Environmental Monitoring of the Project for the Installation of a Hydroscrew for Hydroelectric Generation in the Narcea River (La Florida Dam, Asturias).

Introduction

In 2023, the first hydroelectric power plant in Asturias was built, consisting of two hydro-screws in series, an electricity generation system based on Archimedes Screw technology. With a total power of 700 kW, this system is capable of producing enough clean energy to supply more than 1,000 homes annually, representing a significant step towards a more sustainable future.

The project is located at the La Florida dam on the Narcea River in Asturias. The hydro-screws will take advantage of the ecological flow and excess water, making this technology an ideal option for generating renewable energy with a reduced environmental impact. The fish-friendly design of these devices allows the safe passage of fish, contributing to the conservation of the river’s biodiversity.

The project’s environmental monitoring program, carried out by Taxus Medio Ambiente, was developed to ensure that preventive, corrective and compensatory measures are implemented both during the construction phase and during operation. These measures seek to minimize the negative environmental impacts derived from the execution of the work. In this article, we will detail the phases of environmental monitoring, the methodology used and the results obtained in the project.

What is a Hydroscrew and how does it work?

A hydro screw, also known as an Archimedes screw, is a low-speed turbine used for hydroelectric generation. Its principle of operation is based on the flow of water descending through the spiral of the screw, causing it to rotate and, in turn, generate electricity by means of a coupled generator. This technology is particularly suitable for low-flow rivers with small gradients, as is the case of the Narcea river at the La Florida dam.

Environmental Advantages of the Hydroscrew

• Reduced Environmental Impact: Does not require large infrastructure, which minimizes the alteration of watercourses and their surroundings.
• Fish-Friendly Design: Allows fish to pass through the system without harm, which contributes to the protection of local species.
• Energy Efficiency: It takes advantage of low and continuous flows, generating clean and renewable energy in a constant way.

Environmental Monitoring Methodology

The environmental monitoring of the project included several phases that allowed close monitoring of the impacts during the construction and operation of the hydroscrews. The main phases of the environmental monitoring are described below:

Pre-Construction Phase

Before starting the construction of the hydro-screws, exhaustive studies were carried out to assess potential environmental impacts and design preventive measures. The main actions included:

• Topographic and Bathymetric Survey: A detailed survey of the terrain and the Narcea riverbed in the area of the dam was carried out. These data were used to develop three-dimensional models of the area using GIS software and the hydrodynamic program MIKE 21.
• Hydrodynamic Modeling: Different flow scenarios were simulated, including a minimum flow of 2.48 m³/s to ensure the good ecological state of the river. The simulations confirmed that, under extreme conditions, the stretch of river between the dam and the hydroscrew outlet would maintain a continuous sheet of water without negatively affecting the ecosystem.
• Monitoring the Trophic Status and Ecological Potential of the Reservoir: Since 2012, regular sampling has been conducted to monitor the water quality and biodiversity of La Florida reservoir and its tributary rivers. In particular, the presence of macroinvertebrates, diatoms, macrophytes and nutrients has been monitored.

Construction Phase

During the construction of the hydro-screws, the Taxus Environment team carried out a comprehensive monitoring program to ensure that construction activities did not generate significant impacts on the environment. The main monitoring activities included:

• Water Quality Control: Water quality was monitored throughout the construction phase, measuring parameters such as suspended solids, biological and chemical oxygen demand, pH and conductivity. These data were compared with previous conditions to detect possible alterations.
• Noise Control: Noise generated by construction machinery was measured regularly to ensure that levels remained within the limits established by legislation. On one occasion, high levels were detected due to the use of hydraulic hammers, and immediate corrective measures were taken.
• Fauna and Flora Monitoring: Protection measures were implemented for sensitive species in the area, installing photo-trapping cameras to monitor the local fauna and keep a record of possible impacts on biodiversity.

3. Operating Phase

Once the construction of the hydro-screws was completed, the environmental monitoring program continued to ensure that the operation of the hydroelectric plant did not negatively alter the natural environment. The main actions included:

• Wildlife Video Surveillance: A video surveillance system was maintained, both aerial and underwater, to monitor the behavior of the local fauna, particularly fish and protected species such as the otter (Lutra lutra) and the Iberian desman (Galemys pyrenaicus).
• Environmental Noise Measurement: During the operation phase, noise levels continued to be measured in the vicinity of the project to ensure that the operation of the hydro-screws did not generate noise nuisance in the environment.
• Water Quality Control: Water quality measurements were maintained to detect possible alterations during the operation of the hydro-screws.

Environmental Monitoring Results

The results obtained after the implementation of the environmental monitoring program were highly positive:

1. Ecological Flow and River Condition: Hydrodynamic simulations confirmed that the minimum flow defined in the project was sufficient to guarantee the good ecological condition of the Narcea River. In addition, the additional 0.15 m³/s through the dam improved water circulation in the area, favoring aquatic biodiversity.
2. Status of La Florida Reservoir: Monitoring of the reservoir showed that its ecological potential has been mostly “Ultraoligotrophic”, indicating low productivity and high water quality. No significant alterations in aquatic flora and fauna were detected.
3. Protected Fauna: During the construction and operation of the project, no negative impacts on protected species such as the otter and the Iberian desman were detected. The preventive and corrective measures implemented were effective in mitigating possible impacts.
4. Noise and Air Quality: Noise levels remained within the limits established in the regulations, except on one occasion, which was quickly corrected. Likewise, no negative effects on air quality or surrounding vegetation due to dust deposition were detected.

Conclusions

The project for the installation of the hydroturbines at the La Florida dam has proven to be an effective solution for the generation of hydroelectric energy with a minimum environmental impact. The exhaustive environmental monitoring carried out by Taxus Medio Ambiente hasensured that both the construction and operation phases are carried out respecting the natural environment, complying with the objectives of sustainability and biodiversity conservation.

This project not only contributes to the production of clean energy, but also guarantees the protection of sensitive species and the maintenance of water quality in the Narcea River, consolidating itself as a benchmark in the integration of renewable technologies in the natural environment.

Author: Alea Pulgar Noriega.