Transcript Ahsan Uddin Ahmed

SENSITIVITY OF WATER
RESOURCES OF BANGLADESH
TO CLIMATE VARIABILITY AND
CHANGE
AHSAN UDDIN AHMED
Head
Water and Environment Division
Bangladesh Unnayan Parishad (BUP)
AIACC Regional Workshop: Asia
Sensitivity of Water Resources of Bangladesh
In terms of per capita mean annual availability of
water resources, Bangladesh ranks high.
But there is a great influence of climate variability,
in relation to both temporal and spatial
distribution of water resources.
Such variabilities determine availability and usepotential of water, which in turn characterize agroecological diversity of the country.
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.
AIACC Regional Workshop: Asia
Sensitivity of Water Resources of Bangladesh
Bangladesh is a low-lying delta.
The eastern-Himalayan rivers (GBM) drain
over the landmass of Bangladesh.
The country occupies only about 7% of the combined catchment
area, while it has to drain over 92% of the GBM flows.
AIACC Regional Workshop: Asia
The climate of the
country is strongly
influenced by
monsoon.
Sensitivity of Water Resources of Bangladesh
AIACC Regional Workshop: Asia
Sensitivity of Water Resources of Bangladesh
About 80% of all
rainfall occurs between
June and mid-October.
Such a high seasonal
rainfall variability
results in “too much
water” in monsoon, and
“too little water” in the
dry season.
Peak monsoon brings
flood and flood situation
is accentuated by poor
conveyance capacity,
and high backwater
effect at confluences.
AIACC Regional Workshop: Asia
Usual floods VS Unusual floods
There has been an increase in
frequency for high intensity
floods
Severe floods occurred in 1987,
1988 and 1998
During the deluge of 1998
about 68% of the landmass of
the country was under water
for about 70 days!
Sensitivity of Water Resources of Bangladesh
AIACC Regional Workshop: Asia
Sensitivity of Water Resources of Bangladesh
AIACC Regional Workshop: Asia
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.
Sensitivity of Water Resources of Bangladesh
AIACC Regional Workshop: Asia
Sensitivity of Water Resources of Bangladesh
AIACC Regional Workshop: Asia
Sensitivity of Water Resources of Bangladesh
How climate variability will change under
climate change regime?
AIACC Regional Workshop: Asia
Sensitivity of Water Resources of Bangladesh
100
ECHAM4
HadCM3
80
CSIRO
CCSR
CCC
Monsoon Rainfall Change (%)
60
NCAR
GFDL
40
20
0
-20
-40
-60
1860
1880
1900
1920
1940
1960
1980
2000
2020
2040
2060
2080
Year
A-O Coupled GCM projections of monsoon rainfall (IS92a).
AIACC Regional Workshop: Asia
Sensitivity of Water Resources of Bangladesh
10
Observed
CTL
GHG (2041-60)
9
8
Rainfall (mm/day)
7
6
5
4
3
2
1
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Months
Under climate change scenarios, mean monthly rainfall will show
significant changes over normal (i.e., current variability).
AIACC Regional Workshop: Asia
Number of rainy
days in Bangladesh
will increase by
about 20 days.
Sensitivity of Water Resources of Bangladesh
AIACC Regional Workshop: Asia
Sensitivity of Water Resources of Bangladesh
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.
AIACC Regional Workshop: Asia
Sensitivity of Water Resources of Bangladesh
Thank you so much