Odeleite Dam

The design and development of the project comprised the following components:

Odeleite Dam

Located in the municipality of Castro Marim, Odeleite Dam is a rockfill embankment dam with a waterproofing coating of reinforced concrete on upstream face.

Main characteristics:

- Crest length/width: 350 m / 12 m;

- Maximum height above foundation level: 65 m;

- Upstream slope inclination: 1.3/1 (H/V);

- Downstream slope inclination: 1,4/1 (H/V);

- Area of the upstream concrete face slab: 22 800 m²;

- Volume of compacted fill: 1 x 106 m³.

The catchment area at the dam site is approximately 352 km² and the average annual inflow is around 89 × 10⁶ m³, corresponding to a runoff depth of 253 mm. The mean flow rate is 2.8 m³/s.

The location and crest elevation of the dam required the construction of a saddle dam on a saddle located on the left bank and an embankment across a valley on the right bank. This embankment, operating under balanced hydraulic loads upstream and downstream, was required to restore road connections, as National Road EN 122 became submerged along the approaches to the existing bridge. The crest elevations of these structures range between 63 m and 75 m.

Odeleite Dam is a rockfill embankment dam with a waterproofing coating of reinforced concrete on upstream face and supported on a concrete plinth. The dam crest, 12 m wide, extends for approximately 347 m at elevation 55 m. The height of the dam, measured from the lowest foundation level, is 65 m.

To enable construction of the dam, the Odeleite stream was diverted through a horseshoe-shaped diversion tunnel with a horizontal invert and a diameter of 7.7 m. Two cofferdams were constructed: an upstream cofferdam with crest elevation at 17.3 m and a downstream cofferdam with crest elevation at 11 m.

 Flow restitution was achieved through a hydraulic jump energy dissipation basin of trapezoidal section, 45 m long, with a width increasing from 14 m to 24 m.

The design discharge for the temporary river diversion, corresponding to a 50-year return period, is 485 m³/s.

The frontal spillway is located on the left bank, with its crest at elevation 42 m. It comprises two 6.7 m wide bays equipped with automatically operated radial gates. Upstream of the spillway crest, a 45° shaft connects to the temporary diversion tunnel, discharging into the stilling basin.

The temporary diversion tunnel was subsequently adapted to function as the bottom outlet. Upon completion of its role as a temporary river diversion, the tunnel was sealed with a concrete plug, inside which the bottom outlet conduit was installed, having a maximum discharge capacity of 50 m³/s.

The dam crest is at elevation 55 m. The Full Supply Level (FSL) of the reservoir is at elevation 52 m, the Maximum Flood Level (MFL) is at elevation 54 m and the Minimum Operating Level (MOL) is at elevation 26 m.

At the Full Supply Level, the reservoir has a flooded surface area of approximately 720 ha. Total storage capacity is approximately 130 × 0⁶ m³, while live storage capacity is approximately 117 × 10⁶ m³. The reservoir regulation index is 1.31, based on inflows from its own catchment.

A small water intake structure was also constructed on the left bank of the Odeleite reservoir, adjacent to the dam, to supply irrigation water to approximately 250 ha of agricultural land in the Odeleite valley as far as the banks of the Guadiana River.

This intake comprises a rectangular tower with an overall cross-section of 2.0 × 2.0 m, incorporating three intake openings measuring 0.8 × 0.8 m at Elevations 26.5 m, 35.5 m and 44.5 m. The gate is operated from a platform located at Elevation 55.0 m and connected to the bank by a footbridge approximately 50 m long and 1.6 m wide.

The Odeleite Dam was followed by these subsequent projects:

Beliche – Tavira Water Treatment Plant Conveyance System

The following constructions were carried out at this stage of the project:

Water intake at Beliche Reservoir: reinforced concrete intake tower with a pentagonal cross-section, 33 m high, incorporating three intake levels with openings fitted with gates and gratings;

Beliche Tunnel • PS1: approximately 350 m long, connecting the intake structure to Surge Tank No. 1, with the same cross-section as the Odeleite–Beliche Tunnel;

Surge Tank No. 1: circular section with an internal diameter of 11 m and a height of 41 m;

Pumping Station PS1: equipped with horizontal split-case variable-speed pump units, comprising four pumps rated at 2.6 m³/s and two pumps rated at 1.3 m³/s, providing a maximum pumping capacity of 10.4 m³/s, an average pumping head of 80 m, an installed capacity of 14 MW and a 60 kVA substation;

Pipeline Section: approximately 560 m long, connecting PS1 to Surge Tank No. 2, comprising DN 2500 prestressed reinforced concrete pipes with rubber-ring watertight joints;

Surge Tank No. 2: circular section with an internal diameter of 11 m and a height of 30 m;

Pipeline Section: approximately 25 km of DN 2500 prestressed reinforced concrete pipes with rubber-ring watertight joints extending to PS2, designed for operating pressures up to 1.4 MPa and embankments up to 4 m high. Along the pipeline, irrigation flows are supplied through six offtakes equipped with MONOVAR flow control valves;

Pumping Station PS2: booster pumping station equipped with three horizontal pump units, each rated at 2.1 m³/s, providing a pumping head of 10–13 m and an installed capacity of 1.2 MW;

Pipeline Section: DN 2500 mm reinforced and prestressed concrete pipes with rubber-ring watertight joints, extending approximately 3 km to the reservoir;

Santo Estevão Reservoir: open hilltop reservoir formed by the construction of a perimeter embankment ranging in height from 0.5 m to 15 m, with a total storage capacity of 150 000 m³ and a free water surface area of approximately 2.8 ha. The reservoir is lined with an HDPE geomembrane and incorporates a range of hydraulic safety structures and water outlets for the different users;

Pumping Station PS3-U: installed at the reservoir, it pumps the water to the Tavira Water Treatment Plant, equipped with vertical pump units comprising two pumps rated at 1.1 m³/s and two pumps rated at 0.55 m³/s, providing a pumping head of 21 m and an installed capacity of 900 kW;

Pipeline Section: Water supply pipeline to the Tavira Water Treatment Plant, comprising DN 1200 mm reinforced and prestressed concrete pipe with rubber-ring watertight joints, approximately 1.8 km long. 

Odeleite – Beliche Tunnel

The Odeleite and Beliche reservoirs are interconnected by a tunnel so that they can operate as communicating vessels. The tunnel has a portal-shaped cross-section with rounded corners, 3.3 m wide and 3.3 m high, providing a hydraulic area of 9.5 m². The maximum flow capacity is 25 m³/s.

The tunnel invert is at Elevation 23 m on the Odeleite side and Elevation 26 m on the Beliche side. The tunnel extends for approximately 2,950 m and is fully lined with reinforced concrete.

Key dimensions:

- Straight alignment length: 2,958 m;

- Excavation cross-sectional area (portal section): 17 m²;

- Finished reinforced concrete lined cross-sectional area: 9.5 m²;

- Upstream and downstream control towers of circular section, with an internal diameter of 4 m, an average wall thickness of 0.30 m and a height of 32 m. 

Tavira Water Treatment Plant (Phase 1)

Designed to provide treated water for the Eastern Algarve, the Tavira Water Treatment Plant has a maximum production capacity of 2.2 m³/s. During Phase 1, the plant was designed to produce 1.1 m³/s of potable water.