The beach looks ready for war: in the sparse lakeshore shade hundreds wait, sweaty from the heat, weapons at their feet.

In Kenya's hot, dry and lawless north even the fishermen are armed, but guns will not save them.

They live on Lake Turkana, the biggest desert lake on earth and a World Heritage Site, but the lake is threatened and so is their way of life.

"There are fewer and fewer fish," said 41-year-old Maurice Echerait, sitting next to handmade nets with discarded plastic bottles for floats by the ramshackle row of improvised shelters that make up Nayenae camp.

The reason, he says, lies 600 kilometres (370 miles) northwards up the Omo River, Turkana's main tributary, and rises 243 metres (797 feet) into the sky: 'Gibe III', Africa's tallest hydroelectric dam unveiled by Ethiopia last year.

The dam is now filling up so Turkana's water levels are falling and the seasonal flooding that helps the fish breed is disrupted.

"The fish that are left are all gathered in the Omo delta" to the north, which is rich in nutrients, Echerait said.

- Blood in the water -

Life in Kenya's arid north is a relentless battle for scarce resources, and the changing fish patterns mean the traditional, sometimes deadly, rivalry has intensified between the neighbouring Turkana and Dessanech people.

"Now that we put our nets in the same places, in the delta, there is fighting on the water," Echerait said.

"We don't negotiate when we meet the Dessanech, we fire on sight and so do they," said Echerait, whose cousin was killed in a shootout late last year.

Nayenae camp looks like a militant outpost, stocked with AK-47s, G3s and FAL rifles. Fishing boats are camouflaged with thick stripes of jade green and pastel blue "to go unnoticed" among the delta's plants and waters, said Echerait.

In the past, a good catch meant nets overflowing with carp, perch and tilapia. Today, fishermen are happy to return to shore with their lives.

"One single river, the Omo, contributes 90 percent of the total freshwater inflow into Lake Turkana," said Sean Avery, a hydrologist, who studies the lake, "so if there's any change in that one river system, it's going to have a direct impact."

- No flooding, no fish -

Ethiopia's impact assessments for Gibe III -- just one of a series of dams planned for the Omo -- "do not take into account the possible consequences on the other side of the border," said Avery, where 300,000 people depend on fishing.

When the dam began to fill two years ago the Omo's flow decreased and the lake dropped by two metres, drying out the tilapia's shallow breeding grounds. Once the dam is full this problem will be reversed, but the long-term impact on seasonal flooding is of greater concern.

John Malala, of the Kenya Marine and Fisheries Research Institute, said 60 percent of Turkana's fish "rely on the river Omo to breed because they are migratory fish."

No flooding means no migration and no breeding. Ethiopia has promised to trigger artificial floods, but they are untested.

"If I knew where this dam was I would go and break it down myself!" said Loito Ibuya, an enraged young fisherman in a camouflage T-shirt.

Like others in Nayenae, Ibuya abandoned his village, 10 km to the north, because it was too close to the Dessanech and he refuses to move any further south because he would be further from the delta and fuel costs for his outboard motor would increase.

Fishermen, he said, were betrayed by successive Kenyan governments which marginalised and neglected the Turkana region for generations and now seems more interested in buying Ethiopian electricity from Gibe III than protecting their interests.

- Africa's Aral Sea -

But Ethiopia's ambitions are not only electrical but agricultural, and the impact on the lake could prove catastrophic.

Irrigation projects for sugar cane and cotton plantations downstream of Gibe III will require the diversion of unknown quantities of river water.

Uncertainty and controversy surround these plans but Ethiopia's taciturn government does little and says less to dispell concerns.

Analysing satellite imagery, the pressure group Human Rights Watch estimated that roughly a third of 100,000 hectares have already been planted, with possibly more to come.

"We've seen figures mooted of up to 450,000 hectares (1.1 million acres), that would remove 50 percent of the river," said Avery.

The lake would then drop by dozens of metres, splitting in two across its narrow, shallow waist in a replay of the Aral Sea, which was drained by the diversion of rivers for irrigation in Central Asia.

Alarmed by these existential dangers, some Turkana and Dessanech leaders began peace talks in March. Michael Irgiena, a Dessanech fisherman who crossed the lake to parley, asked: "When the lake is empty, what will we have been fighting for?"

Source: AFP