Hydro - Environmental Impact Assessment (EIA)

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An environmental impact assessment (EIA) is an assessment of the possible impact - positive or negative - that a proposed project may have on the environment, considering natural, social and economic aspects. The purpose of the assessment is to ensure that decision makers consider the ensuing environmental impacts to decide whether to proceed with the project.

As a policy instrument the EIA ensures that the environmental implications of a project are anticipated and minimised. They are applied for all types of projects like infrastructure development, and also for hydropower projects. They might be applied on river basin scale in the case of cumulative Environmental Impact Assessments (CESIA). At European level the EIA Directive 2011/92/EU defines the frame for the application of EIAs.

Environmental Impact Assessment (EIA)

“An Environmental Impact Assessment (EIA) is a systematic process used to identify, evaluate and mitigate the environmental effects of a proposed project prior to major decisions and commitments being made” (UNEP). It thus also figures as a means to ensure that projects are implemented with full awareness of environmental factors. An EIA normally results in an Environmental Management Plan (EMP) that elaborates mitigation and monitoring measures. In most industrialized countries EIAs are legally required when a proposed (hydropower) project exceeds a certain size.

EIA Procedure

Although EIA is a largely standardized approach, concrete implementation depends on the legal context and thus can differ in various countries. Figure 1 shows the European Union’s approach.


'Figure 1': EU Procedure[1]

 During screening it is determined whether or not a full EIA is to be carried out. The European EIA Directive (2011/92/EU, Art.5[2]), for example, always demands an EIA when storage or water held back by the dam project exceeds 10 million cubic meters (Annex I, 15). Another common approach is to classify dams into categories A, B or C, depending on type, location, sensitivity, and scale, as well as on the nature and magnitude of potential impacts, and then demand different depth of study (e.g. World Bank OP 4.01).

During scoping stage content and level of detail of analysis is defined. The EU directive, for example, states as minimum information to provide: 

  1. a description of the project comprising information on the site, design, size and other relevant features of the project;
  2. a description of the likely significant effects of the project on the environment;
  3. a description of the features of the project and/or measures envisaged in order to avoid, prevent or reduce and, if possible, offset likely significant adverse effects on the environment;
  4. a description of the reasonable alternatives studied by the developer, which are relevant to the project and its specific characteristics, and an indication of the main reasons for the option chosen, taking into account the effects of the project on the environment;
  5. a non-technical summary of the information referred to in points (a) to (d)
  6. any additional information specified in Annex IV relevant to the specific characteristics of a particular project or type of project and to the environmental features likely to be affected.

EIAs are project-specific, predicting the potential outcomes of a certain project. The search for alternatives is therefore usually limited to  technical design issues. Although the EU Directive demands the description of project alternatives, this is limited to those “studied by the developer” (Article 5, 3d). Instruments that seek to include assessment of alternatives at the earliest appropriate stage of decision-making are the Strategic Environmental Assessment (SEA; see below) and Hydropower Sustainability Assessment Protocol (HSAP), where the Early-Stage Tool is of particular relevance for this aspect (->WIKI-LINK: HSAP). EIAs provide extensive public participation mechanisms during the whole process.

Some finance institutes ask as part of their standard approval procedure EIAs to cover additional aspects that can go beyond legal requirements. The involvement of international finance institutes can therefore lead to the application of higher standards compared to non-involvement. Usually the project proponent has to pay for the study. In the case of the EU, EIAs[3] account for less than 1% of total project costs and take 1-2 years for completion[4].

Cumulative Environmental Impact Assessment (CEIA) of Large Hydropower

In combination with the impacts of other hydro projects within the same river basin, impacts can change or intensify. Therefore the scope of the impact assessment should not be limited to one project, but analyze the impacts with a view to other existing and planned projects. As an advanced version of an EIA, the Cumulative Environmental Impact Assessment (CEIA) seeks to incorporate these effects into the assessment of a proposed project. It therefore enlarges the scale of analysis to regional river basin level.

