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Better Hydro: protecting biodiversity at Reventazón, Costa Rica

This case study is featured in Better Hydro: Compendium of Case Studies 2017, which highlights examples of good practice in hydropower sustainability across all aspects of project development. You can download the full compendium here.


Key project features

Developer/operator: Instituto Costarricense de Electricidad (ICE)
Associated projects: Reventazón (305.5 MW)
Region/basin: Reventazón river, Limón province


The Reventazón Hydroelectric Project (RHP) is one of the first Latin American hydroelectric projects to use a river offset approach. This case study demonstrates how strategic basin planning can help develop the hydropower potential of a river whilst making a significant contribution to biodiversity conservation. 

Instituto Costarricense de Electricidad (ICE), Costa Rica’s national power company, developed the Reventazón Hydroelectric Project (RHP) between 2012 and 2016. RHP was built on the Reventazón river in the Limón province, with a 130 m dam and an 8 km long reservoir. 

The project is the fourth in a cascade of projects on the Reventazón river, and is designed to maintain a downstream flow of 40 m3/s. It comprises an additional small powerhouse, with a single 13.3 MW turbine, to utilise the environmental flow release. The project is located in an area of very humid tropical forest.

Reventazón was partially funded by the Inter-American Development Bank (IDB) and as such was required to meet international environmental and social safeguards.

Project studies anticipated that, in the absence of environmental management strategies, RHP would make a significant impact on migratory fish species and critical habitats and connectivity. 

Studies indicated that the project would affect around 471 species of fauna, of which 34 are at risk of extinction and 58 are under threat. It would also affect 193 species of flora, of which 15 are at risk of extinction, and six are under threat. 

ICE designed an offset plan that included protecting the perpetuity of the Parismina river, an intact river that joins the Reventazón river downstream of the dam on the coastal plain. 

RHP is one of the first Latin American hydroelectric projects to use the river offset approach. The IDB estimated that the offset would cost USD 2.7 million over 2013–15, and USD 800,000 per subsequent year.

This case study is an example of how strategic basin planning can help develop the hydropower potential of a river whilst protecting and avoiding development in other free-flowing rivers in the same basin. It also demonstrates how effective mechanisms can be used to offset environmental impacts. 

The project shows how hydropower projects can make a significant contribution to biodiversity conservation at regional and basin level through offset programmes designed with relevant stakeholders.

The offset programme was based on environmental and social criteria and designed and implemented with stakeholders

ICE, with assistance from IDB, designed and implemented a river offset programme to compensate residual and cumulative biodiversity impacts. 

  • The programme was designed to:

  • protect a free-flowing river with similar characteristics to the Reventazón river;

  • improve water quality and riparian habitats;

  • compensate the loss of critical habitat and impacts on terrestrial and aquatic connectivity, especially impacts on big cats and migratory aquatic species; and

  • facilitate a possible net gain of critical habitats.

The offset programme had to be implemented in a river stretch with similar ecological conditions and services to the Reventazón river. The Parismina river and its tributary, Dos Novillos river, were selected for the implementation of the programmes (a total stretch of 105.5 km). 

ICE designed an offset plan that included protecting the perpetuity of the Parismina river, an intact river that joins the Reventazón river downstream of the dam on the coastal plain."

The selection process involved analysing nine river basins discharging into the Caribbean Sea. Three of the nine basins were selected due to their equivalent fluvial ecosystems meeting the following criteria: complex aquatic ecosystems and migratory species with high biodiversity; a continuous flow without barriers; good aquatic and terrestrial habitat conditions; and socio-economic services (e.g. eco-tourism, or sites of cultural heritage importance). Parismina was selected because it receives several tributaries and is key to fish migration. Dos Novillos was selected for offering the best aquatic and riparian environmental quality. The project carried out a feasibility study of the Parismina and Dos Novillos rivers in order to avoid the loss of, or ensure positive biodiversity gains, with respect to the residual impacts, and especially connectivity impacts. 

