influenced flow in lower iza river...
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INFLUENCED FLOW IN LOWER IZA RIVER BASIN
PANDI G.
1, STOICA F.
2
ABSTRACT. Influenced flow in lower Iza River Basin. The Maramureş
Depression is drained by Vişeu and Iza rivers. Both have a partially influenced
regime. The flow in lower Iza Basin is influenced by the Runcu Reservoir and by
the Runcu – Valea Neagră derivation that are situated on the upper Mara River.
The flow is controlled by three hydrometric stations – Mara and Vadu Izei on
Mara River, and Vadu Izei on Iza River. We took into analyse the time period
1993 – 2012 using drained and influenced monthly average discharge data. The
variation of monthly and annual deviations for Mara Station shows positive values
for each year and for almost each month. The flow influence degree, in absolute
and relative values, is evaluated for all three stations. The hydrometric stations are
situated into a certain type of influenced flow by using the Q infl. / Q rec. ratio.
Keywords: Natural and influenced flow, water using utility, absolute and relative
deviation, flow influence degree, influenced flow type.
1. INTRODUCTION
The rivers from Iza hydrographic basin, with those from Vişeu Basin, drain
together The Maramureş Depression. The two parallel rivers display different
characteristics, due to their different river network evolution. The Vişeu River has
higher discharge values, is stronger due to its strong tributaries that come from the
Maramureş Mountains. The Iza River has lower discharge values, with an almost
depressionary nature, and its only big tributary is Mara River, descending from
Gutâi Mountains and joining in the Mara lower river sector.
The two basins present differences not only in their flow aspects, but also
in their morphology. Both basins are asymmetric, but in a reversed direction. Vişeu
Valley is narrower, with more stepper transverse and longitudinal slopes. Iza has
the aspect of an old stream, with a very large sweeping river bed due to its low
slopes, meandering and sometimes braiding.
Both rivers have a partially influenced flow. The Vişeu water regime is
influenced by the mining activity from Borşa area, in the upper basin. The flow of
lower Iza River is influenced by Runcu Dam – on upper Mara River, and Runcu–
Valea Neagră derivation, that transfer a part of Mara waters into the Strâmtori
Storage.
1 Babeș-Bolyai University, Faculty of Geography, Cluj-Napoca, Romania
E-mail: [email protected] 2 National Administration Romanian Waters, Somes-Tisa Water Branch, Cluj-Napoca, Romania
E-mail: [email protected]
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Fig.1. Maramureş Depression
2. DATA BASE AND METHOD
The flow in lower Iza Basin is controlled by three hydrometric stations:
Mara and Vadu Izei on Mara River, and Vadu Izei on Iza River, which is placed
after the confluence with Mara, as a closing station for the entire basin (Ujvari,
1972). Mara hydrometric station monitors a mountainous basin containing the
Gutâi Mountains volcanic space, with an average altitude of near 1000 m. Vadu
Izei Station on Mara River monitors almost the entire basin because it is situated
400 m before the river’s confluence. The flow at station from Iza River is
influenced only by Mara’s water regime, slowly diminished only by discharges
values’ growth.
Table 1. Morphometric data of basin’s hydrometric stations
River Hydrometric
station Area H med
Total
length Downstream
Length km
2 m km km Iza Vadu Izei 1126 714 69.8 10.2 Mara Mara 155 901 19.1 18.9 Mara Vadu Izei 410 749 37.6 0.40
The monthly average discharge data series includes the period 1993 –
2012. We’ve calculated the reconstructed discharges for the using water using
utilities monitoring Mara River. It must be mentioned that, in accordance with the
regulations in force, reconstructions shall be used only for monthly average
discharges.
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The analysis is based on the calculation of absolute and relative deviation
between reconstructed and influenced discharges, expressing the influence degree
of the natural runoff:
( )
The influence degree evaluation is made using monthly absolute and
relative deviation analysis, and also multiannual monthly deviations for all three
hydrometric stations.
3. WATER USING UTILITIES THAT INFLUENCE THE RIVER
RUNOFF
Runcu Storage is part of the Firiza – Săsar Plant, comprising: Strâmtori
Storage, in operation since 1965, and Runcu – Firiza Hydrotechnical System, with
the functions flow regulation and water deviation from Mara River into Strâmtori
Storage. The construction of Runcu Dam began in 1987 and is the oldest
hydrotechnical investment in Romania, unfinished yet. This project regards water
discharge supplementation for Baia Mare and creating a water network for all
villages from Mara water basin and for Sighetu Marmaţiei.
