Environmental impact of hydropower

Many hydropower plants and other dams were built so long ago that they have never been reviewed for environmental impact or existing permits are very old. Most Swedish hydropower plants, just over 2,000, do not have modern permits according to the Environmental Code. SwAM has in collaboration with the Swedish Energy Agency and the agency with responsibility for the electricity system (Svenska Kraftnät) developed the National Plan for Modern Environmental Conditions for Hydropower (NAP), decided by the government in June 2020. The purpose is to review hydropower's environmental conditions and decide on measures to get both the greatest possible benefit for the aquatic environment and a national efficient access to hydropower. NAP has a national holistic view and describes, among other things, which water systems should be reviewed at the same time (review groups) and when applications within a review group must be submitted to the Land and Environment Court.

Work on permit reviews of hydropower plants will begin in 2022 and is expected to last for 20 years. In general, no environmental impact statement is required in accordance with Chapter 6 of the Environmental Code in connection with a review. For a better dialogue and to make it easier for hydropower owners to prepare applications and facilitate trials in the courts, a new provision has been introduced in the Environmental Code, which means that the County Administrative Boards must carry out cooperation processes within each review group (Figure 1). These are at once simple and complex processes because they are based on dialogue and weigh values against each other. Cooperation means an opportunity to discuss current natural values, how these could be developed with different measures, and how measures impact on different interests. It is also valuable that this discussion addresses a wider area than a single hydropower plant.

Hydropower and other dams affect hydromorphology and change the conditions in and around watercourses and lakes. This is one reason why biodiversity is threatened in many running waters. The facilities change the flows in the systems, which affects species, ecosystems, water chemistry and hydromorphology, as well as activities such as fishing and outdoor life. To sustainably use natural resources, biodiversity and ecosystem services, human activities need to be planned and implemented from a holistic perspective that takes into account the needs of species and ecosystems, ecological connections, effects of human use, and a changing climate, in other words: an ecosystem-based management.

Green infrastructure means ecologically functional networks of habitats and structures, natural areas, semi-natural areas and landscaped elements that are designed, used and managed in such a way that biodiversity and socially important ecosystem services are preserved throughout the landscape. The term green infrastructure was coined in the United States and later defined in the Convention on Biological Diversity (CBD). The ecosystem approach is a working method originating in the CBD for the conservation and sustainable use of natural resources by balancing the ecosystem's function. The approach means that documentation to support decisions is produced during an exchange of knowledge where all relevant stakeholders and actors are involved in structured consultation. The strategy provides good conditions for appropriate measures, as the transparent working method enables conflicts to be handled quickly and reduce hierarchical levels.

The catchment areas of water systems are suitable objects for developing management according to the ecosystem approach with a focus on green infrastructure. According to the EU Water Framework Directive, all water bodies must have at least good ecological status (or potential) and anthropogenic impact from point sources and diffuse sources must be assessed in order for suitable measures to be implemented where necessary to reach good water status. The natural processes in running water often extend the impact to areas downstream and upstream of the source. The cumulative effects of several types of impact can also be evident in aquatic systems and these processes lead to many challenges for measure planning and fisheries management (in Swedish: fiskevård) at a water system level. Environmental data from both research and several decades of monitoring has provided knowledge about certain types of impact on life in the water and shows that ecosystems in running water are among the most endangered in Swedish nature. Changes in the hydrological and geomorphological processes and their effects on the biological systems are forms of impact where a continued need for research has been identified on individual species, ecosystems, and landscapes.

The European Commission is in the final process of developing a new biodiversity strategy. A proposal for legally binding nature restoration targets is expected to come summer 2022 and all member states are urged to implement the strategy in their respective administrations. This strategy contains clear requirements for the restoration of natural environments, including the re-creation of 25,000 km of free-flowing water. Here, Sweden's handling of reviewing hydropower permits, and supplementary restoration initiatives planned on the basis of an ecosystem initiative will be crucial for the implementation of our part of the strategy.

In a synthesis, existing research results and practical experiences within a specific topic are compiled. In addition to peer reviewed articles, the compilation should include government reports and other ”gray” literature. The method used for the literature search must be specified as well as the criteria applied for the selection of the literature included.

The synthesis is a holistic evaluation of the available knowledge where the validity and reliability of the findings are analysed. Both national and international perspectives must be considered. Findings may need to be transferred to, and aligned with, Swedish conditions to be applicable. The syntheses should provide recommendations for how the findings can be used in the context of the Swedish national hydropower environmental permit review and planning processes. Knowledge gaps must be identified.

We encourage syntheses that include active collaboration with target groups and the surrounding society. It is important that the synthesis work is well grounded among researchers and recognised expertise. An executive research group consisting of relevant competencies is thus necessary.

