RESERVOIRS
1. Mare aux Vacoas Reservoir
Purpose: Potable Water Supply
Mare aux Vacoas is the largest reservoir in Mauritius. It is located in the district of Plaines Wilhems, to the south of the town of Curepipe. The reservoir has a capacity of 25.89 million cubic metres and supplies water to the upper Plaines Wilhems and Moka.
Origin of Mare aux Vacoas:
In 1885, a one-meter-high masonry dam was built across Riviere du Tamarin in the marshy land at Mare aux Vacoas draining an area of 13 km2. The purpose of the dam was to store water for domestic water supply. In 1892, the level of the dam was raised to an elevation of 558.54 m (amsl) and the capacity of the reservoir was increased to 2.58 Mm3. In 1915, following a prolonged drought, the level of the dam was raised to an elevation of 560.06 m and the storage capacity increased to 5.27 Mm3. In 1922, Tatamaka feeder canal was constructed to divert water from Riviere du Poste into the reservoir.
The carrying capacity of the canal is presently 4.25 m3 /s, which represents an annual contribution of 15 Mm3. The capacity of the reservoir was subsequently raised to 16.15Mm3in 1928, to 27.63Mm3. in1961 with a water spread area of 5.6 km2 .
Several feeder canals have thereafter been constructed to increase the inflow into the reservoir, namely:
- Parc aux Cerf Feeder Canal constructed in 1971 to divert flows from the upper catchment area of River Citron and North East part of the local catchment representing an average annual contribution of the canal is 1.75 Mm3;
- the Pradier Canal constructed in 2002; and
- The Arnaud diversion dam constructed in 2014 representing an annual contribution of up to 10Mm3.
A hydrographic survey of the reservoir was carried out for the first time in the year 1996, and the gross storage capacity of the reservoir was determined as 25.89 Mm3.
2. La Nicoliere Reservoir
Purpose: Storage of Water Supply to potable use as well as for Industrial and Irrigation purposes
La Nicolière Reservoir, constructed in the year 1929 across Rivere du Rempart, near Grande Rosalie, is one of the main sources of water supply to the northern districts of Mauritius and part of Port Louis. The reservoir has a storage capacity of 5.26 Mm3as determined after a hydrographic survey carried out in 1996.
In December 2002, the Midlands Dam was constructed to serve as a buffer reservoir to La Nicolière Reservoir. Water from Midlands Dam is released to the Grand River South East which connects to the La Nicolière Feeder Canal (LNFC). The LNFC was built in 1929. It has a design capacity of 4.25 m3 /s and is 27 km long. Following the construction of the LNFC, the regulated annual yield of the Nicoliere Reservoir increased from 30Mm3 to 71 Mm3.
Salient features of La Nicolière Reservoir:
- Capacity: 5.26 Mm3
- Catchment Area: 1.08 km2
- Regulated Annual Yield: 71 Mm3Length of Dam: 819.08 m
- Spillway: Ungated ogee shaped concrete spillway
- Length of Spillway: 36.58 m (2 bays of 18.29 m each)
- Feeders: (i) River du Rempart(iii) Streams in local catchment Nicoliere Feeder Canal (iii) LNFC (iv) Local catchment of the La Nicoliere reservoir
3. Piton du Milieu
Purpose: Storage of water for potable use
Piton du Milieu Reservoir is situated in the district of Moka. It is fed mainly from River Vacoas and Bateau. It supplies water for domestic use to the eastern part of the island.
Salient features of Piton du Milieu Reservoir:
- Year of Construction: 1952
- Catchment Area: 6.30 km2
- Feeders: River Vacoas, River Bateau and Seasonal Streams
- RegulatedAnnual Yield: 8.3 Mm3
- Reservoir Capacity: 2.99 Mm3
- Dead Storage: 0.10 Mm3
- Full Reservoir Level: 438 m
- Type of Dam: Earth dam
- Maximum height of dam: 13.5 m (above foundation level)
- Length of Dam: 836.16 m
- Type of spillway: Ungated concrete crest wall With of Spillway: 363.12 m (2 spillways)
- Maximum height of dam: 13.5 m (above foundation level)
4. La Ferme Reservoir
Purpose: storage of water for irrigation purpose
La Ferme reservoir is located in the village of Bambous and the district of Black River. The reservoir is mainly fed through Trianon Grosses Roches Feeder Canal, La Fenetre Feeder Canals and local catchment. The construction of the reservoir started in 1914 and was completed in 1918.
