Flood Control Drainage and Irrigation Projects
Flood Control Drainage and Irrigation Projects Bangladesh faces flooding at least in 20% of its area in a normal year because of the low-lying topography. In extreme cases, as in 1998, the flood-affected area could be as high as 67%. Flood control and drainage is used as a means to reduce the depth of flooding or eliminate it through 'controlled flooding', so as to provide greater security for crop production.
In 1964, a master plan was prepared envisaging 58 flood protection and drainage projects covering about 5.8 million-hectares of land. Three types of polders were envisaged: polders with gravity drainage, tidal sluice drainage and pump drainage. In 1993, the total area of wetland was 3.14 million ha of which 1.55 million ha were cultivated and 1.38 million ha drained through surface drains. In addition, the irrigated areas equipped for drainage represent about 1.17 million ha. The flood-protected areas in 1999 were estimated at 4.62 million ha. To reduce the harmful effect of floods and to use the surplus water for irrigation, the bangladesh water development board constructed a number of embankments, barrages and canals. Some major flood control drainage and irrigation projects are described below.
The Ganges-Kobadak Irrigation Project (G-K Project) Located in the districts of Kushtia, Chuadanga, Jhenaidaha and Magura. It is a flood control drainage and irrigation project covering a gross area of 197,486 ha (Phase-I: 84,986 ha and Phase-II: 112,500 ha). The project was started in 1954 and put into partial operation in 1962 and finally completed in 1981 at a cost of Tk 828 million. A pumping station is located at Bheramara for lifting water from the ganges. Three main pumps, having a total capacity of 110.4 cumec and twelve subsidiary pumps having a total capacity of 42 cumec are used. Water is carried to 142,000 ha of paddyfields through an intricate gravity canal system consisting of 193 km of main canals, 467 km of secondary canals, 631 km of tertiary canals and 3,500 field outlets.
Dhaka-Narayanganj-Demra (DND) Project located between the cities of Dhaka and Narayanganj and bounded by the buriganga and the shitalakshya river. It was started in 1964 and completed in 1968 at a cost of Tk 22.9 million. A dual purpose pumping station is located at Shimrail having a total capacity of 4.2 cumec. The project provides flood control for 4,860 ha, irrigation for 6,070 ha, pumped drainage for 4,860 ha and gravity drainage for 2,470 ha of land. But as the project is located close to Dhaka city, urbanisation is taking place rapidly. So the initial objective of boosting agricultural production has been frustrated.
Karnafuli Multipurpose Project located in the district of Rangamati on the river karnafuli. It is a multipurpose project with the aim of generating hydropower and providing flood control facilities. The principal features of the project area are a main dam, a gated spillway, outlet works, cargo transfer systems and hydropower plants. The main dam is a rolled earthfill structure with a total volume of 3,440,500 cubic m. The length of the dam is 610m at its crest and its maximum height above the streambed is 43m. The storage capacity of the reservoir behind the dam is 5,336 million cubic meters of water. The maximum discharge capacity of the spillway is 16,000 cumec and is regulated by 16 Tainter gates (each 11.51m high and 12.2m wide). At the beginning, the power generation capacity was 80 MW but this has since been raised to 230 MW. Originally, the cargo transfer system consisted of three elevated trolleys operated on a looped monorail tract. Another cargo transfer system was added later. The flood peaks in the Karnafuli could be reduced by 30% by reservoir operation. This reservoir is also important for fishery and other aquatic flora and fauna.
Coastal Embankment Project located in the coastal belt of the districts of Cox's Bazar, Chittagong, Feni, Noakhali, Lakshmipur, Bhola, Barisal, Patuakhali, Jhalokati, Barguna, Pirojpur, Bagerhat, Khulna and Satkhira. The objectives of the project are to protect the coastal lands from saline water intrusion as well as from the monsoon and tidal floods to boost agricultural production through a complex system of embankments and drainage sluices. It covers a gross area of 1.38 million ha, of which 1 million ha is cultivable. Under this project 4,037 km of embankment and 1,039 drainage sluices in 104 polders were constructed. It is said to be an earth-moving project on the scale of the Great Wall of China.
Tubewell Project in Northern Bangladesh located in Thakurgaon and Dinajpur districts. Initially, 380 tubewells of 254-mm diameter and an average depth of over 92m were drilled and installed from 1962 to 1964. Another 830 tubewells were added from 1985 to 1989. Subsequently, another 240 tubewells were sunk. Over the years more tubewells were sunk with the total reaching 1,219. With these tubewells 56,052 ha of land are irrigated.
Brahmaputra Right Bank Embankment located on the right bank of the tista and the brahmaputra. It aims at providing flood protection and gravity drainage to 240,180 ha, of which 159,000 ha are cultivated. The project was started in 1963 and completed in 1968 at a cost of Tk 80 million. Originally, a continuous embankment of 217 km was constructed from Kaunia to Sirajganj, which had to be relocated, at places several times, due to erosion by the Brahmaputra.
