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ISSN (Print): 1844-6116
ISSN (Online): 1884-6116 http://www.cmu-edu.eu/jmte
Journal of Marine technology and Environment Year 2018, Vol.1
7
ANALYSIS OF RIVER LEVEL AND OF THE VOLUME FLOW ON THE DANUBE
CLOSE TO THE CITY OF TULCEA, BASED ON IN SITU MEASUREMENTS
Alexandru Banescu1, Lucian Puiu Georgescu 1, Catalina Iticescu 1 & Eugen Rusu 1
1 “Dunarea de Jos” University of Galati, 47, Domneasca Street, 800008, Galati, Romania, e-mail address:
alexandru.banescu@yahoo.com; lucian.georgescu@ugal.ro; catalina.iticescu@ugal.ro; eugen.rusu@ugal.ro
Abstract: This work presents a review of hydrological data known as water levels and volume flows that have been
recorded and then processed to render a contour about the hydrological situation of the Danube River near Tulcea. On-
site measurements have generated daily data on river flows and levels over a 3-year period (2003, 2004, 2006), their
interpretation being important for knowing the water drainage regime. Moreover, the characteristic values can have a
practical interest in some river design works, such as hydrotechnical flood defense constructions that may occur as a
result of elevated levels above a certain threshold or may be beneficial during works or exploitation of river bed
resources. In order to accurately present the importance of knowing the river level variation, it is necessary to process,
verify and interpret all data on the levels and flows, establish links and graphical correlations, and determine the
characteristic values over the multiannual period. The results obtained from the measurements are described in the four
periods of the year, and the conclusion shows that each period is manifested both in climatic and hydrological terms by
specific characteristics and phenomena.
Key words: Danube River, Tulcea, water level, volume flow, measurements
1. INTRODUCTION
The Danube River is the second river in Europe,
crosses 2840 km from the Black Forest, the
Donaueschingen in Germany, to the Black Sea. The
Danube has build up one of the most interesting and
beautiful deltas in Europe and even in the world. The
arms of the Danube are the major arteries by which the
river provides the deltaic space, the solid and liquid
flow. The deltaic space is directly influenced by the level
and the amount of flow that the river carries in different
proportions depending on the period [1], [2].
The hydrographic network of the Danube Delta is
extremely complex, showing a particular geographic,
economic, and tourist interest. It provides water supply
to lakes as well as airworthiness. This hydrographic
network comprises the Danube arms (Chilia arm, Tulcea
arm, Sulina arm, Sfantu Gheorghe arm), lakes, ponds,
marshes, channels, and sheds [3].
At present, the activities of valorizing the Danube's
natural resources, the tourism and trade have increased
the transport on water, requiring the balanced
development of both the waterways and the types of
ships, correlated with the conditions of protection the
natural environment of the river, which requires
knowledge of the Danube's drainage regime [4].
Very important issues in order to ensure a proper
circulation of the water on the Danube are not the very
large flows of the river, produced over a short interval in
spring, but, in particular, the existence of a long period
of time with relatively high flows. In this case, given the
correspondence between flows and levels, an active
circulation of the water can be ensured in the inner
depression areas, facilitating the evacuation of the
wastewater loaded with noxious waste at the end of the
summer [5], [6].
The drainage regime of the river is depending on
variation in time over a month, a season, a year or more
of the amount of water flowing within a river section.
The liquid leak can come from rains, snow and even
from groundwater. The study of the regime is given by
the knowledge of the variation in leakage and sources of
supply. The variation of the river supply sources over a
year requires a similar variation in the flow of the river
water, uniformed in a sequence of characteristic periods,
referred as drainage phases. The frequency and often the
duration and the dimensions of the phases show the
variation in time of the supply sources, which in turn are
ISSN (Print): 1844-6116
ISSN (Online): 1884-6116 http://www.cmu-edu.eu/jmte
Journal of Marine technology and Environment Year 2018, Vol.1
8
strictly dependent on the interference of the climatic
factors in the climatic seasons [7].
Regarding the influence of the physical geography
factors on the rivers, the processes and the hydrological
phenomena within the river basins are determined by the
position of our country, the height and orientation of the
relief and, to a greater extent, the physical geography
factors in the basin. In the processes of the leakage
formation and evolution, the main role is played by the
climate, which, due to the precipitation, temperatures,
wind, evapotranspiration and frost regime, inflates
decisively the water reserves as well as the leakage
regime [8].
