National Institute of Meteorology and Hydrology Bulgarian Academy of Science The last flood in Maritsa, Toundja and Basins in 10-20 November 2007 Results of Hydrological Simulation and Forecast

High water level at - the Bulgarian-- border

Station Max. daily Daily Return period Total for precipitation maximum of the 10-20 in November 10-20 maximum November (1931-1984) November as yearly 2007 2007 maximum Elhovo 45 mm 41 mm (18) 37% 150 Kardjali 73 mm 66 mm (19) 17% 154.5 Smoljan 88 mm 63 mm (18) 25% 159 The return period of accumulated precipitation, considered as monthly sum by station, is about 5-7%. The return period of the precipitation event over a large area - a hydrological statistics question.

Precipitation total 10-13 Nov ember 2007 Pr ecipitation total 15-20 November 2007 Modeling results – Water Budget Components

Snow accumulation - 20 November 2007 Precipitation total 10-20 November 2007

Evaporation total 10-20 November 2007 Runoff total 10-20 November 2007

Runoff partitioning for 17 November Runoff partitioning for 20 November

Drainage Drainage

Surface runoff Surface runoff

Daily averaged discharge series – measured, simulated with measured precipitation and forecasted with use of forecasted precipitation – four anthropized basins.

Simulation-Tundja-Elhovo 1000 Simulation-Maritsa- 600 Measured Discharge Measured Discharge 900 Average Forecast 500 Average Forecast 800 e e g g a a r

700 r e e 400 v v a a

600 y y l l i i a a d 500 d

300 ] ] s s / / 3 3 400 m m [ [

e 200 e 300 g g r r a a h h 200 c c s s i

i 100 d d 100

0 0

9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 0 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 ------0 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -2 -2 -2 -2 -2 -2 -2 -2 -2 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 ------1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2

1400 Simulation-Maritsa- Simulation-Maritsa- Parvomaj 2000 Svilengrad Measured Discharge Measured Discharge 1200 1800 1600

e Average Forecast Average Forecast e g 1000 g a r a 1400 r e e v v a

a

800 1200 y l y i l i a a d 1000

d ]

]

s 600 s / / 3

3 800 m m [ [

e 400 e 600 g g r r a a h h 400 c c s s i

200 i d d 200 0 0

9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 -0 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -2 -2 -2 -2 -2 -2 -2 -2 -2 0 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1- 1- 1- 1- 1- 1- 1- 1- 1- 1- 1- 1- 1- 1- 1- 1- 1- 1- 1- 1- -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 07 07 07 07 07 07 07 07 07 07 07 07 07 07 07 07 07 07 07 07 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Daily averaged discharge series – measured, simulated with measured precipitation and forecasted with use of forecasted precipitation – not anthropized basins.

Simulation-Chepelarska- 180 550 Simulation-Vurbitsa-Djebel Bachkovo Measured Discharge 160 Measured Discharge 500 Average Forecast 450 e e g 140 g

a Average Forecast r a 400 r e e v

120 v a

a 350

y l y i l i a 100 a 300 d

d ] ] s s /

/ 250

3 80 3 m m [ [

200 e

60 e g g r r

a 150 a h 40 h c c s s 100 i i d d 20 50 0 0

9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 0 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 ------0 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -2 -2 -2 -2 -2 -2 -2 -2 -2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2

Simulation-Arda-Vehtino Precipitation daily series for Kirkovo – Vurbitsa basin 550 Measured Discharge 500 e

g Average Forecast

a 450 r e

v 400 a

y

l 350 i a

d 300

] s

/ 250 3

m 200 [

e 150 g r

a 100 h c

s 50 i d 0

9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 0 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 1- 1- 1- 1- 1- 1- 1- 1- 1- 1- 1- 1- 1- 1- 1- 1- 1- 1- 1- 1- -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 07 07 07 07 07 07 07 07 07 07 07 07 07 07 07 07 07 07 07 07 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Results validation using data from automatic stations and actual rating curves Basin measured average average simulation average forecast River-Station area volume 17-28 measured runoff simulated error % / R2 forecasted error % [km2] XI [m3E6] height [mm] runoff height coefficient runoff height & R2 Arda-Vehtino 839 69 83 116 40/0.87 134 62/0.89 Vurbitsa-Djebel 1144 127 111 156 41/0.95 135 22/0.87 Chepelarska-Bachkovo 794 49 62 63 3/0.78 65 5/0.83 Tundja-Elhovo 5549 39 7 32 363/0.10 29 321/0.12 Maritsa-Plovdiv 8077 295 37 36 -2/0.36 39 7/0.39 Maritsa-Parvomaj 13399 337 25 36 44/0.26 38 51/0.27 Maritsa-Svilengrad 21379 557 26 33 27/0.12 31 19/0.24

The validation consists: 2. To compare the simulated and forecasted runoff height for the period to the measured runoff height. The result is an error estimate in percents. 3. To compare the daily water discharge series of the simulated and forecasted river flow to the measured one. The result is a correlation coefficient. The correlation of measured against simulated and forecasted daily discharge is good for the not-anthropized drainage basins – Arda, Vurbitsa and Chepe- larska, however the simulations and the forecast generally overestimate the runoff height (Chepelarska is an exception). This is a calibration problem of the model itself. The precipitation forecast is proved to be enough reliable, especially for long-lasting and large a rea precipitation events. Conclusion:

C. A precisely calibrated hydrological model could produce high quality simulations with use of dense enough precipitation measurement network. D. It is possible to produce hydrological forecasts of reliable quality for the river flow up-to 3 days ahead with use of Aladin precipitations. E. Downstream large dams or reservoirs with big retention capacity the results are highly influenced from the dam operation. Therefore data from the dam operation are necessary to be included in the simulation/forecasting procedure in order to achieve a reasonable forecast quality.