WHAT IF CLIMATE CHANGES? IMPLICATIONS FOR BANGLADESH

1. WHAT IF CLIMATE CHANGES? IMPLICATIONS FOR BANGLADESH AHSAN UDDIN AHMED Executive Director BANGLADESH UNAYAN PARISHAD (BUP)

2. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed

3. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed

4. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed Bangladesh has always been vulnerable to climate variability. Why? Geophysical features & location Highly influenced by monsoon and regional flow patterns ‘Too much water in monsoon’ & ‘too little water in the dry season’ Socioeconomic realities Population density Equity and deprivation Poverty & per capita resource endowment Development practices and malpractices …………… Since climate variability and change will significantly affect the hydrology, the overall impacts of climate change will also be significant

5. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed The location of the country in its regional setup adds an element of vulnerability by giving rise climatic extremes. The regional aspects of water management put additional difficulties towards adaptation to climate variability and change. Bangladesh is a low-lying delta. The eastern-Himalayan rivers (GBM) drain over the landmass of Bangladesh.

6. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed The climate of the country is strongly influenced by monsoon.

7. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed The country occupies only about 7% of the combined catchment area, while it has to drain over 92% of the GBM flows.

8. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed >> Impeded drainage Source: Ahmed et al., 1998

9. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed Under climate change scenarios, mean monthly rainfall will show significant changes over normal (i.e., current variability). Extent of Change: There will be a general rise in surface average temperature: 1.3°C by 2030s; 2.6°C by 2070s. Monsoon rainfall will increase by 11% by 2030s and 27% by 2070s. Number of rainy days in Bangladesh will increase by about 20 days. Courtesy: IITM

10. Climate change in Bangladesh Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed RVCC National Workshop, Dhaka

11. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed IMPLICATIONS OF CLIMATE CHANGE FOR BANGLADESH Under climate change scenario about 18 per cent of current lowly flooded areas will be susceptible to higher levels of flooding while about 12 to 16 per cent new areas will be at risk of inundation (varied degrees). On an average about a quarter of the country’s landmass is currently flood prone in a normal hydrological year, which may increase to 39 per cent, while the frequency of a catastrophic flood (engulfing about two-thirds of the landmass of the country) could be increased under climate change scenarios.

12. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed Current and Future Flooding-Bangladesh Source: Mirza, 1998

13. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed Prolonged flooding can effectively reduce overall potential for HYV Aman production. Courtesy: BUP

14. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed Source: Ahmed et al., 1998

15. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed In the post-monsoon to pre-monsoon period, rainfall diminishes while temperature increases. Low rainfall runoff reduces river flows, consequently salinity penetrates along the coastal rivers. A combination of increased temperature and reduced rainfall results in an increase in evapo-transpiration, which is detrimental for crop growth. Courtesy: BUP

16. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed In the dry season, already low rainfall will be further diminished. However, winter and pre-monsoon temperature will rise significantly. The consequent effect will be a sharp rise in evapo-transpiration. Diminishing winter rainfall will further reduce available flows in rivers. As a consequence, salinity regime will penetrate inland. Source: Ahmed, 2003 Source: Karim, 1996; Huq et al., 1996

17. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed Beneficial effects of CO2 fertilization will be diminished by increased devastation induced by extreme water-related events. Agriculture will suffer. Prolonged flooding can effectively reduce overall potential for HYV Aman production. In the post-monsoon to pre-monsoon period, diminishing rainfall and increasing temperature will cause moisture stress. However, the lowering of rainfall runoff will either limit irrigation or put increased economic constraints on poor farmers. Salinity will further restrict choice for the most preferred crops.

18. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed Deficit of moisture on the top soils will increase in a large number of Thana, where the farmers will have no choice other than switching from shallow tubewell irrigation to deep tubewell irrigation. As a result, production of irrigation dependent crops will cause economic hardship for the marginal and poor farmers. Production of wheat and HYV Aus and Boro might no longer be economically suitable under climate change. Increased surface temperature will tend to release more carbon from the topsoil, which in turn will reduce fertility of the soils.

19. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed

20. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed Impact of Drought Courtesy: Sk.G. Hussain

21. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed Δ April Maximum Temperature Courtesy: Sk.G. Hussain

22. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed Δ Rabi Precipitation Courtesy: Sk.G. Hussain

23. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed Change in Boro Rice Yields under different Climatic Scenarios and Irrigation Levels (DSSAT ver 3.5) Karim, Hussain and Ahmed, 1998

24. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed Irrigation Requirement by Major Cropping Patterns Courtesy: Hussain, Sk.G.

25. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed Increased water demand for irrigation will lead to increased withdrawal from the already lean surface water systems leading to decrease in lean season flow in the rivers. An additional quarter of a million hectare land will become saline affected, on top of currently saline 3.05 million ha, forcing farmers to grow crops of lesser economic return. Lean flows in the distributaries of the Ganges will jeopardize the forest succession processes in the Sundarbans, resulting in low productivity and poor vegetative cover of the forest. That will in turn affect the rich biodiversity of the forest.

26. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed Ingress of 5 ppt isohaline front along coastal river systems Isohaline lines showing salinity ingress

27. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed Salinity ingress in river water in the SW Salinity in surface water will increase significantly in the SW

28. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed T. Aman Suitability – Current status Transplanted Aman is suitable almost everywhere in the SW

29. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed T. Aman Suitability – SLR Scenario Suitability of T. Aman diminishes significantly with increasing SLR

30. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed Impact on Paddy Production under different SLR scenarios

31. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed Salinity condition with adaptation

32. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed Impact on Paddy Production under different adaptation options

33. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed Human health High salinity in water, in both surface and groundwater sources, in the Southwestern areas of Bangladesh is affecting human health. What will happen if salinity penetrates further inland under climate change? Rise in temperature will favour pest/pathogen activities and human health will be at higher risk. Increased risk of dengue, malaria, diarrhea, … Floodwaters would tend to destroy the poor sanitation facilities. Cyclones with increased vigour will have similar adverse effects. Reaching the MDG targets will be extremely difficult under climate change. Photo courtesy: The New Nation & The Daily Star (Aminur Rahman)

34. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed Implications for the Sundarbans and biodiversity Lean flows in the distributaries of the Ganges will jeopardize the forest succession processes in the Sundarbans, resulting in low productivity and poor vegetative cover of the forest. That will in turn affect the rich biodiversity of the forest. Potential drying up of the remainder of the wetlands? What will happen to the wetland aquatic biodiversity? Photo courtesy: RVCC Team

35. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed Degradation of forest vegetation due to SLR induced salinity (88cm SLR) Good quality timber species will be replaced by poor quality woody species & shrubs

36. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed IMPLICATIONS FOR BANGLADESH The projected sea level rise along the coastal areas of Bangladesh will be about 88cm by the year 2100. Due to SLR a majority of the low-lying non-embanked coastal areas will be completely inundated. There will be increasing risk of coastal salinity (both soil as well as surface water, including drinking water from wells). Scarcity of saline-free drinking water will be even more pronounced. SLR will have compounding effect on coastal drainage & erosion. The mixing zone between sweet water and saline water will be shifted. Land use suitability, particularly in relation to current agricultural practices will change. Embanked coastal agricultural areas will be at higher risk of tidal surge and subsequent inundation with saline water.

37. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed Drainage congestion inside polder system due to SLR Inside polders, there will be higher levels of waterlogging

38. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed Performance of existing embankments will be diminished due to SLR

39. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed SLR vs Cyclone Intensity SLR MAY INCREASE CYCLONE INTENSITY SLR Shoreline retreat  Increase the basin area  Increase the cyclone path length  More time in water  Acquire and release more latent heat  More Energy/Intensity/Wind Speed Courtesy: A Ali

40. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed CYCLONE STATISTICS FOR THE BAY (1877-1997) Frequency of Dead Cyclones • If there were higher SSTs, some of the dead cyclones could have further developed and struck any littoral countries. • In this way at least, the frequency of land-falling cyclones could have increased. • Any future SST rise may lead to such situations. Courtesy: A Ali

41. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed SST vs Cyclone Intensity - Emanuel’s Table Courtesy: A Ali

42. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed Shallow Water Effect • Surge height is inversely proportional to water depth. • SLR will increase water depth  Decrease surge height • However, the newly inundated land areas due to SLR will form the new shallow water areas where increased surge height is likely to occur. • Plus cyclones will stay longer in the expanded water area  increase wind speed  increase SS • SLR will push further inland the RZ and HRA. • This may upset the coastal management plan including cyclone shelter construction Courtesy: A Ali

43. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed SST- SLR – WIND - STORM SURGE Courtesy: A Ali

44. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed Conclusions Water resources and hydrology of Bangladesh are highly sensitive to current climate variability. Within Bangladesh, climate variability has two major dimensions: temporal and spatial. Both are highly significant. There are various elements of vulnerability associated to current climate variability. Under climate change, observed climate variability will only increase causing extreme climate conditions. Floods, droughts and salinity ingress will occur more frequently and with higher intensity. The country has to implement adaptation measures in order to reduce its current vulnerability to climate variability and change.

45. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed IMPLICATIONS FOR THE SOUTHWEST REGION Maximum impact zone High salinity Choking up of smaller rivers Water logging Embankment breaching and overtopping Cyclonic storm surges Riverbank erosion Agriculture will be severely affected Upper reaches will face drought Saline-free drinking water? Photo courtesy: The New Nation & RVCC Team

46. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed ADAPTATION It is indeed possible to manage the risk environment through adaptation Risk reduction Individual basis Household level Community level Longer term approach: Planned adaptation Modifying the risk environment Integrating micro-planning with meso-scale water sector planning Attending emergencies (Contingency plan)

47. Module 5: Climate Variability & Change: Implications for Bangladesh Ahsan Uddin Ahmed Successful adaptation approaches RVCC examples and good practices Methodological issues Identifying the right actors Integration Another example Community Based Flood Management approach by BUP Emphasize on participatory approaches Actions must be taken (addressing time lag) Research Acknowledging and trust building Sharing

48. On behalf of Research and Development Community, of BUP and on my personal behalf, I would like to thank you all for allowing me to share our research-supported experience of analyzing Climate Variability and Change in Bangladesh.