Zahir-­‐ul  Haque  Khan  Sarafat  Hossain  Khan  Dr.  M.  Shah  Alam  Khan  Farhana  Akter  Kamal  Nasim  Al  Azad  Khan    

Future  ProjecAon  of  surface  water  resources  of  the  Ganges  coastal  zone  of  

Bangladesh  

Present Condition: Spatial variation of Salinity and Freshwater Availability

 External  Drivers  of  Change  

Final List of Key External Drivers and Their Ranking

Scenario  Genera6on    

Scenario  Genera6on  Workshop                            

Combina6on  of  Drivers  

Scenarios  

•  Scenarios  developed  in  a  par6cipatory  approach  

•  Done  collec6vely  by  experts,  policy  makers,  service  providers,  prac66oners,  and  stakeholders  

•  Examined  different  combina6ons  of  external  drivers  as  likely  scenarios  

•  14  scenarios  selected  ini6ally  •  Further  consolidated  into  5  

scenarios  

Scenario:  Effect  of  Transboundary  flow  and  Climate  Change  

Ganges  Basin  

Upstream  Boundaries  (Q,  Sal  =  0pt)  Minimum  and  maximum  flow  in  Gorai  in  dredged  condi6on  

Downstream  Boundaries  (WL,  Sal)  +  Sea  Level  Rise  

Transboundary  flow    Best  case  scenario:  maximum  flow  since  GWT  Worst  case  scenario:  minimum  flow  since  GWT  

Climate  change:  A1B  condi6on  (PrecipitaAon,  Temperature  and  Sea  

Level  Rise)  

Scenario  :  2030  

Scenario:  Transboundary  Flow,  Land-­‐Use  Change  and  Climate  Change  

Ganges  Basin  

Land-­‐use  change  

Climate  change:  A1B  and  A2  condi6ons  (PrecipitaAon,  Temperature  and  Sea  

Level  Rise)  

Scenario  :  2030  

Transboundary  flow    Best  case  scenario:  maximum  flow  since  GWT  

Upstream  Boundaries  (Q,  Sal  =  0pt)  Minimum  and  maximum  flow  in  Gorai  in  dredged  condi6on  

Downstream  Boundaries  (WL,  Sal)  +  Sea  Level  Rise  

Scenario:  Effect  of  Mul6ple  Drivers  on  Water  Resources  

Ganges  Basin  

Transboundary  flow  (worst  case  scenario:  minimum  flow  since  GWT)  

Popula6on  growth:  water  extrac6on  from  the  river  system  

Climate  change:  A1B  condi6on  (PrecipitaAon,  Temperature  and  Sea  

Level  Rise)  

Scenario  :  2030  

Land-­‐use  change  

Downstream  Boundaries  (WL,  Sal)  +  Sea  Level  Rise  

Upstream  Boundaries  (Q,  Sal  =  0pt)  Minimum  flow  in  Gorai  in  dredged  condi6on  

Scenario:  Effect  of  Mul6ple  Drivers  on  Water  Resources  

Ganges  Basin  

Downstream  Boundaries  (WL,  Sal)  +  Sea  Level  Rise  

Transboundary  flow  (best  case  scenario:  maximum  flow  since  GWT)  

Popula6on  growth:  water  extrac6on  from  the  river  system  

Climate  change:  A1B  condi6on  (PrecipitaAon,  Temperature  and  Sea  

Level  Rise)  

Scenario  :  2030  

Land-­‐use  change  

Upstream  Boundaries  (Q,  Sal  =  0pt)  Maximum  flow  in  Gorai  in  dredged  condi6on  

Scenario:  Infrastructure  Development  

Ganges  Basin  

Land-­‐use  change  

Transboundary  flow  (best  case  scenario:  maximum  flow  since  GWT  

Popula6on  growth:  water  extrac6on  from  the  river  system  

Climate  change:  A1B  condi6on  (PrecipitaAon,  Temperature  &  Sea  Level  Rise)  

Scenario  :  2030  

Change  in  water  management  prac6ces  

Change  in  water  governance  and  ins6tu6ons  (including  policy  change)  

Water  infrastructure  development  

Downstream  Boundaries  (WL,  Sal)  +  Sea  Level  Rise  

Upstream  Boundaries  (Q,  Sal  =  0pt)  Minimum  flow  in  Gorai  in  dredged  condi6on  

Methodology

Salinity  Modelling  

Water  Flow  boundary  

Q  Q  

Q  

WL  WL   WL   WL  

WL  

1  Dimensional  Model  South-­‐West  Regional  Model  Known  Water  flow  and  water  level  at  boundaries    

2  Dimensional  Model  (Bay  of  Bengal  Model)  Water  flow  boundary  from  SWRM  Water  level  from  Global  Tide  Model  

