Case study:Fish pass on the Najerilla River

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Location: 42° 27' 54.52" N, 2° 42' 21.08" W

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Project overview

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Status	Complete
Project web site
Themes	Habitat and biodiversity
Country	Spain
Main contact forename	Rincón Sanz
Main contact surname	Gonzalo
Main contact user ID
Contact organisation
Contact organisation web site
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Parent multi-site project
This is a parent project encompassing the following projects	No

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Project summary

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The concerning weir was small and it served to supply irrigation communities in the area. In origin, the weir was of an approximate height of 40 cm. However, over time, an erosion was generated downstream the obstacle so its height increased to 1.5 meters and the weir became impassable. This was a problem since the community of fish in the river is very varied and this obstacle became a serious problem for its movement through the river.

Among the variety of existing fishways, in this particular case the chosen option was the installation of a rock ramp. This type of device mimics the natural conditions of the river. Usually have an inclined plane with a slope always ≤ 10%, in which blocks of stone of considerable size are inserted.

The advantages of this kind of devices are:

- It offers better conditions of passage (both upstream and downstream).

- Its appearance is better integrated with the environment.

- It allows the evacuation of flows (including ecological flows).

- It does not alter the structure of the obstacle.

- Low maintenance cost.

On the other hand the disadvantages are:

- It requires more space to be built.

- It needs more flow to ensure their functionality.

- It is only applicable to obstacles with small-medium heights (less than 2.5 m).

In this case, the Najerilla River presents marked contrasts of flow between high and low waters, so that it was proposed to make two sections of the fishway: a deeper central ramp of about 10 m wide and two shallower lateral ones of 4 m wide each. Stone blocks of about 1 meter diameter were placed so that no channels were formed where the water reaches a high speed and impedes the ascent of the fish. Finally, gravels have been embedded in the surface of the ramp in order to increase the roughness of the ramp bottom. The slope of the ramp was 5%

Monitoring surveys and results

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The implementation of monitoring programs is essential to evaluate the correct functioning of the fishways. In this regard, there is a lack of information about this action.

Lessons learnt

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Image gallery

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Rock ramp in the Najerilla River with a low flow (left) and with a higher flow (right). Photo credits: Pedro Boné.

Catchment and subcatchment Select a catchment/subcatchment Site Edit site Name WFD water body codes WFD (national) typology WFD water body name Pre-project morphology Reference morphology Desired post project morphology Heavily modified water body No National/international site designation Local/regional site designations Protected species present No Invasive species present No Species of interest Brown trout (Salmo trutta), Luciobarbus graellsii, Barbus meridionalis, Parachondrostoma miegii, Gobio lozanoi Dominant hydrology Dominant substrate River corridor land use Average bankfull channel width category Average bankfull channel width (m) Average bankfull channel depth category Average bankfull channel depth (m) Mean discharge category 10 - 100 m³/s Mean annual discharge (m3/s) 16.516.5 m³/s <br />16,500 l/s <br /> Average channel gradient category Average channel gradient Average unit stream power (W/m2) Project background Edit project background Reach length directly affected (m) Project started Works started Works completed Project completed Total cost category 50 - 100 k€ Total cost (k€) 61.861.8 k€ <br />61,800 € <br /> Benefit to cost ratio Funding sources Part of this work was supported through FEADER funding (European funding to improve the rural development). Cost for project phases Phase cost category cost exact (k€) Lead organisation Contact forename Contact surname Investigation and design Stakeholder engagement and communication Works and works supervision Post-project management and maintenance Monitoring Reasons for river restoration Edit reasons for restoration Mitigation of a pressure Barriers to fish migration Hydromorphology Continuity for organisms Biology Fish: Abundance, Fish: Species composition Physico-chemical Other reasons for the project It generates a profit in the agricultural communities of the zone. Measures Edit Measures Structural measures Bank/bed modifications Floodplain / River corridor Planform / Channel pattern Other Non-structural measures Management interventions Social measures (incl. engagement) Other Monitoring Hydromorphological quality elements Edit Hydromorphological quality elements Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Biological quality elements Edit biological quality elements Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Physico-chemical quality elements Edit Physico-chemical quality elements Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Any other monitoring, e.g. social, economic Edit Other responses Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Monitoring documents Upload monitoring documents Additional documents and videos Upload additional documents Additional links and references Edit links and references Link Description http://europe.wetlands.org/publications/river-fragmentation-analysis-spain/ A link on the Wetlands International website to a document that describes the project. http://http://www.ecohidraulica.com/ All information on this page is copied from the document mentioned above which is written by Ecohidráulica, S.L. Supplementary Information Edit Supplementary Information References Boné P. (2015) Rampa para peces en el Río Najerilla (Torremontalbo, La Rioja). Buena práctica para recuperar la continuidad del curso fluvial. Confederación Hidrográfica del Ebro (2009). Pasos de peces para permeabilizar estructuras transversales en la cuenca del Ebro. Tecnoma. Sanz-Ronda, J. et al. (2015) Sistemas de adaptación de pasos de agua a la migración de los peces. Ejemplos realizados en España. Seminario técnico LIFE-Miera: Gestión de un corredor ecológico.