Presented at a workshop on "Developing regional collaboration in river basin management in response to climate change” Thursday 19 – Friday 20 December, 2013 Thimphu, Bhutan

1. Workshop on
Developing regional collaboration in river basin management
in response to climate change”
Thursday 19 – Friday 20 December, 2013
Thimphu, Bhutan
Jagat K. Bhusal
Chairperson, The Society of Hydrologists and
Meteorologists – Nepal.
bhusaljagat@gmail.com
Climate change consideration in hydro‐power
development in the Nepal Himalayan region

2.  Nepal Himalayan river systems
 Water Power to Hydroelectricity
 Conclusion
 Flows trends, Observations and Facts
 Propositions (Climate change and Hydro Potential)
 Uncertainties ?
Presentation includes

3. Two rainy seasons
 June to September
(70% to 80% of the
total rainfall)
 Other months
(remaining 30% to 20%
of the total rainfall
More than 6000 rivers and rivulets are located in Nepal
Approximat
ely 78% of
Nepal is the
mountainou
s region

4. Electric power (P) = Q*H*g
Height
Flows are dynamic and
variable, influenced by
several factors like
rainfalls and climatic
conditions, climate
changes, watershed
characteristics and
changes etc
[The energy of the Hydrologic Cycle, which is
driven by the sun, is tapped most efficiently
with hydropower].
The mean monthly flows.
The flow duration curves
The design floods for
The return periods of 50, 100 yr, so on.
The diversion flood (construction time) ie 20 yr
Sedimentconcentration and sediment
load in the river
The potential GLOFs risk &
snow melt

5. Increase
Production
Decrease
Production
Climate change
Change in precipitation Change in temperature
DecreaseIncrease DecreaseIncrease
Snow and glacier melt
increase
Evaporation
decrease
Increase
discharge
Decrease
discharge
Temporal
variability Evaporation
increase
Temperature rise
continues - No more
glaciers
CLIMATE CHANGE HYDRO POTENTIAL

6. Trends in Temperature, Precipitation and Runoff
0.04°C to over 0.06°C over Nepal (Shrestha et al 1999, Baidya et al 2008).
 0.032°C and 0.016°C at a Met Stn at Mustang (Ele 2566 meter)
The raising
trend is seen
in daily
maximum
temperatures
The increasing
trend is seen
in annual
runoff in
glacier fed
rivers

7. Trends in Annual Runoff of main rivers
Among three large rivers, Karnali (c) and Sapta Kasi (a) show a
decreasing trend, but Narayani (b) shows an increasing trend.
All three major non snow-fed rivers show a declining trend

8. Trends in flow durations of main rivers
Rivers with snow-glaciered rivers: shift in duration curves observed.
Q25 : + 34% ,
Q65 : +14 %
Q mean 40% , 17%
Q25 : +7%
Q65 : (- )20 %
Q mean 8% , (-) 9%
Q25 : (-) 10% / (-2%) ;
Q65 : (- ) 10 %/ (-2%)
Q mean 2% and 5% and (-) 13%

9. -30%
-20%
-10%
0%
10%
20%
30%
0% 20% 40% 60% 80% 100%
Differenceinpercentileflow%
Probability of Exceedance (%)
Kasi river basin
Q_77-06 Q_84-85
Q_94-96 Q_04-06
Flow duration curve
derived from whole data
series (1977 to 2006 for
Kosi and 1963 to 2010 for
Bagmati river) is
considered as base data
for comparison
-60%
-40%
-20%
0%
20%
40%
60%
80%
100%
120%
0% 20% 40% 60% 80% 100%
Differenceinpercentileflow%
Probability of Exceedance (%)
Bagmati headwater basin
Q_63-2010
Q_64-66
Q_84-85
Q_94-96
Q_04-06

10. Trends in flow durations curves of main rivers
Rivers with non snow fed rivers: Alteration in flow duration curves as
observed.
Bagmati river, the long term 92.3% dependable flow, which is currently
21.1 m3/sec, is projected to decline to 9.86 m3/sec by 2030, and will be
only 7.43 m3/sec under CO2 doubling (Shakya 2003).

