Water Resources

Revision as of 01:40, 18 June 2021 by ::1 (talk) (Content Updated.)
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)

Water Resources Bangladesh is endowed with plenty of surface and groundwater resources. The surface water resources comprise water available from flowing rivers and static water bodies as ponds, beels and haors. Surface water inflows of the country vary from a maximum of about 140,000 m3/s in August to a minimum of about 7,000 m3/s in February. Two main rivers, the brahmaputra and the ganges account for more than 80% of streamflows. The highest flood discharge of the Ganges observed at hardinge bridge in1987 was 76,000 m3/s and that of the Brahmaputra observed at Bahadurabad in 1988 was 98,600 m3/s. the minimum discharges of the rivers are 261 m3/s and 2800 m3/s, respectively. The average daily flow of the Ganges is about 10,874 m3/s, which reduces to 1366 m3/s during season and increases to 32,00 m3/s. The highest flow is about 44,000 m3/s which is usually received in August. The annual average discharge of the Meghna at Bhairab Bazar is approximately 4,800 m3/s and the maximum flow occurs generally around mid August.

The alluvial aquifer systems of Bangladesh are some of the most productive groundwater reservoirs. The aquifer system generally consists of three lithological units, an upper silty clay and silt layer, a middle layer of fine to very fine sand, and a lower layer of fine to coarse sand constituting the main aquifer. The upper layer is usually 30 to 60 m thick, the middle layer is about 20 m thick and lower aquifer is about 100 m thick. The transmissibility of the main aquifer ranges from 500 to 2500 m2/day and the storage coefficient varies from less that one percent to 15 percent. At places water table can be found within a few meters below the ground surface. Bangladesh also receives plenty of rainfall in the monsoon extending from June to October.

The country receives plenty of rainfall and the amount of annual rainfall ranges from about 3200 mm in the northeast to about 1600 mm in the southwest region. Over the annual cycle rainfall exceeds evapotranspiration by about 10% in the northeast and southeast region whereas they are almost equal in northwest and in the southwest evapotranspiration exceeds rainfall by about 10%. During the seven-month dry season extending from November to May, evapotranspiration is greater than average rainfall except in the northeast region. Most of the winter crops and some summer crops can be grown under rain fed conditions. Generally it can be said that Bangladesh has plenty of water but its uneven distribution, overabundance in monsoon often causes catastrophic floods and scarcity in dry season causes severe drought conditions leading to loss of crops, livestock, public health problems and environmental degradation.

Availability and demand Water is needed for meeting consumptive demands, which include agricultural, domestic and industrial use and non-consumptive demands which comprise in-stream use (navigation, fisheries, salinity control, dilution of pollution) and water required for ecolological protection and wetland preservation. For proper planning, development and utilization of water resources, correct assessment of available water resources is essential but difficult. Water becomes really a scarce resource in Bangladesh during the dry months of the year and maximum water demand occurs in March. First assessment of availability and demand of water resources in the critical month of March was made by the Master Plan Organisation (now Water Resources Planning Organisation) and presented in the National Water Plan prepared in 1986. In 1991 MPO updated the National Water Plan together with the demand and supply of water.

Gross water demand is based on the irrigation requirement, salinity control in the estuaries, riverine fisheries, inland navigation, fisheries and salinity control, and domestic and industrial uses. There are about 7.56 Mha (million hectare) of cultivable land of which about 6.9 Mha of agricultural land can be brought under irrigation at full development by the year 2018. The total water requirement has been estimated at 24,370 Mm3 (million cubic metre) which includes 14,209 Mm3 for agriculture, 9,910 Mm3 for navigation and 170 Mm3 for domestic and industrial use. The total water supply in this month is 23,490 Mm3 which comprises 5,360 Mm3 of groundwater, 6,390 Mm3 from regional rivers, beels and haors and 11,740 Mm3 from main rivers. Agricultural water requirement is 58.6% of the total, navigation, salinity control and fisheries demand 40.7% and domestic and industrial need accounts for only 0.7% of total demand. Out of these entire requirement, 77.2% is expected to be provided by surface water and the balance 22.8% is expected to come from groundwater.

Water balance, shown in the Table, was estimated by the MPO in 1991 for the month of March for a 1983 benchmark year followed by 1990 and the likely position in the years 2005 and 2018. The year 2018 was contemplated as the projected earlier possible date for full development of the Ganges and Brahmaputra barrage projects. '

Table Water resources.

