The Future of Hydropower
According to European Renewable Energy Council, the main benefits and relevance of hydropower for both the renewable energy and the energy sector are obvious. In particular, hydropower will play a key role in 2030 and 2050 by:
• Developing hybrid systems in which several technologies are combined in order to guarantee the maximum energy production in the most efficient way. Since hydropower plants do not require any fossil-based primary energy, hydropower provides relief for the energy bill of every country and increases the security of the energy supply. Having hydropower plants in the home market reduces the problem of potential supply disruptions, as has often been the case of late with natural gas or administered prices. These are all important arguments for finan- cially strapped countries in particular, as are often still to be found in the region of Southeastern Europe;
• Developing multi-purpose hydropower plants with the applications in the fields of drinking water supply systems, irrigation channels, flood control and protec- tion, the creation of adjoining environmental areas, wastewater treatment plants, and recreational purposes;
• Adding security and stability to the European grid thanks to the pump storage;
• Mitigating Climate Change. Emissions are basically only an issue in the con- struction phase of the hydropower plant. The extremely long phase of plant operation, by contrast, is largely emission free. In addition, plant operation requires virtually no materials and supplies, produces at smaller amounts of solid waste and generates practically no waste heat. Thanks to negligible CO2 emissions over the full life cycle of hydropower plants of up to 100 years and the still far from exhausted the scope for economic exploitation in many coun- tries, the development and upgrading of hydropower is an important instrument in the process of reducing global CO2;
• Supporting the development of rural areas by the installation on economically advantageous conditions of off-grid units.
According to the Situation Report on Hydropower Generation in the Alpine Region Focusing on Small Hydropower (2011), other benefits of hydropower gen- eration are self-evident since the consumption of electricity in one form or another is central to our daily life. Since hydropower has the benefit to be an almost emis- sion free form of electricity generation, the requirement to reduce greenhouse gas emissions acts as an additional driver for its further development. Below are included other benefits for both, small and large hydropower generation, grouped according to three categories, economic, social and environmental benefits:
• Economic benefits: An assured supply of energy is a key prerequisite for a modern economy and civilization. However, considerable shares of energy demand are at present met by imports of oil, natural gas, coal, or uranium from regions of the world with sometimes rather fragile political stability. Hydropower—being a domestic and renewable source of energy—can con- tribute to reduce energy dependency from external sources. Furthermore, investments in this sector are characterized by a long life span, relatively low operational and maintenance costs, attractive long-term payback ratios, and a low need for support schemes (compared with other renewable energy sources), thus contributing further to the security of energy supply. Hydropower plants can cover parts of the base load, but more particularly can contribute to cov- ering the peaks of demand, thus contributing strongly to guarantee stability of the transmission grid and to the stability of supply. This contribution becomes all the more important as an increasing share of supply comes from other, less reliable renewables such as wind or solar power with their high variability, which has to be compensated in order to avoid “black outs.” Hydropower has a crucial role here, as variations in demand can be compensated at very short notice, much faster than thermal power plants may be able to do. Last, but not least, hydropower plants and in particular small hydropower plants are highly decentralized and close to the consumer, thus contributing further to security of supply; furthermore, losses due to the transmission grid are low due to the short distances involved. These local benefits stand in contrast to, for example, nuclear power plants. Development and manufacturing of hydropower components, planning, construction, and operation of hydropower facilities and the transmission grids require considerable technological knowledge and research. This contributes to the creation of new and safe (green) jobs and to the growth of domestic economies as well as bringing a positive net fiscal contribution to national budgets. The EU (mostly in Alpine countries) and Switzerland are world leaders in the hydro industry. The export of technology and knowledge creates additional income for the national economies of this particular group of states.
• Social benefits: Hydropower plays a major role at the local and regional level because of its importance for the socioeconomic development. Whenever hydro- power facilities are built, this is done in combination with new infrastructure. If charges are levied for the use of water by regional administrations, considerable contributions to local or regional budgets may result. Further benefits may come from the multi-functionality of the reservoirs used for hydropower generation. For example, in periods of low flows (or drought), water stored in reservoirs can contribute to enhance flows for downstream regions, in periods of flood reser- voirs may contribute to water retention and mitigation of floods. Reservoirs may be further used for tourism and recreational purposes, as well as for drinking water, irrigation, or other needs. Hydropower plants also become part of the his- torical, cultural landscape (such as old mills or historical monuments of industry) and, therefore, a specific feature for the community.
