When mathematician Lassana Koita left the "thirst zone" of Senegal to make his way in the world, he never forgot his duty to give something back to his beloved homeland.

Nine years later, enjoying a successful civil aviation career in his adoptive France, he has returned, brimming with pride over a water project he and other migrants helped build that is changing lives.

"I went to primary school here in Diawara, in classrooms built not by the state but by migrants. I'm not sure I would have got to where I am today without it," he tells AFP in the town of his birth in eastern Senegal.

With a postgraduate diploma in mathematics, Koita decided he wanted to study for a PhD but says he "found other opportunities and went into aviation, a passion for me".

"I was already working here in Senegal... I did not want to leave for any price," says the bespectacled educator, hair cut short and sporting a neatly-trimmed beard.

Arriving in France, Koita taught for a year before winning a competition for mathematicians that eventually led to a job in France's Directorate General of Civil Aviation.

His business card describes him as being "responsible for aerodrome safety studies" but he seems most proud of his work in the Diawara Renovation Committee, known by its French acronym, Coredia.

The committee has helped build an imposing water tower with a "purification unit" for inflows from the Senegal river, his way of giving back to a town which gave him so much, he says.

Coredia covered around a fifth of the project's 190,000-euro ($210,000) cost, with the remaining funding coming from various French and Senegalese organisations.

- 'Water galore' -

The tower was inaugurated at a recent festive ceremony attended by Diene Faye, a government minister for rural water provision, and French ambassador Jean Felix-Paganon.

Diawara is situated in the Bakel district, part of Senegal's "thirst area", the minister explained in a speech, praising "an important work" that would bring high quality water to the area "for several decades".

"We did a lot of drilling but the volumes are very low and not capable of feeding the population," Faye said, explaining that bore holes had tended to dry up within a few years of being drilled.

Diawara resident Coumba Thiam, resplendent in a bright orange traditional robe and headdress, and weighed down with gold jewellery, proclaimed her joy in several local languages.

"With this tower, we are all happy here! Before, fetching water exhausted us. There were accidents, diseases," she told AFP.

"Now that's all over and there is water galore, and we are no longer backward."

Diawara's 15,000 inhabitants have in the past had to make do with an unreliable supply system set up by the state in 1992 which fed 20 fountains for two hours each day, many several kilometres from residents' homes.

The network provided the town with just 22 percent of its needs, the deficit being made up from ponds, artisanal wells and the river, none of which provide safe drinking water.

"Today we have more than 500 private connections, and the water comes into people's homes," Koita says.

He recognises that he is spreading himself thin with an important job in France and commitments in his home town, but he is happy to continue his hectic lifestyle.

"It's a sacrifice I make for my relatives, family, my town, my city, my community," he says.