Q  Q  Q  

WL  

River    Network  Model  and  Bay  of  Bengal  Model  

Salinity  boundary  

Measured  Q  Sal  0  ppt  

1  Dimensional  Model  South-­‐West  Regional  Model  salinity  is  zero  at  upstream  Downstream  salinity  is  taken  from  calibrated  BoB  model    

2  Dimensional  Model  (Bay  of  Bengal  Model)  Measured  salinity  at  upstream  boundaries  Sea  Salinity  =  30  to  35  ppt  

Sal  

Salinity  =  32  ppt  

Sal  Sal  

Sal  

Measured  Q  Sal  0  ppt  

Measured  Q  Sal  0  ppt  

WL,  Salinity  in  12  downstream  boundaries  

Salinity  Model  

Salinity  Model  

Driver:  Transboundary  Flow  Transboundary  Flow  

1. Hisna ~ Mathavanga ~Kobadak ~ Kholpetua

2. Kobadak ~ Sibsa

3. Bhairab ~ Rupsa ~ Pussur

5. Gorai ~ Nabagonga ~ Atai ~ Rupsa ~ Pussur

6. Gorai ~ Madhumati ~ Baleswar

4. Gorai ~ Rupsa ~ sholmari ~ Sibsa

7. Arial Khan ~ Baleswar

8. Arial Khan ~ Biskhali

9. Arial Khan ~ Buriswar

Driver:  Infrastructure  development  (Ganges  Barrage)  

Ganges  Barrage  

182  m3/s  

May2012,  Base  condi6on  with  maximum  Transboundary  flow  under  Ganges  Treaty  

Effect  of  Transboundary  Flow  :South-­‐west  Zone  of  Bangladesh  

May2012,  Base  condi6on  with  minimum  Transboundary  flow  under  Ganges  Treaty  

Effect  of  Transboundary  Flow  :South-­‐west  Zone  of  Bangladesh  

May,  2030  climate  change  (A1B)  with  minimum  Transboundary  flow  under  Ganges  Treaty  

Effect  of  Climate  Change  and  Transboundary  Flow:  South-­‐west  Zone  

May,  2030  Climate  change  (A1B)  +  Transboundary  flow  with  Ganges  Barrage    

Effect  of  Infrastructure  Development:  Ganges  Barrage  

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

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

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

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

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

Decrease  of  Freshwater  and  mild  brackishwater  area  (0-­‐2ppt):  q Transboundary  flow:  1100  sq.  km  q Climate  Change:  800  sq.  km  

1. Hisna ~ Mathavanga ~Kobadak ~ Kholpetua

2. Kobadak ~ Sibsa

3. Bhairab ~ Rupsa ~ Pussur

5. Gorai ~ Nabagonga ~ Atai ~ Rupsa ~ Pussur

6. Gorai ~ Madhumati ~ Baleswar

4. Gorai ~ Rupsa ~ sholmari ~ Sibsa

7. Arial Khan ~ Baleswar

8. Arial Khan ~ Biskhali

9. Arial Khan ~ Buriswar

 Effect  of  infrastructure  development:  Ganges  Barrage  

Ganges  Barrage  

182  m3/s  

Increase  of  Freshwater  and  mild  brackish-­‐water  area  (0-­‐2ppt):  q Khulna  division:  addiAonal  2600  sq.  km  area  become  less  than  2ppt  q Barisal  division:  addiAonal  60  sq.  km  area  become  less  than  2ppt  

 Effect  of  infrastructure  development:  Ganges  Barrage  

Effect  of  Sea  Level    on  2ppt  Salinity  contour    (A1B,2050)  A1B  scenario,  March  2050  

2ppt  salinity  line  

Base  2050  

Addi6onal  Area  to  be  affected  by  salinity:  More  than  1  ppt:  7000  km2  

More  than  2ppt:  8400  km2  

CONCLUSIONS  

•  The  present  fresh  water  pocket  in  the  south  central  zone  (Barisal)  is  likely  to  be  more  saline  (2-­‐4ppt)  with  52cm  sea  level  rise,    in  2050  

 •  Regional  CooperaAon  is  crucial  for  trans-­‐boundary  flow  sharing  for  salinity  

Control  in  the  changing  climate  •  AdaptaAon  measures  like  Ganges  Barrage    and  Brahmaputra  Barrage  are  

important  for  water  security  under  climate  change    •  New  salt  tolerant  cropping  technology  needs  to  be  introduced  

•  There   is   abundant   fresh   water   for   irrigaAon   in   much   of   Barisal  Division   throughout   the   dry   season.   The   water   will   remain  suitable  for   irrigaAon  all  over  the  year   in  the  changing  climate   in  2030  with  22cm  SLR.    

29  

Thanks for kind attention