Runcu Storage is a rockfill dam with PVC geocomposite as a sealant. The
dam’s maximum height will be 90 m, and crown’s length 324 m. The reservoir’s
basin area is 85 km2. Upon completion of the Runcu Dam, the accumulated water
volume will be 26 million m3.
The Runcu Storage is part of the General Development Plan for complex
use of Săsar and Firiza river basins, comprising: the Baia Mare Hydrotechnical
System with Strâmtori-Firiza Storage and the Runcu- Firiza Hydrotechnical
System, which main purpose is water regularization and diversion of Mara River
into Strâmtori Storage. Suring the first step was constructed the Runcu-Valea
Neagră deviation gallery, in operation since 1975, with a natural flow discharge of
600 l/s through a concrete gallery of 8.3 km in length and 2.2 m in diameter. In
second stage, the Runcu Storage will provide an additional discharge of 1.2 m3/s.
Finally, the flow discharge will reach 3.55 m3/s.
4. DEVIATION VARIATION DURING 1993-2012
Deviations were analyzed at Mara hydrometric station, because here the
flow is most influenced. In Figure 2 can be observed that the monthly deviations
are mostly positive, but there are a few months with negative values. The absolute
values range between 4.93 m3/s and -2.20 m
3/s, and the relative values between 65
% and -19 %. Note that absolute and relative deviations values are not
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proportionate as they relate to the variable reconstituted discharges. But, deviations
direction must be the same, as resulting in the chart.
The allure of absolute and relative deviations trends indicate reconstruction
correctness of natural flow calculations. We can identify several large deviations
periods (1999-2000, 2004-2009) and small (1997-1998, 2001-2003, 2010). The
most important deviations oscillations are observed at the period’s beginning
(1993-1996) and end (2011-2012). The 6th degree polynomial trends are very
similar, with higher amplitudes for relative deviations.
Fig.2. Absolute and relative monthly deviation at Mara Station
Fig.3. Reconstituted and influenced annual average discharges at Mara Station
-4
-2
0
2
4
6
8
10
12
14
16
-60
-40
-20
0
20
40
60
80
19
93
19
94
19
95
19
96
19
97
19
98
19
99
20
00
20
01
20
02
20
03
20
04
20
05
20
06
20
07
20
08
20
09
20
10
20
11
20
12
Q (
m3
/s
ε (%
)
relative deviation
absolute deviation
2
3
4
5
6
7
8
9
19
93
19
94
19
95
19
96
19
97
19
98
19
99
20
00
20
01
20
02
20
03
20
04
20
05
20
06
20
07
20
08
20
09
20
10
20
11
20
12
Q (
m3
/s)
Reconstituted discharge
influenced discharge
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Flow influence during 1993 - 2012 results also from the superposition of
mean annual reconstituted and influenced discharges. In Figure 3 we can see that
the differences between mean annual discharges vary over the years, depending on
rainfalls quantities and on Runcu – Valea Neagră running regime. The most
influenced years have been 1993, 2004, 2007 (over 1.0 m3/s) and minimum
influences were registered in 1998, 2002, and 2010 (under 0.10 m3/s).
5. FLOW’S INFLUENCE DEGREE
The analysis of multiannual monthly values variation is made for each
station. It is noted that at multiannual level, the deviations are positive in all
months. This is due to the water using utilities’ nature, which primary function is
the diversion of a water quantity from Mara River into Valea Neagră, and further in
Strâmtori Storage through Firiza River.
At Mara Station, the highest discharges (over 0.6 m3/s) are routed into
Valea Neagră River and Strâmtori Storage during the months to high discharges
(April-May) and in November-December. The highest relative influence degree
was recorded in July-August (over 20 %) when, although derived discharges are
smaller, they are linked to a lower flow.
The annual average influence degree is 0.63 m3/s, which corresponds to 13
% in relative values.
Fig.4. Absolute and relative deviation at Mara Station
At Vadu Izei Station on Mara River, the influence is similar, but the
catchment’s area difference has an influence too. Here appears February together
with the months April-May and November-December for the absolute maximum
degree of influence. The difference between minimum and maximum values is
more pronounced than at Mara station. Some months (March, June) present with
discharges of only 0.2 m3/s.
