fulco ludwig: salt intrusion and water supply
TRANSCRIPT
Climate change impacts on Salt water intrusion in Coastal Bangladesh
Dr. Fulco Ludwig Earth System Science Group
Wageningen University 27 January 2016
Ganges
Brahmaputra
Meghna
GBM BASINS The GBM Basins drain 1.72 Mi km2 area 93% of the area outside Bangladesh 75-80% of flow in 5 months of monsoon
Saltwater intrusion is caused by a combination of sea level rise and reduction of dry season river flows
Dis
char
ge
(m2/
s)
Water Supply for the city of Khulna
§ Khulna is the 3rd largest of Bangladesh § Local water is saline during the dry season § Only deep groundwater can be used for drinking water § Large parts of the Khulna residents drink saline water
during part of the year § ADB and Japanese gvt wanted to invest 250 million US$
in a new drinking water plant § The question is where to build to plant and where to get
the water from and will this be affected by climate change
Salt intrusion in May in Southwest Bangladesh
Modelling framework to assess future salt intrusion
Future Sea Level Rise – end of 21st Century – From IPCC AR5
IPCC 2013
0 SLR 32 cm SLR 88 cm SLR
Impact of SLR on Salinity Intrusion
Hiron Point
Bay of Bengal
Mongla
Khulna
Movement of 5 ppt Salinity line
Source: IWM
Climate change impact on flow of the Ganges under 2 degree warming
-‐60%
-‐40%
-‐20%
0%
20%
40%
60%
80%
100%
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Change in Ganges Flow
Com
pared to
1985
-‐200
5 (%
)
CNRM RCP8.5 (2035-‐2055) SMHI RCP8.5 (2029-‐2049)
Reduction in flow in May when salt intrusion is highest
Climate change impact on salt water intrusion
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Salinity
(PPT)
Atharobanki R: Avge. Salinity in RCP 8.5 Scenario RCP 8.5 (2029-‐2049) Base (1985-‐2005) RCP 8.5 + Gorai Dredging2 degree warming Gorai dreding + 2 degree warming
Where to develop the drinking water plant
Conclusions
§ Combined reduced dry season river flows and sea level rise result in large scale increases in salt water intrusion
§ Salt intrusion is likely to increase in the future in Southwest Bangladesh unless dramatic infrastructure measures are taken
§ Water intake for drinking water supply near Khulna is not suitable due to increasing salt water intrusion
§ This study recommends Mollarhat as intake point due to low salinity
§ In addition a reservoir can be developed