Up to date the CEIA as instrument is restricted to large hydropower and is not applycated to small hydro.

Environmental Impacts of Small Hydro Power Projects

Small, run-of-the-river projects are free from many of the environmental problems associated with their large-scale relatives because they use the natural flow of the river, and thus produce relatively little change in the stream channel and flow. The dams built for some run-of-the-river projects are very small and impound little water - and many projects do not require a dam at all. Thus, effects such as oxygen depletion, increased temperature, decreased flow, and rejection of upstream migration aids like fish ladders are not problems for many run-of-the-river projects[5].

Strategic Environmental Assessment (SEA)

The Strategic Environmental Assessment (SEA) complements the environmental impact assessment. The main difference: The SEA applies in an earlier stage of decision making than the EIA and at a broader, national level. While the EIA is employed only in the case of the approval of proposed environmentally significant projects, the SEA is already being done at the national planning level. Important strategic decisions with environmentally significance are often made already in the course of national planning and programing. (BMUB 2013)[6]

Thus, while the EIA analyses specific projects the Strategic Environmental Assessment (SEA) focuses on strategic directions which are incorporated in (public) plans and programs. It thereby ensures that potential impacts are “fully included and appropriately addressed at the earliest appropriate stage of decision-making” (Sadler & Verheem, 1996).

The results obtained from the SEA are primarily relevant for national plans and programs and set the basis for strategic decisions. SEA addresses the coordination between different sectors, the appraisal of sectorial interests and objectives, as well as the ranking of priorities to establish coherent national policies. This can, for example, include prioritization of individual technologies and their regional allocation. Compared to EIA, the search for “reasonable alternatives taking into account the objectives and the geographical scope of the plan or programme” (EU) plays a pivotal role and often is mandatory (e.g. EU Directive 2001/42/EC[7]). While both EIA and SEA are instruments for impact assessment, the scope of SEA is enlarged in order to adequately cover large scale developments that cannot be represented by single EIAs.

Case Studies & Examples

This paper outlines the advantages of SHP, barriers in the development of SHP, EIA process in India, regulatory framework, EIA of SHP projects, case studies of EIA of six SHP projects in the state of Uttarakhand, their impacts on ecological resources & human environment and EMP. It is concluded that there has been low to medium impacts of the projects on the surrounding environment.

Good Practice Handbook for Large Hydro (by IFC/International Finance Corporation)

IFC published a Good Practice Handbook on Cumulative Impact Assessment and Management. It provides guidance for the Private Sector in Emerging Markets and introduces a six-step process to identify cumulative impacts, as well as a guide for the effective design and implementation of measures to manage such cumulative effects.

Cumulative Impact Assessment and Management: Guidance for the Private Sector in Emerging Markets

  •  Guidelines for CEIA/Turkey

Turkey developed guidelines for cumulative EIAs together with the World Bank. The Government of Turkey promoted investments in hydroelectric power plant (HEPP) projects as a policy priority, in response to concerns about the environmental and climate change impact of other power generation technologies, as well as with an eye to compliance with EU regulations and targets. The rapid growth in investments raises concerns about the associated impacts (such as minimum environmental flow, temporary/permanent roads opened for the investment, etc.) and the significance of the cumulative impact of multiple HEPP projects on the river basins. Guidelines to Cumulative Environmental Impact Assessment (CEIA) have been prepared within the scope of a CEIA technical assistance study (CEIA study) supported by the World Bank. The CEIA study was developed based on the need to assess the cumulative impacts of hydropower projects in Turkey and was conducted in coordination and cooperation with the relevant departments of the Ministry of Environment and Urbanization (MoEU) and the Ministry of Forestry and Water Affairs (MoFWA).

ESMAP Website

  •  SEA by Mekong River Commission (MRC)

2010 the Mekong River Commission (MRC) conducted a SEA on potential developments in its river basin.

 Strategic Environmental Assessment of Hydropower on teh Mekong Mainstream

Further Information

Literature &  References

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