DATA ON STORAGE RESERVOIRS

Presently, there are 11 man-made reservoirs in , out of which, Dagotière and Valetta reservoirs are privately owned. The locations and the salient features of the impounding reservoirs are given in Fig.5.1 and Table 5.1.

Nicoliere

Dagotiere La Ferme Valetta

Piton du Milieu Cascade Diamamouve

Midlands Tamarind Falls Mare aux Vacoas Eau Bleue

Mare Longue

Fig 5.1 Location of Impounding Reservoirs

RESERVOIRS CAPACITY MAXIMUM SURFACE PURPOSE (Mm3) AREA (Km2) Mare aux Vacoas 25.89 5.60 Domestic Midlands 25.50 2.98 Domestic, Irrigation Mare Longue 6.28 1.05 Hydropower, Irrigation La Ferme 11.52 2.28 Irrigation Piton du Milieu 2.99 0.76 Domestic Nicoliere 5.26 1.02 Domestic, Irrigation Tamarind Falls 2.30 1.68 Hydropower, Irrigation Eau Bleue 4.10 0.75 Hydropower Cascade 4.30 0.43 Hydropower Dagotiere 0.60 - Mill, Irrigation Valetta 2.00 - Mill, Irrigation

Table 5.1 Salient Features of Impounding Reservoirs

Fig. 5.2 to 5.6 show the daily and normal* storage variation, the monthly outflow, the schematic diagrams and feeder characteristics of the 5 important storage reservoirs. Fig 5.7 shows the daily storage variation and the schematic diagrams and feeder characteristics of the Midlands Dam. *period 1985 to 1995 MARE AUX VACOAS RESERVOIR FEEDERS SCHEMATIC DIAGRAM

Grand Ruisseau La Marie Conduit NATURAL STREAMS : Ruiseau Gros Cerf Release to La Gros Ruisseau Gros Ruisseau & others Ferme Res. Abandoned Rui. Gros Cerf Release to DESIGN LENGTH Tamarind Falls FEEDER CANAL RIVER CAPACITY Res. (Km) 3 MARE m /s Parc Aux Cerfs AUX Grand VACOAS Tatamaka 2.0 du Poste (South) 4.25 Ruisseau Parc-aux-Cerfs 3.2 Citron(South) 9.5 Des Anguilles & Tatamaka Spills into Riv. Pradier 4.1 tributaries 2.63 Feeder Pradier Du Poste Feeder Leckraz Canal

History Notes

In 1885, a masonry dam of one metre height 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. That was how the Mare aux Vacoas Dam has come into existence.

In 1892, the level of the dam was raised to an elevation of 558.54 m (amsl) and the capacity of the reservoir to 2.58 Mm3. In 1915, after a prolonged drought, the level of the dam was raised to an elevation of 560.06 m and the storage capacity to 5.27 Mm3.

In 1922, Tatamaka feeder canal was constructed to divert water from Riviere du Poste into the MAV reservoir. The carrying capacity of the canal is presently 4.25 m3/s and the annual contribution is of the order of 15 Mm3. In 1928, with the contribution of the Tatamaka Feeder Canal, the reservoir capacity was further raised to 16.15 Mm3, and finally in 1961 to 27.63 Mm3 with a water spread area of 5.6 km2. In 1971, Parc aux Cerf Feeder Canal was constructed to divert flow from the upper catchment area of River Citron and North East part of the local catchment. The average annual contribution of the canal is 1.75 Mm3.

In 2002, the Pradier Canal was constructed to increase the inflow into MAV reservoir. Its annual contribution is estimated as 4 to 5 Mm3. Contribution of local reservoir catchment is estimated as 11 Mm3/year. 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 determined as 25.89 Mm3.