About 16 communities had a direct influence on the Parismina and Dos Novillos rivers, with a total population of 6,787 in 2013. The feasibility study used recognised indicators to measure riparian habitats, hydro-geomorphological conditions and riparian forest quality. The study concluded that the rivers would be suitable for the programme and would enable a net gain of 40 per cent in riparian habitats.

ICE designed the Parismina–Dos Novillos water offset management plan, which included actions to reforest the riverbanks, reduce agrochemical water pollution, promote best agricultural practices, and improve water resource management. 

The programme engaged local communities, who were involved in capacity-building activities and monitoring.

ICE also worked with small farmers and other stakeholders in the basin to implement the planned environmental actions.

Other major challenges to the offset programme's long-term sustainability included obtaining a site protection legal framework from Costa Rica’s Environment and Energy Ministry, and ensuring financing for the management and operation.

The programme protects a free-flowing river and the perpetuity of intact ecosystems

The programme was the region’s first river offset programme. ICE protected migratory routes for three fish species in the Parismina river. An offset agreement guaranteed the prohibition of artificial river or natural flow pattern modifications, including dams and other barriers to fish migration. 

The programme involves ongoing work between ICE and landowners in the Parismina and Reventazón watersheds to reduce erosion, sedimentation and pesticide run-off. 

The effectiveness of protection measures would be verified through a permanent monitoring programme for water quality, biodiversity and key habitats.

A biological corridor was created to safeguard critical jaguar habitats

The reservoir location would have a significant impact on one of Costa Rica's most important biological corridors, the Barbilla-Destierro biological subcorridor. This corridor plays a key role in the migration of jaguars in the Mesoamerican biological corridor between Nicaragua, Costa Rica and Panama. The Barbilla-Destierro biological corridor was identified as an area of importance for the connectivity of jaguar populations since 1990. 

The project performed studies on the effectiveness of the Barbilla-Destierro biological subcorridor management and the role of different stakeholders. 

This process contributed to strengthening the corridor’s management structure. The project implemented habitat restoration measures to preserve the subcorridor’s role in the movement of jaguars and their genetic flow. 

Measures included in the offset programme involve riverbank restoration that could create additional jaguar habitats and improve habitat connectivity from Tortuguero National Park on the coast up into the central mountain range. 

The project aimed to restore degraded land and raise local awareness on the importance of protecting the biological corridor. 

The project also included payments to forest owners for environmental services, environmental education, and agroforestry technical support. For example, farmers were able to learn how to raise pigs in enclosures rather than letting them run free. This way, waste produced by the pigs can be converted into fertiliser and gas, and will not affect water quality in the reservoir. At the same time, the pigs will be less exposed to jaguar predation, reducing the potential for conflicts between farmers and conservationists.

Offset measures address multidisciplinary objectives

The offset measures will contribute to meeting a number of environmental and social objectives that will benefit the environment and improve the performance of the project. 

For example, the reforestation of a buffer strip around the reservoir would help to: 

  • reduce erosion and sedimentation, increasing the useful life of the reservoir;

  • reduce the risk of landslides; and

  • create connectivity routes and new habitats for amphibians, reptiles, birds, insects, and mammals.

The project also prepared a reforestation plan using local tree and plant species and local nurseries.

The project aimed to restore degraded land and raise local awareness on the importance of protecting the biological corridor."

Contributing to biodiversity conservation in Costa Rica

The programme contributed to meeting the policies and objectives on biodiversity in Costa Rica. 

In addition to the protection of the Parismina river, the president of Costa Rica declared that the Savegre and Pacuare rivers would be protected from hydropower development for a period of 25 years from 2015. 

The decision was made as part of a national framework for hydropower development. 

The Savegre and Pacuare rivers were selected for their ecological, biological, economic and social importance. 


The case study is featured in Better Hydro: Compendium of Case Studies 2017, which highlights examples of good practice in hydropower sustainability across all aspects of project development. You can download the full compendium here.