Estimation of Snow Cover for Year 2013 (Indus...

Estimation of Snow Cover for Year 2013 (Indus Basin)

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PAKISTAN SPACE & UPPER ATMOSPHERE RESEARCH COMMISSION

Contents

Summary ............................................................................................................................................. 4

1. Introduction ............................................................................................................................ 6

2. Objective of the Study ....................................................................................................... 7

3. Methodology ........................................................................................................................... 7

4. Results .................................................................................................................................... 12

5. Conclusion ............................................................................................................................. 35

6. References ............................................................................................................................ 36

Acronym Description

AJK Azad Jammu & Kashmir

UIB Upper Indus Basin

MODIS Moderate Resolution Imaging Spectroradiometer

HKH Hindu Kush-Himalayan

NDMA National Disaster Management Authority

Estimation of Snow Cover for Year 2013 (Indus Basin)

Summary

The major source of rivers flow in Pakistan originates from Hindu Kush

Karakoram-Himalaya Mountains mostly covered with snow throughout the

year. Monthly averages of snow covered areas from 2008 to 2013 have

been calculated to assess the runoff situation in the Indus. Analysis of the

data show that for January and February 2013, monthly average snow

covered area is 232775 km2, 344981 km2 respectively in March it is

298850 km2 while for April, May and June it is 236270 km2, 176608 km2

and 116587 km2 respectively for the entire Indus Basin. Similarly the

monthly average snow covered area from January 2013 to June 2013 for

upstream Tarbela is 132026 km2, 191813 km2, 172949 km2, 146415 km2,

98940 km2 and 76196 km2 respectively.

The analyses were performed using supervised classification

followed by manual editing to get best possible results. The analyses

show that in May 2013 the snow covered area is 17% higher as compared

to 2012 and 14% higher as compared to 2011.

It may be concluded that as runoff not only depends on snow cover

but also on the thermal conditions and if the temperatures remain the

same as that of previous years then there would be higher runoff

contribution due to snowmelt as compared to the previous years (2008-

2012). Archer (2004) indicates that 1°C rise in mean summer temperature

would result in 16% increase in summer runoff into the Hunza River.

In May 2013 snow cover is 29037 km2 in Kabul River basin above

Nowshera which is higher than the rest of the years (2012-2008),

similarly in June 2013 the snow covered area is 18510 km2, which is also

higher than rest of the years.

Fig 1: Study Area

1. Introduction

A number of studies have been conducted in the HKH region to assess

snow cover and its contribution to river runoff. 90% of the Indus River

basin above Tarbela reservoir may be covered by snow (Hewitt et al.

1989). Snow and ice meltwater supplies 75% of the flow of the Kabul

River at Warsak, 80% of the Swat River, 85% of the main Indus River at

Tarbela reservoir, and 65% of the Jhelum River at Mangla reservoir.

Mostly maximum snowfall is experienced in the months of January and

February in the middle Himalayas and in March in the greater Himalayas.

Winger et al. (2005) reports 50% of total annual runoff in the Indus River

due to snowmelt. Archer (2003) indicates that Indus River flows are

primarily controlled by winter precipitation and energy inputs during

summer. Less than 10% of the average runoff is the result of rainfall over

the Indus plains. Maxima in river runoff are expected between June and

August, where an early peak in June indicates particularly an influence of

snowmelt and a peak in July to August the influence of glacial melt.

The first 8 years of 21st century have surpassed all past trends, with 2005

believed to be the hottest for Pakistan, when a snowmelt flood in June

created havoc in the downstream Indus. Previous studies have shown

significant correlations between Gauged river flows and observed climate

in the Upper Indus Basin (UIB), notably, concurrent temperature or

preceding season precipitation (Forsythe et el. 2012).

The Indus River receives 85% of the annual flows from snow and ice melt

(Hewitt, 1985) and a modelling study suggests that snow melt runoff is

roughly 40% (Immerzeel et al., 2009). Hunza, Shigar and Shyok basins

are mainly glacier-fed while Jhelum, Kabul, Gilgit, Astore, and Swat are

mainly snow-fed basins.