The chart of relative deviations closely resembles that of Mara Station,
showing similarity in the absence of some major tributaries in the inter-basins
space. Maximum values appear in February, July-August and November (over 10
%) and a big minimum in March (1 %), but also in June (3 %).
0.00
0.20
0.40
0.60
0.80
1.00
1.20
I II III IV V VI
VII
VII
I
IX X XI
XII
Year
ΔQ
(m
3/s
)
0
5
10
15
20
25
I II III IV V VI
VII
VII
I
IX X XI
XII
Year
ε (%
)
353
The annual average value is almost identical (0.64 m3/s) for absolute
deviation, but is only half for the relative one (7 %) compared with the values at
Mara hydrometric station.
Fig.5. Absolute and relative deviation at Vadu Izei / Mara Station
Vadu Izei Station on Iza River is the last to suffer the influence of Runcu -
Firiza system. Due to the significant increase of basin area, the discharges are
higher and the influence degree is reduced. The allure of absolute deviation chart is
similar. Discharges over 1.0 m3/s are recorded in February, April, May and
November, and below 0.5 m3/s in March, August - October. Much lower influences
of natural flow appear from the analysis of relative deviations. Only one month has
a deviation of over 8 % (July). In March and October deviations are minimal (less
than 2 %).
The annual average discharge value is 0.73 m3/s, which corresponds to 4 %
relative deviation.
At this station is more clearly observed that the months with poor drainage
present high values for the influence degree. This happens because the derived
discharges are related to lower natural values. In the months with rich flow the
situation is the reverse.
Fig.6. Absolute and relative deviation at Vadu Izei / Iza Station
0.00
0.20
0.40
0.60
0.80
1.00
1.20
I II III IV V VI
VII
VII
I
IX X XI
XII
Year
ΔQ
(m
3/s
)
0
2
4
6
8
10
12
14
I II III IV V VI
VII
VII
I
IX X XI
XII
Year
ε (%
)
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
I II III IV V VI
VII
VII
I
IX X XI
XII
Year
ΔQ
(m
3/s
)
0
1
2
3
4
5
6
7
8
9
I II III IV V VI
VII
VII
I
IX X XI
XII
Year
ε (%
)
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6. INFLUENCED REGIME TIPIZATION
The Runcu Storage and Runcu – Valea Neagră derivation transfer water
from Mara River to Strâmtori Storage. Under these conditions the ratio between
reconstructed and influenced discharge has subunit values every month, meaning
the water quantity flowing in the river is smaller than under natural conditions.
This type of runoff influence is included in deficitary influenced flow type (Pandi,
2011).
Fig.7. The expression of deficitary influenced flow type
All three analysed stations belong to this influenced flow type. Of course,
the values vary from a station to another, and also every month.
7. CONCLUSIONS
In the lower basin of Iza River the natural flow is influenced by the Runcu
- Firiza Hydrotechnical System, which includes Runcu Storage and Runcu – Valea
Neagră derivation.
The discharges analysis from the three stations that monitor the flow shows
a variable influence degree, but existing at both annual and the monthly discharges.
Deviation’s absolute and relative expression allowed the establishment of obvious
realities in temporal and spatial differences.
As a result of the hydrotechnical system’s main function - water transfer -,
the influenced flow at all three stations may be included in the deficitary type,
representing a subunit ratio between influenced and reconstructed discharges.
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
I II III IV V VI VII VIII IX X XI XII
Qin
fl/Q
rec
Mara / Mara
Vadu Izei / Mara
Vadu Izei / Iza
355
REFERENCES
1. Pandi G. (2011): The Influenced Flow Regimes, Aerul şi apa – Componente ale
mediului, p.38-44, Edit. Presa universitară clujeană, Cluj-Napoca
2. Sorocovschi V., Pandi G. (2012): Particularities of seasonal and monthly flowing
regime on the small rivers of Maramureş Mountains, Water resources and
wetlands, p.39-47, Edit. Transversal, Târgovişte
3. Ujvari I. (1972) Geografia apelor României, Edit. Academiei, Bucureşti
4. Ujvari J., Pandi G., Dumescu F. (1996): A román - magyar határvidék
vízkészleteinekértékelése és értékesítése, Határon innen, határon túl, p.106-115,
Szeged