Water Inflow 1983 1990 2005 2018
Border Inflows (m3/s):
Brahmaputra 3990 3900 3900 3800
Ganges 870 770 836 836
Tributary Inflows (m3/s):
Measured 450 370 284 284
Unmeasured (net) 480 790 480 480
Total Inflows (m3/s) 5790 5830 5500 5400
Diversions (m3/s):
Normal Diversions 200 200 200 130
New pumps and improved offtakes - - 600 370
Possible diversions by barrage:
from Brahmaputra - - - 1000
from Ganges - - - 830
Total diversions (m3/s) 200 200 800 2330
Outflows to the Bay of Bengal (m3/s) 5590 5630 4700 3070

The water balance shows that on an annual basis more surface water flows through Bangladesh into the Bay of Bengal than is needed for all consumptive and non-consumptive uses. In the benchmark year 1983, the inflow of 3,990 m3/s of the Brahmaputra river accounts for 69% of the total inflow. The Ganges contributes about 15%. All other measured tributary inflows account for only 7.7%, and the unmeasured tributary inflows (net) are estimated to be 8.3%. The net unmeasured inflows represent the summation of all unmeasured inflows and outflow to the system between Bahadurabad on the Brahmaputra (about 80 km downstream from the Indian border), Hardinge Bridge on the Ganges (about 30 km east of the Indian border) and Barura just below the confluence of the two rivers. By 2005 about 600 m3/s is expected to be used by diversion into existing canal system by pumps operating 12 hours per day. It would be possible to divert 1830 m3/s by means of constructing barrages in future over the Brahmaputra and the Ganges rivers.

Realization of surface water potential is constrained by a number of factors although an immense quantity of surface water flows through Bangladesh. Most importantly there are no opportunities for surface storage and little scope for gravity diversion without any barrages over the Brahmaputra and the Ganges. Under the existing conditions, annual outflows from these two major rivers to the Bay of Bengal are essentially equal to the inflows from India. Amount of present diversion within Bangladesh is far less than the errors of measurement. A water balance study for March, the most critical dry month, indicates that even relatively high abstraction in this month for irrigation the net diversion is about only 5% of the inflows.

Bangladesh has become increasingly dependent on groundwater sources for meeting irrigation needs. Farmers have to use groundwater to grow Boro rice in the winter when there is little rainfall and that local rivers and water bodies dries up. Tran-boundary inflows of rivers are also diminishing alarmingly due to progressively increasing withdrawal in the upper riparian countries.

Water quality Main sources of surface water pollution are municipal sewage and untreated industrial wastes that are mostly discharged into rivers and other water bodies. The worst pollution is found in Buriganga river at Dhaka mostly due to tannery wastes and domestic sewage. Rivers near other industrial towns like Khulna and Chittagong have also become polluted. At places dying industry is also causing serious pollution. Excessive sediment load of rivers also constitutes a water quality problem because water is rendered unsuitable for certain uses without treatment.

In groundwater, presence of iron is found in areas like Pabna, Atghoria, Thakurgaon and Ashuganj. This problem may usually be overcome by sinking deeper tubewells. Arsenic contamination, which was first detected in groundwater in 1993, has created widespread problem. Some 20 million people are now considered at risk due to consumption of groundwater contaminated by arsenic. Severe problem areas have been found in the southwest, southeast and northeast regions of the country. Government and a number of international agencies are studying the arsenic problem in order identify the causes and remedial measures for arsenic contamination. Efforts are being made to filtering devices for removal of arsenic without any success yet. Only feasible option to save the affected people is to stop drinking groundwater and harness water from alternative sources-surface water and rainwater.

National Water Plan The first systematic and comprehensive planning for water resources development started in 1964 when a Master Plan was prepared by the then East Pakistan Water and Power development Authority (now Bangladesh Water Development Board) with the assistance of the International Engineering Company of USA. The major emphasis in the IECO Master Pan was on reducing flood damages, which was a major articulated national objective at that time. The Master Plan has been described basically as a massive scheme for flood embankment construction, empoldering large areas of the country into some 58 major projects which would provide flood protection and drainage facilities to about 12 million acres and irrigation facilities to about 8 million acres by 1985.

The projects were estimated to cost Rs 9960 million (US$ 2,100 million, at an exchange rate of Rs 4.75 to a dollar) over a 21-year period ending in1985. Out of this about Rs 4,226 million was proposed to be spent by 1970 and Rs 7,846 million by 1975. Most of these projects were implemented between the mid 1960s and 1980s. Notable are the Coastal Embankment project (protected area 950,000 ha) completed in 1980, the Brahmaputra Right Embankment Project (225,900 ha) completed in 1970, Ganges-Kobadak Irrigation Project (Phase-I to provide kharif irrigation to 48,000 ha) completed in 1970, and the Dhaka-Narayanganj-Demra Irrigation scheme (4,000 ha now urbanized due to expansion of Dhaka city) completed in 1968. In the 1965-70 five year plan period EPWAPDA proposed an extensive programme of infrastructure development including the Chalan Beel Project, Dhaka-Southwest, Chandpur Irrigation Project, Karnafuli Irrigation Project, Pabna Irrigation Project, Meghna-Dhonagoda Irrigation project and the Meghna-Muhuri transfer scheme and almost all of these projects were implemented in due course. In the 1980-1985 plan period, government proposed a long-term water resources development strategy and intended to undertake the National Water Plan (NWP) preparation in the plan period.

