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Water Supply And Sewerage System
Alexandre Yersin
sadfasHome > Da Lat City > Water Supply And Sewerage System
Water Supply And Sewerage System 

1. Water Supply System

Water supply system of Da Lat was built in the early period of city formation.

In the past, the city's water supply was resolved by using a portion of the Cam Ly Stream, through Than Tho Lake and Xuan Huong Lake. After 1975, water supply was supplemented with Chien Thang Lake and Dan Kia Lake. Currently, Da Lat city is supplied by three water plants in Than Tho Lake, Xuan Huong Lake and Golden Stream, with a total maximum capacity of 31,000m3.

1.1 Establishment:

The first water supply plant came into operation in 1920. It only had small a capacity to ensure clean water supply for some buildings and sparse citizens around the Great Lake. This plant was dismantled and there is no specific document about it.

1.1.1 The period before 1945:

In 1937, Than Tho Lake was built in the upper Cam Ly Stream. This is not only a scenic lake but also a reservoir to ensure water supply for Da Lat city. In 1937, the Public Works Department established a plan to develop the water supply and distribution systems. Than Tho Lake water plant, built in 1938, has the largest capacity of 4,300 m3 per day. This water plant treats water from Than Tho Lake. It deposits sediment, purifies, sterilizes and store water in a 300 m3 tank. Then water is pumped to three connected tanks with a total capacity of 1,875 m3; one tank placed in the Governors Palace, another one near the Mayor Office (Resimaire 1) and the last one in Pasteur Institute (Calypso).

Water plant in Than Tho Lake

From these tanks, water is supplied to high areas of the city. The highest area is provided by a booster pumping station. The next phase was completed in 1943. It included the construction of a main tank (Resimaire 2) and two secondary tanks (West lake 1, 2), along with the development of sewage networks.

The amount of water consumption in 1938 was 235,797 m3; in 1939, it was 191,819 m3.

1.1.2 The period 1945 to 1975

Because fresh water demand increases along with the development of the city, in 1949, Xuan Huong Lake water plant was built with a capacity of 8,400 m3 per day. This plant treats water from Xuan Huong artificial lake with a 200 m3 water tank. Then water is pumped into the first position - the three connected tanks (Resimaire) in the Mayor Office - with a total capacity of 1600m3 and the second position – the two connected tanks (Calypso) with a total capacity of 575m3. From these tanks, water is provided to the lower parts of city’s high area.

The above water supply system provides water for 10km2 residential areas compared with the whole city which is 69 km2 in area. Supplied area between altitudes of 1465 to 1560 m compared with sea level is divided into a low area and two high areas.

Total amount of fresh water produced in 1973 was 2,226,609 m3 and 847,080 m3 were sold. Only 38% of the amount of produced water was sold; the rest was for the plant itself and the water lost due to leakage through the pipeline distribution network. If losses were eliminated, the plant could have provided clean water for 60% of the city’s population. Among the amount of water sold in 1973, 70% was water for household, 8% was for trading and tourism, administration and public use was 22%. Water sold to each person was approximately 35m3 each year.

In 1974, the total capacity of two water plants in Xuan Huong Lake and Than Tho Lake was not enough to supply for the whole city of Da Lat. The number of households having water meters was 3,085 with a total population of 27,000 people. The remaining population used water from springs, shallow wells or rainwater tanks. Most pipeline distribution networks installed from 1938 to 1949 were corroded and sedimentary; water pressure in some high areas became too small during peak hours.

1.1.3 The period after 1975:

Because the raw water source and water supply systems in Than Tho Lake and Xuan Huong Lake were no longer ensured both in terms of quantity and quality, the development of a new water supply system became necessary for the development of Da Lat.