The dam was comprehensively rehabilitated in the year 2000. Salient features of MAV Dam Location : Across marshy area, called Mare aux Vacoas in the of Plaines Wilhems and about 25 kms South of Year of Construction : In 1885, height and capacity increased in stages (in 1892, 1915, 1922, 1928, 1941) and finally in 1961 Catchment Area : 19.50 km2 Mean Annual Rainfall : 3330 mm Regulated Yield : 33 Mm3 year approx. Reservoir Capacity : 25.89 Mm3 after hydrographic survey of 1996 Maximum water spread area : 5.6 km2 Full Reservoir Level : 566.35 m amsl Feeder Canals : (i) Tatamaka canal (1922), capacity 4.25 m3/s (ii) Parc aux Cerfs Canal (1971), capacity 9.5 m3/s (iii) Pradier Canal (2002), capacity 2.63 m3/s Feeders in local catchment (iv) Ruisseau Gros Cerfs (v) Gros Ruisseau (vi) Grand Ruisseau Type of Dam : Cogliano and Tamarin dams are homogenous earthen embankments Mare Soulier Spillway and Second Spillway dams are of masonry

Maximum height of dam : - Cogliano : 10 m; - Tamarin : 11 m; - Mare Soulier : 6 m; and - Second Spillway dam : 3.5 m Length of Dam : 2948.50 m Width of Spillway : 1063.5 m Purpose : Potable Water Supply MARE AUX VACOAS RESERVOIR DAILY STORAGE VARIATION

YEAR : 2000 YEAR : 2001

30 30

25 25 ) ) 3 3 20 20

15 15

10 10 STORAGE (Mm STORAGE STORAGE (Mm STORAGE

5 5

0 0 JFMAMJJASOND JFMAMJJASOND

YEAR : 2002 YEAR : 2003

30 30

25 25 ) ) 3 3 20 20

15 15

10 10 STORAGE (Mm STORAGE STORAGE (Mm STORAGE

5 5

0 0 JFMAMJJASOND JFMAMJJASOND

YEAR : 2005 YEAR : 2004

30 30

25 25 ) 3 ) 3 20 20

15 15

10 10 STORAGE (Mm STORAGE STORAGE (Mm STORAGE 5 5

0 0 JFMAMJJASOND JFMAMJJASOND

YEAR NORMAL Outflow Fig. 5.2 Daily and Normal Storage Variation for Mare Aux Vacoas LA NICOLIERE RESERVOIR FEEDERS SCHEMATIC DIAGRAM Riv. Du Rempart (North) Nicoliere Feeder Canal NATURAL STREAMS : from G.R.S.E Catchment Riv. Du Rempart 11 Springs (North) DESIGN LENGTH Spills into A03 FEEDER CANALS/ RIVER DIVERSIONS RIVER CAPACITY E008c (Km) Riv. Du (m3/s) 11 No.Small Small Rempart Streams L.N.F.C 27G.R.S.E And R. Rempart 4.25

CHEVRETTES Div * 0.47 CHEVRETTES & GONTRAN 0.67 LA NICOLIERE VACOAS VACOAS Div * 0.47 1.68 NP5 Bassin FRANCOISE MercierBassin FRANCOISE Div * 4.1 0.42 CWA Filter Plant Mercier * diverted to La Nicolière Feeder Canal M1 Pipeline

History Notes

La Nicolière Reservoir , constructed in the year 1929 across River du Rempart, near Grande Rosalie, is one of the main sources of water supply to the northern of Mauritius and part of Port Louis. Its water is used for domestic, industrial and irrigation.

The reservoir has a storage capacity of 5.26 Mm3. The annual average regulated yield from the reservoir of the order of 30 Mm3 has increased by about 41 Mm3 after the contrustion of Midlands Dam in December 2002. It is fed by the La Nicolière Feeder Canal (LNFC), River du Rempart and eleven small streams. In December 2002, the Midlands Dam was constructed to serve as a buffer reservoir to La Nicolière Reservoir. Salient features of La Nicolière Reservoir

Location : On River du Rempart (North), in the district of Pamplemousses about 5 kms North East of Port Louis. Year of Construction : 1929 Catchment Area : 7.75 km2 Reservoir Capacity : 5.26 Mm3 after hydrographic survey of 1996 Maximum water spread area : 1.08 km2 Full Reservoir Level : 249.02 m (amsl) Type of Dam : Homogenous Earthen Embankment Maximum height of dam : 13.5 m above ground level Length of Dam : 819.08 m Type of spillway : Ungated ogee shaped concrete spillway Width of Spillway : 36.58 m (2 bays of 18.29 m each) Purpose : Potable, industrial and irrigation water supply Feeders : (i) La Nicolière Feeder Canal from GRSE, designed capacity of 4.25 m3/s and of length 27 km (ii) River du Rempart (iii) Streams in local catchment

