International conference: ‘Global Change and the World's Mountains’

Perth, Scotland,

26-30 September 2010

Hydro-climatology Of Sarız Creek Watershed, and Simulation of the

Snowmelt Runoff Using Remote Sensing and Geographic

Information Systems

İbrahim Gürer, gurer@gazi.edu.tr

İbrahim Ucar, iucar@gazi.edu.tr

Gökhan Tasdemir,tasdemirgok@hotmail.com

Faculty of Engineering, Gazi University, Ankara, Turkey

Introduction

The significant part of annual runoff volume of central

Taurus mountain basins in Turkey, which are at

altitudes above 1200m, and have a great snow

potential, is constituted by melting of the accumulated

snow in spring months. Modeling of accumulation and

melting of snow is important in view of operating

integrated water resources of such high altitude basins

which are recharged by snow melting as efficient and

sustainable as possible.

Case Study Area

In this study, Sarız basin is chosen as case study area. At

the outlet of Sariz creek, Sarız town is located. The

history of Sariz town goes back to 7000 B.C., and

located at 123km to the east of Kayseri city, the river

basin covers a surface area of 1410km2, and the mean

elevation is 1560m, surrounded by mountains. The main

economy is animal husbandry and agriculture. The

population is about 12700 people according to 2007

census, 8000 live in downtown, but 4610 live in rural area.

There is a strong immigration from Sariz town to big

towns and EU.

Location of Sariz Basin Sarız town

Ankara

İstanbul

Black Sea

Mediterranean Sea

Agean Sea

Kayseri

As in many high plato settlements, the local economy had to be

improved by providing necessary infrastructure by the public sector,

e. i. Turkish State. In this case, Turkish State Hydraulics Works DSI

constructed a weir at about 300m upstream in 1983, to raise the

water level in Sariz creek; of which the annual inflow was basicly

from snowmelt floods, and provided the possibility of gravitational

irrigation of 1080 ha. The Sariz town and the villages around use the

Sariz water during irrigation season starting from the beginning of

May.

To convert dry farming into irrigated farming increases the grains

production tenfold. The state also expects to stop immigration and

keep the people in their original land by providing work in local

industry and decreasing the unemployment.

09.12.2010 6

Irrigation From Sarız Creek

Diversion is 300m u/s from

18-17 stream gauging

station

Size of the area planned to

be irrigate d is 1080 ha.

Operated by local farmers.

The start of the irrigation

season is mid-April and/or

the 1 st of May.

Sariz basin has continental climate, with maximum of 33 oC and the

minimum of -24 oC. The land is covered by low bushes and small

tress of oak and too much erosion at barren surfaces.

Sarız Creek watershed is a sub-basin of Seyhan Basin, with the

coordinates of 3827’ - 3841’ N, and 3627’ - 3640’ E. The flow is

planned to be forecasted by simulation of hydrographs of Sarız

Creek watershed, for the special winters’ of 2004 and 2005 snow

melting seasons (March-April).

Hydro-meteorological Observations

The Sariz creek is equipped with discharge measuring station,

located at 1550m elevation, labelled DSI 18-17 and operated by

Turkish State Hydraulics Works (DSI). In this study the total

hydrographs of spring snowmelt flood, which comes during March-

April periods of 2004 and 2005 are simulated.

Weir, Discharge measuring; 18-17 and Sarız MGİ precipitation stations.

The watershed is covered by snow up to 70% of the winter season

which usually extends from the beginning of January through April.

Perennial snow cover area starts to decrease in March and melts

away completely before the end of April. The main reason to select

the 2004 and 2005 snow melting periods is the more snowfall during

these two years.

The meteorological data is from the station of Turkish Meteorological

Office (DMI) in Sariz located at 1591m elevation. The snow data from

two snow courses of Electric Survey Administration (EIEI), labelled as

18-K10 located at 1670m and 18-K11 located at 1760m.

Simulation Model Used

In this research, snowmelt runoff model (SRM) is used to compute the

runoff produced by melting of the snow accumulated during winter

season. The rate of melting is computed by using the temperature

index. Remote Sensing (RS) and Geographic Information System (GIS)

tools are also utilized to obtain more reliable results in a shorter period

of time. The part of the watershed covered by snow can be defined by

MODIS sensors put in TERRA and AQUA satellites.