The raw water supply system from Chien Thang Lake

Located in north of Da Lat city, Chien Thang Lake was built and completed in 1981. The lake is 6.5 km2 in area; water surface area is 43ha and water capacity is 2.15 million m3. Chien Thang Lake provides 3,120 m3 of water per day for the Xuan Huong Lake water plant by a pumping station with two electric pumps (each pumps 265m3 per hour - 15m water column) and a 4.8 km long, Ø300 wide cast-iron transmission pipes.

The Dan Kia water supply system.

Dan Kia water supply project was researched and prepared to invest in 1974. After the reunification in 1975, the project continued under the Agreement dated 19-11-1975 between the Danish Government and the Vietnamese Government. The total project investment was 12.17 million dollars, of which the loan from the Danish government was USD 6.25 million and the Vietnamese Government’s capital was 5.92 million.

The Dan Kia water supply was began construction in 1980 and completed in 1984. The plant treats raw water from Dan Kia Lake, then water is pumped into storage tanks in Tung Lam hill with a capacity of 5,000 m3 and from there to the tanks in the city. From these tanks, water is provided too many areas of the city.

Loan from the Danish government was invested in designing, supplying mechanical equipment, electrical equipment, transmission pipes and supervision. The capital of Vietnamese Government was invested in the construction category; installation of mechanical equipment, electrical equipment and pipes.

Equipped with modern technology and equipments, the Dan Kia water supply system has improved the water supply to the population of 179,000 in Da Lat city with a maximum capacity of 25,000 m3 per day. The project also prepared reserve land for expanding the system to have a maximum capacity of 45,000 m3 per day for the future population of 250,000 people.

The Dan Kia water supply system (1986)

Meanwhile, water plants in Than Tho Lake and Xuan Huong Lake were used for backup because equipments in these two facilities were so outdated.

Renovating and upgrading the supply system in 1997 – 1999

In the years 1997-1999, with the help from the Danish Government, the second phase of water supply projects were executed. The main goal was to renovate and expand the water distribution network, upgrade water plant equipments, increase the total water production capacity of two water plants in Golden Stream and Xuan Huong Lake, ensure water supply for the city.

The project includes:

- Renovating and upgrading pumping station I in Chien Thang lake to provide 6,360 m3 of raw water every day for the Xuan Huong water plant.

- Improving some categories of Golden Stream water plant, including: replacement of two level II pumps; building one more mud tank; dredging raw water pumping station and building embankment.

- Renovating and upgrading Xuan Huong Lake water plant’s capacity into 6,000 m3 per day.

- Installing Scada water-level control system of intermediate tanks.

- Renovating, installing 73 new categories of pipeline network with a total length of 60km with diameters of Ø100, Ø150, Ø200, Ø300, Ø500.

Pipeline distribution network was built and renovated several times. In 2000, there were 12km of pipeline delivering raw water, nearly 100 km replaced distribution pipeline, a system of 11 water tanks to regulate pressure and flow. The water supply network now can cover most of the city. The service quality is pretty good; water leak ratio is below 20%; water quality meets the standards in the region. The water supply system is one of the best in Vietnam nowadays.

Actual state of water supply

The number of customers in 2007 was 35,349, approximately 89% of the population, increasing 11.5 times compared with that in 1974.

As time went on, the production capacity, and the number of customers increased together with the population and socio-economic development of the city.

Production in 2007 was the commercial 9,821,013 m3, increasing 11.6 times compared with 1973 (847,080 m3).

Total production in 2007 was 12,110,440 m3, in which Xuan Huong Lake water plant: 1,870,157 m3, Than Tho Lake water plant: 1,016,434m3. Golden Stream water plant: 9,223,849 m3.

Water price in 2007 was 2,500 – 5,000đ per m3 for daily life uses, 4,000đ per m3 for administration, 5,000đ per m3 for manufacturing and 7,000đ per m3 for business and services.

