Did you know dams can induce earthquakes?

By Oweyegha-Afunaduula

Earthquakes can be induced by dams. Globally, there are over 100 identified cases of earthquakes that scientists believe were triggered by reservoirs. The most serious case may be the 7.9-magnitude Sichuan earthquake in May 2008, which killed an estimated 80,000 people and has been linked to the construction of the Zipingpu Dam in China.

The most widely accepted explanation of how dams cause earthquakes is related to the extra water pressure created in the micro-cracks and fissures in the ground under and near a reservoir. When the pressure of the water in the rocks increases, it acts to lubricate faults which are already under tectonic strain, but are prevented from slipping by the friction of the rock surfaces."  Many dams are being built in seismically active regions, including the Himalayas, Southwest China, Iran, Turkey, and Chile.

In the past, people never thought that human activity, especially through damming, could have such a big impact on societies and land but it can. It can even wash out any development that may have been achieved over a period of time.

China has got a lion’s share of dam related, earthquake-based disasters. It is estimated that 25% of Britain’s recorded seismic events were caused by human activities. However, most of these human-caused quakes are tiny, registering less than four on geologist’s seismic scales.

Reservoir –induced seismology has been recorded in Zambia, China and Brazil. In 2002, Gupta H.K. gave a review of recent studies of dam-triggered earthquakes.  Experts expect more deadly earthquakes in the over-dammed south of China.
In Zambia, there were a few minor earthquakes prior to construction of the 128 meter Kariba dam. Kariba Lake began filling in 1958 and was filled completely by 1963. Almost immediately there were 2000 local shocks during filling.

Jesus predicted there would be more and more earthquakes and other otherwise natural phenomena. But he did not add that the majority of them would be man-made.

Apparently, China is building most of the 53 big dams of Africa the rulers have planned to build since 2008. Recently China got the contract to build Karuma dam in Uganda. China is also building the gigantic Ethiopian dam on the Blue Nile currently. These damming activities and others to follow will make the Nile Basin, which is a landmine of poverty, also a landmine for earthquakes.

Uganda lies in the pathway of earthquakes. With increasing damming of the Nile basin in general and Uganda in particular we should expect dam induced disasters to be on the rise. In the late 1960s, an earthquake in Toro, in Uganda, killed 100 people and displace thousands. Just before the construction of Bujagali dam there were many earth tremors in 2007.

Bujagali dam was completed recently and has been filling with water. It is possible that the extra weight of water on the rocks below is responsible for the recent tremors in Uganda. On Tuesday July 2, there was a mild tremor. And on the night of July 3, there was a stronger one around 10.00 pm. Then there was one a mild one in the early morning of July 4. Might it be that the tremor marked the complete filling of Bujagali dam? If Kariba dam recorded 2,000 tremors, how many should we expect in the aftermath of Bujagali dam filling with water? What should we expect when the Chinese complete the construction of Karuma dam? If all this is a possibility is it not timely for Uganda decision-makers to rethink the damming ideology?

The writer is an environmental conservationist

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4th July 2013