Archer and Flower (2004) indicates that a 1°C rise in mean summer

temperature would result in a 16% increase in summer runoff into the

Hunza River. It is very important to estimate the winter snow

accumulations (November to February) at high altitudes.

Swat River annual snowmelt runoff contribution to the total runoff may

range 65–75 %. During the monsoon season, the peak snowmelt runoff

is augmented by monsoon rains to produce higher discharges and

occasional peak floods (Zakir et.al., 2011). The average snow cover area

in the Upper Indus River Basin changes from 10% to 70%. Snow cover in

the area is at a maximum of about 70‒80% in the winter December to

February-snow accumulation period and at a minimum which about

10‒15% in the summer June to September-snow melt period (Immerzeel

et al., 2012).

2. Objective of the Study

Objective of the study is mapping of snow cover in the Indus Basin for

runoff estimation for preparation of contingency planning by National

Disaster Management Authority (NDMA).

3. Methodology

MODIS images with less than 20% cloud cover were selected. Pixel based

classification was performed for extraction of snow cover area. Maximum

likelihood parametric rule was set to perform classification. Snow cover

area was estimated after the post classification. Statistical analyses were

performed for trend analysis of snow cover area during 2008-2013.

4. Results

This study focuses on the assessment of the snow cover dynamics on

monthly basis from 2008-2013. MODIS (Onboard TERRA Satellite) daily

images of 250m spatial resolution have been processed for snow cover

extraction. The snow cover has been calculated for the whole Indus River

basin which includes both eastern as well as western tributaries. The

trend in the snow covered area has been calculated including monthly

snow cover averages. Maximum snow cover for February-2013 is 344981

km2 while minimum value of 125520 km2 in the month of June – 2013

(Table 1).

Table 1: Monthly Average Snow-Covered Area of Indus Basin (Sq.km)

Month/Year 2013 2012 2011 2010 2009 2008

January 232775 264024 241307 252052 259353 264817

February 344981 295129 256358 269122 268563 289518

March 298850 220978 260068 220693 238787 210634

April 236270 166800 233030 175626 188812 176423

May 176608 145766 152359 146211 161688 146119

June 116587 85453 128823 116608 113485 104172

July - 77172 101011 93754 105155 36118

August - 37142 71141 47736 56155 34591

September - 96631 65004 103964 76349 76055

October - 171954 64456 121307 132601 128679

November - 101040 113110 106872 224127 55488

December - 204419 148282 94544 236093 189758

Similar trend has been observed for Indus River basin upstream Tarbela.

Maximum snow cover of 191813 km2 in February-2013 and minimum

snow cover of 76196 km2 in June-2013 (Table 2) is recorded.

Table 2: Up-stream Tarbela (Upper Indus Basin) snow area (Sq.km)

Month/Year 2013 2012 2011 2010 2009 2008

January 132026 136262 130088 141189 137722 120623

February 191813 142021 147927 134267 142541 130043

March 172949 103817 141333 124307 137499 116138

April 146415 98576 131729 103684 105713 105847

May 98940 88757 95312 90793 95112 87340

June 76196 54199 70558 74831 70145 69714

July

47486 46802 61590 64558 27158

August

26016 39335 32628 38551 20518

September

66693 44871 68090 46604 55151

October

113479 42799 76033 83478 81725

November

67998 83423 65789 128753 93929

December

101742 92342 61180 133844 105689

In Kabul River basin, above Nowshera snow cover in May 2013 is 29037

km2 which is higher than rest of the years (2012-2008). Similarly in June

2013 the snow covered area is 18510 km2, which is also higher than rest

of the years (Table 3). Further it is assumed that not only snow cover

extent is increased but its depth would also be increased indicating that

snowmelt runoff may be higher this year.