1.2 The water supply plants:

1.2.1 Than Tho Lake water plant:

Than Tho Lake water plant, also known as the old water plant, built in 1938, has the maximum capacity of 8,400m3 per day. The plant includes one raw water collecting station, one pumping and chemical injecting station, one precipitation tank, two rectangular sedimentation tanks, eight sand filters and one fresh water tank.

The plant previously collected raw water from Than Tho Lake by an Ø300 cast-iron pipeline. Since 1981, the plant has used water transported from Chien Thang Lake.

1.2.2 Xuan Huong Lake Water Treatment Plant:

Built in 1949, Xuan Huong Lake water plant is near the city center. The plant collects raw water from Xuan Huong Lake by Ø300 cast-iron pipes supported by concrete bridge; it is no longer used nowadays. Since 1981, raw water is transported from Chien Thang Lake.

The plant includes raw water collecting station, one pumping and chemical injecting station, two sedimentation tanks, three sand filters and one fresh water tank.

The plant’s capacity was upgraded in phase II of the project in 1997 into 6,000 m3 per day.

1.2.3 The water supply plant in Dan Kia Lake

Dan Kia Lake

Dan Kia Lake and Golden Stream were built in 1945 on Da Dong river to run Ankroеt hydroelectric plant, having an area of 141 km2 with capacity of 15.2 million m3.

Dan Kia Lake

Dan Kia water supply plant includes:

- Raw water pumping station with five units in Dan Kia Lake, a substation and a raw water transmission pipeline between the raw water pumping station to the treatment plant;

- Water treatment plant with a capacity 25,000 m3 per day, located near the lakeshore, including: mixing and distributing tank, three accelerating sedimentation tanks, six ordinary filters (open filter) with lean-to, a 3,000 m3 water tank, pumping station with six units and a substation;

- The Ø600 wide, 7,200 m long pipeline transports water from pumping station to Tung Lam water tank;

- Clean water tank with a capacity of 5,000 m3 located in Tung Lam hill (Pin Thousand) with the height of 1560 m;

- Transmission pipeline from the Tung Lam tank to Da Lat city includes 2.8 km of Ø600 steel pipes. It’s then divided into two branches: one branch consists of 5.4 km of Ø500 steel pipes divided into two Ø300 wide 6.5 km long branches (supply water to Hung Vuong, Gougal and Dinh 1 tanks); and the second branch consists of 1 km of Ø500 steel pipes and 2 km of Ø300 pipes (supply water to Resimaire and Calypso tanks).

1.3 Distribution Network:

The old distribution network has about 8,000 m cast-iron pipe installed in 1938, 24,500 m pipes installed from 1948 to 1949, 5,000m pipes installed in 1967 and 18,000m cast-iron pipes installed from 1974 to 1975. It uses Ø40, 60, 80, 100, 150 and 200 mm pipes.

Now, the pipeline transmission network has 33,000 m of Ø500 – 600 transshipping pipe and 160.000m of Ø100 - 300 delivering pipe. The map of Da Lat water supply system belongs to the first diagram, supplying water in accordance with catchment area.

CATCHMENT AREA

Catchment area

Supply tank

W (m3)

Terrain essence (m)

Tung Lam

Tung Lam

5 000

1561.3

Cao Thang

Cao Thang

1 000

1536

Calypso

Calypso

1 000

1536.3

Resimaire

Resimaire

1 730

1531.6

Dinh I

Dinh I

500

1545

Dinh II

Dinh II

500

1536.3

West Lake

West Lake

2 700

1550.9

Trai Mat

Trai Mat

500

1610

Total of regulated capacity (m3)

13 000

The map of Da Lat water supply network is a type of mixed diagram network; pipes in the center, in the main streets joint into closed circles. Lopped pipes are used to supply water to residential areas. The distance between the two farthest points of the network is from Cam Ly to Phat Chi (Xuan Truong), approximately 35 km. The total length of the pipeline level I and level II network is approximately 200,000 m.

