Green scene

GLANCING around Stavanger as I made my way to the conference hall on the first morning of Hydropower ’05, it struck me that the most dominant sight on the horizon was the very thing I was there to discuss – water. With its many harbours and never-ending blue horizons, the beautiful Norwegian city was the perfect place to get into the right frame of mind for a three-day conference on hydro power.

Hydropower ’05 took place between 23 and 25 May 2005, under the slogan ‘the backbone of sustainable energy supply’. Sixty-two papers were presented with representation from more than 30 countries. The opening address was made by T. Widvey, Minister of Petroleum, who delivered statistics about hydroelectric power in Norway, including the fact that its average production capacity is 119TWh/yr, its installed capacity 27,300MW and that hydro is the country’s largest land-based industry. Dams in Norway are mainly used for hydroelectricity, and less so for irrigation or flood control, she told the audience.

Widvey then went on to say that 85% of Norwegian hydroelectric production is owned by the state or local companies. Since 1991, 2.3TWh/yr has been commissioned – 4227GWh/yr of which is small hydro. In her address, she pointed out that there are two major challenges that anyone involved in energy production has to face: the damage that is being done to the planet’s ozone and the fact that the world’s energy consumption is primarily based on non-renewable fossil fuels.

Cumulative impact assessment

An interesting paper was presented by J. P. Bramslev of Norplan AS, Norway, entitled ‘Modelling of the Mekong for Nam Theun 2 impact assessment’. The Nam Theun II hydro project will be the largest hydro power plant in Laos, with an installed capacity of 1000MW and active storage of 3530Mm³. Its planned site is upstream on the Nam Theun river – a tributary of the Mekong river. Nam Theun II will divert a large part of runoff into the neighbouring Xe Bang Fai basin to the south.

Bramslev began the presentation by showing some affecting pictures of flooded areas Nam Theun II is designed to aid. He then talked about the Cumulative Impact Assessment (CIA) that was carried out at the project site in 2004. CIAs are part of the Asian Development Bank (ADB) and the World Bank’s safeguard procedures for hydro projects; they are a supplement to the plant’s project-specific Environmental Impact Assessment (EIA). In this case, the hydrological and hydraulic impacts of Nam Theun II were analysed not just in the site’s surrounding area but also further down into the lower Mekong – a provision that previous EIAs had neglected, a fact which was considered a shortcoming of the earlier studies.

Water balancing modelling was carried out at the rivers which are subject to diversion – Nam Theun, Nam Hinboun and Xe Bang Fai – in addition to the Mekong upstream of Cambodia. Catchment runoffs, river discharges and reservoir water levels were part of the study, but hydraulic parameters like river water levels and velocities were not. The operational regime was based on the turbines operating at 16hr/day for six days a week, discharging an average of 330m³/sec. The average diversion corresponded to 280m³/sec, although Bramslev pointed out that at the end of the dry season it is likely that less water will be available in the reservoir.

The water balance simulation studied the monthly runoff series for the 50 year period 1950-2000, and concluded that the runoff in the Lower Mekong has gradually decreased during this time. With the Nam Theun II in place, the Mekong’s water level should be higher in the dry season and lower in the wet season, keeping a more pleasing balance.

An area that the 2004 CIA paid particular attention to was the Tonle Sap lake system in Cambodia, carrying out hydraulic modelling in this region. It was discovered that, with a 20-year perspective in mind, flood levels in Tonle Sap will be reduced by over 50cm, and the lake area will be reduced by 9% during flooding. The paper further revealed that there are plans for many more hydro power stations in Laos.

Climate change

Gavin Harrison of the University of Edinburgh, UK, presented his paper ‘Climate change in Scotland: impact on mini-hydro’. Harrison delivered an overview of the UK’s renewables obligation – 10% of energy from renewables by 2010 (18% in Scotland), which he described as a manageable target, and 20% by 2020 (40% in Scotland), which he described as ambitious but obtainable.

In his paper, Harrison says that with these targets it seems that the UK government is showing a renewed interest in mini hydro. Unfortunately, climate change is a factor that can hinder the efficiency of such schemes. He points out that climate change is more of a risk for smaller plants; since run-of-river mini hydro power schemes have little or no storage they are especially vulnerable from the variations in river flow that climate changes can bring. So chiefly of concern for the paper was how to adapt mini hydro to survive climate change.

