Impact of Climate Change on Himalayan Water Resources Dr Manohar Arora National Institute of Hydrology, Roorkee

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’ Climate Change 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.

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 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 Evidences of Climate Change

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 −1 over the period 1993 to 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 INDUS BASINBRAHMAPUTRA BASIN J&K Indus,Nubra,Shyok, Jhelum,Gilgit Glaciers Area km 2 Avg.size sq.km H.P Chenab,Beas,Ravi Satluj Rivers Glaciers Area Avg.Size km 2 SIKKIM Tista River Glaciers Area km 2 2 Avg.Size -1.59km ARUNACHAL Kamang River Glaciers -162 Area -228km 2 Avg.Size km 2 GANGA BASIN Indus : 8039 Glaciers Area : km 2 Ganga : 968 Glaciers Area : 2857 km 2 Brahmaputra : 611 Glaciers Area :934 km 2 Uttarakhand Glaciers- 968 Area- 2857km 2 Avg.size km 2 NEPAL&BHUTAN 3500 Glaciers Total India 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 32N 28N 24N 72E 80E Summer Monsoon + Winter snow regime (Himalayan catchment) 88E 96E

AVERAGE SNOW COVERED AREA IN DIFFERENT HIMALAYAN BASINS BasinTotal AreaMax. SCAMin. SCA (km 2 ) Chenab Basin up to Akhnoor Ganga Basin up to Devprayag Satluj Basin up to Bhakra Dam Beas Basin 5278 up to Pandoh Dam (70%) 9080 (46%) (65%) 2700 (51%) 5400 (24%) 3800 (19%) 4528 (20%) 780 (14%)

SNOW AND GLACIER MELT RUNOFF IN DIFFERENT HIMALAYAN BASINS River Chenab River Satluj River (Indian part) Ganga River Site Akhnoor Bhakra Dam Devprayag Av. snow & glaciers melt contribution to annual flows 49% 60% 30%

TYPE OF BASINS RAINFEDSNOW/RAINFEDICE/SNOW/ BASIN RAINFED BASIN (Outer Himalayas)(Middle Himalayas)(Greater Himalayas) STREAMFLOW

Snow * * * * * * * * * Snow and rain * * * * * * * * *.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.*.* Rain Figure 1: A schematic presentation of the rainfed, snowfed and glacierfed basins.

NIH Roorkee 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.

NIH Roorkee 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: m. Snow covered area : About 65% after winter Glacierized area: About 10% Important hydropower scheme: Bhakra Dam (1000 MW) Effect of increase in temperature on mean monthly snow melt runoff for a period of 3 years (1996/ /99) in the Sutlej River Basin.

NIH Roorkee 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. Objective: To study the impact of warming on the snowmelt runoff and total streamflow

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 Total drainage area up to the gauging site ~ 16.13km km2 (60%) is covered by snow and ice. Elevation range m. Length ~ 5.5 km, Width ~ km. Maximum glacier area (12.86%) lies in m range and 12.44% in the m. EFFECT OF CLIMATE CHANGE ON FLOW REGIME OF A GLACIERISED HIMALAYAN BASIN (Dokriani Glacier)

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

How certain are the changes ? “ Climate is changing, the risk is unacceptable! “ Scientist Water manager

Scientist “ How much.. ? “

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