A small pool of water at the bottom of Cyprus's largest reservoir is shrinking by the day: without rain, the main source of surface water for most of the island will dry up by the end of the year.

The sun-baked earth in the empty pit at Kouris is a sign of the unprecedented water crisis facing the Mediterranean island. As climate change takes effect, authorities face the dilemma of how much to use energy-intensive desalination to beat the shortage.

"It's bad. Very bad," says Vlassis Partassides, head of water management at Cyprus's water development department. "If the drought continues for a fourth year, the consequences will be very severe," he told Reuters.

Reservoirs are less than 9 per cent full and residents - accustomed to treating water as a precious commodity - are braced for another dry winter.

Cypriots' water bills come with graphs showing monthly consumption, and authorities are swift to alert households to abnormal spikes in use.

"I water my garden with water I have used for mopping up, and think twice about putting on the washing machine if I don't have a full load. It is something that worries us all," said Eleni Ioannou, 43, a resident of the Cypriot capital Nicosia.

Two desalination plants running at full capacity are not enough. Plans include emergency drilling to tap precious underground water deposits, further cuts to agriculture and a new desalination unit to come on stream next July.

With one of the highest concentrations of reservoirs in the world, Cyprus is no stranger to water shortages. While hydrologists can factor in inevitable periods of drought, the island can do little to arrest climate change.

Mr Partassiades said that since 1972, rainfall had fallen by 20 per cent but the runoff - the inflow into reservoirs - had declined by 40 per cent, because of rising temperatures and the resulting increase in evaporation.

"Climate change is clearly evidenced in Cyprus," said Costas Papastavros, head of the island's national climate change unit.

"Climate change is not only about a rise in temperature, but also about extreme weather conditions, and drought is one of them. Desertification is also becoming a serious problem.

"It is not just that we do not have water in dams for irrigation, but we are looking at a decline in the productivity of soil, and we have a tremendous problem."

Cyprus was a predominantly agricultural economy when it became independent in 1960, but agriculture's contribution has since dwindled to 2.8 per cent of gross domestic product.

In the past century, temperatures in Cyprus have risen by almost one degree Celsius and annual rainfall has fallen by 80 mm - a staggering amount by meteorological standards.

According to the Intergovernmental Panel on Climate Change, global average surface temperatures have risen by about 0.74 degrees Celsius in the past 100 years, although changes vary widely by region.

Brimming with water until three years ago, the chalky slopes of Kouris are bare of vegetation because they are normally submerged in water.

Juggling demand is an exercise in maths, and the figures do not add up. From now until the end of the year, Cyprus will require five million cubic metres of water.

Kouris, the primary source of a pipeline feeding the districts of Nicosia and the southern districts of Limassol and Larnaca, now holds 3.23 million tonnes, and is 2.3 per cent full.

Desalination can meet up to 45 per cent of demand from some places but others are at the whim of the weather, cuts in irrigation, and the tapping of aquifers. An emergency desalination unit may help next summer, but authorities are in a bind about what to do from January onwards.

Even in the worst periods of drought, hydrologists say, there has been an inflow to reservoirs. Asked what will happen if it does not rain, Mr Partassides said: "That won't happen. There is no case of it not raining."

Desalination of seawater is not an ideal choice for the authorities, but it has saved Cyprus before.

"We don't desalinate lightly, without being aware of the consequences," said Mr Partassiades. "It is energy-consuming... and this causes (greenhouse gas) emissions Cyprus has to pay fines for.

"But while may we have the cash, we don't have the water," he said.

Now greenhouses, seasonal vegetables and permanent crops will be denied water supplies: "We don't have the water. If this continues the trees won't make it until next summer."

Mr Papastavros said the situation was unlikely to improve without radical change to water management and farming practices.

Ultimately, he said, Cyprus would need to get used to life under global warming: "This is what happens when natural cycles are broken by human influence."