Bragado test case

Introduction

The Bragado Hydropower plant (HPP) is located in the North of Portugal, on the Avelames river, which is a tributary of the Tâmega river (Douro river basin).

The Avelames river is characterized by a strong seasonal variation in flow, with the highest discharge peaks occurring during the wet semester (October-March). Inter-annual variation in precipitation and, consequently, in runoff, is also large, as it is typical of a river with a Mediterranean flow regime. Mean long term annual discharge at Bragado weir amounts to 1.4 m3/s. The catchment area of the Avelames river at the section of Bragado weir is 78.8 km2. There are no other HPPs in the same river.

The water body at the HPP Bragado is classified as a natural water body with Good Ecological Status.

About the hydropower plant

Bragado is a run-of-river HPP with partial daily flow regulation. It has an installed capacity of 3.1 MW and a mean annual electricity production of 9.0 GWh. The small reservoir created by the weir has a useful storage capacity of 25000 m3 (total capacity of 34000 m3), located between the full reservoir level, FRL=495.1, and minimum drawdown level, MDDL=492.8. The weir was designed for the 100-year peak flood discharge of 230 m3/s.

The powerhouse of Bragado was designed for a maximum turbined discharge (or design discharge) of 2.2 m3/s and a net head of 155.2 m and it is equipped with one Francis turbine with horizontal shaft. The water permit of Bragado was issued in 1996, the construction of the scheme started in August 1997 and the first connection to the national electricity grid took place in December 1998.

Layout

The Bragado HPP is placed in a rural zone that is dominated by shrub and forested areas. The small parish of Bragado (544 inhabitants in 2011) is the nearest village (approx. 700 m from the weir).

The Bragado HPP includes a small weir equipped with a submerged water intake. The weir creates a reservoir with a useful capacity and an area at the FRL of 25000 m3 and 5600 m2, respectively. Downstream of the water intake is the conveyance system which includes an open canal (2490 m long), a fore bay, a penstock (f=900 mm and 290 m long) and a powerhouse (installed capacity of 3.1 MW). The bypassed reach of the Avelames River, comprehended between the weir and the tailrace of Bragado, is 3.7 km long.

The minimum instream flow/ecological flow release by the weir is of 0.064 m3/s. Due to the low river connectivity downstream of Bragado HPP no fish pass was built in the weir.

The Operator: Hidroerg

The HPP is operated by Hidroerg – Projectos Energéticos, Lda, incorporated in 1989 and headquartered in Lisbon. The object of the Company is to build, manage and operate power facilities designed for the production of electricity from renewable energy sources. The company has a strong focus on hydropower, being skilled in the identification of sites, in the conception and planning of systems and schemes, in the feasibility evaluation and impact assessment, in the coordination of the civil construction works and of the equipment installation, and in the management of energy production facilities, in a framework of sustainable development and of generation of both national and entrepreneurial economic value. Read more

Pressures on the water body's ecosystem

The river quality is influenced by discharges from wastewater treatment facilities as well as from agriculture and animal husbandry. The hydromorphology of the river is influenced by the operation of the Bragado HPP. Nevertheless, according to the Douro River Basin Management Plan, the natural water body PT03DOU0211 where the HPP is placed is in a Good Ecological State.