Download Dr Manohar Arora

Impact of Climate Change
on
Himalayan Water Resources
Dr Manohar Arora
National Institute of Hydrology,
Roorkee
Climate Change
United Nations Framework Convention on Climate Change
(UNFCCC) defines “climate change” as: ‘a change of climate
which is attributed directly or indirectly to human
activities that alters the composition of the global
atmosphere and which is in addition to natural climate
variability observed over comparable time periods’
General Definition: Any systematic change in the long-term
statistics of climate elements (such as temperature, pressure, or
winds) sustained over several decades or longer.
Evidences of Climate Change
The globally averaged combined land and ocean surface
temperature data as calculated by a linear trend, show a
warming of 0.85 [0.65 to 1.06] °C over the period 1880 to 2012.
On a global scale, the ocean warming is largest near the surface,
and the upper 75 m warmed by 0.11 [0.09 to 0.13] °C per
decade over the period 1971 to 2010.
The average rate of ice loss from glaciers around the world,
excluding glaciers on the periphery of the ice sheets , was very
likely 226 [91 to 361] Gt yr−1 over the period 1971 to 2009, and
very likely 275 [140 to 410] Gt yr−1over the period 1993 to 2009.
The rate of sea level rise since the mid-19th century has been
larger than the mean rate during the previous two millennia (
high confidence). Over the period 1901 to 2010, global mean sea
level rose by 0.19 [0.17 to 0.21] m
Inaccessible & inhospitable mountainous conditions
Variation in altitude, slope, aspect, soil, and landuse
Hydro-meteorological characteristics change over short
distances (say on windward and leeward sides)
Quite sparse hydrological network in various basins
Need for high density of hydrometric stations for reliable
assessment of hydrological variables
In addition, need for proper design of hydrometric
network and installation of automated telemetry stations
Hydrological network and database
Impact of climate change on regional water resources
Changing glacial resources
Flash floods generated from Cloudburst/GLOF
Excessive soil erosion and siltation in river flows
Conservation & management of lakes & springs
Distribution of Glaciers in the Indian Himalaya
J&K
INDUS BASIN
H.P
BRAHMAPUTRA BASIN
Indus,Nubra,Shyok,
Jhelum,Gilgit
Chenab,Beas,Ravi
Satluj Rivers
Glaciers - 5253
Area - 29163 km2
Avg.size - 10.24 sq.km
Glaciers -2786
Area -4466
Avg.Size - 3.35km2
SIKKIM
ARUNACHAL
Tista River
Kamang River
Glaciers - 449
Area - 706 km2
Avg.Size -1.59km
2
Glaciers -162
Area -228km2
Avg.Size - 1.41 km2
GANGA BASIN
Indus : 8039 Glaciers
Area : 33629 km2
Uttarakhand
Glaciers- 968
Area- 2857km2
Avg.size - 3.87km2
Ganga : 968 Glaciers
Area : 2857 km2
NEPAL&BHUTAN
Brahmaputra : 611 Glaciers
Area :934 km2
3500 Glaciers
Total - 13075
India- 9575 glaciers (GSI)
Climate & Hydrology vary across the Himalayas offering diverse
challenges
Glacio-Hydrological regimes of the Himalaya
Winter Snow
regime (Alpine)
Cold-Arid regime
36N
Chenab Basin
Summer Monsoon +
Winter snow regime
(Himalayan
catchment)
32N
28N
24N
72E
80E
88E
96E
AVERAGE SNOW COVERED AREA IN
DIFFERENT HIMALAYAN BASINS
Basin
Total Area
(km2)
Max. SCA
(km2)
22200
15590 (70%)
5400 (24%)
Ganga Basin
19700
up to Devprayag
9080 (46%)
3800 (19%)
Satluj Basin
22275
up to Bhakra Dam
14498 (65%)
4528 (20%)
Beas Basin
5278
up to Pandoh Dam
2700 (51%)
780 (14%)
Chenab Basin
up to Akhnoor
Min. SCA
(km2)
SNOW AND GLACIER MELT RUNOFF
IN DIFFERENT HIMALAYAN BASINS
River
Site
Av. snow & glaciers
melt contribution to
annual flows
Chenab River
Akhnoor
49%
Satluj River
(Indian part)
Bhakra Dam
60%
Ganga River
Devprayag
30%
TYPE OF
BASINS
RAINFED
BASIN
SNOW/RAINFED
BASIN
ICE/SNOW/
RAINFED BASIN
(Outer Himalayas)
(Middle Himalayas)
(Greater Himalayas)
STREAMFLOW
STREAMFLOW
STREAMFLOW
Snow
Snow and rain
*********
*********
*********
*********
.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*
.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*
.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*
.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*
Rain
Figure 1: A schematic presentation of the rainfed, snowfed and glacierfed
basins.
Chenab Basin Study
Elevation of the study area varies
from
~ 305 m to 7500 m.
Total catchment area up to
Akhnoor is
22,200 km2.
Total Number of Glaciers is 989.
Glacierized Area is 2280 sq km.
8000
Observed discharge
Simulated discharge
Rainfall runoff
Melt runoff
Baseflow
Discharge (m3/s)
6000
4000
2000
NIH Roorkee
0
O N D J F M A M J J A S O N D J F M AM J J A S O N D J F M A M J J A S
1996
1997
1998
1999
Objective: Effect of climate variation on runoff regime of River Chenab
Results:
•An early response for snowmelt runoff is noticed under the warmer climate.
