G4 impact of climate change, food demands and trans-boundary agreement on water resources in the ganges basin in  bangladesh
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G4 impact of climate change, food demands and trans-boundary agreement on water resources in the ganges basin in bangladesh

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by Bharat Sharma, U. Amarasinghe, M. Lal, and P. Saikia ...

by Bharat Sharma, U. Amarasinghe, M. Lal, and P. Saikia
Presented at the GBDC Reflection Workshop, November 2013

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  • The increasing sedimentation, loose texture of the soil and the varying discharge from the Farakka barrage into the Bhagirathi has led to a meander bend of the river channel. When the discharge is high the river forms a long stretch by meandering but, when the discharge is reduced it causes erosion of the bank. The eroded material is carried downstream which gets accumulated in the river bed forming sandy shoals. Several cut-offs are formed with the sedimentation deposited inside the bend and soil erosion outside the bend. These cut-offs are subsequently separated from the old channel and an ox-bow lake is formed. The fluctuation of water discharge from the barrage into the feeder canal at Jangipur is a one of the major reasons for the bank erosion of Bhagirathi River and increasing number of cut-offs As a result of the cut-offs the length of the river is reduced, which increases the hydraulic gradient of the river. The rise in hydraulic gradient increases the velocity of the river which further causes erosion of the bank. Several cut-offs took place along the Bhagirathi at Dear-Balagachi, Baidyanathpu, Shankhapur-Moyapur, Bishnupur-Charchakundi.
  • The morphological changes in Hooghly because of siltation have limited the usage of these ports by big vessels and even small vessels are not able to navigate during lean period. Under such condition, the port is also loosing its cargo volume as two of its major traders Nepal and Bhutan arenow shifting its dependency to the Mongla and Chittagong Ports of Bangladesh. ‘The Kolkata Port was never an ideal port for the movement of big vessels. The port is located nearly 120 kms north of the delta and the Bhagirathi lost its connection with the main channel of the Ganges, much before the construction of the Kolkata Port (The Kolkata Port was commissioned on 17 Oct 1870 under Calcutta Port Act). During the 1768 and 1777, the Bhagirathi channel remained almost dry during the winters’. - Jenia Mukherjee 