11. Annual Mean Rainfall Trend
[Suggestion to a hydropower project ( based on data of a stream 87 km2)]
The country receives about 79.6%, 4.2%, 3.5% and 12.7% of the
total annual rainfall during Monsoon, Post-monsoon, winter and Pre-
monsoon seasons respectively. A preliminary study carried out by
DHM/SOHAM/Practical Action indicated that there is an annual
variation trend of about (+/-) 4 mm to 40 mm of rainfall per year. It
means there will be fluctuation in flows of 0.9 to 1.37 m3/s annually.
Therefore, if the present climate change exist, there is a probability of
decrease in flows by 3% per year
There are several findings on regional level by various researchers

12.  Science Daily, 2009 said - South Asia’s climate and hydrological cycles are
significantly impacted by the monsoon, is likely to alter by climate change
MoPE (Nepal) /UNEP, 2004 – (Considers the average environmental lapse rate of 6.5o C /km)
 1 0C rise → almost 20 % of the glaciated area above 5000 m is likely to be
snow and glacier free area
 2 0C rise → Lead a loss of almost 40 % of the snow and glacier area.
 3 0C & 4 0C rise → Expected loss is 58 % and 70 % of snow and glacier areas
respectively in Nepal.
 Changes in snow and glaciated area are directly linked to runoff generation
and hydropower potential. Temporal and spatial variability in precipitation and
evaporation is additional effect to hydropower added by climate change.
The increase in temperature would shift the snowline upward, which reduces
the capacity of natural reservoir. While such changes will cause an increase
in hydro energy for some years but do not sustain for longer time.
 The number of flood days and consecutive days of flood events appeared to be
increasing (Shrestha and Shrestha 2003
 The high melting season in the Himalayas coincides with the summer monsoon
rainfall, which contribute to increased summer runoff and flood disasters (IPCC, 2001b,
p.565).

13. • A direct result of rainfall—splash
erosion, sheet erosion, rill erosion,
and gully erosion.
• In splash erosion, the impact of a falling raindrop creates a
small crater in the soil, ejecting soil particles.
Increasing trends in Rainfall Intensities has been increasing
sediment in rivers.
RIVER SEDIMENT and CLIMATE CHANGE
 Melting of Permafrost intensified by warming causes increase of sediment load
in rivers
 Shakya (2003) points out that 90% of debris volume in Nepal is transported by
approximately 20% of rainfall.

14. Neither model is perfect to quantify the nature. The variation in models’ outputs
is believed due to the smaller hydrometeological observation network and short
data series (Soito, J. L., Freitas D. S. 2011).
Unsolved question is whether the rise in temperature is to be expected to be
linear over the time; whether the present rate of temperature rise over the
Himalayan region will continue or will show some discrepancies/stability in
future.
The water storage might be a potential adaptation to response to increased
variability in stream-flow and reduced dry season flows for sustainability of
forecasted energy output from hydro projects.
But there is also a risk of environmental objectives that might conflict
with large storage projects. Dams could potentially exacerbate vulnerability to
another potential impact if breached. Trans-boundary or regional dimension to
certain impacts also demands need for regional coordinated strategies to cope
with impacts of climate change.
UNCERTAINTIES ?

15. • Hydroelectric plants are highly dependent on predictable runoff
patterns, greater unreliability of dry season flows, in particular,
poses potentially serious risks to hydro electric energy production in
the lean season.
• The dark side of glacial lake outburst floods is that floods pose
significant risk to hydropower infrastructures and facilities.
• Intense precipitation events, increased floods, landslides, and
sedimentation (particularly during the monsoon) are expected to
result from climate change. River sedimentation possesses high risk
to Hydropower turbines, infrastructure and facilities.
• Melting of Himalayas will increase hydro energy for some years
while the potential will decrease in longer time.
Changes in electricity production depends on climate alterations, but
vulnerabilities vary on types and scales of hydropower whether, it is a run-of-
river, a reservoir, or a pumped storage. Large-scale reservoir dams are able
to regulate flow, produce electricity as desired but increase to evaporation
losses.
CONCLUSION

16. CONCLUSION
The effect of climate changes is observed to be heterogeneous over different
ecological zones of Nepal Himalaya. Several studies find that there is change
in rainfall and temperature pattern in specific areas which impinge
significantly on the water resources.
Shift in temporal pattern in precipitation and longer dry months has been
altering recession curves and flow duration which emphasizes in
considering adoptive measures in development of hydropower.
Regional coordinated strategies are required to minimize impacts of climate
change on Trans-boundary rivers. Therefore, the regional cooperation and
collective efforts are vital in the development of hydropower and to cope
with climate change.
Above all, neither a river nor the Sun (Solar Power) and the atmosphere are
constrained by man made political boundaries. Climate change impact
significantly spreads over local to global and vice versa.
Regional cooperation in water resources would be further strengthened by
developing collaboration in river basin management in response to climate
change.

17. THANK YOU