Simulated results under warmer climate show that the peak runoff is increased
for whole water year for all the years
•The average value of increase in snowmelt runoff for T+1C and T+2C scenarios
are obtained to be 10% and 28% respectively
•The average value of increase in total streamflow runoff for T+1C and T+2C are
obtained to be 7% and 19%
•It also indicates that no significant change in the winter streamflow could be
produced for this basin.
•Changes in rainfall by 10% have resulted in increase in streamflow by  10%.
NIH Roorkee
SATLUJ BASIN
Basin Area (Indian part) : 22,275 km2
Elevation Range: 500-7000 m.
Snow covered area : About 65% after winter
Glacierized area : About 10%
Important hydropower scheme: Bhakra Dam
(1000 MW)
2800
Observed streamflow
1996/97
1997/98
Simulated baseflow
2000
3
Streamflow (m /s)
800
1998/99
Mean monthly snowmelt runoff (m3/s)
2400
Simulated streamflow
1600
1200
800
400
T+2 oC 1996/97
1997/98
1998/99
600
400
200
0
0
T+0 oC
N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N
N D J F MA M J J A S O N D J F MA M J J A S O N D J F MA M J J A S O
Effect of increase in temperature on mean monthly snow melt runoff for a
period of 3 years (1996/97-1998/99) in the Sutlej River Basin.
Figure 4: Observed and simulated daily streamflow for the Satluj River at Bhakra for a period of 3 years (1996/97 - 1998/99).
NIH Roorkee
Objective: To study the impact of warming on the snowmelt runoff and total
streamflow
Results:
• Changes in distribution of melt runoff were more pronounced in summer
showing a decrease of about 10% for a temperature increase by 2°C; annual
decrease is about 5%.
• Considering only the lower and middle part of the basin, where snow
disappears in summer, the reduction in snow melt runoff is about 27%.
• High altitude zones containing permanent snowfields/ glaciers throughout the
ablation period produce higher melt under warmer climate.
• On basin scale, reduction in melt from lower zones is counterbalanced by the
increase in melt from upper zones.
NIH Roorkee
Gangotri Glacier Study:
NIH Roorkee
OBJECTIVES
 Continuous observations of hydro-meteorological data to obtain
monthly and seasonal water yield and its variability from the year to
year .
 To study melt water storage and drainage characteristics .
 To simulate daily streamflow using a conceptual hydrological
model using degree-day approach.
 To identify contribution of snow melt, ice melt, rain and
groundwater in total streamflow using isotopic method and to study
their variability during melt season.
 Estimation of suspended sediment concentration and load.
NIH Roorkee
EFFECT OF CLIMATE CHANGE ON FLOW
REGIME OF A GLACIERISED HIMALAYAN
BASIN (Dokriani Glacier)
Total drainage area up to the gauging site
~ 16.13km2
9.66 km2 (60%) is covered by snow and
ice.
Elevation range - 3950-5800 m.
Length ~ 5.5 km, Width ~ 0.1-2.0 km .
Maximum glacier area (12.86%) lies in
5000-5100m
range and 12.44% in the 5100-5200m.
NIH Roorkee
Objective: To study the changes in flow duration curve under different climate
change scenarios of Dokriani Glacier basin located in Garhwal Himalayas
Results:
• The flow currently exceeded 60% of the time (3.2 m3/s in 1998) would be exceeded 70%
of the time under a warming of 2C.
• The flow exceeded 80% of the time would increase by 2% (from 1.5 m3/s to 1.53 m3/s)
when rainfall is increased by 10% and would decrease by 8% (from 1.5 m3/s to 1.37
m3/s) when rainfall is decreased by 10%.
• Temperature has greater influence than rainfall on water
availability
• Under different rainfall scenarios - rainfall influences low flows more in comparison to
high flows
NIH Roorkee
How certain are the changes ?
“ Climate is changing,
the risk is
unacceptable! “
Scientist
Water manager
“ How much.. ? “
0,7
(Pscenario-Ppresent)/Ppresent
0,5
0,3
0,1
-0,1
-0,3
-0,5
-0,7
jan
feb
mar
apr
may
jun
jul
aug
sep
oct
nov
dec
CSIRO-Mk2
CGCM1
ECHAM4
HadCM2 Gga1
HadCM2 Gga2
HadCM2 Gga3
HadCM2 Gga4
CCSR-98
HADCM2 GSa1
Scientist
Water manager
With time, water demands are increasing while supplies
are getting limited in quantity & quality
In such scenarios , water is getting considerable
attention for its optimum utilization
Himalayan region suffers from some hydrological
problems related to sparse hydrometric network, climate
change impact, flash floods, and sedimentation
There is a need to create the dense hydrometric network
and generate long-term hydrological database for the
region
Glacier and snow-melt have major contribution to the
river flows in the region. It is necessary to characterize
the glaciers in different climatological regions of the basin
To develop adaptation strategies to cope up with the likely
climate change impacts, it is important to carry out
hydrological modeling studies for different basins with
probable climate change scenarios
In view of the enormous hydropower potential in the
basin, plan should be developed to generate maximum
hydropower from the available resources
Sedimentation being a major concern for development of
new projects, watershed prioritization measures may be
adopted to control sediment generation & movement