Cooperation (in Swedish; samverkan) is a mandatory first step in the environmental permit review process according to the national plan, see Figure 1 and SwAM’s guidelines (in Swedish on SwAMs website; Vägledning om samverkan inför prövning enligt nationella planen). New regulations have been developed specifically for this purpose, which provides new and specific conditions for how to implement the collaboration process. In support of the forthcoming environmental permit review processes, which will last for many years to come, increased understanding is needed of how these mandatory collaboration processes can be organised and implemented in order to achieve their purpose. Experiences from ongoing and already completed collaborations in hydropower review processes can be analysed and put to use to increase our understanding about obstacles and success factors.

The permit review process and the decisions that are finally made in court affect the operation of the hydropower plant. Conflicts between different interests can arise when there are diverging views on facts, different framing of problems and different takes on need for action. Experience and ”best practice” from other management areas, for example wildlife management or fisheries where strong and diverging stakeholder interests can create conflicts, may be useful. At the same time, the legal framework for the current permit review processes according to NAP is new and unique, and more knowledge is needed about how the current regulations and directives affect the conditions for collaboration.

Hydropower is necessary for Swedish society, but measures are required to adapt most hydropower plants to the environment. It is important to assess the measure's impact on electricity production and regulatory power, and in order to estimate the full benefit of the measure, models are also needed to estimate the costs of not making the measure: the cost in money, for the ecosystem and for society. Cost-effectiveness of various measures is also important to take into account when the best solution is to be developed for each individual hydropower plant or dam plant when ecology is weighed against economics, for example through Chapter 11, Section 28 of the Environmental Code's requirements for consideration of aquatic environment benefits. For the environmental assessment of the small and medium-sized hydropower plants, it is especially important to understand the different values and benefits that can be in dispute in a collaborative situation.

There are different perspectives on the benefits of hydropower plants, dams and measures. The perceived benefit can be direct economic benefit from electricity production or a cultural ecosystem service as a beauty value or opportunity for outdoor life. The ecological benefit can sometimes be valued in money if it is possible to calculate the value of increased fishing, but can also be a ”soft” ecosystem service that increases commitment and knowledge of individual species and the biological diversity in and around the water after a measure has been taken. The benefit can also be evaluated in the form of increased knowledge about certain species and their status in a specific watercourse or improve the statistics that form the basis for stock calculations and status assessments. The different interests around facilities make it difficult to evaluate the effects of measures or to maintain the status quo. When essential goals, benefits and risks are to be weighed against each other, facts are needed. However, facts can be valued in different ways and a strategy for communication between authorities, landowners and other stakeholders is also required.

New knowledge is needed about how costs and benefits can be valued for society, the individual and for ecosystems in the context of review of hydropower and other dam facilities and as a basis for other decision-making processes in society. We invite applications for research projects that include studying values and other processes in environmental review of hydropower, and that develop methods for interpreting and compiling value studies for decision-makers so that it is easier for them to make well-informed decisions.

There is a need for a compilation of knowledge about the facilities' impact in the entire water systems, both upstream and downstream of the power plants and dams. An analysis of impacts can be divided into two subject areas: impacts on the landscape through flows of water or sediment and impacts on ecosystems and species. These areas are tightly integrated, but it is sometimes necessary to clarify whether one is talking about one or the other. The reviews within NAP will be done over river system catchment areas and cumulative effects of both dams and measures will therefore be important to understand.

Landscape impact arises when water level and flow dynamics affect and reshape beaches and riverbeds. The flow regulation of hydropower plants causes wear and flushing of material from the littoral zone and also changes the natural disturbance in the form of habit or water level variations in the transition zone between land and water. Downstream large power plants there is also a dry furrow. Landscape impact includes transport and deposition of sediment. One effect of dams is that sediments and particulate matter are deposited there instead of in calm river stretches and the river delta. Indirect effects, such as changes in water chemistry or the impact of suspended mineral matter on organisms, are also transported by, for example, hydromorphological changes in the watercourse. The flow or amount of water required to build and maintain stable ecosystems is an important factor and management needs tools to determine this for different sized water systems.

Impacts on species and ecosystems can extend over several bodies of water, both upstream and downstream, and also the riverbanks, flooding areas, deltas, and the coastal environment. For fish ecology and management (In Swedish: fiskevård), this topic is central. Several regulatory dams together will cause cumulative effects on watercourses and their ecosystems, including on individual species, such as fish species with weaker swimming abilities, and genetic effects within species, such as different strains of trout. To understand and take into account the cumulative impact and cumulative effects of measures is needed when hydropower permit reviews is done over entire catchment areas. Reduced, absent or unnatural water level variations or disturbances increase the dominance of competitive species, while the number of species in or adjacent to regulated watercourses decreases. The water reservoirs upstream of our largest hydropower plants are extremely nutrient-poor with low concentrations of zooplankton and phytoplankton, which affects the growth of fish. Fragmentation in watercourses also complicates exchange and gene flows between local populations, which in the long run reduces the genetic variation within a population. Ecosystems with reduced biodiversity are relatively more sensitive to changes, such as climate change or new diseases, and also generate fewer of the ecosystem services on which human societies depend.

