poster conference environment

1. EENVIRO 2020, 21-23 October, Bucharest, ROMANIA
The 7th Conference of the Sustainable Solutions for Energy and Environment
ABSTRACT
The study analyses the qualitative
influence of different parameters on
Dambovita River water temperature
along the 17.5km length reach of
concrete canal passing through
Bucharest City, Romania. Air
temperature has been increasing during
the investigated last 4 decades with
detrimental consequences on the river
ecosystem. The simplified physical
processes taken into account, equations
and numerical methods used to develop
a deterministic water temperature model
are explained. Different scenarios of
possible extreme summer heatwaves
with influence on river water
temperature are defined analysing the
available data. A sensitivity analysis is
performed for meteorological
parameters such as: air temperature,
humidity, short wave solar radiation,
cloudiness and wind speed to determine
their influence on river temperature.
INTRODUCTION
In most european rivers, water
temperature has increased by 1-3 C
over the last century. River systems
crossing cities are additionally stressed
by urbanization and consumption and
sometimes by intensive engineering
works. In terms of temperature
variability, urbanization brings additional
stressors on river water temperature
regimes, leading to the so-called urban
stream syndrome. This possibly entails
eutrophication with algal bloom or weed
spreading and /or death of fauna. The
necessity of the study emerged after
aquatic weeds started to invade the
Dâmbovița canal from Bucharest
(Romania) and several episodes of
dead fish occurred in the upstream
reservoir due to low oxygen
concentration in the water, caused by a
prolonged high temperature period.
OBJECTIVES
1. To analyse the thermal regime of
Dambovita River in Bucharest, during
hot summers.
2.To set up a 1D hydraulic and
temperature numerical model for the
case study considering the involved
physical processes ;
3. To process available data and define
heatwave modeling scenarios;
4. To perform a sensitivity analysis for
the weather parameters, to indicate the
degree of change in water temperature
when each of them is modified;
METHOD and DATA
A 1D numerical model (hydraulic and
thermal) was developed in HEC-RAS
software to reproduce water
temperature. Scenario definition and
variability range of parameters were
acomplished using hourly weather data
sets for a period of 30 years. For the
hottest day of the one-week heatwave
scenario sensitivity analysis was
performed for the determining
parameters in their range of variation
during summer heatwaves: solar
radiation, air temperature, relative
humidity, air pressure, wind speed and
cloudiness.
RESULTS
Results prove the thermal model is
sensitive particularily to shortwave
radiation and air temperature, which
induce water temperature variations of
over 1C. Other two influencing
parameters are cloudiness and wind
speed, inducing water temperature
variations of less than 1C.
CONCLUSIONS
The results are useful to gather and
prepare data to calibrate temperature
numerical model with sufficient accuracy
and resolution for the further one-week
scenario of heatwaves.
2. METHOD:
2.1 Mathematical and numerical model
Figure 1. Plan view of Dâmbovița canal through Bucharest City, with the 11
control structures; b) a typical cross-section profile; c) weed harvesting
1. SITE AND DATA
Figure 3. Hourly air temperature variation 1980-2020. 3 extreme heatwave
periods are emphasized (max. daily Tair > 40C)
3. RESULTS AND DISCUSSIONS
Figure 4. Mean annual air
