Adaptation hydrological model_en

IPA CBC Programme Bulgaria - Serbia
ADAPTATION OF HYDROLOGICAL MODEL FOR NISHAVA RIVER BASIN

The determination of the maximum run-off with different security is a key task in flood
risk assessment. The availability of reliable and spatially distributed parameters of
extreme maximum run-off is essential for adequate flood risk management. In flood
risk mapping and planning of mitigation measures, it is crutial to calculate the
repetition period correctly.

Implementation of the regionalization method of maximum run-off for Nishava
River Basin

Theoretical approach

Eight factors and characteristics of drainage basins and river systems that are
essential for the formation of maximum flow are set out in LUBW, 2007:

• area of the catchment AEo [km2]
• urbanized territory S [%]
• afforestation W [%]
• average slope Ig [%]
• river length L [km] along the main rivers of the watershed to the confluence
• river length LC [km] from the center of gravity of the catchment to its estuary;
• average annual rainfall in the catchment hNG [mm]
• landscape factor LF [-]

The described characteristics and factors are included in multiple linear regression
equation, which equation is used to determine the maximum run-off with a different
security (ie, MHQ and HQT), especially for the unobserved catchment:

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Bulgaria – Serbia IPA Cross-border Programme
“Assessment of flood risk – a base for sustainable development in upper part of Nishava
catchment”


ln Y   C0  C1  ln  AEo   C2  ln S  1
 C3  ln W  1  C4  ln I g 
 C5  ln L   C6  ln LC 
 C7  ln hN G   C8  ln LF 

where: Y, YT are dependent variables

Y  MHq regionalization of the values of average maximum water levels / MHQ /;

Hq T : T = 2, ..., 10 000 a - for the regionalization of the values of maximum
YT 
MHq

discharges HQT;

MHq: module outflow average maximum annual flow MHQ (m³ / s/km2)

HqT: module flow of maximum annual flow to a particular security or repetition period
(T) - HQT (m³ / s/km2)

C0 - C8: regression coefficients.

Used information

For the implementation of the method of regionalization (HQT-model), information
about the maximum run-off from 6 HMS located in the upper catchment of the river
Nisav was used. Information about the HMS and the observation period and their
catchment area is presented in Table. 1 and the spatial location of the HMS is
presented in Figure 1.

Table 1. HMS and observation period

Subbasin HMS-Nr. Observations Number Area

Name From/to years km²

Visochica River (HMS Brachevci – R. Serbia) 47937 1961 - 2010 49 227.00

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Erma river (HMS Strezimirovtsi – R. Bulgaria) 452 1961-1967 7 117,00

Erma River (HMS Trunski Odorovtsi – R.
557.00
Serbia) 47914 1961-2010 49

Erma River ( HMS Trun – Bulgaria) 11650/95 1937-1983 37 360,5

Nishava River (HMS Dimitrovgrad – R. Serbia) 47910 1961-2010 49 232.00

Nishava river (HMS Kalotina – R. Bulgaria) 11800/223 1967-1983 16 267,00

Fig. 1 Gauging stations in the basin of Nishava river

The estimated empirical probability curves of maximum run-off are presented in
Fig.2.

Figure 2 Empirical probability curves of maximum run-off

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Empirical distribution curve of Nishava river, HMS
Dimitrovgrad
m3/s
120

100

80

60

40

20

0
0 20 40 60 80 100 120
p%

Empirical security curve of Nishava river, HMS Trnski Odorovtsi
m3/s
180

160

140

120

100

80

60

40

20

0
0 10 20 30 40 50 60 70 80 90 100
p%

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Empirical distribution curve of Visochica river, HMS Brachevtsi
m3/s
140

120

100

80

60

40

20

0
0 10 20 30 40 50 60 70 80 90 100

The statistical parameters that define the curve of security log-Pearson Type III are
presented in Table. 2.

Table 2. Statistical parameters of the curve log-Pearson Type III.

