By Ed Cropley
JOHANNESBURG, Oct 26 (Reuters) - Namibia's capital, Windhoek, is four years from running out of water should a recent pattern of above-average rains end and it needs to start filling aquifers artificially to counter the threat, a senior government official said on Wednesday.
With administrations across Africa struggling to meet the needs of rapidly urbanising populations, the city of 300,000 in the middle of the arid southwest African nation serves as a perfect test case for better water management.
Every year, its people and businesses consume 25 million cubic metres, or 10,000 Olympic swimming pools, of water from three reservoirs near the city, said Greg Christelis, a geohydrologist at the Department of Water Affairs and Forestry.
However, in 12 months these reservoirs will also lose more than 37 million cubic metres to evaporation -- a problem that is avoided if water is pumped underground into aquifers, or large chunks of porous rock.
"Essentially, we're building a water bank -- putting the water back in the ground for dry times," Christelis told a conference in the South African commercial capital, Johannesburg, which faces its own water supply problems.
A range of quartzite mountains immediately south of the city should be able to absorb 35 million cubic metres of water, Christelis said, and the high-pressure pumping process is not that complex.
The bigggest problem is getting the government to appreciate the severity of the situation and find the estimated 575 million Nambian dollar ($73 million) cost of the project, he said.
"This is something that should have been completed several years back," Christelis said. "We can't wait until 2020 to do this."
A severe drought in 1996/97 brough the city close to exhausting its water -- an eventuality that would halt all new construction or business growth, dealing a hammer blow to the $12 billion, mining-dependent economy.
Already, the lack of water was preventing the opening of a copper mine near Windhoek, Christelis said.
"Not many people realise that in '96/97 there were only six weeks of water left," he said. ($1 = 7.922 Namibian dollars) (Reporting by Ed Cropley, editing by Ed Stoddard)