The National Water Council (NWC) was constituted in February 1983 to guide and oversee the national water resources planning activities. The Master Plan Organisation (MPO) was created at the same time and entrusted with the task of preparation of the NWP.

The first National Water Plan was completed by MPO in 1986 and updated in 1991. In June 1992 MPO was renamed as the Water Resources Planning Organisation (WARPO). The severe floods of 1987 and 1988 drew widespread support from the international community for the Flood Action Plan (FAP) comprising 11 main and 15 supporting studies aiming at water and flood management strategies. The FAP studies were completed over a period of 5 years from 1990 to 1995. Although FAP was a large-scale study with the contribution of a number of donors under the coordination of the World Bank and involvement of many international and local consulting firms not much was achieved in terms of concrete plans except a Bangladesh Water and Flood Management Strategy report prepared in 1995 and revised in 1998. WARPO again embarked on the preparation of the National Water Management Plan (NWMP) in March 1998 and completed in March 2001 with four main components:

Development strategy - a consensus document setting out a consolidated goals and objectives, and issues and options for the NWMP;

Water management programme - a priority programme for the period up to 2005, within the context of a long-term programme up to 2025, identifying and assessing the structural and non-structural measures to be implemented nationally and for each region;

Investment portfolio - national, regional and sub-regional projects, as prepared by WARPO for inclusion in the above programmes; and

Ganges dependent area studies - a review of the opportunities arising after signing of the Ganges Water Treaty with India in December 1996.

Other outputs of the project include the National Water Resources Database (NWRD), a People's Participation and Consultation System, procedures and criteria for WARPO to act as a clearing house for water sector projects, and reports on institutional arrangements, legistaive reforms, guidelines, regulatory and economic instruments, as well as environmental protection, management, monitoring and evaluation.

National Water Policy published in January 1999 is intended to guide both public and private actions to ensure optimal development and management of water that will benefit both individuals and society at large. It attaches special importance to the conjunctive use of ground and surface water. Directions are provided on such issues as river basin-wide planning, water rights and allocation, public and private involvement, public investment, water supply and sanitation, fisheries, navigation, agriculture, industry and environment. The national water policy sets following main objectives: (i) to address issues related, (ii) to ensure availability, (iii) to accelerate development, (iv) to bring necessary institutional, and (v) to develop state of knowledge and capability.

The Policy also underlies the importance of effective institutions and legal framework. The National Water Resources Council (NWRC) provides the means to oversee all water resources management activities in the country and the WARPO will act as the Secretariat under the direction of the NWRC's Executive Committee. Government is also committed to revising the legislative framework governing ownership, development, appropriation, utilization, conservation and protection of water resources and to enact a National Water Policy Code soon.

Ganges Water Sharing Treaty The treaty between the Government of the Peoples Republic of Bangladesh and the Government of the Republic of India on sharing of the Ganga/Ganges waters at Farakka was signed by the two Prime Ministers on 12 December 1996. The treaty sets out the following arrangement for sharing between Bangladesh and India the dry season flow of the Ganges at Farakka by ten-day periods from 1 January to 31 May every year.

Availability at Farakka Share of India Share of Bangladesh
70,000 cusecs or less 50% 50%
70,000-75,000 cusecs Balance of flow 35,000 cusecs
75,000 cusecs or more 40,000 cusecs Balance of flow

The treaty makes special provision for each country to receive a guaranteed minimum of 35,000 cusecs on alternate ten-day periods over six such periods during March 11 to May 10. In the event flow at Farakka falls below 50,000 cusecs in any 10-day period, the two Governments will enter into immediate consultations to make adjustments on an emergency basis, in accordance with the principles of equity, fair play and no harm to either party. In the interim, India shall release downstream of farakka barrage, water at a rate not less than 90% of Bangladesh's share until such time as mutually agreed flows are decided upon. Further India shall limit abstraction of water downstream of Farakka to a maximum of 200 cusecs. The water sharing arrangement is based on 40 years (1949-1988) 10-day period average availability of water at Farakka. Every effort would be made by the upper riparian to protect flows of water at Farakka as in the 40-years average availability as mentioned above.

The sharing arrangement under the Treaty shall be reviewed by the two Governments at five years interval or earlier, as required by either party adjustments, based on principles of equity, fairness, and no harm to either party made thereto, if necessary. It would be open to either party to seek the first review after two years to assess the impact and working of the sharing agreement as contained in the Treaty. [M Fazlul Bari]