Planning future irrigated agriculture |
Perspective water sharing
Md. Saeedur Rahman
Like many other Asian countries, farmers in Bangladesh are among the poorest and food insecure population. Seventy five percent of the Bangladesh's populations are directly or indirectly dependent on the agriculture. In 1999-00 a total of 4.03 million ha was under irrigated agriculture compared to only 0.49 million ha in 1970. Out of 7.6 million ha of irrigable land about 4.3 million ha are presently under irrigation, 70 percent of which is served by tube wells technology and the rest is by surface water irrigation schemes. Agriculture is still contributing about 60% employment opportunities of rural population. The draft National Water Management Plan estimates of irrigation expansion forecast a virtual saturation by 2025. About 5.3 million ha of land already have some form of flood protection. It is envisaged to increase controlled flood area and increase irrigation facilities through surface water projects by 0.70 million ha and 0.30 million ha respectively in the next five years. Groundwater resources are fast depleting due to it's over exploitation in the dry season irrigation. Arsenic contamination of the shallow aquifer has set back past successes in bringing safe drinking water supply to the rural population in particular. It has also raised a concern regarding the use of groundwater sources for the continued development of agricultural produce in the country. Large portion of this country seemingly to continue to remain in poverty, if the agriculture sector does not get the critical source of nourishment i.e. irrigation water. Irrigated agriculture is because a powerful medium for the economic development.
Irrigation development and management in Bangladesh, as the lower riparian country, is closely interlinked with and largely dependent on 57 transbourdary rivers having shared basins with the neighboring countries. The non-navigation treaties between Bangladesh and neighboring country for international water courses over the decades remain weak for lack of water allocation, poor water quality provision, lack ofmonitoring/enforce-ment/conflict resolution mechanisms and failure to include all riparian states. The water sharing agreement/ treaty between the Govt. of Bangladesh and the Govt. of India in assessing their relative merits in terms of the dry season water availability in Bangladesh has been so found that the dry season flow at Hardinge Bridge has dropped significantly after commissioning of Farakka Barrage in India with a sharp declining trend in the flow reaching Hardinge Bridge since 1975; the year of upstream withdrawal. The actual post Farakka flow from 1975 to 2003 has been found to be less than the simulated flows as per the 1977 Agreement and the 1996 Treaty.
A study revealed that the lowest average monthly discharge of the Ganges was found to be 316 m3/s in March 1993 against the pre-diversion average monthly discharge of 2213 m3/s for the same month. During the year 1992-93, the lowest average monthly discharge was found 544 m3/s in February 1993 against the pre-diversion monthly average of 2519 m3/s for the same month and again 430 m3/s against 2008 m3/s in April 1993. It is also observed that due to diversion minimum discharge has reduced to as low as 270 m3/s in April 1993 as against a minimum discharge of 2081 in April 1974. The water level has also been recorded as low as 4.22 meter in April 1993 as against a minimum value of 6.70 meter in March 1974. Another analysis undertaken to compare discharges in various years at Hardinge bridge utilizing 1956 to 1987 further revealed that the averages of the highest annual discharge (August-September) before and after 1975 are 46998 m3/s and 55570 m3/s respectively. On the other hand the averages of the lowest discharge (March-April) before and after 1975 were found to be 2006 m3/s and 809 m3/s respectively. This showed that average peak discharge has increased by about 12% compared to average peak flow before 1975. On the same basis the average annual low flow had decreased by 60%. Similar result has been reported by FAP-4 studies (FPCO 1993). The average post-diversion flow will decrease even more unless the sharp declining trend is reversed.
Consequently, dry season flow of the Gorai, major distributaries of the Ganges, has also been seriously affected due to low flow in the Ganges since diversion by Farakka Barrage. Due to reduction of flow in the Ganges during lean flow season, the Gorai is gradually silting up at the off take. An analysis conducted on the discharge entering into the Gorai from the Ganges on a monthly basis before 1975 and thereafter showed that significant reduction of discharge has taken place in the Gorai especially during January-March period. Before 1975, percent of discharge entering into the Gorai was (during January-March) some 8 -12% of the Ganges discharge. This gradually further shrank and reduced to about 0.15% during the last few years for the same period; necessitating dredging of the river with little increase in flow in the recent time. Dry season flows had been cut off completely by 1992 and has it been possible to partly restore only through substantial dredging in 1998.
The Ganges by itself is noted for massive discharge and sediment load. Changes in flow and sediment load have induced sediment deposition in the reach within the territorial boundary of Bangladesh. Sedimentation as high as 3 meter at some places has been found. The sediment flow in the Ganges showed a decreasing trend. The excessive lowering of the discharge due to upstream diversion during low flow season has reduced the depth of flow hampering navigation and accelerated the silting up of the bed. The hydraulic geometry of the river has undergone significant changes creating problems in the distribution of sediment load. As a consequence, the shifting character and meander parameters has also changed.
