Prof. Dr. Hari K. ShresthaNepal Engineering College

December 16, 2015New Delhi, India

Ongoing activity of “Hydropower development in the context of climate change: Exploring conflicts & fostering cooperation across scales & boundaries in the Eastern Himalayas”

(CoCooN-CCMCC Project)

Developing regional collaboration in river basin management in response to climate change: Final Workshop

The impact of hydropower projects on water availability in Tamor Basin, Koshi, in the context of climate change

Tamor River Basin Location

Satellite image of Tamor River Basin Rivers in Tamor River Basin

Tamor River Basin: Background Info

(Pathak, 2014)

Location of past disaster events in the Tamor Basin (DesInventar, 2011)

Regional Geological Map of the Tamor Basin

Tamor River Basin: Background Info

(Pathak, 2014)

Land use map of the Tamor Basin

Landslide hazard map of the Tamor Basin

Tamor River Basin: Background Info

(Pathak, 2014)

No basin specific dataHydrological Similarity

of nearby stations

Trend of average annual flow (m3/s)

Trend of peak flow (m3/s)

River flow is decreasing in Teesta.

Panday et al., 2013

Daily

mea

n di

scha

rge

(m3 /

s)

Decreasing River flow at Tamor (Majhitar) Data source: DHM

River flow is decreasing in Tamor.

Climate Change Projection of Hewa Sub-basin, Tamor Basin, Nepal

Data Source: DHM/ADB

Projection: Precis A1B Scenario

Type: Daily Bias Corrected

Hydrological Model: VMOD

JanFe

bMar

AprMay

Jun JulAug

Sep Oct Nov

Dec0

0.51

1.52

2.53

3.54

2.24

3.523.22

2.33

1.15

1.821.98 1.86 1.88

2.59

3.27 3.23

Increase in average temperature (2050's)Station: Melung

Month

Incr

ease

in a

vera

ge T

empe

r-at

ure

0C

Projected Average Temperature Change in MelungProjected: 2050’sRange: +1.15 to + 3.52 0CAverage: + 2.42 0CLocation: Melung Meteorology station

Melung

Phidim

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec0

1

2

3

4

5

2.54

4.28

3.34

1

1.77 1.671.44

1.811.94

1.77

2.452.72

Increase in average temperature (2050's)Station: Phidim

Month

Incr

ease

in a

vera

ge T

empe

ratu

re 0

C

Projected Average Temperature Change in PhidimProjected: 2050’s, Range: +1.0 to + 4.28 0CAverage: + 2.22 0C, Location: Phidim Meteorology station

Changes in Rainfall MelungAnnual Rainfall: + 12.5 %Monsoon rainfall: +16%Winter: -26.6% PhidimAnnual Rainfall: + 21 %Monsoon rainfall: +24.6%Winter: -26%

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec0

100

200

300

400

500

600

700Melung Rainfall , mm

Rain

fall,

mm

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec0

50100150200250300350400

Phidim Rainfall, mmRa

infa

ll, m

m

CC 2050’s

CC 2050’s

Rainfall will reduce in dry period and increase in wet period. Not a good news.

Upper Hewa KholaAnnual average flow: + 22 %Rainy season average flow: +33%Winter: -5.3%Pre-rainy season average flow: -24%Post-rainy season average flow: +20%

Lower Hewa KholaAnnual average flow: + 34 %Rainy season average flow: +50%Winter: -8%Pre-rainy season average flow: -19%Post-rainy season average flow: +28%

Summary of CC modeling

• Decrease in dry season flow → water availability for HPP and other productive uses decrease → potential source of conflict

• Increase in wet season flow → flood, landslide, debris flow, river bed aggradation, reservoir fill up

• Increase in temperature, number of high temperature days will increase → decrease in production, increase in evapotranspiration rate

• 24-hr max rainfall of 100 years return period now in 10 years• Flow duration curve shift → Q40 value will decrease• HFL level and scour depth will increase → need to design

structures accordingly, traditional design may not work

Blurred figureBlurred data

Approximate HPP locations in Hewa Khola Basin, Tamor, Nepal

Hewa Khola

Pheme Khola

Layout of Lower Hewa HPP → More than five km of dry river stretch in the absence of e-flow

November 18, 2015: Hewa discharge: 4.5 m3/s, Pheme Discharge: 2.0 m3/s. Difference between estimated/adopted and real river flow affects water availability for HPPs and other productive uses of water, and can cause conflict.

Factors considered: monthly variations in (a) river flow, (b) e-flow, (c) crop cycle/type, (d) population increase, (e) water supply, (f) rainfall(g) industrial and “other” water needs, (h) return flow and (i) CC.

Concept too simple?Does not consider details of each parameter?Compromise accuracy?Has to be, in the beginning, if it is to be adapted/implemented by policy makers and decision makers.

Activities related to linkage between Hydropower and Water Availability

• Environmental Flows Assessment (EFA) syllabus prepared (jointly with IWMI), approved by Pokhara University: expected to have sustained impact as some of the graduates will eventually work in water management sector

• EFA training conducted jointly with IWMI and participated by policy makers and HPP designers; lower level officers convinced; discussion with decision makers under progress

• CC modeling to estimate changes in river flows• Water requirement estimation based on crop cycle, crop type and other

livelihood activities• Conceptual water availability accepted by district level officers, further

works needed for implementation by DDC and MoSTE• Primary data monitoring started, for data quality check

Planned Activities• Additional hydro-meteorological data collection, interaction

with local residents on perceived CC and impact on livelihood• E-flows assessment seminar• Interaction with DoED, NEA and MoSTE on adoption of e-

flows assessment method for HPPs• Interaction with MoSTE and DDC officials on HPP water

availability assessment method• Revise trend and CC modeling• Finalize tool to estimate water availability for HPPs, in each

basin.

Regional Collaboration in response to CC

• Policy analysis related to hydropower and water availability jointly by institutes in Nepal and India

• Biophysical issues, like e-flow, hydropower tunnel-spring relation jointly being studied, and data shared between Nepal and India; Pani-satsang, e-flows training to policy makers organized jointly, CC model outputs shared.

• Post-doc candidates having study sites in Nepal and India.• Hydropower proponents, HPP designers and policy makers

represented in joint discussions.• Hoping to raise level of mutual confidence, which is the

fundamental issue in developing regional collaboration in river basin management.

The activities related to the CoCooN-CCMCC Project is funded through Netherlands Organization for Scientific Research (NWO) by the Department of International Development (DFID), UK.

Thank you.For further query: email: hari@nec.edu.np