2. Sewerage System:

2.1 Streams:

Among the low hills in the center and the higher peaks around Da Lat are the upper flows of of the Da Nhim, the Da Dong, the Cam Ly river. These rivers are major tributaries flowing into the Dong Nai River. Water sources of rivers are many in the rainy season but dry in the dry season.

To the north, the stream flows in the southeast - northwest and pours into Golden Streams such as Phuoc Thanh stream, Phu Da stream. To the east, there are small streams pouring into the Da Nhim River, the upstream of Don Duong Lake. The southern streams such as Datanla stream and Prenn stream flow in the direction of northeast - southwest and pour into Da Tam stream. Flowing through the city center, Cam Ly stream is 20 km in length in Da Lat with the area of 50 km2. The network of small streams is thick with an average rate of 1.2 km in each km2.

Cam Ly stream originates near a high mountain in Lac Duong district, flows through some artificial lakes: Than Tho Lake. Me Linh Lake, Xuan Huong Lake, then pour into Cam Ly waterfall.

During the rainy season, the average flow reaches the maximum (about 2 to 2.5 m3 per second) from September to October. In the dry season, the streams are almost exhausted; the average water flow from February to April is 80-90 liters per second. In March, it reaches the minimum with only 40 liters per second.

The planning and construction of the city was carried out mostly along the banks of streams, following the idea of forming the functional areas of the city based on a series of artificial lakes.

2.2 Lakes:

Lakes in Da Lat are mostly artificial lakes. 16 large and small lakes are scattered around the city. Some lakes are filled and become vegetable fields such as Van Kiep Lake, Me Linh Lake. The big lakes in Da Lat become landscapes to regulate irrigation water such as Da Thien Lake, Than Tho Lake, Tuyen Lam Lake, Xuan Huong Lake. Golden Stream Lake is used to produce hydroelectric power. Before 1984, raw water sources to produce fresh water for Da Lat city was from Xuan Huong Lake, Chien Thang Lake, Than Tho Lake and then the water is mostly from Dan Kia Lake. Dan Kia Lake and Golden Stream (Ankroеt) in the northwest of Da Lat have great influence on daily life of the citizens.

LAKE’S AREA AND CAPACITY


Lake’s name

Location

Catchment area (km2)

Water surface area (ha)

Lake’s capacity
(millions m3)

Tuyen Tam Lake

ward 4

32.8

296.0

10.6

Xuan Huong Lake

City center

26.0

33.0

0.7

Chien Thang Lake

Army Academy

6.5

43.0

2.15

Lake 3 Da Thien

Ward 8

4.500

28.000

0.485

Than Tho Lake

Ward 12

5.340

5.910

0.131

26/3 Tu Phuoc

Ward 11

0.650

0.800

0.096

Lake 6 Da Loc – Loc Quy

Xuan Tho

1.200

0.700

0.056

Lake 8 Da Loc – Loc Quy

Xuan Tho

1.600

0.500

0.082

Lake 1 Dat Lang

Xuan Truong

0.500

0.800

0.128

Lake 5 Cam Ly - Doc Troi

Ward 5

1.100

4.000

0.250

Ta Nung

Ta Nung

2.570

0.350

0.130

Van Kiep

Ward 7

2.000

3.000

Dry up

Van Thanh 2

Ward 5

2.000

1.440

0.922

Golden Streams

Lac Duong

145

1.00

Dan Kia Lake

Lac Duong

141

15.2

Than Tho Lake

Than Tho Lake is the first lake from the upstream of Cam Ly stream and a well-known landscape of Da Lat. Lake is 5.31 km2 in area, the surface area is 5.91 ha, and the largest capacity of the lake is 350,000 m3. Lake’s capacity declines steadily due to the deposition of eroded mud in the basin. Now, it only has about 130,000 m3.

