Presentation at ARRCC-CARISSA workshop 29 Jan 2019 to 31 Jan 2019

1. Climate Risk Assessment of the
Hydropower Sector in Nepal: Issues and
Challenges of Using Climate Projections
Divas B. Basnyat
Nepal Development Research Institute (NDRI)
divas@ndri.org.np
1
30 January 2019, ICIMOD, Kathmandu, Nepal
Regional Workshop - Future Climate Projections and their Applications in South Asia

2. Outline
• Current and Future Climate (Projections) of
Nepal
• NDRI’s experience using climate projections
• Background- Climate Risk Assessment of the
Hydropower Sector in Nepal
• Issues and challenges in using Climate
Projections
2Regional Workshop- Future Climate Projections and their Applications in South Asia

3. Precipitation - variability
3
GPCC Precipitation
Observed Precipitation
Lack of reliable and long-term hydro-met data especially in higher elevations is a key
limitation to understanding current risks and future changes. Source: NDRI et al (2017)
Regional Workshop - Future Climate Projections and their Applications in South Asia

4. Hydrological Variability
4
High seasonal and
inter-annual variations
-Higher in rain-fed than
in snow-fed catchments
-Higher in smaller
catchments
Variability is influenced by
catchment elevation, size
and location
Source: NDRI et al (2017)
Regional Workshop - Future Climate Projections and their Applications in South Asia

5. Climate Projections : 2040-2059
5
• Most models project higher monsoon precipitation but winter
precipitation is more uncertain
• Warmer future but models vary in magnitude of change
Source: NDRI et al (2017)
Regional Workshop - Future Climate Projections and their Applications in South Asia

6. • Higher extreme precipitation means higher flood and related
sediment load
• GCM models project increase in 1-day and 5-day maximum
precipitation
Extreme Precipitation
6
Source: NDRI et al (2017)
Regional Workshop - Future Climate Projections and their Applications in South Asia

7. NDRI Experience on Climate
Projections
Project GCM/RCMs Used
Disaster Risk Reduction
and Climate Change
Adaptation in the Koshi
River Basin, Nepal
(2012) – START/CDKN
• Two RCMs- PRECIS – HadCM3Q0 and PRECIS – ECHAM05
(IPCC SRES A1B) - DHM Data Portal
• Bias corrected using power- transformation method for P
and simple mean and standard deviation correction for T
• Both models are wet biased over the Koshi Region
• RCMs models are cold-biases for most of the study area.
Flood inundation
analysis in lower West
Rapti Basin (2010) -
ICHARM
• Two GCMs, MRI-AGCM 3.1S and 3.2S under IPCC A1B
(ESGF portal)
• Bias Correction - Distribution mapping; APHRODITE used
• Magnitude and frequency of floods projected to increase
Adaptation to climate
change in
Hydroelectricity sector
in Nepal (2016) - CDKN
• 23 CMIP5 GCM models for scenarios, RCP4.5 and RCP8.5
(http://climatewizard.ciat.cgiar.org)
• Wide variations and uncertainty in projections
• Bottom-up CRA adopted
7Regional Workshop - Future Climate Projections and their Applications in South Asia

8. Climate Risk Assessment (CRA)
8
Source: García, L.E. et al., 2014; Ray & Brown, 2015
Regional Workshop- Future Climate Projections and their Applications in South Asia

9. Key Indicators – Water, Food and Energy
Security
Key Climate Parameters of Interest
• Water Availability (Supply) -
flow duration (reliability), daily,
seasonal, low flows (droughts),
floods, sediments, landslides
• Renewable energy – solar, wind
• Precipitation (P) variation –monsoon pattern,
intensity and frequency (shorter intervals –
hours, days), cloud bursts, rain, no-rain days …
• Temperature – temporal and spatial variation
• Solar radiation, cloud cover, wind
• Agriculture – crop water
requirements, cropping
patterns, yield ..
• Precipitation (reliability, variation)
• Reference Evapotranspiration (ETo) - daily mean
global solar radiation, air temperature, humidity
and wind speed
• Energy (electricity) – heating,
cooling, lighting
• Precipitation, temperature – mean and variation
• Other uses- recreation, aquatic
life, navigation, flood control
• Precipitation, temperature variation
• Intensity and frequency of P (hourly, daily)
9Regional Workshop - Future Climate Projections and their Applications in South Asia

10. Precipitation
Rainfall
Infiltration
Soil
Evaporation
Lateral
Flow
Plant Uptake
and
Transpiration
Percolation
Shallow
Aquifer
Deep Aquifer
Return Flow
Surface
Runoff
Streamflow
Transmission
loss
Snowfall
Snowcover
Snowmelt
Seepage
Time delay Time delay
Threshold Temperature
Understanding Runoff response to Climate Change
using SWAT Model
10
Rainfall- Run-off - Curve Number
PET Calculation - Hargreaves
Snow melt–
Degree Day Model

11. Runoff response to CC-
Jammu
11
U/S Outlet D/S outlet (JAMMU)
Water Yield(mm) for Pre Monsoon
U/S
D/S
MID
Source: NDRI et al (2017)
Regional Workshop - Future Climate Projections and their Applications in South Asia

12. 12
T-Sensitivity: Impact on Water
Balance(Jammu)
U/S
D/S
MID
Upstream Mid-stream Down-stream
Snowfall(mm)Snowmelt(mm)ET(mm)Yield(mm)
T-Sensitivity: Impact on Water Balance

13. • Nepal has complex, climate, hydrology and topography
• Wide differences in vulnerability, plants, locations, etc
• Future climate change is very uncertain
• Technically possible to address all risks ,
but danger too much or too little
• Trade off between costs now
versus future benefits later
Adaptation is challenging
13Regional Workshop - Future Climate Projections and their Applications in South Asia

14. We want to know what to do
now! not what to do in 2050
14
IRR 12%
IRR 11.2%
IRR 10.9%
IRR 11.4%
Base
CC
Adapt
in
design
Learn,
Act
later
+40
+80

15. Impacts of climate and non climate factors on project
economics of Hydropower Projects
%
0%
5%
10%
15%
20%
UP UP UP UP Phased Phased Phased Phased
Hewa Kabeli RG KGK Hewa Kabeli RG KGK
IRR
IRR
Base Median Scenario Worst Case + Extreme
Discount Rate
Regional Workshop - Future Climate Projections and their Applications in South Asia

16. Issues and Challenges
• Deep uncertainty – multiple projections, data scarcity, model limitations
• Downscaling and bias correction (scarce observations, current climate highly
variable)
• Skill to model Asian Monsoon esp. the Himalayan region (topography, micro-climate
etc.)
• Skill of Climate Models at appropriate temporal (daily/monthly) and spatial scales,
extreme events (floods and droughts) relevant to water projects
• Selection of Climate Models (envelop method) – sectoral needs
• IPCC’s 1.50C warming target- what does it mean to mountain catchments?
• Communication gaps among climate scientists, hydrologists/analysts, decision
makers – e.g. on information on basic principles and dynamics (process) of climate
models
• Conventional hydrological analysis (e.g. frequency analysis) based on “stationarity”
of the variables, climate change introduces “non-stationarity”
• Stakeholders’ perspective (private sector, government, ..) – future impacts?
• ?
16Regional Workshop - Future Climate Projections and their Applications in South Asia

17. 17
Thank You