Salient Features of La Ferme Reservoir:
- Year of Construction: 1914
- Catchment Area: 19.61 km2
- Annual Regulated Yield: 17 Mm3
- Reservoir Capacity: 11.52 Mm3
- Dead Storage: 0.2 Mm3
- Full Reservoir Level: 146.0 m
- Type of Dam: Earth cum masonry
- Length of Dam: 1526.54 m
- Type of spillway: Ungated masonry with concrete hearting Width of Spillway: 145.26 m
5. Midlands Dam
Purpose: storage of water for potable use and irrigation purposes.
The Midlands Dam site was chosen at the beginning of the twentieth century to create a reservoir. Works started in 1926 but were stopped in 1931. The dam was finally constructed in December 2002 on Grand River South East near Midlands Village for the purpose of serving as buffer storage to the Nicoliere reservoir with a view to meeting an increasing water demand in the northern part of the island.
Salient features of Midlands Dam:
- Year of Construction: December 2002
- Catchment Area: 17.2 km2
- Regulated Annual Yield: 41 Mm3
- Reservoir Capacity: 25.5 Mm3
- Full Reservoir Level: 395.00 m (amsl)
- Maximum Reservoir Level: 398.24 m (amsl)
- Dam Crest Level: 399.00 m (amsl)
- Type of Dam: Rockfill with upstream asphalt concrete surface sealing and cutoff wall Maximum height: 19.5 m above ground level 30.0 m above foundation level
- Length of Dam: 2449 m including spillway
- Type of Spillway: Ungated concrete ogee shaped spillway
- Height of Spillway above foundation: 30 m
6. Bagatelle Dam
Purpose: storage of water for potable use
The Bagatelle Dam was constructed to mobilize additional water resources and meet the increasing water demand of the district of Port Louis and the lower parts of the Plaines Wilhems district namely, Quatre Bornes, Rose Hill, Stanley, Beau Bassin and Coromandel. The construction of the dam started in 2012 and was completed in 2017. It is mainly fed from River Terre Rouge and River Cascade.
Salient features of Bagatelle Dam:
- Catchment Area: 25.85 km2
- Regulated Annual Yield: 25.3 Mm3
- Reservoir Capacity: 14.76 Mm3
- Normal Reservoir Level: 396.5 m
- Maximum Reservoir Level (PMF): 399 m
- Dam Crest Level: 400.00 m
- Type of Dam: Rockfilland Earthfill
- Height: 48 m above ground level (rockfill) and 27 m (earthfill) above foundation level
- Length of Dam: 2,550 m including spillway
- Type of Spillway: Morning Glory spillway
- Height of Spillway above foundation: 39.5 m
7. Mare Longue Reservoir
Purpose: Potable Water Supply as from October 2011
Mare Longue Reservoir was constructed in the year 1948. It receives water from three feeders, the main one being River des Aigrettes. As from October 2011, the storage water from Mare Longue is being diverted to La Marie treatment plant for domestic use.
Salient features of Mare Longue Reservoir:
- Year of Construction: 1948
- Catchment Area: 6.53 km2
- Regulated Annual Yield: 9.7Mm3
- Reservoir Capacity: 6.28 Mm3
- Full Reservoir Level: 576.91 (amsl)
- Type of Dam: Homogenous earthen embarkment
- Maximum height of dam: 13m
- Length of dam: 768m
- Type of Spillway: Ungated semi-circular concrete crest slab
- Width of Spillway: Circumference length- 152.4m
- Downstream channel - 11.35m
