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Newsletter Issue 6 No 2

Hydro Dams – Outdated Technology?

By Graeme Collins

   
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In terms of population, no other country in the world relies more on hydro-generated electricity than New Zealand.

This is partly because we have decided to be ‘nuclear-free’; although the planning and building of our dams has a much more complex background.

Our hydro era probably reached its zenith with the opening of the Clyde Dam by the Prime Minister in April 1994. The project was long and costly, and divided the country. Much more than that, it directly affected the direction of our democratic process. In 1982, in an incredible 24 hours in Parliament, the then Prime Minister, Mr Muldoon, and his Cabinet overthrew the high Court of New Zealand with the Clyde Dam Empowering Act, thus departing from the Westminster System.

The political and social ramifications of this and other ‘Think Big’ projects have been written about extensively elsewhere, and have continued to occupy an important place in New Zealand politics and media etc. Suffice it to say the fight-back by the legal fraternity and free-thinkers culminated in the Resource Management Act, 1991.

While the rest of the developed world started waking up to the inherent problems with dams, i.e. loss of free-flowing rivers, fisheries, farmland etc., New Zealand kept planning more dams, even after the World Bank had ceased to fund such projects. Dam reservoirs can also affect weather and seismic activity.

‘Friends of Beaumont’ was formed to oppose the next dam after Clyde on the Clutha River, at Tuapeka. Because of Clyde, with its historical and legal implications, we attracted extensive legal and public support, and in 1996 the Tuapeka Project was deferred indefinitely, effectively bringing to an end our hydro era.

These days we’re building wind-farms, or using natural gas.

It has been a great privilege for me to have been founder and Chairperson of Friends of Beaumont, and to have been a part of this history-making process. Through the course of it all, I have taken the time to learn everything I can about electricity, and the different ways it can be generated. FOB has an Internet website, which has attracted a great deal of international attention.

Dams, at least on the large scale, are almost solely being built in third world dictatorships these days. The United States has 35,000 dams, behind which lie 600,000 miles of stagnating water that was once free-flowing river. When the Florida Everglades began to dry up and threaten rare species there, the US Government began to decommission dams by the hundred. In Tasmania the dam that divided the Australian nation at Lake Pedder was decommissioned last year. Here in NZ we have belatedly woken up to the fact that dams collect silt behind them, with devastating floods in Canterbury and at Alexandra.

In the third world the situation is radically different. China is building the world’s largest dam at the Three Gorges; a project which displaces hundreds of towns and millions of people, and in the process destroys some of China’s best scenery. At Bakun, in Sarawak, Malaysia, a huge dam threatens 70,000 hectares of prime rainforest, and is hugely controversial. The cost is $8.5 billion. In Laos, in Lesotho, in Argentina, in Chile huge dams are built with the aid of the military to suppress opposition.

The country worst affected is Brazil, where huge dam projects have equally huge opposition groups. In March this year, the first international convention on dam-affected people was held in Curitiba, Brazil, resulting in the Curitiba Declaration – a call for a total moratorium on large dam-building worldwide, signed by representatives from 20 countries. New Zealand was not represented. An annual convention on 14th March each year (actually 11th - 14th) is planned, and an International Day of Action.

As we approach the millennium, the availability of fresh water in the world looms as one of the most important issues of all. Some have predicted it will replace oil as an international flashpoint. Already armed insurrection by dam-affected people in third world countries is a real problem.

I believe it is important that someone represent New Zealand at the next Curitiba Convention in March 1998. As a country where rainfall is abundant, and our reliance on hydro-generated electricity is considerable, we have something to share. More importantly, it is through such contact we can learn essential lessons about energy generation that will help all of us survive in the future.

     
  The World Bank’s view  
  The World Bank, which finances many of the world’s large dams, has this to say about hydro dams. I quote the World Bank E.A. Sourcebook:

"Large dam projects cause irreversible environmental changes over a wide geographic area and thus have the potential for significant impacts. Criticism of such projects has grown in the last decade. Severe critics claim that because benefits from dams are outweighed by their social, environmental and economic costs, the construction of large dams is unjustifiable. The area of influence of a dam project extends from the upper limits of the catchment of the reservoir to as far downstream as the estuary, coast and off-shore zone. It includes the watershed and river valley below the dam. While there are direct environmental impacts associated with the construction of the dam (eg. dust, erosion, borrow and disposal problems), the greatest impacts are from the impoundment of water, flooding of land to form the reservoir and alteration of water flow downstream. These effects have direct impacts on soils, vegetation, wildlife and wildlands, fisheries and especially the human population in the area. The dam’s indirect effects, which on occasion may be worse than the direct effects, include those associated with the building, maintenance and functioning of the dam (eg. access roads, construction camps, power transmission lines) and the development of agriculture, industrial or municipal activities made possible by the dam.

The major environmental factors affecting the functioning and lifespan of the dam are those caused by land, water and other resource use in the catchment above the reservoir (eg., agriculture, settlement, forest clearing) which may result in increased situation and changes in water quality in the reservoir and river downstream. Damming the river and creating a lake-like environment profoundly changes the hydrology and limnology of the river system. Dramatic changes occur in the timing of flow, quality, quantity and use of water, aquatic biota and sedimentation in the river basin.

The decomposition or organic matter (eg. trees) on the flooded lands enriches the nutrients accumulating and recycling in the reservoir. This not only supports reservoir fisheries, it also stimulates the growth of aquatic weeds such as water lettuce and water hyacinth. Weeds and algal mats can be expensive nuisances when they clog dam outflows and irrigation canals, damage fisheries, curtail recreation, increase water treatment costs, impair navigation and substantially increase water loss through transpiration. If the inundated land is heavily wooded and not sufficiently cleared prior to flooding, decomposition will deplete oxygen levels in the water. This affects aquatic life, and may result in large fish kills. Products of anaerobic decomposition include hydrogen sulfide, which corrodes the dam turbines and is noxious to aquatic organisms, and methane, which is a greenhouse gas. The main gas produced, carbon dioxide, also exacerbates greenhouse risks.

Additional effects of changes in the hydrology of the river basin include altered levels of the water table, both above and below the reservoir and salinization problems which have direct ecological impacts and affect downstream water users."

"The greatest impact in wildlife will come from loss of habitat resulting from reservoir filling and land use changes in the watershed. Migratory patterns of wildlife may be disrupted by the reservoir and associated developments, Large reservoirs may alter tectonic activity. Though the probability that they may induce seismicity is difficult to predict, the full destructive potential of earthquakes, resulting in landslides, damage to dam infrastructure, and possible dam failure must be considered. Finally, a variety of alternatives, such as the following, exist for the design and management of dam projects.

1. Avoid or postpone the need for dam construction altogether by reducing demand for water or energy by conservation measures, efficiency improvements, fuel substitution, or restrictions on regional growth."