Ho Xuan Huong

Xuan Huong Lake is the artificial lake in the center of Da Lat city. The lake formed in 1919 after finishing the first dam (from today Thuy Ta house to Dinh Tien Hoang crossroads). It was expanded in 1923 after finishing the second dam. In 1932, Typhoons destroyed the two dams. From 1934 to 1935, a large dam (Ong Dao bridge) was built below the two destroyed dams and formed the Xuan Huong Lake as today.

Xuan Huong Lake is recognized as a historical cultural relic. Together with the Cu Hill, it forms a park and becomes the nucleus of the city center, where the facilities for tourism, malls, restaurants, sport centers and other public works are placed.

Catchment area of Cam Ly stream up to Ong Dao bridge is 24.5 km2; lake’s capacity was 1.2 million m3 in 1935; the surface area is 43ha, stream length is 8 km to the dam. Average flow is 0.7 m3 per second; the average total amount of water every year is 22.1 million m3.

The plant includes water tanks, flood discharging siphons, earth dams and bridges. Reinforced building’s height is 1478.5 m; normal building’s height is 1478.0 m.

Xuan Huong Lake’s sedimentation rate is quite fast and severe. In 1974, the lake capacity was 0.9 million m3. In 1997, its capacity is only 0.72 million m3 and surface area was 32 ha.

Xuan Huong Lake’s renovation.

Xuan Huong Lake project has undergone many times of rebuilding. In 1947, repairing sand outlet; in 1953, repairing cracks in concrete structures; in 1979, reinforcing energy dissipation ground and 3 parts in the siphons No. 5, 6, 7; in 1984, dredging sediment, reinforcing the eroded siphon base and ferroconcrete strengthening the siphons; in 1990, building energy dissipation ground with ferroconcrete.

The most large-scale repair was from 1998 to 1999. It includes four major categories: repairing and reinforcing flood discharging siphons in conjunction with traffic bridge; dredging the lake, restoring its surface water and initial capacity; embellishing lakeshore to prevent crash down, building small parks and sightseeing bridges; building four to sedimentation and water pollution preventing lakes.

2.3 The drainage system

There’re many areas in Da Lat with the drainage system used for rainwater and wastewater, each system covers smaller catchment areas. Water in culverts and ditches normally flows along roads and pours into small lakes and then into the main streams.

In 1974, the drainage system included 1,095m of brick ditches, 1,079m of Ø800 concrete culverts, 383m of Ø1000 concrete culverts and 350m of Ø150 concrete culverts.

In 2000, Da Lat had a total of 41,700m ditches and culverts of all kinds, including: 15,646m of sealed ditches with knitted lids (brick, stone), 4,628m of open ditches (brick, stone), 20,730 earth ditches, 3,200m of reinforced concrete culverts (Ø800 and 1,000 mm). The sewage system is only built on approximately 60% of total length of streets, wastewater and rainwater flow out in the same sewer - culverts – trench system. Along with the investment in developing urban streets, the sewage system also gradually becomes more and more complete and permanent.

In the early period of city formation, wastewater sewerage system was not considered an urgent matter because the construction of this system was very difficult in the conditions of uneven hilly terrain, in a vast and divided area while the population density was very low. The most popular wastewater treatment method was septic tanks. However, when the city started to develop and the population was growing, untreated wastewater created many negative impacts on the environment, polluted the water and reduced the beauty of the landscape.

3. Concentrated Wastewater Treatment System:

Concentrated wastewater treatment system is a category of Sanitation Project of Da Lat city, executed by the agreement signed in 2000 between the Danish Government and Vietnamese Government. The total initial investment was about 321 billion; capital grant from the Danish Government was 257 billion and the Vietnamese Government of capital was 64 billion.

Concentrated wastewater treatment system began construction in March 2003. The key constructions were completed and started operating in December 2005. At the end of 2007, the work of connecting household wastewater to the drainage system was completed.

The scope of wastewater treatment system in the city center includes Ward 1, Ward 2 and part of Ward 5, 6 and 8. This area has a high population density and large wastewater pouring into Phan Dinh Phung Stream, Xuan Huong Lake and Cam Ly Stream.

