By Peter Greste
BBC News, Northern Kenya
More a sea than a lake, Turkana is the life-force for the otherwise arid northern Kenya.
After driving for hours across bone-dry stony plains and past desperate looking salt-bushes, the vast emerald-green expanse of water appears above the horizon without warning, almost as a mirage.
About 300,000 people depend on its waters either directly or indirectly, for their survival. But if you believe environmentalists like Richard Leakey, the lake is on the verge of dying.
Mr Leakey and others blame Ethiopia for the plight of the lake. More than 600km away up the Omo River valley, the Ethiopian Electricity Company is building a dam that critics say will condemn the lake to a not-so-slow death.
The Ethiopian government maintains that is simply not true.
It is building the Gilgel Gibe III hydroelectricity dam - the second largest in sub-Saharan Africa - to solve a national energy crisis.
According to the authorities, once the dam has been built the total amount of water flowing into the lake will not change.
The only difference will be a more moderate rate of flow over the year as the authorities release water to generate electricity - more than normal during the dry season, and less during the wet.
But an independent collection of European, American and East African scientists who have banded together as the "Africa Resources Working Group" insist the dam will have a catastrophic impact on Turkana and its people.
The Omo River provides 80% of Lake Turkana's water. The other two main tributaries - both entirely within Kenya - are perennial rivers that turn to dust during the dry season.
Lake Turkana is already shrinking
During the time it takes to fill the Gibe III dam - one or two wet seasons according to the electricity company - the river will be reduced to a typical dry season flow.
The dam will retain 11 billion cubic metres of water. According to the ARWG, that is enough to reduce the level of Lake Turkana by as much as four or five metres.
Over recent decades, the lake has been gradually shrinking and becoming increasingly salty. It is already highly alkaline and only barely drinkable for either humans or animals.
Turkana hydrologist Paul Ikmat believes that if the level falls any further, there is a very real danger that the water will become too alkaline to drink, and seriously damage the delicately balanced fisheries.
"It is still unclear how much the Gibe III dam will impact Lake Turkana," he says.
"Nobody has really done the studies. But as a hydrologist I find it hard to see how it couldn't have a significant effect. I'm very worried indeed."
For the five communities who live around the lake, that is more than worrying. The largest group is the Turkana.
With enormous strands of beads wrapped around their necks and decorating their bodies, Turkana women are some of the most striking in Kenya.
Like almost all the communities, they are principally cattle-herders who have fallen back on alternatives as traditional grazing lands have become squeezed by commercial farms, declining rainfall and increasing populations.
Many Turkana have turned to fishing. The lake is rich with about 40 different species, though only three are commercially harvested: tilapia, Nile perch and catfish.
Each day, fishermen push their boats out through the swampy fringes of the lake now choked with prosopis juliflora - an invasive species imported from South America that has taken over much of the Turkana shoreline.
With hand-cast nets, they haul in the day's catch that has been diminishing over the years.
Turkana women are famous for their necklaces
With no refrigeration and only rough dirt roads to take the catch to market, the only way of making an income from fishing is to dry each day's haul.
The authorities believe the fisheries are under-utilised, but still the catch has been declining, and they blame increasing salt-levels.
Even so, nobody is really certain how sensitive any of the fish species are to changes in salinity.
"That's the problem," said Mr Ikmat. "We just don't have enough information to accurately judge how this is all going to turn out."
But local activists like Ikal Angelei argue that the stakes are terrifyingly high. If the lake becomes undrinkable and the fish start to die, all the communities are finished.
"I'm full of rage when I think about it," she says. "Every time two people die anywhere else, the government stands up to make a fuss about it.
"Here, I think there's a possibility of thousands of people losing their livelihoods and possibly losing their lives and no-one is talking about it."
Ms Angelei has been organising a campaign to raise awareness about the threat to the lake, but Turkana is both physically and politically remote.
But Kenya also stands to benefit from the Gibe III dam.
The generating plant will double Ethiopia's electricity supply overnight, producing far more than it can use for the foreseeable future.
Half of its capacity - about 900 megawatts - has been earmarked for export to electricity-hungry neighbours like Sudan and Kenya.
That is one reason critics like Richard Leakey believe the Kenyan government has so far been silent on the potential impact on Lake Turkana - an area he has strong personal connections to.
In his role as one of the world's leading paleoanthropologists, Mr Leakey has unearthed some of the earliest evidence of human evolution around the lake - discoveries that have prompted scientists to think of the region as the cradle of humankind.
"I think the work that I've done over the last 40 years has made me feel very protective, very identified with the people who live here," says Mr Leakey.
"There are some really very fine people who deserve better than the marginalisation that they've suffered, and I think the proposed dam is going to have a negative impact on a people who really have little chance of getting the help they need to make their lives more successful."