Statistical HMS HMS HMS
parameters Dimitrovgrad Trnski Brachevtsi
Odorovtsi

X 1,4334 1,5569 1,5237

S 0,3212 0,2913 0,2749

G 0,1 0,2 0,1

Based on this, the annual probability of exceedance is determined and persented in
table 3

Table 3. Maximum run-off with different security of Nishava river

Annual HMS HMS Trnski HMS Brachevtsi, Repetition interval
probability Dimitrovgrad, odorovtsi, 3
Q m /s
3
Q Q m /s

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catchment”

3
m /s

1,0 2.0229 3.94 3.6276 Each year

0,5 26.7285 35.25 33.0469 Every two years

0,2 Every five years

0,1 70.428 86.28 75.6502 Every ten years

0,02 129.1611 153.43 126.7377 Every fifty years

0,01 160.0589 189.26 152.5291 Every hundred
years

0,002 247.6213 292.58 223.0177 Every five hundred
years

The theoretical distribution functions which best approximate the empirical
security curves of the studied HMS and the statistical parameters that define them
are shown in Fig. 3

Figure 3. Theoretical distribution curve Nišava River HMS Dimitrovgrad

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catchment”

300
m3/s

250

200

150 Имперична крива
Теоретична крива
100

50

0
0 20 40 60 p% 80 100 120

Theoretical distribution function of Nishava river, HMS Trnski Odorovtsi

350

300

250

200
Имперична крива
150 Теоретична крива

100

50

0
0 20 40 60 80 100 120

Theoretical distribution function of Visochitsa river, HMS Brachevtsi

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catchment”

250

200

150

100 Теоретична крива

50

0
0 20 40 60 80 100 120

Определяне на ландшафтните фактори

Figure 4. Main geological types in Nishava river basin

Figure 5. Main geological types

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Figure 6 Landuse map, Corine 2006

Determination of the maximum run-off by the regiuonalization method

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catchment”

the values of water quantity (HQT), determined by the method of regionalization and
the empirical values of the maximum run-off /Plotting Positions/ are shown in Fig.7.
These graphics show that authoritative (relevant) HMS model adapted to the
regionalization can well estimate the values of water quantity.Fig.7.

Figure 7. Maximum run-off with different security of Nishava river determined by the
method of regionalization, HMS Dimitrovgrad
300

250

200
150
100 Регионализирана крива

50

0
0 20 40 60 80 100 120

Figure 8. Maximum runoff with different security of Erma river set by the method of
regionalization, HMS Trnski Odorovtsi
350

m3/s
300

250

200 Имперична крива
150
Регионализирана крива

100

50

0
0 20 40 60 80 100 120
p%
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Figure 9. Maximum runoff with different security of Visochitsa river set by the method
of regionalization, HMS Brachevtsi

250
m3/s

200

150
100
Регионализирана крива

50

0
0 10 20 30 40 50 60 70 80 90 100 110

Determination of the maximum run-off with different security of Nishava river
by the method of regionalization

Through regionalization (adapted to regional run-off values with a certain probability)
it is possible to easily and quickly determine the water levels with a certain probability
anywhere on the river area for future research in this area.

The values of the parameters and the factors of maximum run-off in Nishava river in
Godech are presented in Table.4

Table 4. Parameter values and factors of the Nišava river in Godech town

LF
HMS- Peri Leng AE NJa (Gemittelt LF
River - HMS № od ht . 0 AE0 U W IG L LC hr ) (Zielwert)

GI m
S km2 % % % km km m
Nishava – 83, 1,1 6 1, 26, 6,7 96 135

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Godech town 05 5 4 3 32 5 0

The values of the maximum run-off with different interval times, calculated by the
regionalization method are presented in Table.5

Table 5. Maximum run-off with different interval times, calculated by the
regionalization method

ln(Y) Y=MHq MHQ YT HqT HQT
[m3/s/km2] [m3/s] [m3/s/km2] [m3/s]
MHq -0.652608 0.520686 43.243
Hq2 50 -0.211010 0.8097661 0.422 35.017
Hq5 20 0.332801 1.3948698 0.726 60.318
Hq10 10 0.620712 1.8602528 0.969 80.443
Hq20 5 0.862025 2.3679504 1.233 102.397
Hq50 2 1.135126 3.1115644 1.620 134.553
Hq100 1 1.318140 3.7364666 1.946 161.576
Hq200 0,5 1.487383 4.4254975 2.304 191.372
Hq500 0,2 1.693249 5.4371176 2.831 235.117

Studies show that the regionalization method developed in Germany is applicable
both for Bulgaria and the Republic of Serbia and provides very good results. By this
method it was possible to reliably determining the maximum water levels in the river
Nishava Godech.

This publication was elaboraed with the assistance of the European Union, through IPA
Cross-border co-operation programme CCI No 2007CB16IPO006.
The contents of this publication is a responsibility of the SRD-SU „St. Kliment Ohridski” and
should in no way be accepted as a statement of the European Union or the Managaing
Authority of the programme.

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