• Environmental benefits: The key environmental benefit of hydropower generation is the positive contribution to climate change mitigation through the avoidance of burning fossil fuels. Hydropower allows the generation of elec- tricity from a renewable source virtually without emitting carbon dioxide. This acts as a driver for further exploitation of the remaining limited potential of hydropower, in particular as so far this seems to be the least expensive form of renewable energy. Hydropower plants can also lead to positive affects in river restoration, for example, by raising the riverbed and the associated groundwater level.
A further benefit of hydropower as a form of energy generation is that there are hardly any emissions of pollutants, neither to the atmosphere nor to the water bod- ies. However, despite the fact that hydropower can be considered a clean form of energy generation with regard to emissions of pollutants, it is also clear that there exist negative impacts on the aquatic ecology, natural scenery, and ecosystems, which are not always perceived by the wider public. This is not only the case for large dams, reservoirs, and related hydropower facilities, but also for small and very small hydropower plants.
The main environmental concerns in connection with hydropower generation include the following:
• Interruption of river continuity: Dams and weirs used for hydropower gen- eration cause an interruption of the longitudinal river continuity, which can have significant adverse effects on the river’s biocenosis. Migrating species such as fish are heavily affected by the fragmentation of their habitat. An effective way to reduce these negative effects of hydropower plants is the installation of fish migration aids;
• Changes in river morphology and loss of habitats: Hydropower plants can
cause changes to a river morphology. The morphological degradation affects not only the composition of natural structural elements and the loss of dynamic pro- cesses in the riverbed, but can also cause fundamental changes to the river type;
• No residual water or lack of sufficient residual water: A high number of
hydropower plants, particularly in the Alpine region, are diversion plants. Therefore, the problem of no or non-sufficient residual water in the affected reaches of Alpine rivers is an important issue causing a number of negative effects on the river ecology notably: homogenization of the flow character and degradation of habitat, continuity disruptions for migrating fish and, changes of the natural temperature conditions. To mitigate such negative impacts, it is nec- essary to ensure sufficient residual water in the downstream stretches of diver- sion plants;
• Hydro-peaking: Mainly caused by large hydropower plants in combination
with reservoirs. The demand for electricity varies strongly during the day as well as over the year. Reservoirs with their huge storage volume and their high head provide the perfect means to adjust production to variations in demand. Hydro-peaking can have severe ecological effects on a river. Depending on the rate of discharge acceleration, benthic invertebrates and also juvenile and small fish can get washed away with the flush, which results in the decimation of soil fauna, reduction of fish biomass, and also changes to the structure of fish popu- lations. During the down-surge, benthic invertebrates and fish can get trapped in pools that might dry out later on, so the animals either die or become easy prey for predators;
• Impoundment: Impounded river stretches, which can occur over a longer dis-
tance, especially at large hydropower plants, show a significant reduction of flow velocity, which can cause an increase of water temperature and decrease of oxygen content, increased deposition of fine sediment in the impoundment as well as disturbed bed load discharges and sediment transport, leading to erosion and deepening processes underneath the impounded section;
• Flushing of reservoirs and impounded river stretches: In reservoirs and
impounded river stretches, the reduced flow velocity leads to an increased deposition of fine sediment that makes periodical flushing of the reservoirs necessary. Both can cause a number of negative effects on freshwater ecology.
To sum up, the generation of electricity by hydropower can have severe impacts on the aquatic ecology and the natural landscape. Innovative technologies, improved methods of operation and the willingness of all actors to integrate environmental concerns in the planning process, and also by the adaptation of already existing hydropower plants, can mitigate negative effects and make hydropower a more sustainable way for generating electricity. This has to be assured through a legislative framework that has regard to these environmental concerns and is backed up by integrated planning processes.
Hydropower has, at the same time, further advantages over many of the other renewable energy sources: One example is efficiency levels of up to 97 %. This makes hydropower a more efficient type of electricity generation than solar cells or wind farms, which achieve efficiency levels of around 20 and 40 %, respectively, in practice. In addition, hydropower is in most cases independent of the time of day, i.e., it is not governed by the amount of sunshine or wind speed. This enables sustainable, uninterrupted power generation. Besides, individual types of hydropower generation, such as storage power plants, are well suited for flexibly bridging temporary demand peaks.
There should be no doubt that hydropower advantages over fossil-fuel-based electricity are many, and particularly it does not cause any climate-damaging emissions, and that no fuel purchase costs are incurred. Furthermore, small-scale power plants are widely accepted by the public of almost all EU member states. In addition, hydropower outscores the new renewables by offering high levels of efficiency and greater flexibility and it is a multiple-use resource.
In the coming paragraphs, a brief description of the use of hydropower for the generation of electricity in a select group of European countries is included