An important problem is the flooding of deltaic
space, as a complex hydrological process. This is very
important in the dynamics of the evolution of all
components of the natural system. Strongly dependent
on the Danube water regime, the degree of flooding
supports both surface alluvial processes at elevated,
linear levels at low levels, as well as the water supply of
indoor lake depressions. Also, related to the process of
flooding, the deltaic territory imposes restrictions on the
location, sizing, and realization of various constructions,
habitable surfaces, etc. [9]
The main premises that condition the flooding
process are its hypsometric peculiarities, the amplitude,
and periodicity of the Danube's maximum levels, to this
being added, at present the restriction of flooded areas,
having as a result the covering of some areas [10].
Both for the Danube Delta and for the Danube
localities, there is a risk of failure, where it may occur
the phenomenon of settlement the dam, or if not, there is
a major danger of producing an infiltration because of
the duration of the very long flood. Also, there is a
permanent risk of erosion sometimes accompanied by
landslides which endanger housing and households. At
the same time, there is a permanent risk of erosion
sometimes accompanied by slopes of ground that
endanger habitats or households [11].
In this context, the present work describes the
situation of levels and flows in different forms of
analysis for a 3-year period, how these data were
collected and the methods of analysis used.
2. MATERIALS AND METHODS
The target area is located on the Danube at Km
71 near the city of Tulcea. The location of the
hydrometric station is shown in Figure 1.
The recording of the results of the water levels
in the Danube River was determined by direct reading a
hydrometer placed on the river, using a recorder called
the limnometric device. It has the role of knowing the
evolution over time, by discrete (discontinue) values of
water levels and of checking and correcting the recorded
levels [12].
Figure 1 Map with the location of the hydrometer
station at Km 71 on the Danube
The level measurement programs (hydrometric
reading) are set by the hydrological station staff
according to the flow regime (small, medium, or high
water). When there is a constant treatment regime, the
recordings of the level and the flow of the river are made
at the standard observation hours (8 and 20).
The recorded water levels are used directly to
indicate the imminence of production floods and
indirectly to specify the hydrograph of the water flow
using the limnometric key [13].
As regards the water levels, given the short time
they have been observed or recorded, they are
considered as instantaneous values. Level records are
expressed in meters, relative to ''0 graduated tool''. The
share ''0 graduated tool'' is expressed in mrMN (Black
Sea landmark).
The level values are important, both as values in
themselves, notably by specifying flood areas and the
moment when the flood is produced, as well as indirectly
by determining with the help of the limnometric key the
hydrographic water flow and the hydrographs useful for
hydrological forecasting and monitoring of basin water
resources.
The evolution of water flow hydrographs over time
is helpful for all activities of knowledge of the evolution
of the river flow regime over time (hydrological forecast,
hydrological parameters, integrated water resource
monitoring).
The determination of the water flow hydrographs is
achieved by: direct measurements with specific
equipment or with the help of determinations (discreet
values) of water flows and/or slopes and sections. On the
basis of these and the levels existing at the time of the
water flow determination, it is specified a correlation
"flow-level" - limnometric key.
ISSN (Print): 1844-6116
ISSN (Online): 1884-6116 http://www.cmu-edu.eu/jmte
Journal of Marine technology and Environment Year 2018, Vol.1
9
With the help of this, and the help of level
hydrographs, the water flow hydrographs are then
determined [14].
The frequency of the water flow measurements
shall be determined by the personnel of the hydrological
stations, mainly in the phase of the regime, by the
requirements marking the limnometric keys. The basic
condition is to specify at any time the value of
instantaneous and average hourly / daily water flows
with an error below 15%.
The determination of the water flow is done by
measuring the speed rate of the water and the wetted
section. The water flow results from the multiplication of
the watered section at the average speed. Speed is the
most difficult variable given by the determinant due to
the fact that it varies with width and depth in the profile
[15].
The usual hydrometric technique for measuring the
water flow consists in launching into a watercourse, in
the direction of the water flow a propeller in order to
determine the water velocity at different points located
on several vertical sections of the watered section. The
method of calculating the flow is called '' speed section ''.
The evolution of water flow rates over the course of the
river is determined by means of level records and
limnometric keys, "water flow-level" curves. The
"speed-section" method, as mentioned above, is based on
the determination of water depths at various points of the
wet section and its velocity at different vertical points
located within the perimeter of the wet section.
The method of determining the average velocity in
one vertical is called the "five-point" method, which,
depending on the depth of water in the bed, is reduced to
the one-three-point method.
For measuring the water flow the hydrometric
propeller has been used. The hydrometric propeller is a
device designed to measure the water current for the
calculation of water flows.