Transcript

  • 1. Impact of Climate Change, Food Demands and Trans-boundary Agreement on Water Resources in the Ganges Basin in Bangladesh (G4 Project) Bharat Sharma, U. Amarasinghe, M. Lal, and P. Saikia International Water Management Institute Ganges Basin Development Challenge Reflection Workshop of the CPWF Sarina Hotel, Dhaka, Bangladesh; November 12-13, 2013 Water for a food-secure world www.iwmi.org
  • 2. Annual Water Balance Components – Ganges ( 1981- 2010) 2000 1800 1600 1400 1000 800 600 400 200 Year Precipitation ETa Water yield Rainfall - 609 to 1796 mm/y Water yield - 250 to 1300 mm/y Water for a food-secure world www.iwmi.org 2010 2009 2008 2007 2006 2005 2004 2003 2002 2001 2000 1999 1998 1997 1996 1995 1994 1993 1992 1991 1990 1989 1988 1987 1986 1985 1984 1983 1982 0 1981 mm 1200
  • 3. Climate Change Scenario CC data : Climate data from the GCM, Hadley Centre Coupled Model, version 3 (HadCM3) was downscaled with PRECIS for the GRB under A1B Special Report on Emission Scenarios (SRES) scenarios. Future projection years : 2030, 2050 To represent the hydrological variables in 2030, the average values between 2025 and 2035 were taken. The average values of the hydrological variables between 2045 and 2055 were used to represent the values in the year 2050. Water for a food-secure world www.iwmi.org
  • 4. Areas with increased and reduced precipitation in 2030 and 2050 compared to the baseline In 2030, precipitation will be reduced over 47% of the basin area compared to the baseline period and this value will be 36% in 2050 Water for a food-secure world www.iwmi.org
  • 5. Spatial Distribution of Precipitation, Water yield, ETa and Snow melt ( baseline) Water for a food-secure world www.iwmi.org
  • 6. Spatial Distribution of Precipitation, Water Yield, ETa and Snow Melt ( 2030) Water for a food-secure world www.iwmi.org
  • 7. Spatial Distribution of Precipitation, Water Yield, ETa and Snow Melt ( 2050) Water for a food-secure world www.iwmi.org
  • 8. Implications of the Analysis:  In the A1B scenario considered in this study, precipitation is projected to increase.  This would lead to higher PET and increased ETa in 2030 and 2050 compared to the baseline period.  For agriculture sector, this could mean a higher demand for irrigation water. In future, the average water yield over the GRB will increase by about 172 mm and the average shallow aquifer recharge will increase by about 27 mm in 2050 compared to the baseline period. Water for a food-secure world www.iwmi.org
  • 9.  This is attributed to the higher precipitation in some parts of the basin, especially during wet season.  A1B climate change scenario will have positive effect in terms of the water availability in the GRB. But with a lot of spatial and temporal variability within the basin. This implies increase in extreme events in the basin. A holistic approach of developing infrastructure to capture the increased flow in the river, and enhanced groundwater recharge techniques should be a priority in the GRB. This will help in mitigating adverse effects of climate change in the future. Water for a food-secure world www.iwmi.org
  • 10. 2. Water for Food in Bangladesh: Outlook to 2030 Water for a food-secure world 11/17/2013 www.iwmi.org 10
  • 11. Composition of daily calorie supply per person in Bangladesh Water for a food-secure world 11/17/2013 www.iwmi.org 11
  • 12. Actual and forecasts of GDP and calorie supply from various cereal, animal and other crop products Water for a food-secure world 11/17/2013 www.iwmi.org 12
  • 13. Change in cropping and irrigation patterns in Bangladesh Water for a food-secure world 11/17/2013 www.iwmi.org 13
  • 14. Auto Regressive Integrated Moving Average (ARIMA ) models predict: • Further decline in Aus rice area—to 0.7 Mha by 2020, and 0.2 Mha by 2030, • No significant changes in Aman rice area. It shall stabilize between 5.7 to 6.1 Mha, and • Further increase in Boro rice area-- to 5.7 Mha by 2020 and another 1 Mha by 2030. The predicted increase in Boro rice area will be significantly more than the decline in Aus rice area Water for a food-secure world 11/17/2013 www.iwmi.org 14
  • 15. Area and yield of Aus, Aman and Boro rice in Bangladesh Water for a food-secure world 11/17/2013 www.iwmi.org 15
  • 16. The ARIMA models predict: Aus rice yield to increase 2.0% annually between 2010 and 2020; 1.2% annually in the 2020’s; and to reach 2.4 t/ha by 2030. Aman rice yield to increase 1.8 and 1.1% annually in the next two decades, and reach 2.8 t/ha by 2030; and Boro rice yield to increase 1.2 and 1.0% annually in the next two decades, and reach 4.8 t/ha by 2030. Water for a food-secure world 11/17/2013 www.iwmi.org 16
  • 17. Variation of yield and WP with total CWU across 23 districts Water for a food-secure world 11/17/2013 www.iwmi.org 17
