Introduction:
The
increasing rate of warming is significantly higher in the
Hindu Kush Himalayan (HKH) region than the global
average in the past century (Duet al 2004). The
warming influence is much higher in the Eastern
Himalayas compared with the Greater Himalayan
region (Sheikh et al 2014). These temperature variations can have a potential impact on water resources of the UIB and the dependent downstream irrigation
demand areas, which are of great concern. In HKH region snow melt and glacier melt yield collectively account more than 70% of UIB stream-flows. Most part of HKH lies above 5,000 meters and contains the second-highest peak of K2 mountain i.e. above 8,000meter. Most of the annual precipitation in UIB falls during winter and spring (December-April, DJFMA) due to western disturbances that is eastward propagating synoptic systems embedded into westerly flow (Madhura et al 2014). Whereas the summer monsoon and local circulations only accounts 1/3 of annual precipitation (Young and Hewitt 1990). The climatic conditions of UIB are different from other regions of the country; as the monsoon circulation weakens towards northwest in UIB where high mountains of the Himalaya decrease the effect of monsoon circulation. Although the lower elevation stations do not monitor very high precipitation during both the winter and summer, but in contrast high altitude stations usually recorded much higher precipitation. Previous studies suggested very significant precipitation gradient at high altitudes and even at some parts (>5000 meters) of the basin the annual precipitation exceeds 2000 mm (Mukhopadhyay and Khan 2014). Fowler and Archer (2006), reported an increasing trend in both precipitation and temperature during winter while a cooling in summer temperatures over the past century. The average river flow to Tarbela reservoir at Besham Qila reaches 2425 cumecs (cubic meters per second) with the variation between 80% to 130 % from the mean. There are eight meteorological observatories (Kakul, Garidupatta, Balakot, Astor, Bunji, Skardu, Gilgit, and Gupis) in the study area.
Climate projections:
In RCP8.5, the increase in temperature
for 2006–2035 is 2.2 °C, for 2041–2070 it is 4.2 °C, and
for 2071–2100 it is 5.8 °C. In RCP4.5 the increase in
temperature for 2006–2035 is 0.5 °C, for 2041–2070 it
is 1.5 °C, and for 2071–2100 it is 2.0 °C. The increase in
minimum temperature is high in both scenarios for all
future periods, which is an important parameter for
the sustainability and growth of agriculture in the
region. Northern parts are more likely to
experience an increase in precipitation and temperature in comparison to the southern parts. A higher
increase in temperature is projected during spring and winter over southern parts and during summer
over northern parts. Moreover, the increase in minimum temperature is larger in both scenarios for all
future periods.
The precipitation increase in
both scenarios is almost the same while in 2071–2100
the precipitation increase is 12% (decreasing trend in
comparison with 2041–2070) in RCP4.5 and 20% in
RCP8.5 by 2071–2100.
GCISC References:
Khan, F., Pilz, J., & Shaukat Ali. (2017). Improved hydrological projections and reservoir management in the Upper Indus Basin under the changing climate. Water and Environment Journal.
Mountain Research Initiative EDW Working Group. Muhammad Zia ur Rahman Hashmi (2015). Elevation-dependent warming in mountain regions of the world. Nature Climate Change, 5(5), 424-430.
Shaukat Ali, Li, D., Congbin, F., & Khan, F. (2015). Twenty first century climatic and hydrological changes over Upper Indus Basin of Himalayan region of Pakistan. Environmental Research Letters, 10(1), 014007.
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