The operating principle of the hydrometric propeller
is based on counting the rotations that make them in a
unit of time a propeller under the influence of the water
current.
In the present work there are presented
developments in water levels and flows of the Danube
River at the Tulcea arm for the years: 2003, 2004 and
2006. In those years, there were correlated daily data of
water flows and levels in Tulcea harbor, the level records
are expressed in meters, relative to ''0 graduated tool''.
The share ''0 graduated tool'' is expressed in mr MN
(Black Sea landmark). – Fig. 2 [subplots (a), (b), (c), (d),
(f), (g), (h)], and the flows being expressed in m3/s – Fig.
2 [subplots (a), (b), (c), (d), (e), (i), (j), (k)].
3. RESULTS
The results are presented in the first phase in the
form of tables and in the second phase as figures.
Figures are graphs showing the levels and the water
flows of Danube near Tulcea for the years: 2003, 2004,
2006, in different forms of representation. Tables contain
the volume water flows and levels for the four periods of
the year: winter, spring, summer, and autumn periods.
Table 1. Sets of minimum and maximum levels
distributed over the four periods of the year
Period
..
2003
2004
2006
Max
Level
ll [m]
Min
Level
ll [m]
Max
Level
ll [m]
Min
Level
ll [m]
Max
Level
ll [m]
Min
Level
ll [m]
Win.
period
3.63
1.15
2.86
1.31
3.51
1.21
Spr.
period
3.06
1.93
4.15
2.29
4.93
2.99
Sum.
period
2.13
0.74
3.04
1.56
4.52
1.69
Aut.
period
2.24
0.61
2.83
1.18
2.62
1.05
Table 2. Sets of minimum and maximum volume water
flow distributed over the four periods of the year
Period
2003
2004
2006
Max
Flow
[m3/s]
Min
Flow
[m3/s]
Max
Flow
[m3/s]
Min
Flow
[m3/s]
Max
Flow
[m3/s]
Min
Flow
[m3/s]
Win.
period
4742
1612
3608
1629
4383
1683
Spr.
period
3793
2510
5124
2937
7845
3291
Sum.
period
2713
1010
3538
1975
6511
2197
Aut.
period
2778
913
3367
1513
3056
1570
ISSN (Print): 1844-6116
ISSN (Online): 1884-6116 http://www.cmu-edu.eu/jmte
Journal of Marine technology and Environment Year 2018, Vol.1
10
ISSN (Print): 1844-6116
ISSN (Online): 1884-6116 http://www.cmu-edu.eu/jmte
Journal of Marine technology and Environment Year 2018, Vol.1
11
Figure 2 Graphics describing the situation of water
levels and the volume flows with data collected during
2003, 2004, 2006
4. DISCUSSIONS
The analysis made showed that the maximum
level and flow was recorded in 2006 and the lowest level
and flow in 2003. The level and maximum flow in 2003
were registered by the middle of January, continuing
with decreases and rises in values all over the year
during the year, thus setting in September the lowest
level and flow, comparing with the rest of the analysed
years - Fig. 2 (a), Fig. 2 (d), Fig. 2 (e), Fig. 2 (f), Fig. 2
(i). The 2003 situation is similar to the one of 2004 and
2006, only in terms of the minimum level / flow. The
minimum level / flow for the three years considered in
the analysis have been recorded during the autumn - Fig.
ISSN (Print): 1844-6116
ISSN (Online): 1884-6116 http://www.cmu-edu.eu/jmte
Journal of Marine technology and Environment Year 2018, Vol.1
12
2 (a), Fig. 2 (b), Fig. 2 (c), Fig. 2 (d), Fig. 2 (e), Fig. 2
(f), Fig. 2 (g), Fig. 2 (h), Fig. 2 (i), Fig. 2 (j), Fig. 2 (k).
The autumn periods can also record extremely
different situations from one year to another, as in other
years not too many can trigger a rainy episode that can
generate large autumn waters. The occurrence of such a
massive leakage episode is also facilitated by the sharp
decrease of the air and soil thermal regime. In the above-
mentioned case, it was shown that at the end of the
summer period and the beginning of the autumn period
the precipitations were missing in the territory resulting
in low levels / flows.
The year 2006 is similar to 2004 in terms of the
maximum level / flow recorded during the spring period
- Fig. 2 (c), Fig. 2 (d), Fig. 2 (e), Fig. 2 (g), Fig. 2 (h),
Fig. 2 (i), Fig. 2 (k).