temperature (1980-2020)
EXTREME HEATWAVE SCENARIOS WITH IMPACT ON THERMAL
REGIME OF DÂMBOVIȚA RIVER IN BUCHAREST, ROMANIA
Daniela Elena GOGOASE NISTORAN *, Cristina Sorana IONESCU*,
Ioana OPRIȘ**, Ionela ENACHE*
University Politechnica of Bucharest, Power Engineering Faculty, Bucharest, Romania,
(*) Department of Hydraulics, Hydraulic machines and Environmental engineering, dnistoran@gmail.com
(**) Department of Energy Use
No.
Name of control
structure (NH)
13 Grozavești
12 Șt. Furtună
11 Eroilor
10 Operetă
7 Mara-șesti
6 Timpuri Noi
5 M. Bravu
4 Vitan
3 Sere
2 Popești
1 Glina
Dâmbovița canal crosses from N-W to S-E Bucharest along a 17.5km distance. 12
in series reaches (pools) are separated by 11 control structures equipped with
gated broad-crested weirs (barrages). The top width varies between 30 and 100m.
Depths can vary between 1.5÷4.5 m, and mean bank slope is of 1.5 along the
entire reach for normal pool level (NPL) elevation. Mean longitudinal slope of
Dâmbovița canal along all pools is about 7 ‰. Discharge varies from the minimum
ecological flow of 3 m3/s, to intermediate values of about 20 m3/s (required for
periodic flushing), and up to a maximum of 45 m3/s crossing the pressurised
culvert of Unirii Square without flooding the banks.
5. REFERENCES (Selected)
• Caissie D 2006 Freshwater Biol. 51(8) 1389
• Dugdale S J, Hannah D M, Malcolm I A 2017 Earth-Sci. Rev. 175 97
• Dokulil M T 2013 Inland Waters 4 27
• Kedra M, Wiejaczka L 2018 Sci. Total Environ. 626 1475
• Driscoll M O, Jefferson A, Clinton S M and Manda A K 2010 Water 2(3) 605
• Gogoașe Nistoran D E, Ionescu C S, Georgescu M and David D Șt 2019 E3S
Web Conf. 85 06007
• Drake J, Bradford A, Joy D 2010 J. Hydrol. 389(3-4) 390
• Leonard B P 1991 Comput. Methods Appl. Mech. Eng. 88 17
• Oprea C 2005 Solar radiation. Theoretical and practical aspects (In
Romanian Radiația solară. Aspecte teoretice și practice) (București)
• Matuszko D, Węglarczyk S 2014 Int. J. Climatol. 34 145
y = -0.0007x2 + 0.1723x + 19.868
y = 0.0017x2 - 0.4211x + 62.846
10
20
30
40
50
60
70
80
90
100
110
10
15
20
25
30
35
40
45
0 50 100 150 200 250
Rel.
huminidity
(%)
temp.
(0
C)
no. of hours
Air temperature and relative humidity 2-9 July 2000 - 9 days
air temp.
rel. humiditity
y = 0.1084x + 19.664
R²= 0.9993
22.8
23.0
23.2
23.4
23.6
23.8
24.0
24.2
20 25 30 35 40 45
water
temp.
(deg.
C)
air temp. (deg. C)
Water-airtemp.
Water-air temp.
y = 0.0076x+ 23.658
R² = 0.9817
23.80
23.85
23.90
23.95
24.00
24.05
20 25 30 35 40 45 50
water
temp.
(deg.
C)
min.daily rel.humidity.(%)
Water temp. - air humidity
water temp. -
min. rel. humidity
Figure 13. Spatial variation of
water temperature at midday and
midnight of the one-day scenario
Figure 8. Water temperature
variation with air temperature
y = 0.005x + 20.227
R²= 1
23.6
23.7
23.8
23.9
24.0
24.1
24.2
24.3
660 680 700 720 740 760 780 800 820
water
temp.
(deg.
C)
shortwave radiation(W/m2)
Water temp - shortwaveradiation
water temp.-
shortwave radiation
Figure 10. Water temperature
variation with air relative humidity
y= 0.8117x2 - 0.0044x + 24.002
R²= 1
23.9
24.0
24.1
24.2
24.3
24.4
24.5
24.6
24.7
24.8
24.9
0% 20% 40% 60% 80%
water
temp.
(deg.
C)
cloudiness(-)
Water temp. - cloudiness
cloudiness
Figure 11. Water temperature
variation with cloudiness
y = 0.0019x2 - 0.0597x + 23.998
R² = 0.9984
23.55
23.60
23.65
23.70
23.75
23.80
23.85
23.90
23.95
24.00
24.05
0 2 4 6 8 10 12
water
temp.
(deg.
C)
wind speed (m/s)
Water temp. - wind speed
wind speed
Figure 12. Water temperature
variation with wind speed
0
1
e
l
V V V h
S S
g t g x x
V h h
h V q
x x t

