Reflections on dam safety

Everyone realises the importance of dam safety,’ says Alessandro Palmieri, senior dam specialist at the World Bank’s Washington, DC head office in the US. ‘But when you get down to the bottom line and have to make an economic analysis, it’s not so easy to convince a government – which has a host of other priorities – that dam safety must be a top concern for its country.’

Palmieri, however, believes more countries are now taking a pro-active approach to dam safety. ‘It is no longer just a matter of compliance,’ he says. ‘More and more dam safety projects are coming together with reservoir conservation projects and energy efficiency improvement schemes. If you blend dam safety with other quantifiable issues, such as sedimentation management, it makes a difference. And this is how our new generation of dam projects are shaping,’ he says, adding that Bank involvement with existing dams has increased substantially over the past seven years.

Hidden dangers

Before joining the World Bank, Palmieri spent 22 years working in the private sector as a consultant. He has been involved with many dam projects worldwide. ‘My conviction is that the mindset [with regards to the operation, maintenance and safety of dams] is changing,’ he says, reflecting on past experience.

In the late 1970s and early 1980s, data for a new dam would just be sent to the host country. The approach was ‘here is the design for a new dam, take it and implement it’. From a financial point of view, Palmieri says that this was good — there were no financial implications as no one was in the field. But governments from different countries soon saw that documentation on the design and maintenance of dams was gradually piling up in their offices. ‘I even saw an office in Africa where dam drawings were used under a table leg to steady the table,’ Palmieri adds. Changes have been taking place over the past ten years, however, and consultants are now visible in the field with their client.

From his own experience, does Palmieri believe that dam safety issues differ from developed and developing countries? ‘They do,’ he says, ‘but if you get down to the real essence of it, the answer is no. My own conviction from working in 32 countries worldwide is that the relationship between the likely failure of a dam is relative to its size.’

Surprisingly, Palmieri points to smaller dams. ‘These are the hidden dangers,’ he says. ‘I’m not saying don’t build small dams but the problem can be explained by the fact that large dams, due to their size, have more financial resources and more detailed design and construction.’

To illustrate his point, Palmieri takes the example of the recent Gujarat earthquake in India, which recorded 6.9-7.5 on the Richter scale on 26 January 2001. Following the quake, 21 dams totally collapsed. All of these structures, which fortunately had empty reservoirs at the time, were small dams built in the 1970s. Larger dams in the vicinity escaped major damage.

One of the largest dams that Palmieri has encountered recently is located at Lake Sarez in Tajikistan. Over 600m high, this natural dam was formed by a 2.2B m3 landslide following an earthquake in 1911. At 3020m asl, the river impounded and formed a 60km long lake containing 17B m3 of water – which is equivalent to half the size of Lake Geneva in Switzerland, and three times Lake Shaste in California. ‘This is an uninhabited area and it is a very beautiful, clear lake,’ Palmieri says. ‘However, there are a lot of people living downstream.’

Concerns over the safety of Lake Sarez are concentrated on potential seismic activity; particularly as the earthquake which struck Afghanistan in 1998 was only 120km away. If a strong earthquake occurs in the vicinity, a partially collapsed body of 1B m3 of earth and rock could fall into the lake, generating a wave that would overtop the natural dam. Such a flood of this scale has the potential to affect up to 5M people living along the Bartgang, Pyandhz and Amu Darya rivers in Tajikistan, Afghanistan, Uzbezistan and Turkmenistan. When Tajikistan was part of the former Soviet Union satellite surveys of the area were taken, but this information was just sent straight to Moscow. Consequently, people downstream have little information about potential safety problems. ‘They may be warned after a few hours,’ says Palmieri,’ but by then everything could be washed out.’

This was the cue for World Bank involvement, which is working with NGOs on the Lake Sarez Risk Mitigation Project (LSRMP). Tajikistan could not afford to undertake such a task by itself and so the US$4.3M project is being funded by the Swiss government, along with the Aga Khan Development Network, US Agency for International Development and the World Bank.

The project will focus on the most urgent measures to minimise the hazard. A monitoring system on the lake shores will be connected to an early warning system, while vulnerable communities are being taught emergency preparedness should an accident occur. Long term solutions are also being investigated.

aral sea basin

The opening up of the former Soviet Union has unveiled other potential dam safety problems. Concern has been raised over a stock of large dams sited within the catchments of the Syr Daria and Amu Daria rivers which drain into the Aral Sea – one of the most remote areas of the old USSR.

Dam safety experts became aware of problems when preparing for the Water and Environmental Management Project (WEMP) in 1997. Part of this scheme, which is being implemented by the International Fund to Save the Aral Sea to investigate overuse and degradation of the basin’s international waters, focuses on the management and operation of dams and reservoirs in the area. Safety concerns have been aroused as Soviet design philosophy does not recognise that designs and methods need to be continually reviewed and upgraded, particularly for earthquakes and flood management.

The break up of the country has also led to changes in dam operating conditions and the central control of dams and reservoirs is no longer practised, while expenditure on routine maintenance and replacement has been severely limited over the past 20 years. Many instruments are no longer working.

An inspection of ten dams concluded that, with the above in mind, the structures are potentially high hazard as they impound large storage volumes and are mainly located above densely populated areas.

The World Bank is one of many players working on the programme. As Palmieri explains, funding for the dam safety component of WEMP means that it will not be possible to ‘fix’ these large dams. Monitoring and early warning systems at ten dams will be upgraded on a pilot basis, while detailed designs for priority dam rehabilitation will be prepared. The main aim, however, is to promote awareness and a positive attitude towards dam safety in the region.

Until decision-makers hear about problems, and are made aware of safety concerns, Palmieri says it will be hard to get governments to allocate financial resources to remedy them. He believes decision-makers have the attitude that if you cannot be certain exactly when a dam will fall down, they may as well channel financial resources elsewhere. ‘But as we all know,’ Palmieri says, ‘dam safety does not work like that.’
Tables

the ten dams studied under WEMP...