Hydro-meteorological Analysis of Langtang Khola Catchment, Nepal

Tirtha R. Adhikari1, Lochan P. Devkota1, Suresh .C Pradhan2, Pradeep K. Mool3

1Central Department of Hydrology and Meteorology TribhuvanUniversity2Department of Hydrology and Meteorology, Nagpokhari, Nepal3International Centre for Integrated Mountain Development, Lalitpur, Nepal

Contents

• Introduction and Background

• Objective of the study

• Study area

• Meteorological information

• Hydrological information

• Old snow survey information

• Methodology for flow simulation by SRM

• Future work

Introduction and Background

• Water is main natural resource of Nepal, socio-economy of the country through hydro-electricity and irrigation depends on it

• The current global mean temperature is projected to riseby 0.3 to 4.8 °C by the late-21st century ( IPCC, 2013)

• Due to increase of temperature water cycle is intensifiedcausing an increase in global mean precipitation (IPCC,2013)

• At the same time, there is redistribution causing someareas to receive more or less precipitation depending onthe season (IPCC, 2013)

9/11/2015 3

contd …

• High variability in climate, lack of data, large uncertainties inclimate change projection by models and uncertainty aboutthe response of snow and glaciers

9/11/2015 4

Objective

• The main objective: Impact of climate change on flow simulation specially to understand the contribution of snow melt at Langtang Khola Hydrological Station

Data collection

Hydro-meteorological data are collection from DHM, government of Nepal, DHM is initiated snow and glacier hydrological activities in the year 1987 with the GTZ, Germany as a pilot project for 2 years. Full fledge project was started in the year 1990 and completed in 1997.

Introduced tracer technology for determination of river discharge andEstablished a tracer laboratory

6 hydroclimatic stations were established in high Himalayas of Nepal

During the project period:

Location of High altitude Hydro- meteorological Stations in Nepal

0 100 200

Kilometers

Trans-Himalaya

Higher Himalayas

Mahabharat Range

Siw alik

Terai

Central Hills

Legend:

Kathmandu

C HI NA

Langtang

Annapurna

Kanjuroba

Simara

Mt Everest

• Langtang – 3800 m. Langtang

•Khumbu – 4335 m Imja

•Annapurna – 3470 m Modi

•Makalu – 3980 m Barun

•Kanjiroba – 3770 m Sanu Bheri

•Humla – 4220 m Humla Karnali

Study Area

Meteorological station:Latitude: 280 12’ 43”Longitude: 850 31’ 34”

Hydrological stationLatitude: 280 13’ 41”Longitude: 850 34’ 28”

Area: 361 Km2

8

Meteorology of Langtang Khola Kyangjing

Precipitation data information

166

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0

20

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

Co

effe

. of

vari

atio

n

PP

T (m

m)

Month

Kyangjing Average Monthly PPT and its Variations (1988-2014)

Avarage PPT (mm) Coeff of Vearation

Percentage of Seasonal PPT (1988-2014)

76 % of PPT occurs in monsoon season

5% of PPT occurs in winter season

11

4 %

15 %

76 %

5 %

DJF

MAM

JJAS

ON

y = 11,477x - 22299

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1200

19

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PP

T (m

m)

Year

Kyangjing Annual PPT (mm) (1988-2014)

Monthly Average Rainy Days (1988-2014)

26

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0

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30

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

Rai

ny

Day

s

Month

Kyagjing Annual Rainy Days (1988-2014)

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Monthly Average Temperature (1988-2008)

Warmest is July, the average TMAX is 12.3 0C

Coldest is Feb, the average TMIN is 7.2 0C

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

Mean Temp. 0C -1,9 -2,4 0,5 3,4 6,0 8,3 9,9 9,4 7,9 4,5 1,8 0,2

Maximum Temp. 0C 3,1 2,4 5,2 8,0 10,0 11,4 12,3 11,9 10,7 8,5 6,4 5,2

Minimum Temp. 0C -7,0 -7,2 -4,2 -1,3 1,9 5,2 7,5 6,9 5,0 0,5 -2,8 -4,8

-10,0

-5,0

0,0

5,0

10,0

15,0

Tem

pre

atu

re(

0C

)

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Monthly Average Sunshine duration situation (1988-2008)

Lowest sunshine duration Jun and July due to monsoon cloud activity

Highest sunshine duration occurs in April

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

Sunsine Duration (hour) 6 6,5 6,5 7,5 7 3 3 3,5 3,5 6,5 6,5 6

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Sun

shin

e D

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ur)

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Historical Snow Measurements in Langtang valley

Snow measurements work in Feb,1991Department of Hydrology and Meteorology, Governments of Nepal

Historical Snow Measurement Data

Date: 25 Feb 1991 Plce Tsergo-Ri Langtang

Height 4980 m Time15 PM

Exposition SE Air Temperature -80C

Slope Gentile Weather Cloudy

Level 1 Height cm 1 WE (mm) 2 Height (cm) 2 WE (mm) 2 Height (cm) 3 WE (mm)4 Mean density