We propose that a compilation and analysis of knowledge in these areas would provide valuable insights, for example that the synthesis would clarify knowledge gaps that still exist in how hydropower and other dams affect species and ecosystems, as well as knowledge gaps in the cumulative effect of several hydropower plants and / or measures in the same water system.

The efficiency of different measures and effects on individual species, ecosystems, water systems and hydromorphology need to be compiled and analysed in order to be able to put the right measure in the right place. The interdependence of measures and the combined effects of measures are also important topics. It is especially important to be able to justify measures that are perceived as drastic, such as the removal of a dam or changes in water regulation, as this can have financial consequences for the hydropower plant owner. Managers needs to be able to provide an ecological justification for why the measure is necessary. A specific challenge is when there are many dam constructions in one river system and the review must take into account the cumulative ecosystem effect of several dams in the same catchment area or river stretch. The administration needs to be able to develop environmental targets for a larger area that can also be used when reviewing each individual dam construction. Small hydropower dams will also impact the water, especially cumulatively within a catchment area.

Fauna passages, fishways and other measures have traditionally benefited salmonids. Perch, pike and several other weaker-swimming fish species also have a natural behaviour of migrating upstream or downstream but can rarely cope with the high current speeds that occur in fishways and other technical fishing routes. For many benthic fauna species such as mollusks and crustaceans, fishways are also obstacles to the spread of the species. When implementing measures, it is necessary to take into account the existing and potential water flow for downstream effects, how much water is needed for different species or ecological processes, and what measures can be used. *According to a recent dissertation (Widén 2021), for example implementing rules that mandate minimum discharge, i.e. that some water must constantly flow through the turbines, could promote ecosystems and biodiversity as a cost-effective measure (*2022-06-16: The sentence has been reformulated).

A compilation of organisms' dependence on water flows with an analysis of the needs of different species or ecosystems is needed. It would be useful both in preparing the application within the environmental assessment and when appropriate environmental adaptation is to be produced.

The complex relationships between water regulation, hydromorphological impact and ecosystems need to be compiled and analysed to provide a basis for models that describe reference conditions and effects of measures. These in turn can be used to develop biological indicators of physical impact and assessment criteria that can be used in hydromorphologically affected waters. Improved methods are also needed to prioritize where measures should be put in place for the best ecological effect at system level. This also requires modeling of reference conditions and of the effects of measures in different ecosystems or on individual species such as salmon, eel or crayfish, as well as on other species that are not economically relevant. Sweden's assessment basis for hydromorphological status needs to be developed with regard to affected waters and there is no systematic environmental monitoring or description of the hydromorphological conditions along most water systems. On the other hand, there is a lot of knowledge in the areas, and an analysis based on a compilation of methods / models for hydromorphological mapping, status classification or impact or action effects on individual species would be of great benefit to the management.

Assessing reference conditions is a challenge, especially in watercourses that are constantly changing naturally. Just looking back at older map material is not enough because land use, hydrology, climate may have changed as well. In parts of Sweden, we also have the world's largest land uplift, which leads to faster development. A reference relationship must therefore be determined locally based on the conditions of the landscape and the catchment area and above all focus on the dominant hydromorphological and physico-chemical processes, not only the appearance of the watercourse. There is normally a lack of knowledge about the hydromorphological processes before a dam was built and before water regulation was introduced. Environmental monitoring in hydropower-affected watercourses is often limited and water regulation has changed over time without being documented. As there is no reference relationship and full understanding of ongoing hydromorphological processes, there will also be uncertainties about which target image to use for environmental adaptation or restoration. In many cases, it may be better to model a reference relationship and the sensitivity to the changes that have occurred through hydropower. A Swedish methodology for developing a reference relationship and goal picture is lacking for watercourses and hydropower plants.

There is need for an understanding of how the watercourse or the lake's processes would work if there was no hydropower in place, given all the other conditions in the catchment area. In some cases this analysis may be simpler than, for example, for cleared waterways, where watercourses are so affected that the reference state can not be traced, but one needs to turn to corresponding water types that have not been cleared to see how blocks and stones may have been distributed in the watercourse. We invite applications for syntheses that compile and analyse methods for producing reference conditions regarding processes and also methods to draw up a user history for water affected by hydropower or other dams.