SRM model computes the runoff components from the daily snowmelt

and rainfall contributions on the watershed, and superimpose them on

flow recession curve and convert it to watershed outflow by using the

following equation.

n n n n n nn+1 Rn n+1 n+1Sn

A.10000Q =[c .a (T +ΔT ).S +c .P ]. .(1-k )+Q .k

86400

Where

Q= Daily mean discharge (m3/s)

c= Ratio expressing the losses,runoff coefficients(runoff/precipitation) Cs for snow, Cr for

rain

a= Degree day factor(cm/ C.day)

T= Number of degree days (C.day)

T= temperature variation due to elevation difference (C)

S= Snow covered area / Total area

P= Precipitation contributing flow (cm)

A= Basin or area of specific elevation zone(km2)

k= Flow recession coefficient

n= Order of the days

It is necessary to measure T, S, and P and also determine the

parameters of Cr, Cs, T, critical temperature Tkr, k and lag time L,

which are characteristic parameters for a basin and even for climate.

Model Inputs

SRM model uses the spatial variation of snow covered area as input

in model improvement. The images obtained by MODIS sensors of

Terra and Aqua satellites are utilized to determine the variation of

snow borders. For SRM analysis two 500m elevation bands were

selected. In forming the recession curve of snow cover, basicly

images from Terra satellite was used. The Runoff coefficients ; Cs

and Cr were computed from flow data of flow measuring station AGI

18-17.

Flow recession coefficient are derived from consecutive daily flow

data of dry-no precipitation periods.

To compute the daily snowmelt water (M expressed as cm), degree-

day factor (a expressed as cm/0C/day), and daily degree days (T

expressed as oC), are used. Temperature gradient T value is

assumed to be 0.65 oC/100m.

The critical temperature value is assumed as 0.01 oC. Rain

contribution area; RCA was assumed 1 for both 2004 and 2005. In

assessing the lag time, the World Meteorological Organization Study

done by comparative estimates of lag times was utilized.

1500

1600

1700

1800

1900

2000

2100

2200

2300

2400

2500

2600

2700

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210

Altitu

de

(m

)

Area (km2)

The area-elevation curve of the Sariz Basin

-12

-8

-4

0

4

8

12

16

1 M

art

04

3 M

art

04

5 M

art

04

7 M

art

04

9 M

art

04

11

Ma

rt 0

4

13

Ma

rt 0

4

15

Ma

rt 0

4

17

Ma

rt 0

4

19

Ma

rt 0

4

21

Ma

rt 0

4

23

Ma

rt 0

4

25

Ma

rt 0

4

27

Ma

rt 0

4

29

Ma

rt 0

4

31

Ma

rt 0

4

2 N

isan

04

4 N

isan

04

6 N

isan

04

8 N

isan

04

10

Nis

an 0

4

12

Nis

an 0

4

Sıc

aklık (

C)

Günler

Ortalama Sıcaklık 2004 Zon A Zon B

Temperature variation during Melting Season

R² = 0.9431

R² = 0.9369

R² = 0.9725

R² = 0.9741

0

100

200

300

400

500

600

1350 1400 1450 1500 1550 1600

Mean P

recip

itation,

Port

(m

m)

Altitude, h (m)

Annual Winter February March-April

Linear (Annual) Linear (Winter) Linear (February) Linear (March-April)

Tomarza Pınarbaşı

Sarız

Variation of Mean precipitation with altitude in Sarız Basin

0

10

20

30

40

50

60

70

80

90

100

1-M

ar

3-M

ar

5-M

ar

7-M

ar

9-M

ar

11

-Mar

13

-Mar

15

-Mar

17

-Mar

19

-Mar

21

-Mar

23

-Mar

25

-Mar

27

-Mar

29

-Mar

31

-Mar

2-A

pr

4-A

pr

6-A

pr

8-A

pr

10

-Apr

12

-Apr

14

-Apr

16

-Apr

Sn

ow

Co

ve

red

Are

a (

%)

Days

Zone A Zone B

Depletion of the snow covered area in the Sarız Basin

Samples from Satellite data of snow covered,

no snow and cloudy parts of the Sarız Basin.

Model Outputs

SRM was run for two different cases for the snow melt seasons of

the years 2004 and 2005. The variables computed and parameters

estimated before the simulation were directly included in analysis.

Hydrograph simulations for March and April of 2004 and 2005 for case 1.

Hydrograph simulations for March and April of 2004 ve 2005 for case 2.

Conclusions

With the available data of limited representation of the basin

characteristics, the simulations of the snowmelt runoff hydrographs

were resulted quite satisfactorily. Especially in Case 2, the average

values of Cs, Cr and flow recession coefficients helped to improve the

hydrograph simulation. If the coefficients and model parameters which

are natural inputs of the SRM simulation are computed from direct field

data, more successful model simulations can be obtained

Acknowledgment

This research was supported by SCR of Gazi University, by Project

Contract No 2006 -02

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