Activists are warning of a potential "thirst uprising" in Tunisia following protests over severe water shortages after one of the North African nation's driest summers on record.

Residents in the interior are suffering long water supply cuts, reservoirs are running dry and farmers are seeing significant losses, adding to social tensions in a country still struggling with instability since its 2011 revolution.

The Tunisian citizens' water observatory, known as Watchwater, warned last month the country could face a "thirst uprising" reminiscent of the protest movement that spread across Tunisia nearly six years ago.

"The failure to find urgent and serious solutions will increase protests across the country," it said.

Water scarcity has long been a problem for Tunisia, but in recent years the challenge has been exacerbated by growing urbanisation and increasing demand from agriculture and industry.

This year has seen the country particularly hard-hit, with rainfall -- Tunisia's main water source -- down by some 30 percent, the state secretary for water resources and fishing, Abdallah Rabhi, told AFP.

In August, the agriculture ministry warned Tunisia would be facing a "catastrophic" situation if it did not rain by the end of the summer. The few rainstorms since have not been enough to replenish groundwater reserves or reservoirs.

Agricultural losses for this year have already reached nearly two billion dinars ($900 million/800 million euros), according to the Tunisian Union of Agriculture and Fisheries.

- Call to 'pray for rain' -

The ministry of religious affairs has even called on the people to "pray for rain".

Since mid-May, the authorities have announced more than 700 water supply cuts. Officially they last from several hours to three days, but Alaa Marzouki of Watchwater said that in some regions the cuts have lasted nearly a month.

Protests have erupted in several affected areas, with the water shortages adding to the frustrations of many residents who feel their concerns are being ignored by authorities in Tunis.

At one demonstration in the northwestern town of Fernana earlier this month, protesters gathered at a local pumping station and threatened to disrupt supplies to the capital, according to local media reports.

"Economic protests resembling those that sparked the 2010 Jasmine Revolution are spreading throughout Tunisia and may grow into nationwide civil unrest," the Washington-based American Enterprise Institute warned in a report this month.

In the southwestern Gafsa region, local farmer Mabrouk said frustration was growing.

"We are suffering," said Mabrouk, who declined to give his last name.

"We had to buy a water tank for 30 dinars for what we use and what our animals use. We've sent requests to the government but they remain unanswered. All we can do is wait for rain, God willing."

Tunisia has some 30 dams and reservoirs that provide irrigation of agricultural land and drinking water, but by the end of August their reserves were less than 40 percent of what they were at the same time last year, Rabhi said.

- 'Very dangerous situation' -

Some, like the Nabhana reservoir in central Tunisia, are completely dry.

At the Sidi Salem dam near Beja in northern Tunisia, reserves are about half what they were last year.

"You have to go back to 1993-1994 to find such a level," said the dam's manager, Cherif Gasmi.

"If rain does not come by the end of September... we will have to tap the dam's strategic reserves and that's a very dangerous situation," he said.

Groundwater levels in areas without dams have also fallen, in some cases by 25 percent, said Mohamed Dahech, the CEO of SONEDE, the national water supply authority.

With consumption increasing by an average of four percent a year, SONEDE has urged Tunisians to use less water.

But Marzouki of Watchwater said more needed to be done.

"The state has not put in place the necessary strategies," he said, pointing in particular to decrepit water pipelines that leak 10 to 30 percent of supplies.

SONEDE's Dahech said a major issue is unpaid bills, which have reached the equivalent of some 60 million euros so far this year.

The government has promised a raft of measures, including unblocking several dam projects and the construction of three desalination plants in the south.