Regulated Annual Yield : 30 Mm3 prior to Midlands dam and 71 Mm3 after Midlands Dam. LA NICOLIERE RESERVOIR DAILY STORAGE VARIATION

YEAR : 2000 YEAR : 2001

6 0.60 6 0.60

5 0.50 5 0.50 ) ) 3 3 ) 4 0.40 ) 4 0.40 3 3

3 0.30 3 0.30 Outflow(Mm

2 0.20 (Mm Outflow 2 0.20 STORAGE (Mm STORAGE (Mm

1 0.10 1 0.10

0 0.00 0 0.00 JFMAMJJASOND JFMAMJJASOND

YEAR : 2003 YEAR : 2002

6 0.60 6 0.60

5 0.50 5 0.50 ) 3 )

) 4 0.40 3 3

4 0.40 ) 3

3 0.30 3 0.30

2 0.20 (Mm Outflow STORAGE (Mm 2 0.20 Outflow(Mm STORAGE (Mm

1 0.10 1 0.10

0 0.00 0 0.00 JFMAMJJASOND JFMAMJJASOND

YEAR : 2004 YEAR : 2005 6 0.60 6 0.60

5 0.50 5 0.50 ) 3

4 0.40 ) 3 )

3 4 0.40 ) 3 3 0.30 3 0.30 Outflow (Mm Outflow

STORAGE (Mm 2 0.20 Outflow(Mm

STORAGE (Mm 2 0.20 1 0.10 1 0.10 0 0.00 JFMAMJJASOND 0 0.00 JFMAMJJASOND YEAR YEAR NORMALNORMAL Outflow

Fig. 5.3 Daily and Normal Storage Variation for La Nicoliere PITON DU MILIEU RESERVOIR

FEEDERS SCHEMATIC DIAGRAM

River Bateau Riv. Bateau Filter PLant PITON DU NATURAL STREAMS MILIEU

Spills into Riv. Vacoas River Vacoas Riv. Vacoas

History Notes

Piton du Milieu Reservoir is situated in the district of Moka. It is fed mainly from River Vacoas and Bateau. It serves water for domestic use in the East District Water Supply system.

Salient features of Piton du Milieu Reservoir

Location : Piton du Milieu in Moka district, about 20 kms South East of Port Louis

Year of Construction : 1952 Catchment Area : 6.30 km2 Mean Annual Rainfall : 3529 mm Feeders : River Vacoas River Bateau Seasonal Streams Regulated Annual Yield : 8.3 Mm3 Reservoir Capacity : 2.99 Mm3 after hydrographic survey of 1996 Dead Storage : 0.10 Mm3 Full Reservoir Level : 438 m (amsl) 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) Purpose : Domestic Water Supply PITON DU MILIEU RESERVOIR DAILY STORAGE VARIATION

YEAR : 2000 YEAR : 2001

4.0 0.100 4.0 0.100

3.0 0.075 3.0 0.075 ) ) 3 3 ) ) 3 3

2.0 0.050 2.0 0.050 Outflow (Mm Outflow (Mm STORAGE (Mm STORAGE 1.0 0.025 (Mm STORAGE 1.0 0.025

0.0 0.000 0.0 0.000 JFMAMJJASOND JFMAMJJASOND

YEAR : 2002 YEAR : 2003

4.0 0.100 4.0 0.100

3.0 0.075 3.0 0.075 ) ) 3 3 ) ) 3 3

2.0 0.050 2.0 0.050 Outflow Mm Outflow (Mm STORAGE (Mm STORAGE STORAGE (Mm STORAGE 1.0 0.025 1.0 0.025

0.0 0.000 0.0 0.000 JFMAMJJASOND JFMAMJJASOND

YEAR : 2004 YEAR : 2005

4.0 0.100 4.0 0.100

3.0 0.075 3.0 0.075 ) ) 3 ) 3 3 ) 3

2.0 0.050 2.0 0.050 Outflow (Mm Outflow Mm STORAGE (Mm STORAGE STORAGE (Mm STORAGE 1.0 0.025 1.0 0.025

