This document analyzes how climate change may alter snow melt driven flow regimes in the Sunkoshi River basin in Nepal. It finds that under climate change scenarios from 2031-2060: 1) Temperatures are projected to increase by 0.047-0.043°C per year, leading to more winter snow melt and less glacier storage. 2) Precipitation patterns vary between models but generally increase, correlated to increased runoff. 3) Peak flows and magnitude are projected to increase significantly from baseline levels, posing flood risks.

1. ALTERATION IN SNOW MELT
DRIVEN FLOW REGIME IN
CLIMATE CHANGE SCENARIO
Anita Khadka, L. P. Devkota, R. B. Kayastha
Nepal Development Research Institute

2. Precip
itation
Temper
ature
SCA
DDF
Lapse
rate Critical
Temp Runoff
Coeff
Recession
Coeff
RCA Time
Lag
SRM
Model
MODEL
Calibration &
Runoff
Simulation
Runoff in
Climate Change
Scenario
Temperature
Precipitation
PRECIS:
ECHAM05
HadCM3
(2031-
2060)

3. STUDY AREA
Basin Area (Km2) 5187
Area in Nepal 55%
Areal Length, km 140
Area > 5000 m 1970
SCA in Km2 692.31 (13 %)
SCA > 5000 m (%) 27.50
No. of Glacial Lakes 29
Elevation Range, m 545 – 7938
No. of Elevation
Zones
11
Basin Characteristics – Sunkoshi

4. RESULTS

5. Temperature
10
15
20
25
Temperature,°C
Dhulikhel Panchkhal
Stations
(trend)
ECHAM05
(°C/year)
HadCM3
(°C/year)
Panchkhal 0.047 0.042
Dhulikhel 0.047 0.043
15
17
19
21
23
25
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
Temperature,°C
Panchkhal_E Panchkhal _H Dhulikhel_H Dhulikhel_E
Historic
Projected
HYDROMETEOROLOGICAL DIAGONOSTIC

6. PRECIPITATION
y = 28.963x + 2761.9
y = 19.646x + 2818.8
2000
2500
3000
3500
4000
4500
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
Precipitation,mm
ECHAM HadCM3
Projected
y = 23.456x + 2511.2
0
500
1000
1500
2000
2500
3000
3500
4000
4500
Precipitation,mm Historic

7. Discharge
y = -2.5113x + 274.35
0
50
100
150
200
250
300
350
Discharge,m3/s

8. 0
10
20
30
40
50
60
70
800
200
400
600
800
1000
1200
2000
2000
2001
2001
2001
2002
2002
2003
2003
2003
2004
2004
2005
2005
2006
2006
2006
2007
2007
2008
2008
2008
Precipitation,mm
Discharge,m3/s
Average ppt Mesured Computed
0
500
1000
1500
2000
2500
2000 2001 2002 2003 2004 2005 2006 2007 2008
Discharge,m3/s
Measured
Computed
SIMULATION RESULTS Calibration Year:
2001
NSE: 0.88
Dv: 7.32
On average
NSE: 0.81
Dv: 4.74

9. SNOW MELT RESULTS
0
100
200
300
400
500
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
ECHAM HadCM3
00-08 41-50 51-60 31-40
Season % contribution
Average 6.41
Winter 21.17
Pre-monsoon 14.87
Monsoon 4.28
Post-monsoon 19.53
ECHAM05 HadCM3
10.09 9.14
29.07 20.95
18.91 18.27
6.85 6.39
20.52 19.59
Baseline 2030-2060 (av)

10. RUNOFF
y = 1.4974x + 161.39
y = 1.3246x + 163.51
100
130
160
190
220
250
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
Flowinm3/s
ECHAM HadCM3
Season
2031-2040 2041-2050 2051-2060
ECHAM HadCM3 ECHAM HadCM3 ECHAM HadCM3
Average -9.83 -10.25 1.38 2.44 7.33 5.49
Winter -0.92 -3.10 3.56 10.40 5.41 8.10
Pre-monsoon 2.85 -4.75 19.41 5.60 34.18 8.85
Monsoon -12.99 -12.04 -0.78 -4.41 4.54 3.18
Post-monsoon -1.78 -6.21 4.27 42.06 12.50 17.58
PERCENTAGE CHANGE IN FLOW

11. RUNOFF RESPONSE– PROJECTED PERIOD
0
100
200
300
400
500
600
700
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Discharge,m3/s
00-08
31-40
41-50
51-60
0
100
200
300
400
500
600
700
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Discharge,m3/s
00-08
31-40
41-50
51-60
HadCM3
ECHAM05

12. RUNOFF RESPONSE– PROJECTED PERIOD
Decade
ECHAM05 HadCM3
Qmax N Qmax N
2031-2060 2384.53 41 2171.76 31
2031-2040 2000.17 11 1759.63 7
2041-2050 2384.53 17 1736.07 9
2051-2060 2023.42 13 2171.76 15
0
500
1000
1500
2000
2500
3000
2031 2033 2035 2037 2039 2041 2043 2045 2047 2049 2051 2053 2055 2057 2059
Dischage,m3/s
ECHAM
HadCM3
Peak Q
FREQUENCY & MAGNITUDE OF PEAK FLOWS Qmax in baseline = 1195.8m3/s

13. CONCLUSION
 The daily discharge is efficiently simulated by SRM
model in Sunkoshi basin
Gradual increase in snow melt contribution follows
the pattern of increasing temperature.
Changes in precipitation is correlated to variation in
runoff (also peaks) generated in the basin.