling facilities and services such as water parks, golf courses, and landscaping is destroying the very resource it depends on," said Holger Schmid, of WWF's Mediterranean Freshwater Programme.
A golf course needs about one million cubic metres of water per hectare (14 million cubic feet per acre) a year, equivalent to the water consumption of a town of 12,000 inhabitants, according to WWF.
Eight golf courses are being built in Cyprus, which like many coastal areas around the Mediterranean suffers from water shortages during the hottest months of the year.
The Mediterranean coastline attracts about 200 million tourists a year, nearly double the number 20 years ago.
Tourism in the region is expected to expand further by 2025 to attract between 235 million and 355 million travellers a year, according to some estimates.
The coastal population of Spain's Costa Brava region swells from 150,000 to 1.5 million in mid-August, or by 50 percent on the relatively urbanised French Riviera, according to official data cited by the WWF report.
In some Greek islands, summer water demand can be five to 10 times higher than in winter.
The WWF said the current consumption of 350 to 850 litres (77 to 187 gallons) of water per tourist a day could be cut by about half if governments and individual travellers made an effort to save water.
Recommended measures range from simple ones like not leaving taps to run unnecessarily or fitting water-saving devices on them, to tough laws against wastage and the redesign of water distribution systems.
"Insufficient, inefficient or non-existent" water and sewage treatment facilities are also overwhelmed by the summer surge, adding to pollution of the remaining water supplies, the report warned.
"The result is large volumes of sewage discharged to treatment plants, or to the seas and rivers, because many tourist facilities are in isolated areas and are not connected to the water treatment network," it added.
Around the seaside resort of Rimini in Italy, waste water and sewage disposal is three times higher than in winter, while in Greece, hotels near the coast are often not connected to sewage systems, WWF said.
The growing human demand has drawn water away from agriculture, prompting several countries - Egypt, France, Greece, Israel, Libya and Morocco - to set up massive irrigation schemes.
Spain's new government recently cancelled a massive project to transfer freshwater stocks 900 kilometres (600 miles) from northern to south-eastern Spain for irrigation, because of fears about its environmental impact.