0.0 0.000 0.0 0.000 JFMAMJJASOND JFMAMJJASOND

YEAR YEAR NORMAL NORMAL Outflow Fig. 5.4 Daily and Normal Storage Variation for Piton du Milieu LA FERME RESERVOIR

FEEDERS SCHEMATIC DIAGRAM

NATURAL STREAMS : River Belle Isle Trianon Grosses TrianonRoches FeederGrosses Roches Feeder DESIGN LENGTH FEEDERS CANALS RIVER CAPACITY (Km) m3/s La Ferme Outlet W018b U LA FERME 0

Trianon Grosses Roches 8.0 Plaines Wilhems 2.40 Spill from Pierrefonds Spills into Riv. Belle Tunnel Isle T008b

La Fenetre 4.5 Rempart (west) & Papayes 2.83 la Fenetre Feeder

History Notes

Constructed in 1914, with the sole purpose to supply water for irrigation to the western coast of the island. It is located in the district of Black River near Bambous village and about 15 kms South West of Port Louis.

Salient features of La Ferme Reservoir

Location : Near Bambous village in the Black River district about 15 kms South West of Port Louis. Year of Construction : 1914

Catchment Area : 19.61 km2

Mean Annual Rainfall : 1380 mm

Feeders : (i) Trianon Grosses Roches Feeder Canal. (ii) La Fenêtre Feeder Canal

Annual Regulated Yield : 17 Mm3 Reservoir Capacity : 11.52 Mm3 after hydrographic survey of 1996 Dead Storage : 0.2 Mm3 Full Reservoir Level : 146.0 m (amsl) Type of Dam : Earth cum masonry Maximum height of dam : (i) above ground level - Earth dam = 8 m Masonry dam = 8.62 m (ii) above foundation level - Earth dam = 10 m Masonry dam = 12.1 m

Length of Dam : 1526.54 m Type of spillway : Ungated masonry with concrete hearting Width of Spillway : 145.26 m Purpose : Irrigation LA FERME RESERVOIR DAILY STORAGE VARIATION

YEAR : 2000 YEAR : 2001

12 0.30 12 0.30

10 0.25 10 0.25 ) ) 3 3 ) ) 3 8 0.20 8 0.20 3

6 0.15 6 0.15

4 0.10 Outflow (Mm 4 0.10 Outflow (Mm STORAGE (Mm STORAGE STORAGE (Mm STORAGE

2 0.05 2 0.05

0 0.00 0 0.00 JFMAMJJASOND JFMAMJJASOND

YEAR : 2002 YEAR : 2003

12 0.300 12 0.30

10 0.250 10 0.25 ) ) 3 3 ) )

8 0.200 8 0.20 3 3

6 0.150 6 0.15 Outflow(Mm 4 0.100 4 0.10 Outflow (Mm STORAGE (Mm STORAGE STORAGE (Mm STORAGE

2 0.050 2 0.05

0 0.000 0 0.00 JFMAMJJASOND JFMAMJJASOND

YEAR : 2004 YEAR : 2005

12 0.30 14 0.30

10 0.25 12 0.25 ) ) 3 3 10 ) ) 3 8 0.20 3 0.20 8 6 0.15 0.15 6 0.10

4 0.10 Outflow (Mm Outflow (Mm STORAGE (Mm STORAGE STORAGE (Mm STORAGE 4

2 0.05 2 0.05

0 0.00 0 0.00 JFMAMJJASOND JFMAMJJASOND

YEAR YEAR NORMAL NORMAL Outflow Fig. 5.5 Daily and Normal Storage Variation for La Ferme MARE LONGUE RESERVOIR FEEDERS SCHEMATIC DIAGRAM

Spills into Riv. Riv. Des Aigrettes Riv.Des Aigrettes : Bambous Release to Tamarind Falls Reservoir

FEEDER No. 1 MARE LONGUE Riv. Des NATURAL STREAMS: Aigrettes Feeder No.1 FEEDER No. 2

Feeder No.2 FEEDER No. 3 Feeder No.3

History Notes

Mare Longue Reservoir was constructed in the year 1948. Located in the district of Plaine Wilhems, about 30 kms South West of Port Louis. It receives water from three feeders, the main one being River des Aigrettes.

