Windhoek — The Chief Executive Officer (CEO) of Namwater Dr Vaino Shivute maintains that there was nothing the water utility could have done to prevent the floods that devastated the southern town of Mariental.
With more pressure mounting on Namwater as accusing fingers point in its direction, Shivute claims that the company did everything in its power and acted in a most professional and proactive manner to try and prevent the disaster.
However, it emerged after a Namwater press conference yesterday that the company took a higher risk this year when it increased the operating dam levels to around 80 percent of its full capacity.
The company was very much aware that the town of Mariental was flooded in the year 2000 despite the dam being only at 60 percent of its full capacity. The decision to operate the dam at as high as 80 percent was taken in consultation with the Mariental Town Council at the beginning of the current rainy season.
Shivute said this was done with the aim to "create more space for accommodation of floods within the dam basin without necessarily increasing or accelerating possible future water shortages to the farming and town community".
Shivute also noted that his company could not take the risk of decreasing the water in the dam because "rain conditions in Namibia are unpredictable".
Shivute was pressed to provide reasons why his company did not react to earlier weather reports that the southern part of Namibia would receive more rainfall during the month of February 2006, and that Namibia would generally receive more heavy downpours in the second half of the month.
Statistics availed yesterday also indicate that the water level in the dam already reached the set risk of about 80 percent several days before Friday, February 24, when Namwater decided to open the sluices at 10h00.
Relevant stakeholders had only two hours to inform the public as they were notified at 08h00 that morning.
However, Namwater's hydrologist Andre Mostert stated that even though the public was notified within two hours of the pending disaster, this did not mean that the flooding was going to occur right away.
"There is a saying that if something goes wrong, everything goes wrong. What went wrong this time, nothing," he maintained.
Hardap Dam was constructed in 1962 and has a total capacity of approximately 300 million cubic metres of water. This translates to 300 billion litres of water.
The purpose of the dam is to supply irrigation water to the Hardap Scheme, as well as purified water to Mariental town.
Prior to the construction of the dam, flooding is reported to have occurred during flood events in 1923 and 1934, but since the construction of the dam, major flood events were experienced in 1972, 1989 and 2000.
The flood peak experienced in 1972 was highest instantaneous flow, whereas the present flood had the second highest peak inflow in history.
From statistics, it appears that this year, Namwater released water almost the same as in 1972, despite the huge difference of inflows recorded in both instances.
In 1972, the inflow was 6 300 cubic metres per second compared to only 4 000 cubic metres this year.
Shivute noted that the release of water from the dam in 1972 was done over two days, while this year it was over three.
"What is significant however is that the present flood had a much longer duration than any of those experienced in the past and that the total volume of the flood was greater than anything previously experienced," he stated.
He said during the night of February 24, heavy rainfall of 130 mm was experienced in the region, which increased the inflow into the dam.
That night, the inflow peaked at 3 000 cubic metres per second and maintained levels of 2 500 cubic metres per second for a period of 14 hours.
"This resulted in Namwa-ter having to increase the discharge rate at regular intervals throughout the night from 24h00 to a level of 3 000 cubic metres per second in the morning of 25 February.
"At this stage, the dam level had risen to 110 percent of its full supply capacity and the discharge rate had to be increased to match inflow to stabilise dam stress, to protect the structural integrity of the dam and to minimise risks of dam failure," he stressed.
The discharge rate was maintained at 3 000 cubic metres per second throughout Sunday, February 26 and closing of the gates finally on Monday, February 27.