Chandpur Irrigation Project located in Chandpur, Haimchar and Faridganj upazilas of Chandpur district and Ramganj, Raipur and Lakshmipur Sadar upazilas of Lakshmipur district, covering a gross area of 54,036 ha. It provides irrigation facilities to 24,291 ha and drainage facilities to 21,578 ha of land. A 100 km long embankment protects the project area from the flooding of the meghna and the dakatia. The project was started in 1963 and completed in 1978 at a cost of Tk 543 million. The dual purpose pumping plant is located at Char Baghadi having a total capacity of 36.8 cumec. Through this pumping plant, water is pumped during the low flow periods from the Dakatia into the South Dakatia. A canal system of 811 km carries the water throughout the project area. The farmers pump water from these canals to the paddyfields as per requirement. Drainage is effected by gravity through the Hajimara regulator, located at the south end of the South Dakatia river. The pumping plant is also used to drain water. Two navigation locks are located at Char Baghadi and one at Hajimara to handle riverine traffic.
Meghna-Dhonagoda Project located in Matlab upazila of Chandpur district. The project provides flood control and drainage to an area of 19,021 ha and irrigation water to an area of 14,400 ha. There are two pumping stations, one at Udamdi, having a capacity of 43.35 cumec and another at Kalipur having a capacity of 28.9 cumec. These are dual-purpose pumps used both for irrigation and drainage. There are two booster pumping stations, one at Eklaspur (capacity 2.26 cumec) and another at Dubgi (capacity 3.4 cumec). The project includes 65 km of flood embankment, 220 km of irrigation canal, and 125 km of drainage channel.
Manu River Project located in the Maulvi Bazar and Rajnagar upazilas of Maulvi Bazar district. It is an irrigation, flood control and drainage project and covers a gross area of 22,580 ha. An area of 12,090 ha is irrigated by diverting water from the manu river by a barrage. Water reaches the paddyfields through a gravity canal system of 145 km. A 59-km embankment along the Manu and kushiyara provides flood protection to 10,480 ha of land and a 35 cumec pumping station on the left-bank of the Kushiyara provides drainage to 4,250 ha. The project was completed in 1983. A fish pass was added to the infrastructure in 1996 to facilitate movement of fish to and from the Kushiyara to Kawadighi Haor.
Khowai River Project located in Habiganj district, provides flood protection to an area of 25,790 ha. A 40 km long flood embankment has been constructed from Habiganj to Chunarughat along the right bank of the Khowai and a 47 km embankment up to Rajabazar has been built on the left bank.
Pabna Irrigation Project located in the district of Pabna and covers a gross area of 196,680 ha. It was started in 1971 and completed in 1992 at a cost of Tk 3,840 million. A dual-purpose pump, located at Bera on the right bank of the hurasagar provides irrigation to 21,862 ha and water reaches the paddyfields through a gravity canal system. In addition, the pumping station located at Kaitala provides drainage facilities to 138,864 ha.
Gumti Project is located in Comilla district. Embankments of 67 km on both banks of the gumti provide flood protection to 37,440 ha. Pumped water from the Gumti to the paddyfields provides irrigation facilities to 11,00 ha of land.
Muhuri Irrigation Project located in Chhagalnaiya, Feni, Parshuram and Sonagazi upazilas of Feni district. It was started in 1978 and completed in 1986 at a cost of Tk 1568.6 million. A 40-vent regulator across the Muhuri at Sonagazi retains water in the post-monsoon season for irrigation. Water is pumped to the paddyfields through low-lift pumps.
Tista Barrage Project (Phase I) located in the districts of Rangpur, Lalmonirhat and Nilphamari. It covers a gross area of 132,000 ha, of which the irrigable area is 111,406 ha. The project supplies irrigation water by diverting the flow of the Tista with a barrage across it through a gravity canal system mainly for supplementary irrigation during the monsoon. The length of the barrage is 615m, fitted with 44 gates having a discharge capacity of 12,750 cumec. The length of the canal head regulator is 110m, fitted with 8 radial gates, having a discharge capacity of 280 cumec. Other components of the project are (i) silt trap, (ii) flood bypass 610m, (iii) flood embankment 80 km, (iv) main canal 34 km, (v) major secondary canals 120 km, (vi) secondary canals 360 km, (vi) tertiary canals 590 km, (vii) drainage channels 960 km, (vii) irrigation structures 391, (viii) drainage structures 635, and (ix) turnouts 5,000 numbers. The project was commissioned in 1993.
Dhaka Integrated Flood Protection Project located in the western part of Dhaka city. The main objective of the project is to provide flood security to the capital, to improve the urban efficiencies and environmental condition, particularly for the urban poor and to promote long-term economic development. In this project three executing agencies worked together. The Bangladesh Water Development Board was responsible for flood protection works, the Dhaka Water and Sewerage Authority for drainage improvement, and the dhaka city corporation for environmental improvement. The project covers an area of 136 sq km and includes about 87% of the total urban population and some 95% of the commercial and industrial properties in the city including the Zia International Airport.
System Rehabilitation Project located in the districts of Sylhet, Sunamganj, Bogra, Gaibandha, Nawabganj, Magura, Jessore, Chittagong, Cox's Bazar, Patuakhali, Barguna, Nilphamari and Feni. It rehabilitated or improved 38 sub-projects during 1990 to 1999 at a cost of Tk 3,128 million. It improved flood control and drainage facilities to 179,520 ha and irrigation facilities to 27,598 ha. In these sub-projects improved operation and maintenance have been introduced.
Besides all above a Dutch aided project started on 1 April 1975 to implement small labour intensive, quick yielding projects through BWDB and continued up to 2000. The Swedish government participated in the project from 1981 to 1992. Over the years 88 projects were implemented in various regions of Bangladesh covering a gross area of 463,250 ha at a cost of Tk 2,606.6 million. [Giasuddin Ahmed Chowdhury]