Salinity Intrusion and Water Availability under changing climate in the Coastal Ganges Delta in Bangladesh

Transcription

1 Salinity Intrusion and Water Availability under changing climate in the Coastal Ganges Delta in Bangladesh Prof Dr. M Monowar Hossain Zahir-ul Haque Khan Physical Setting of Bangladesh 1

2 THE GANGES, BHRAMMAPUTRA AND MEGHNA BASINS The rivers of Bangladesh drain an of area about 1.73 Million square km (GBM basin), only 7 to 8 percent lies in Bangladesh The annual sediment load is about 1.1 billion ton The annual accretion rate in the Meghna Estuary is about 1900 ha Study Area High Saline Zone Medium Saline Zone Low-saline Zone Ganges Delta in Bangladesh 2

3 Salinity (ppt) 5-Aug 14-Sep 24-Oct 3-Dec 12-Jan Salinity (ppt) mrt Feb mei-2011 jul-2011 sep Apr nov Feb 2012 jan-2012 mrt May mei-2012 jul-2012 sep-2012 nov-2012 jan-2013 mrt Jun 2012 mei-2013 jul-2013 sep-2013 nov-2013 jan-2014 mrt Polder 43-2f (Station-2 (In Side),Para River) 24,0Temporal variation of Salinity: Low saline zone 20,0 16,0 12,0 8,0 2,0 4,0 0,0 1,5 Polder 43-2f (Paira River) 2 PPT POLDER-43/2f Date 1,0 Rabi Kharif-1 Kharif-2 0,5 0,0 Date Temporal variation of Salinity: Medium saline zone Salinity at Kazibacha River POLDER-30 Rabi Kharif-1 Kharif-2 2 PPT 3

4 17 Dec Sep Temporal variation of Salinity: High saline zone POLDER-3 Rabi Kharif-1 Kharif-2 2 PPT Spatial and Seasonal Variation of Salinity in the Coastal Ganges in Bangladesh May, 2012 Base Year: 2012 BARISAL KHULNA Monthly Salinity variation with upstream freshwater flow 4

5 Transboundary Flow Historical Trans-boundary Flow in the Ganges Hardinge bridge in dry season Driver: Sea Level Rise Relative Mean Sea Level (RMSL) = Global SLR + Local Effect Projection of SLR from ,based on IPCC temperature projections for three different emission scenarios(rahmstrof,2009) Rahmstorf (2009) prediction for Global SLR is 124cm, A1B in 2100 over 1990 water level Local effect (from past studies and WL trend analysis) is about 5mm/yr Considering Global and local effects the SLR is 22cm in 2030 and 52cm in 2050 above WL Temperature ranges and associated sea-level ranges by the year 2100 for IPCC emission scenarios 5

6 Driver: Infrastructure development (Ganges Barrage) Ganges Barrage 1. Hisna ~ Mathavanga ~Kobadak ~ Kholpetua 2. Kobadak ~ Sibsa 3. Bhairab ~ Rupsa ~ Pussur 4. Gorai ~ Rupsa ~ sholmari ~ Sibsa 5. Gorai ~ Nabagonga ~ Atai ~ Rupsa ~ Pussur 6. Gorai ~ Madhumati ~ Baleswar 7. Arial Khan ~ Baleswar 8. Arial Khan ~ Biskhali 9. Arial Khan ~ Buriswar Salinity Modelling Methodology South-West Regional Salinity Model 6

7 Boundary Generation Measured Q Sal 0 ppt Measured Q Sal 0 ppt Measured Q Sal 0 ppt 2 Dimensional Model (Bay of Bengal Model) Measured salinity at upstream boundaries Sea Salinity = 30 to 35 ppt Sal 1 Dimensional Model South-West Regional Model salinity is zero at upstream Downstream salinity is taken from calibrated BoB model Sal Sal Sal WL, Salinity in 12 downstream boundaries Salinity boundary Salinity = 32 ppt Effect of Transboundary Flow :South-west Zone of Bangladesh May, Base condition with maximum Transboundary flow under Ganges Treaty 7

8 Effect of Transboundary Flow :South-west Zone of Bangladesh May, Base condition with minimum Transboundary flow under Ganges Treaty Effect of Climate Change and Transboundary Flow: South-west Zone May, 2030 climate change (A1B) with minimum Transboundary flow under Ganges Treaty 8

9 Effect of Infrastructure Development: Ganges Barrage May, 2030 Climate change (A1B) with Ganges Barrage Effect of Drivers: Trans-boundary flow, Climate Change and Ganges Barrage 9

10 Effect of Drivers: Trans-boundary flow, Climate Change and Ganges Barrage Effect of Drivers: Trans-boundary flow, Climate Change and Ganges Barrage 10

11 Effect of Drivers: Trans-boundary flow, Climate Change and Ganges Barrage Effect of Drivers: Trans-boundary flow, Climate Change (2030, A1B) and Ganges Barrage Decrease of Freshwater and mild brackishwater area (0-2ppt): Transboundary flow: 1100 sq. km Climate Change: 800 sq. km 11

12 Effect of Sea Level on 2ppt Salinity contour (A1B,2050) A1B scenario, March ppt salinity line Base 2050 Additional Area to be affected by salinity: More than 1 ppt: 7000 km 2 More than 2ppt: 8400 km 2 CONCLUSIONS The present fresh water pocket in the south central zone (Barisal) is likely to be lost with 52cm sea level rise, which would have effect on irrigated agriculture, freshwater fish habitat and drinking water Regional Cooperation is crucial for trans-boundary flow sharing for salinity Control in the changing climate Adaptation measures like Ganges Barrage is important for water security under climate change New salt tolerant cropping technology needs to be introduced 12

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