WATER-SOUTH AFRICA: Managing Flooding on the Orange River

By Zukiswa Zimela Reprint | | Print |

Zukiswa Zimela interviews PETER PYKE, South African Department of Water Affairs

JOHANNESBURG, Apr 13 2011 (IPS) - Many farms and crops were devastated when the January floods hit South Africa at the start of this year. Farmer organisation Agri South Africa (AgriSa) estimated damages as high as 270 million dollars.

Some critics say that as managers of the country’s water resources, the Department of Water Affairs should have done more to prevent the devastation.

IPS Africa spoke to the department’s Peter Pyke about the importance of flood mitigation strategies.

Q: Did flood mitigation measures put in place by the Department of Water Affairs fail this year? A: For a long time now, the system has been to try and manipulate the floods so that the peaks in the Vaal River and the Orange River do not happen at the same time when they meet at the confluence. The strategy was to let the water in the one river go and to hold on to the water in the other. This is to lessen the impact on the downstream users.

In the case of the very recent floods, somebody had been making estimates of the water flows and according to our estimates round about the tenth of April we would have had the equivalent of seven times the capacity of the Vaal Dam passing Upington.

Q: When too much water is held back in the dams, does this not cause the river banks to break and flood the areas around them? A: if you look at the river morphology you will find that very small floods are caused by the overflow of river banks, and that is probably a flow of about one in two years return period anything above that goes above and to the flood plains.

The problem is that we have had a lot of development on flood plains. These are areas that are naturally prone to flooding and have always been flooded periodically in the historic past and they will be flooded in the future because it is not possible to completely eradicate floods.

Q: Why are people moving onto the floodplains? A: Well the first thing is that it is a flat area and this is the area closest to the water. It is obviously fertile ground, and so people go there for agriculture.

We have legal requirements that every developer has to show the flood lines on any proposed development. We can’t prevent them from building on the flood plain, but we can at least make certain that they are aware of the fact that they are in a flood plain.

Q: Is there an early warning system to warn the people who are in flood-prone areas about releases that are scheduled to take place? A: Yes. You will find that in the case of the Orange, the people in the Lower Orange River had more than a week’s notice before the water reached them. Obviously people closer to the dams had less time.

But we have real time information on the internet, available on the departmental website. During flood times there are predictions on how much water will be where and what will flow into the river.

Q: What about those without internet access: how do they get the information? A: The information is made available to disaster management of each municipality, local authorities over the radio and on the television so the information is broadcast all over. Remember It is possible to prevent the smaller floods but when the huge rains come the dams become full and the water flows out of them as if the dams weren’t there.