Table 3: Average Snow cover in Kabul River Basin (2013-2008) sq.km

Month 2013 2012 2011 2010 2009 2008

Jan 54350 45908 43522 33226 42700 52686

Feb 64240 63680 58727 47738 56765 53753

Mar 61209 50313 35956 42786 36283 40976

Apr 37679 24687 22697 33971 26116 31633

May 24406 22177 17715 14845 19131 24901

Jun 18510 12753 9545 8138 13273 16363

Jul - 9683 2320 7241 10455 16419

Aug - 3998 3669 4690 4492 7162

Sep - 10864 2470 5435 13341 5462

Oct - 20286 12893 14475 10569 16645

Nov - 16838 22942 29223 11488 29291

Dec - 47658 33414 30696 9228 41784

Table 4: Comparison of snow covers 2013 (Ratios)

Ratio January February March April May June

2013 / 2008 0.9 1.2 1.4 1.4 1.2 1.4

2013 /2009 1 1.3 1.1 1 1.2 0.9

2013 / 2010 0.9 1.3 1.4 1.3 1.2 1

2013 / 2011 0.9 1.3 1.3 1.3 1.1 1

2013 / 2012 0.9 1.2 1.4 1.3 1.2 1.1

Statistics show that snow cover in the winter season of 2013 was

record high during 2008-2013. River flows from April to July were used

for analyses during 2008-2012. River flows for the same period during

2013 were projected using snow cover and river flows in 2008-2012.

Snow cover in June 2013 was compared with the snow cover of the same

month during 2008-2012. It was found comparable with snow cover in

June 2011. Therefore river flows in June 2013 were considered to be the

same as were in June 2011. Snow cover in July 2013 was compared with

the snow cover of the same month during 2008-2012 and it was found

that snow cover in July 2013 was almost equivalent to snow cover in July

2008. Therefore river flows in July 2013 were considered to be the same

as were in July 2008 (Figure 4 & 5).

The projected river flows are approximation, in this assessment

variations in weather condition among different years are ignored;

however the river flows are expected to be high keeping in view high

values of snow-covered area.

5. Conclusion

The snow and glacier melt stream flow is especially valuable

because it occurs in the period of April, May and June before the monsoon

rains. Snow Cover in 2013 is higher as compared to rest of the years and

it is expected that snowmelt will be higher as compared to previous years

(2008-2012). Results show large variations in snow cover among years

with an increasing trend from 2008 – 2013, with February, 2013 has

higher snow cover over Indus Basin as compared to rest of the years

under study. If meteorological conditions (Temperatures) remain above

average then it is expected to have higher flows in rivers as compared to

previous years.

6. References

1. Winger, M., Gumpert, M., and Yamout, H., 2005. Karakorum-

Hindukush-western Himalaya: assessing high-altitude water resources. Hydrological Processes. 19, 2329-2338.

2. Archer, D.R., Contrasting hydrological regimes in the upper Indus

Basin. Journal of Hydrology 274,198-210(2003).

3. Nathan Forsythe, Chris G. Kilsby, Hayley J. Fowler, and David R. Archer. Assessment of Runoff Sensitivity in the Upper Indus Basin to

Interannual climate variability and potential change using MODIS satellite data products: Mountain Research and Development, 32(1), 16-29(2012).

4. Hewitt, K., Snow and ice hydrology in remote, high mountain

regions: the Himalayan sources of the river Indus. Snow and Ice

Hydrology Project, Working Paper. No. 1, Wilfred Laurier University,

Waterloo, Ontario, Canada, (1985).

5. Immerzeel, W.W. et al., Large-scale monitoring of snow cover and runoff simulation in Himalayan river basins using remote sensing. Rem

Sens Environ 113(1):40–49(2009).

6. Archer, D. R., and H. J. Fowler., Spatial and temporal variations in

precipitation in the Upper Indus Basin, global teleconnections and

hydrological implications. Hydrol. Earth Syst. Sci., 8, 47–61(2004)

7. Zakir H. Dahri, Bashir Ahmad, Joseph H. Leach and Shakil Ahmad. Satellite-Based Snowcover Distribution and Associated Snowmelt Runoff

Modeling in Swat River Basin of Pakistan. Proceedings of the Pakistan Academy of Sciences, 48 (1), 19–32(2011).

8. Immerzeel, Walter W., van Beek L. P. H., Konz M., Shrestha, A. B.,

Bierkens, M. F. P. Hydrological response to climate change in a glacierized catchment in the Himalayas. Climatic Change, 110, 721–736(2012).

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