The storage water is used for hydro power generation at Tamarind and Magenta power stations and thereafter for irrigation.

Salient features of Mare Longue Reservoir

Location : Mare Longue, in the district of Plaines Wilhems about 30 kms South West of Port Louis Year of Construction : 1948

2 Catchment Area : 6.53 km

Mean Annual Rainfall : 2980 mm

3 Annual Regulated Yield : 9.7 Mm

3 Reservoir Capacity : 6.28 Mm

Full Reservoir Level : 576.91 m amsl

Feeders : River des Aigrettes feeder1; feeder 2; feeder 3

Type of Dam : Homogeneous earthen embankment

Maximum height of dam : 13 m

Length of Dam : 768 m

Type of spillway : Ungated semi circular concrete crest slab

Width of Spillway : Circumferential length - 152.4 m Downstream channel - 11.35 m

Purpose : Hydropower generation at Tamarind and Magenta power stations and thereafter for irrigation MARE LONGUE RESERVOIR DAILY STORAGE VARIATION

YEAR : 2000 YEAR : 2001

7 0.25 7 0.25

6 6 0.20 0.20 ) )

3 5 3

5 ) ) 3 3 0.15 0.15 4 4

3 3 0.10 0.10 Outflow (Mm Outflow (Mm STORAGE (Mm STORAGE STORAGE (Mm STORAGE 2 2 0.05 0.05 1 1

0 0.00 0 0.00 JFMAMJJASOND JFMAMJJASOND

YEAR : 2002 YEAR : 2003

7 0.25 7 0.25

6 6 0.20 0.20 ) 5 ) 5 3 3 ) ) 3 3 0.15 0.15 4 4

3 3 0.10 0.10 Outflow (Mm Outflow (Mm STORAGE (Mm STORAGE 2 (Mm STORAGE 2 0.05 0.05 1 1

0 0.00 0 0.00 JFMAMJJASOND JFMAMJJASOND

YEAR : 2005 YEAR : 2004 7 0.25 7 0.25

6 6 0.20 0.20 ) )

3 5 ) 3 5 ) 3 3 0.15 0.15 4 4

3 3 0.10 0.10 Outflow (Mm Outflow (Mm

STORAGE (Mm STORAGE 2 STORAGE (Mm STORAGE 2 0.05 0.05 1 1

0 0.00 0 0.00 JFMAMJJASOND JFMAMJJASOND

YEAR YEAR NORMAL NORMAL Outflow Fig. 5.6 Daily and Normal Storage Variation for Mare Longue MIDLANDS RESERVOIR

FEEDERS SCHEMATIC DIAGRAM

Release and Spills GRSE into G.R.S.E Midlands G.R.S.E Reservoir NATURAL STREAMS Twinam

Riv. Twinam

History Notes

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 due to scarcity of funds.

Due to an increase in water requirement, the Government commissioned a study in 1991 with a view to finding an optimal solution to meet the water demand of the northern districts of Mauritius. The dam was finally constructed in December 2002 on Grand River South East near Midlands Village.

Salient features of Midlands Dam

Location : Midlands in the district of Moka, on Grand River South East Year of Construction : December 2002 2 Catchment Area : 17.2 km Mean Annual Rainfall : 4000 mm Feeders : GRSE, River Twinam 3 Regulated Annual Yield : 41 Mm 3 Reservoir Capacity : 25.5 Mm 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 Purpose : Potable and Irrigation Water Supply MIDLANDS RESERVOIR DAILY STORAGE VARIATION

YEAR : 2003

30 0.5

25 0.4

) 20 3 ) 0.3 3

15

0.2 Outflow (Mm

STORAGE (Mm 10

0.1 5

0 0 JFMAMJJASOND

YEAR : 2004

30 0.5

25 0.4

) 20 3 ) 0.3 3

15

0.2 Outflow (Mm

STORAGE (Mm STORAGE 10

0.1 5

0 0 JFMAMJJASOND

YEAR : 2005

30 0.5

25 0.4 )

3 20 ) 0.3 3

15

0.2 Outflow (Mm

STORAGE (Mm STORAGE 10

0.1 5

0 0 JFMAMJJASOND

Fig. 5.7 Daily Storage Variation for Midlands