  • 18. Implications for Water Demand upto 2030 Time Season Area (Mha) Total CWU (Bm3) Irrigated Total Total production (Mt) Water productivity (Kg/m3) Savings of irrigation CWU (Bm3) by only meeting the rice demand1 WP growth scenarios2 Irrigation 0% 5% 10% 0.0 4.8 0.0 1.9 0.40 - - - 5.6 0.6 30.7 0.0 12.5 0.41 - - - 4.7 4.5 27.5 16.5 18.3 0.67 - - - Total 11.4 5.1 63.0 16.5 32.8 0.52 - - - Aus 0.7 0.0 3.2 0.0 1.5 0.47 - - - Aman 5.7 0.0 30.8 0.0 14.1 0.46 - - - Boro 5.7 5.7 33.9 20.9 24.6 0.73 2.60 2.74 2.89 Total 12.1 5.7 67.9 20.9 40.2 0.59 - - - Aus 0.2 0.0 1.1 0.0 0.6 0.53 - - - Aman 5.7 0.0 30.8 0.0 15.9 0.52 - - - Boro 6.7 6.7 39.9 24.5 32.1 0.81 6.08 6.40 6.76 Total 2030 1.1 Boro 2020 Aus Aman 2010 12.6 6.7 71.7 24.5 48.6 0.68 - - - Water for a food-secure world 11/17/2013 www.iwmi.org 18
  • 19. 3. Indo-Bangladesh trans-boundary river basin cooperation : A Policy Analysis • Identify the current challenges in Indo-Bangladesh Ganges River water sharing and management. • Review the negotiation history and implementation of the 30-years Indo-Bangladesh Ganges water sharing treaty signed in 1996. • To explore and recommend avenues for cooperation over Ganges not just for water sharing but also a basin-wide development approach. Water for a food-secure world 11/17/2013 www.iwmi.org 19
  • 20. The 1996 Ganges Water Sharing Treaty The 1996 treaty provided the provisions for water sharing of Ganges at the Farakka border during dry seasons, operational between January 1 and May 31 each year. Under the treaty an arrangement/water sharing formula was reached between the two countries on the amount of water transferred from Farakka into the Padma during the lean season. Water available at Share of India Farakka Share of Bangladesh 70,000 cusec or less 50% 50% 70,000-75,000 cusec Residual flow 35,000 cusec 40,000 cusec Residual flow Source: (Salman and Uprety, 2002). Greater than 75,000 cusec 11/17/2013 Water for a food-secure world www.iwmi.org 20
  • 21. Study Findings  Inadequate implementation of the 1996 Ganges Water Treaty.  The 1996 water arrangement is based on the average flow observed (1949-73) which is 12105.4 cumecs and the annual discharge is 382 BCM. There have been considerable changes and variation in the flow of water at Farakka after 1996.  Morphological Changes of the Ganges River system has been noticed which will pose serious threats to the 1996 water sharing arrangement.  The rapid change in the Ganges system and the decrease in the dry season freshwater flow at Farakka barrage is creating a stress in the Indo-Bangladesh cooperation.  Changing course of the Ganges and the threat of the river outflowing the Farakka Barrage. Water for a food-secure world 11/17/2013 www.iwmi.org 21
  • 22.  Similar concerns noticed in both India and Bangladesh over the low dry season freshwater flow in the Ganges:  the Bhagirathi-Hooghly river system in West Bengal and Gorai river system in Bangladesh.  Gorai remains dry during lean season.  Demographic changes in the GDA of West Bengal and Bangladesh has been noticed.  Increasing usages of water in the upstream is also affecting the flow of freshwater at the Farakka point.  Increasing siltation and changing course of the river channel has also resulted in erosion of vast tracts of land around Farakka.  River bed erosion along the Bhagirathi-Hooghly River in West Bengal and Ganges/Padma in Bangladesh is noticed.  Reduced freshwater flow also resulting in accumulation of sedimentation.  Small Rivers and Distributaries along the Lower Ganges Basin is getting dried and disconnected from the main rivers. Water for a food-secure world 11/17/2013 www.iwmi.org 22
  • 23. Map showing the Gorai River 11/17/2013 Source: World Bank 23
  • 24. Map Showing the Farakka Barrage and Feeder Canal Source: Kolkata Port Trust 11/17/2013 Map Showing the Feeder canal and Bhagirathi river 24
  • 25.  The increasing sedimentation, loose texture of the soil and the varying discharge from the Farakka barrage into the Bhagirathi has led to a meander bend of the river channel. Bishnupur-Charchakundi cut-off Shankhapur-Moyapur cut-off Source: Hydraulic Department, Kolkata Port Trust Water for a food-secure world 11/17/2013 www.iwmi.org 25
  • 26.  The reduced freshwater flow along the BhagirathiHooghly River causing major threats for the navigability of the Kolkata port.  The minimum flow of 40,000 cusec, required for the navigability of the Kolkata port has not been met( as mentioned by authorities of Kolkata Port Trust)  Analysis shows that the most benefited area from the water diverted from the barrage is the feeder canal area.  Navigational routes in Bangladesh(mostly the distributaries of Ganges) suffers from low flow of Ganges during dry season causing serious threat to its inland waterways.  The low flow of freshwater has resulted in accumulation of sediments on river bed which has reduced the depth required for navigation of bigger vessels and ships. The country mostly dependent on its inland waterways for trade and transportation is under serious threat. Water for a food-secure world 11/17/2013 www.iwmi.org 26
  • 27. Joint River Commission(JRC) must be strengthened • Joint projects and research studies should be conducted under a joint team consisting of technical and policy experts from both the riparian states. Basin Commissions must be set up in each of the riparian countries supervised by JRC. • Meet an agreement towards the augmentation of flow during lean season. Water for a food-secure world 11/17/2013 www.iwmi.org 27
  • 28. THANK YOU b.sharma@cgiar.org Water for a food-secure world 11/17/2013 www.iwmi.org 28