  

   
   


  
   
   

3/2 3/2
2
d
Q C g BH C H
 
2
2
w w w total
L
p
T T T H
V D
t x x c h

  
   
    
total sw lw l s
H H H H H
   
2.2 Data processing
Hydraulic model: 1D Saint-Venant
equations + flow over weir equation
Temperature model: the 1D heat
advection – dispersion equation
Computation grid: 105 cross-sections at a mean distance of 200m
Boundary conditions: Upstream: Q(t), Tw(t); Downstream: channel slope
Initial condition: z (x, t=0), gate openings, Tw(x, t=0)
Numerical method: finite difference
Figure 2 Details of the a) hydraulic and b) temperature numerical model; c)
simulated daily variation of water temperature at downstr. control structure 3
28Jul2020 00:00:00
Legend
23
23.16667
23.33333
23.5
23.66666
23.83333
24
24.16666
24.33333
24.5
Weather data for Bucharest centre from Open weather – API
(https://openweathermap.org/) consisting in hourly values of: air temperature,
relative humidity, wind speed, cloudiness. Shortwave and longwave radiation,
latent and sensible fluxes were computed by hte softwa re based on
longitude/latitude and atmospheric pressure.
0 2 4 6 8 10 12 14 16 18
50
55
60
65
70
75
80
Lacul_Morii P
lan: Hobo_2020 9/24/2020
Main Channel Distance (km)
Elevation
(m)
Legend
Crit 10SEP2020 0100
WS 10SEP2020 0100
Ground
Popesti
CS
Sere
CS
Vitan
CS
M
Bravu
CS
Timpuri
Noi
CS
Marasesti
CS
Opereta
CS
Eroilor
CS
St.
Furtuna
CS
Grozavesti
CS
DS
dam
Dambovita Bucuresti
0 5 10 15 20 25 30
65
66
67
68
69
70
Lacul_Morii Plan: 2020_neperm 9/17/2020
RS = 6.01 IS Clapeta Timpuri Noi
Station (m)
Elevation
(m)
Legend
WS 30JUL2020 1300
Ground
Bank Sta
.02
Sensitivity analysis
Simulations are performed for the hottest daiy scenario, minimun-ecological flow
Q = 3m3/s and the following weather parameters in the usual summer ranges:
atmospheric pressure = 1010 mbar (950 - 1030 mbar), daily maximum air
temperature = 35 C (30-40C), daily maximum relative humidity = 65% (48 -
80%), daily maximum solar radiation = 740 W/m2 (685 - 805 W/m2), cloudiness =
10% (0 - 90%), wind speed at 10m of ground = 1 m/s (0-10 m/s). One paramenter
is varied at a time and all others kept at the base value, to see the influence on
water temperature at the downstream control structure no. 3 (“Sere”), at the exit of
Bucharest city.
0200 0400 0600 0800 1000 1200 1400 1600 1800 2000 2200 2400
31Jul2019
22
23
24
25
26
27
28
29
d:DANAHIDRAULICAMasuratoriMasuratori Lacul Mori iModelare HEc-RAS_4_Dambovi ta_Eenviro_termo_zi lnicaLacul_Morii.wq14
Time
Water
Temperature
(C)
Legend
Obs: Dambovita Bucuresti 3
Water Temperature (C)
S
i
m
u
l
a
t
i
o
n
4. Conclusions
Figure 5. Tair and relative humidity for the
hottest heatwave of 2-9 July 2000
Variația temperaturii
în spațiu și timp
2.3 Scenario definition
Figure 7 Defined daily scenario
for air temperature, shortwave
radiation and relative humidity
10
15
20
25
30
35
40
45
24/07 25/07 26/07 27/07 28/07 29/07 30/07 31/07 01/08 02/08
Air
temperature
(
o
C)
days
air temperature
Figure 6 Defined weekly scenario
for air temperature
Figure 9. Water temperature
variation with shortwave radiation
• A coupled hydraulic and temperature model has been set up to simulate stream
temperature variation along the channelized Dambovita River for the hottest day of
a weekly heatwave scenario.
• In the absence of measured water temperature values for calibrating the thermal
model, a sensitivity analysis has been performed by changing the values of
atmospheric parameters within the usual summer heatwave ranges. Results
show which are he most important weather paramaeters on stream temperatue
(see Discussions).
• Simulations prove there is a lag of 4 to 5h between extreme air and extreme
water temperatures downstream Bucharest, which means minimum daily stream
temperature is attained between 7:00 and 8:00 in the morning, whereas the
maximum value between 18:00-19:00 in the afternoon (Fig. 2b). Maximum water
computed water temperature for given scenario is of 28.7C at 2.6km from
downstream (Glina) (Fig. 13)
• The results of this paper are useful for further temperature measurements and
simulations during one-week scenario of heatwaves.
a)
b)
c)
Discussion:
Results show the thermal model is
sensitive particularily to air temperature
and shortwave radiation within specified
ranges, which induce stream
temperature variations of over 1C.
Other two important influencing
parameters are cloudiness and wind
speed, inducing water temperature
variations of less than 1C, which
means these could be introduced into
the model as constant values.
Figure 13. Space and time variation of water temperature
0 5 10 15
20
25
30
d:DANAHIDRAULICAMasuratoriMasuratori Lacul MoriiModelare HEc-RAS_4_Dambovita_Eenviro_termo_zilnicaLacul_Morii.w q14
Main Channel Distance (km)
Water
T
emperature
(C)
Legend
31JUL2019 12:00:00-Water Temperature (C)
01AUG2019 00:00:00-Water Temperature (C)
Dambovita-Bucuresti
control structure 3
0200 0400 0600 0800 1000 1200 1400 1600 1800 2000 2200 2400
31Jul2019
22
23
24
25
26
27
28
29
d:DANAHIDRAULICAMasuratoriMasuratori Lacul Mori iModelare HEc-RAS_4_Dambovi ta_Eenviro_termo_zi lnicaLacul_Morii.wq14
Time
Water
Temperature
(C)
Legend
Obs: Dambovita Bucuresti 3
Water Temperature (C)
S
i
m
u
l
a
t
i
o
n
4. CONCLUSIONS
10
20
30
40
50
60
70
80
90
0
100
200
300
400
500
600
700
800
0:00 6:00 12:00 18:00 0:00
Rel.
humidity
(%)
air
temp.
(°C)
Hsw
(W/m
2
)
h/day
Daily scenario for shortwave rad.,
rel. humidity and air temp.
shortwave
radiation
relative
humidity
air temp.