Harrison details the case study of Ormiston mill, a run-of-river plant on Teviot river in the Scottish Borders, where climate impact was assessed at the site. The plant has the potential to produce 240MW from its 2m head, with output predicted as 1200MWh/yr.

The paper states that climate sensitivity can be measured with a sensitivity analysis, where precipitation and temperature levels are altered across a range of changes and the outcomes for river flows, production and financial performance are analysed. It is widely accepted that global temperatures are set to rise – Harrison gave a figure of 5.8°C by the end of the century, and predicted that by 2080 the area of Scotland studied could experience a rise of 2.5 to 3°C over the 1961-1990 mean. Furthermore, precipitation is set to increase by approximately 20%, according to studies. Obviously, higher temperatures tend to lower river flows, and increased precipitation raises mean river flows. This change in flow is inevitably going to affect production.

There are ways to adapt to climate change, and in large hydro power plants there are a number of options. Suggestions include storing more water in the reservoir (usually facilitating the need to raise the dam’s height), raising the head, using more efficient turbines and lowering intakes to increase active storage.

However, while these ideas can be applied in large hydro plants, there are problems for low head, run-of-river schemes:

• The aforementioned lack of storage.

• The low head limits the possibility of using alternative turbine types.

• Future efficiency gains on crossflow turbines may be difficult.

• Increasing the weir height to raise the head would be costly and potentially environmentally unacceptable.

Harrison concludes in his paper that the studies, which also included projections from climate model scenarios, show the conundrum as rather complex, without an obvious solution. More research will need to be conducted into this issue if the problem is going to be resolved.

Challenges in nepal

The country of Nepal was well represented at Hydropower ’05, with several Nepalese delegates and speakers contributing to the conference. One paper that I found interesting was ‘Environmental and socio-economic challenges for sustainable hydropower development in Nepal – experiences from capacity building and migration measures’. The authors are Rita Dhungel, a Social and Cultural Anthropologist of Tribhuvan University, and Reidar Hindrum, an Advisor from the Directorate for Nature Management (DN), Norway.

The paper talked about Nepal’s hydro power potential. The country’s watersheds, also known as ‘water towers’, are the most prosperous resource for development in Nepal, aside from tourism. The Ganges river receives approximately 45% of its flow from Nepal’s 6000 rivers and rivulets, and the total developed, planned and viable hydro power capacity of the country is roughly 36-44TW. Yet despite this, only 1.6% has been developed – making up less than 1% of the total energy consumption.

In 2002, the Nepalese and Norwegian governments, through the DN and the Ministry of Population and Environment (MOPE), began an EIA of hydro projects in Nepal. It was acknowledged that as well as realising the great potential for energy in this abundance of water, there were other issues to deal with. One of the prominent concerns of the EIA was the environmental and socio-economic impacts that hydroelectric power projects can have.

Dhungel talked through the major challenges for sustainable hydro power development in Nepal. There were several, including physical and biological environmental issues. The physical environmental issues are not elaborated on much in the paper (although the special challenges caused by Nepal’s soil erosion and depositing are mentioned), but the biological issues are granted more in depth discussion. The typical environmental impact is that the river is dammed and redirected, affecting the local ecosystem. The biodiversity in Nepal is very high, including as many as 182 species of fish – so the country has a vulnerable system that can be easily disrupted.

The main biological challenges are:

• Protection of fish populations, including their migration pathways.

Dhungel commented that it is obvious that monitoring and mitigation provisions for these challenges need to be made, and more specifically there is a great need for Nepal to construct more fish ladders to help mitigate migration damages to fish populations.

Hindrum finished the session with the declaration that whilst it is obvious that Nepal should extend its hydro power operations, it was important that the country pay attention to the biological, environmental and socio-economical impacts of potential projects, and maintain a balance between the three.

The above examples are just some of the many papers about environmental issues presented at Hydropower ’05, and the amount of interest this subject received from delegates makes it clear that the environment is as important to the hydroelectric industry as ever. The amount of time and resources that are spent on monitoring the environmental aspects of building and operating a hydro power plant is encouraging, and demonstrates that the impact on the environment is as much of a concern as the profit margin.

Author Info:

For more information about the Hydropower 05 conference, please visit www.hydropower05.org

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