(g/cm3 )

1 28 59 29 62 29 60 0.21

2 47 198 47 202 47 194 0.42

3 40 170 42 180 40 172 0.42

Sum 115 427 118 444 116 426 0.37

WE = D* h* 10 Density = WE/(h*10)

Hydrology of Langtang Khola

Validity

Rating Curve No. From To

1 01.01.1991 13.06.1993

2 14.06.1993 08.10.1993

1 09.10.1993 29.04.1997

2 30.04.1997 05.04.1999

1 06.04.1999 04.06.2002

3 05.06.2002 13.09.2002

2 14.09.2002 31.12.2006

0

0,5

1

1,5

2

2,5

3

0 5 10 15 20 25 30 35

Ga

ug

e H

eig

ht

(m)

Discharge (cumec)

Rating Curve of Langtang Khola

Rating Curve - 1:

Q = 2.429(H+0.568)2.126

Rating Curve - 3:

Q = 0.654(H+1.889)2.530

Rating Curve - 2:

Q = 0.632(H+1.562)2.716

0,00

0,25

0,50

0,75

1,00

1,25

1,50

1,75

2,00

2,25

2,50

2,75

3,00

2,50 5,00 7,50 10,00 12,50 15,00 17,50 20,00 22,50 25,00

Stag

e H

eig

ht

(m)

Discharge (m3/s)

Rating Curve of Langtang Khola (2006 - 2013)

Q = 1.943(H + 0.501)^2.188

0,00

0,50

1,00

1,50

2,00

2,50

1-J

an-1

31

1-J

an-1

32

1-J

an-1

33

1-J

an-1

31

0-F

eb-1

32

0-F

eb-1

32

-Mar

-13

12

-Mar

-13

22

-Mar

-13

1-A

pr-

13

11

-Ap

r-1

32

1-A

pr-

13

1-M

ay-1

31

1-M

ay-1

32

1-M

ay-1

33

1-M

ay-1

31

0-J

un

-13

20

-Ju

n-1

33

0-J

un

-13

10

-Ju

l-1

32

0-J

ul-

13

30

-Ju

l-1

39

-Au

g-1

31

9-A

ug-

13

29

-Au

g-1

38

-Se

p-1

31

8-S

ep-1

32

8-S

ep-1

38

-Oct

-13

18

-Oct

-13

28

-Oct

-13

7-N

ov-

13

17

-No

v-1

32

7-N

ov-

13

7-D

ec-1

31

7-D

ec-1

32

7-D

ec-1

3

Wat

er

leve

l (m

)

Langtang Khola Stage Height (m)_2013

Monthly Maximum Discharge in Langtang Kola

3,87

23,09

0,00

5,00

10,00

15,00

20,00

25,00

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

Max

imu

m D

isch

arge

(m

3/s

)

Annual Observed Discharge Trend (1988-2014)

0,00

1,00

2,00

3,00

4,00

5,00

6,00

7,00

8,00

9,00

10,001

98

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Dis

char

ge (

m3/s

)

Methodology for flow simulation by Snowmelt Runoff Model (SRM)

Flow simulation year

• After pre-processing and analyzing the hydro-meteorologicaldata of Kyangjing

• 2000 - 2006 will be taken as parameter calibration year

• 2007 - 2013 will be taken as validation year

Introduction to Snowmelt Runoff Model (SRM)

Developed by Martinec in 1975 in Swiss Snow and AvalancheResearch Institute

Estimation of daily stream flow in Mountain basins

Based on degree day method, can be used tosimulate/forecast

Simple and Efficient

Snow cover map of Langtang Catchment 25 Feb 2015

Snow Cover Mapping of Langtang

•MODIS Daily Snow products

•Preprocessing and processing of MODISsnow products using : MODIS Reprojectiontool

•Which includes;

Mosaicking

Spatial and temporal filtering

Generation of daily snow cover area ofLangtang Catchment

Basic snowmelt runoff model

Qn+1 = [cSn . an (Tn + Tn) Sn + cRn . Pn] (A.10000/86400) (1-kn+1) + Qn kn+1

Snow melt Rainfall Flow Recession

Q : Basin discharge

n : Day indicator

T : Air temperature

P : Precipitation falling as rain

S : Snow covered area

A : Zonal area

kn+1: Recession coefficient

an : Degree day factor

csn,crn : correction for losses due to snowmelt and rainfall

Variables (Inputs)

Temperature PrecipitationSnow Covered

Area %

Cont….

Meteorological Stations

Measured Forecasted

MODIS Snow product

Cont…

7Parameters

Runoff Coefficients (cs,cr)

Degree Day Factor (a)

Temperature Lapse Rate ()

Critical Temperature (Tcrit)

Rainfall Contributing Area

Time Lag (L)

Recession Coefficient

Future work

• Calibration and Validation of SRM

• Simulate daily discharge

• Calculating runoff components in Langtang Catchment

• The research is still going on

Thank You