The spring season coincides with the season
where the average daily air temperature is between 00C –
100C, favoring the melting of snow reserves in the
territory. In this period, the river's levels and flows are
increasing, sometimes faster, sometimes slower,
depending on the rate of the snow melting, and the
possible overlapping of rains over the snow.
It should be noted that the maximum annual
drainage of the water can take two forms, namely: high
water and floods.
In general, the two notions characterize the
same phase of the regim, but they have quite a different
content.
As far as floods are concerned, it is a very
characteristic hydrological phenomenon for all rivers,
being fed by surface sources (rain, snow melting).
Analyzing the three years, we can conclude that the year
2006 shows a significant flood with values exceeding
7000 m3/s - Fig. 2 (c), Fig. 2 (e), Fig. 2 (k). A similar
situation was recorded in 2004, but with much lower
values compared to 2006, with quantitative values
slightly above 5000 m3/s - Fig. 2 (b), Fig. 2 (c), Fig. 2
(e). Despite the large differences in values for the 2
years, their likeness is given by the flood period.
Floods can be defined as sudden and strong
increases in the river level / flow due to the torrential
rains, long-lasting rains, or accelerated snow melting.
The year 2003 recorded in January the highest level
/ debit for that year. A less normal situation, comparing
with the rest of the years, because in the winter period,
the overlapping season in which the average daily air
temperature is below 00C, precipitation is in solid form
(snow) and the river has a generally low drain. On the
river, frost formation of different kinds, of some
intensity and duration, occurs during this period. In most
of the territory, there is a minimum drainage period,
called hydrology, the period of the small winter waters.
Various different climatic and hydrological
situations can be recorded in the summer period, in
spring floods can continue, an example being the first
part of the summer of 2006 - Fig. 2 (c), Fig. 2 (d), Fig. 2
(e), Fig. 2 (h), Fig. 2 (k). Generally, during this period,
there are periods of small summer waters, where the
Danube gradually passes from surface feeding (rain) to
pure underground feeding. At this stage, the river has a
general trend of decreasing flows, from the maximum
value to the minimum value, which in most cases occurs
in September.
In the figures: [Fig. 2 (l), Fig. 2 (m), Fig. 2 (n)], the
normalized values corresponding to the minimum
(down) and maximum (up) levels are presented,
providing a more detailed picture of these data.
Knowing the minimum and maximum levels /
flows, is also relevant in designing, exploiting hydro-
technical constructions and complex water management.
Knowing the duration of the levels / flows is also
important for many practical activities, as: the placement
of machines, hydro-aggregates and machines in the
minor bed during the execution of works or the
exploitation of resources from the bed (ballast, sand,
water supply, etc.) in flood and ice protection, etc.
5. CONCLUSIONS
The analysis made in this work lead to the
conclusion that during one year four characteristic
periods occur in the hydrological regime of the river.
These are: the winter period, the spring period, the
summer period and the autumn period. Each period is
manifested both in climatic and hydrological terms by
specific features and phenomena.
Large waters occur most often in the spring, at the
slow and prolonged melting snow. Their duration and
intensity depending on the physical-geographic
conditions that generate the leakage, namely the
reservoir of the water in the basin, the rapidity of the
melting of the spring snow, the overlapping or not with
the beginning of the spring rains.
Having a detailed and comprehensive picture
regarding the Danube flows and levels is important
because knowing these values can be of a practical
interest for the river development works, such as the
protection of the dikes' height (avoidance of a major
flood risk).
As a general conclusion, the scientific and practical
importance of knowing the fluctuation of the river levels
/ flows, it can be highlighted by several important
aspects, such as the knowledge of level variations during
the year or in a multiannual profile, allows for a general
understanding of the determinant role of the physical-
geographic factors on the formation and the
characteristics of the leakage through the bed.
To playback as eloquent as possible the importance
of knowledge of the level fluctuations of a river, it is
necessary to process, verify and interpret all data on the
levels / flows, establish links and graphical correlations,
ISSN (Print): 1844-6116
ISSN (Online): 1884-6116 http://www.cmu-edu.eu/jmte
Journal of Marine technology and Environment Year 2018, Vol.1
13
and determine the characteristic values over the
multiannual period.
ACKNOWLEDGEMENT
This work was carried out in the framework of the
project proposal ACCWA (Assessment of the Climate
Change effects on the WAve conditions in the Black
Sea), supported by the Romanian Executive Agency for
Higher Education, Research, Development and
Innovation Funding - UEFISCDI, grant number PN-III-
P4-IDPCE-2016-0028.
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