The boundaries of this area are as follows: the west facing Mai Hac De - Ngo Quyen – Bach Dang road; the north bordering the extended Hai Ba Trung - La Phu Tu Son - Nguyen Cong Tru roads; the east facing Dinh Tien Hoang road and the south bordering Cam Ly Stream, Xuan Huong Lake to Ma Trang Son Bridge. The wastewater from about 7,400 households in this area is separated and flows into the sewage systems. Then it flows to the main pumping station and from there, wastewater is pumped to treatment plants by the pressure pipes before pouring into Cam Ly downstream.

About 43km of wastewater sewerage system was built and separated with the existing sewer system. The main pumping station with a capacity of 500 m3 per hour was built near the end of Nguyen Thi Dinh road. Pressure pipelines transports water from the main pumping station to wasterwater treatment plant is 2.2 km in length.

Concentrated wastewater treatment plant.

Having a capacity of 7,100m3 per day, the concentrated wastewater treatment plant was built on the area of 7.5 ha in the Cam Ly downstream - at the end of Kim Dong Street. From here, wastewater is treated with mechanical biological treatment technology before being discharged into Cam Ly downstream.

The plant consists of the following categories: garbage barriers with 60mm coarse net and 4 mm silky net, automatic garbage weeping and squeezing machine; sand depositing tank with three compartments with the same size of 19.4 m x 3.5 m x 1.5 m; two two-shells sedimentation tanks with the size of each tank: 25.8 m x 7.4 m x 11.05 m; two biological trickling filter tanks which is 22m in diameter, 5.95 m in height; two secondary sedimentation tanks which is 31m in diameter, 2.5 m in height; circulator pumping station with the size of 9.8 m x 4.5 m x 5.3 m; three biological and disinfectant tanks in a 2.5 ha area; two mud drying fields with lean-to in an area of 4.000m2, including 20 squares having the size: 34.2 m x 6.4 m each; technical pipes with Ø150 to Ø700 in diameter; backup generator with a capacity of 60 kVA and 160 kVA substation; operating rooms; offices and workshops.

4. Renovating Phan Dinh Phung Stream And Cam Ly Stream:

In the framework of Sanitation Project, Phan Dinh Phung Stream and Cam Ly Stream are embellished. The project also prevents erosion of the stream shores and improves the water flow to let out the flood, prevent flood in some areas along the streams.

4.1 Phan Dinh Phung Stream

The construction was completed in August 2005. The scope of construction is from Son La Phu Tu Bridge to Cam Ly steam junction, with a length of 1,850 m.

Stream is with trapezoid cross-section with height H = 2.3 m, top width Bm = 6 - 7.5 m, bottom width Bd = 2.4 - 4.4 m. Stream is reinforced by precast concrete structures with split stones. Roads are built on both stream shores; the east has 3.5 m wide roads and the west has 2 m wide roads.

4.2 Cam Ly Stream

This construction was built in 2003. The scope of construction is from Ong Dao Bridge to Cam Ly waterfall, with a length of 2,150 m. The construction consists of two parts:

- Part 1: From the Xuan Huong lake to Phan Dinh Phung stream with a length of 1,090 m. Stream is expanded with a 5 x 1m rectangular cross-section and trapezoidal cross-section with height H = 2.5 m, top width Bm = 15 m; bottom width BD = 10 m.

- Part 2: From Phan Dinh Phung stream to Cam Ly waterfall with a length of 1,060 m. Stream is expanded with 5 x 1m rectangular cross-section and trapezoidal cross-section with height H = 2.5 m, top width Bm = 25m; bottom width BD = 20 m.

Stream bed is reinforced by precast concrete structures with split stones. Both stream shores have protective corridors; the width on each side is 3 m. Along the stream, small bridges are built for citizens to pass.

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