Fish Upstream Passage through Gauging Stations: Experiences with Iberian Barbel in Flat-V Weirs

Andrés Martínez-De-Azagra,Francisco Javier Bravo-Córdoba,Ana García-Vega,Jorge Valbuena-Castro,Francisco Javier Sanz-Ronda,Juan Francisco Fuentes-Pérez

doi:10.3390/fishes6040081

Andrés Martínez-De-Azagra, Francisco Javier Bravo-Córdoba + Show 4 more

Open Access

https://doi.org/10.3390/fishes6040081

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Abstract

The monitoring of river discharge is vital for the correct management of water resources. Flat-V gauging weirs are facilities used worldwide for measuring discharge. These structures consist of a small weir with a triangular cross-section and a flat “V”-shaped notch. Their extensive use is a consequence of their utility in the measurement of both low and high flow conditions. However, depending on their size, local morphology and river discharge can act as full or partial hydraulic barriers to fish migration. To address this concern, the present work studies fish passage performance over flat-V weirs considering their hydraulic performance. For this, radio-tracking and video-monitoring observations were combined with computational fluid dynamics (CFD) models in two flat-V weirs, using Iberian barbel (Luciobarbus bocagei) as the target species. Results showed that fish passage is conditioned by both hydraulic and behavioral processes, providing evidence for scenarios in which flat-V weirs may act as full or partial barriers to upstream movements. For the studied flat-V weirs, a discharge range of 0.27–8 m3/s, with a water drop difference between upstream and downstream water levels lower than 0.7 m and a depth downstream of the weir of higher than 0.3 m can be considered an effective passage situation for barbels. These findings are of interest for quantifying flat-V weir impacts, for engineering applications and for establishing managing or retrofitting actions when required.

Highlights

Gauging stations are structures that measure and record water levels in rivers or canals in relation to stream discharge [1]
One of the most common facilities for estimation of river discharge is the use of gauging weirs [1]
The resolution of the transient flow of two fluids separated by a sharp interface was achieved using the prebuilt Eulerian solver interFoam [33], an implementation of the volume of fluid (VOF) method [34]

Summary

Introduction

Gauging stations are structures that measure and record water levels in rivers or canals in relation to stream discharge [1]. They are usually managed by public institutions and act as crucial river monitoring networks with open and real-time accessible data to ensure human safety (flood and drought control), provide correct management of water resources (for domestic, industrial and agricultural supply), to design and plan river-related engineering projects or to monitor environmental flows [2,3]. One of the most common facilities for estimation of river discharge is the use of gauging weirs [1] They consist of well-known hydraulic control structures that make discharge estimation possible by means of discharge–water level relationships [3], together with a monitoring system to record and transmit water level (or discharge after transformation) data. The first group of weirs is recommended in small and low-carrying debris streams, when accuracy is desired and maintenance is possible, while the second and third groups are preferred for larger streams and rougher conditions [4]

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