The Ganges-Kobadak Irrigation Project widely known as 'GK Project' conceived in the early nineteen hundred fifties pioneered the modern irrigated agriculture in Bangladesh. It is the largest lift-cum-gravity irrigation system located in the southwestern part of the country and was taken up for implementation in 1954. Net irrigable area is about 125,000 ha. Phase-I consisting of about 42,000 ha was implemented during 1954--70 and Phase-II covering an area of about 83,000 ha was completed during 1969--83.
At least a 4.5 meter high water flow in the river is required to keep 3 big and 12 small pumps of the project operative, but water in the river flowing far below the minimum required level with silted up intake canal bed has been seriously impeding sourcing the irrigation. The water shortage is being augmented by installation of about 10,385 shallow tubewells abstracting the groundwater within the project area.
Withdrawal of Ganges water during the dry months resulted serious adverse effects on environment, agriculture, industries, fisheries, navigation, river regime, salinity contamination in the surface and groundwater etc. in the southwestern and western areas of Bangladesh covering almost 20% of country's area equaling 30,000 sq. km inhabited by about 30 million people.
Similarly, the use of Teesta River water for irrigated agriculture had been conceived back in 1935 and rolled down till the Govt. of Bangladesh and the Govt. of India in its 25th meeting of the Joint Rivers Commission on 20 July, 1983 reached an adhoc allocation agreement according to which India was to get 39 percent, Bangladesh 36 percent and remaining 25 percent was to be reserved for reallocation later, after further study. Without having this agreement in place, the amount of dry season waters on Bangladesh side gradually decreased and ended up in getting only 59 m3/s in January 1999. The dry season water flow now varied from 22 to 34 m3/s in January 2001 against the requirement of 227 m3/s to irrigate 540,000 ha. of irrigable land. During dry season every year, the barrage at Gojoldoba at the upstream in India is kept closed for diverting the water to Mohanonda River for irrigation. This has turned the mighty river Teesta into a virtual streamlet causing emergence of numerous shoals bringing changes in its hydraulic characteristics. The riverbeds of Teesta have turned into crop lands. The unilateral withdrawal of water from Teesta River at the upstream has been causing havoc in its basin in Teesta project area, severely affecting the ecology and economy.
Between 1984-95, share of agriculture to GDP declined from 41.77 percent to 32.77 percent while the share of the manufacturing and services sectors went up. The composition of GDP on agriculture has further declined to 21.9 percent in 2002 from 50 percent in 1970 resulting corresponding reduction in rural labor employment in agriculture. The eco-migration of agricultural labor at this point of declining share is of concern. At this point the Indian River Linking Plan aims to connect 30 rivers in the country for diverting water from surplus river basins to water-deficient areas. The basin transfer of river waters will affect Bangladesh in terms of loweravailability in the down- stream, which is pivotal to planning future irrigated agriculture in Bangladesh.
The first Earth Summit in Rio in 1992 where 180 countries agreed on a broad framework known as Agenda-21, for eradicating poverty and achieving sustainable development. The second Earth Summit in Johannesburg in 2002 came out with plan of implementation for integrated water resources management for eradication of poverty and protecting the world's environment needs. At this backdrop it is necessary to bring in mind that the Ganges Brohmaputra - Meghna (GBM) region is endowed with huge water and natural resources that contains almost 40% of the world's poor. A rationalized utilization of these water and other resources of the region in integrated manner and coordinated approach may substantiate the regional economic growth and reduce poverty while the water transfer schemes will monster all the past achievements of Bangladesh in water sector and planning future irrigated agriculture including other water dependent / related development efforts.
The discussion indicates that water sharing has a significant role in water resources management as a whole and thus forth sourcing water, in particular, for irrigated agriculture. Sharing water of the irrigation source is directly linked with the irrigated agriculture that guarantees the farmers for their initiatives and investments. Integrated basin wide development and management of water resources is undoubtedly the major option for future development of the Ganges, the Bharamaputra and the Meghna basin to cater for all the needs. Firm political commitment from the governments of China, India, Nepal, Bhutan and Bangladesh is required to undertake joint actions towards the integrated approach in the water resources management in the region. All the water needs for environmental protection, economic uses, energy generation, navigation, food security through irrigated agriculture and aquaculture, safe water supply and sanitation in the region could have met and millions of poverty-stricken population in the region would have enjoyed a better life if we working together to foster close and meaningful cooperation amongst the countries of the region. Meanwhile, the national level water professionals with supports from policy makers are required to scour into the different potentials for protecting the nation's interest in planning future irrigated agriculture in Bangladesh.
Md. Saeedur Rahman is Chief Engineer, Coastal Embankment Rehabilitation Project, BWDB