The report D4.2 Functional application matrix prepared by FIThydro researchers scores and ranks 40 mitigation measures that can be used for mitigating impact of hydropower on fish. A matrix further shows how different mitigation measures can be combined.  

Measure for upstream migration: Eelpass at hydropower plant Trois Ville, France
Habitat creation through placement of gravel in the fishway at the test case Günz, Germany

Eal pass at Trois Ville, France, and placement of spwaning gravel in a fishway at the riger Günz, Germany as measures for upstream migration and habitat creation. (Picture rights: © Pôle Ecohydraulique de l'AFB, © IBF Umwelt)

For mitigation of hydropower impacts, a wide variety of measures exists. The work of D4.2 is based on the previously published report D4.1 A classification system for methods, tools and devices for improvement measures that describes the main types of mitigation measures. These are grouped in the following categories, according to the main challenge they address:

  • Downstream fish migration
  • Upstream fish migration
  • Habitat
  • Sediment management
  • Environmental flows

As the impacts of hydropower plants on fish are numerous, it is often necessary to implement more than one mitigation measure. While some measures complement each other, others might not work well together.

Matrix for combining different mitigation measures

The mitigation measure matrix in the report D4.2 shows how different mitigation measures can be combined. The matrix is originally a three-dimensional matrix, presented as two matrices. One matrix has a scoring system showing which mitigation measures are suitable for combination, including links to references. The other matrix (an extension of Table 8.1 in D4.1) contains challenges and problems related to hydropower and fish listed against the mitigation measures. For an easy handling the scoring and matrix are displayed in a downloadable excel spreadsheet.

Combination of mitigation measure matrix

Combination of mitigation measures. See https://www.fithydro.eu/mitigation-measures-matrix/ for the Excel version of the matrix. (Scource: D4.2)

Identifying potential combinations by using Bayesian Networks

To identify potential combinations of mitigation measures that are most likely to succeed and are most effective, Bayesian Networks have been used. The combinations will include trade-offs between the cost of the mitigation measures and their effectiveness.

Here, measuring the effectiveness is a challenge, particularly given the site-specific nature of hydropower installations and their mitigation measures. As each mitigation measure has a specific target to address, it is important to establish effectiveness indicators which are consistent with the target. To create an estimate for effectiveness, effectiveness data was gathered from two sources:

  • Values from the literature
  • Expert elicitation to update beliefs

If no effectiveness data is available, the Bayesian Networks can use values collected from a literature review and those improved through expert knowledge.

Testing the framework

The developed framework will be tested in selected FIThydro Test Cases. The full test and the application of the framework will be reported in D4.6 (due in October 2020) and a scientific article.

The matrix will be updated and refined till the end of the project. It will be directly linked to the FIThydro wiki (due in October 2020). The combination of the two will allow users to find suggestions and directions about which measures are appropriate to mitigate their challenges and problems.

For more information, download the full report (6MB) and the excel spreadsheet with the mitigation measure matrix.