Journal of Water Resource and Protection, 2013, 5, 64-71 Published Online January 2013 (
Spatial and Temporal Quality of Water in the Itupararanga
Reservoir, Alto Sorocaba Basin (SP), Brazil
Felipe José de Moraes Pedrazzi1, Fabiano Tomazini da Conceição1*, Diego de Souza Sardinha2,
Viviane Moschini-Carlos3, Marcelo Pompêo4
1UNESP, Universidade Estadual Paulista, Rio Claro, Brazil
2ICT, UNIFAL, Poços de Caldas, Brazil
3UNESP, Universidade Estadual Paulista, Sorocaba, Brazil
4IB, USP, São Paulo, Brazil
Email: *
Received October 30, 2012; revised November 30, 2012; accepted December 8, 2012
Considering the great importance of the Itupararanga Reservoir, Upper Alto Sorocaba basin/SP, this study aimed to
report the variations of some parameters of water quality in the spatial and temporal gradients in this multipurpose res-
ervoir. The eutrophication of this reservoir was checked using the Carlson Index Modified and the results indicate that
the surface water were classified as eutrophic and mesotrophic in wet and dry periods, being characterized the better
quality of water in wet period. In the vertical gradient the results showed a stratiphication in all parameters analyzed,
except for the electrical conductivity, with good correlation between total phosphorous and chlorophyll-a, indicating
that eutrophication of the reservoir changes the conditions of algal growth, mainly in its initial area. Immediate inter-
ventions are needed, which must be directed to planning of land use, domestic effluents treatment, taking to an inte-
grated management of this important watershed located in the São Paulo State.
Keywords: Itupararanga Reservoir; Limnology; Eutrophication; Environmental Management
1. Introduction
Water is available in various forms, one of the most
common and important substances found in nature,
covering about 70% of the Earth surface. Fresh water
represents only 2.5% of total water in nature, and the
remaining 97.5% are found in oceans and seas salty.
However, only 0.3% is fresh water exploitable for human
activities, can be drawn from lakes, rivers and aquifers.
The remainder is contained in aquifers, deep aquifers, polar
ice caps, glaciers, permanent snow and other reservoirs.
Recent data show that 1.7 billion people presently live
without water with adequate quality; a number that may
increase to 3.3 billion in 2020 and that may cause con-
flicts if effective water management is not performed.
The classification of water bodies is usually established
according to legal standards and it should be expected to
be improved over time. In Brazil, this classification was
made by Resolution CONAMA (National Council for
Environment) No 357, that defines freshwaters (special,
1, 2, 3 and 4 classes), brackish waters (special, 1, 2 and 3
classes) and saline waters (special, 1, 2 and 3 classes) [1].
São Paulo Electric Company, known as “Light” built
Itupararanga reservoir (Figure 1) in 1912, the aim was
generate electricity to the cities around Votorantim. Later,
in 1976, Companhia Brasileira de Aluminio (CBA) bought
the rights to operate the hydroelectric power generation
for the aluminum industry. This reservoir is located at the
Upper Sorocaba basin, which has its economy based
mainly on agricultural production, where many affluents
compose this basin tributaries that give rise to the Sorocaba
River, which flows into the Itupararanga Reservoir. This
reservoir has fundamental importance in regulating the
hydraulic regime of the Sorocaba River and in the public
supply of the region, serving approximately one million
people in the municipalities of Ibiúna Sorocaba, Votorantim
and Mairinque. However, this reservoir has lack of infor-
mation about its quality, making it essential to carry out
more detailed limnological studies. Thus, the purpose of
this study was to evaluate the water quality in spatial and
temporal scales in Itupararanga Reservoir, São Paulo
State. The results allowed generating an environmental
assessment by providing grants for planning and manage-
ment of pollution control in this important watershed
located in the interior of São Paulo State.
2. Overview of the Alto Sorocaba Basin
Alto Sorocaba basin covers an area of 929 km2 (Figure 1)
*Corresponding author.
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and it is located in the southeastern part of São Paulo
State, between coordinates 23˚45'37''S and 23˚35'02''S
and 47˚21'00''W and 46˚57'29''W. Una, Sorocabuçu, and
Sorocamirim rivers are the main formed the Sorocaba
River, crossing Ibiúna, Cotia, Vargem Grande Paulista,
and São Roque cities. The total population of Alto Soro-
caba basin is 110,577 inhabitants, with an urbanized area
occupying approximately 71 km2, being 55 km2 charac-
terized by small villages. The main land use in this basin
is characterized for an intense agricultural activity of
cabbage, lettuce, potato, and tomatoes crops (393 km2).
The Alto Sorocaba basin is composed for rocks dating
since Medium-Upper Proterozoic until Quaternary des-
ignated the São Roque Group and Embu Complex. The
São Roque Group is formed for metamorphic rocks asso-
ciated with granitic complexes, such as San Francisco
(sienogranites and monzogranites) and São Roque (dio-
rites and granodiorites) granites [2]. The Embu Complex
presents paragneisses and migmatites also associated
with Ibiúna (monzogranites and sienogranites) and Caucaia
(monzogranites and sienogranites) granites [2]. Among
the major types of soils occurring in the Alto Sorocaba
basin, yellow-red ultisols and oxisols cover about 85% of
the area of the basin.
The climate of the region is Cwb type (Köeppen clas-
sification), i.e. tropical rainy weather characterized by
wet summer (October through March) and dry winter
(April through September). The average temperature in
almost all months is higher than 18˚C, reaching 22˚C in
the hottest one (December). The area often has 55 - 65
days of rain per year, with more than 80% of the precipi-
tation falling between October through March. For more
than 50% of the year (October-April) the area is domi-
nated by tropical and equatorial air masses, with the
winds coming from the S and SE. The mean annual rain-
fall was 1493 mm between 1960 and 2004 [3]. Figure 2
shows both the monthly average precipitation and dis-
charge at Itupararanga Reservoir, which indicates that the
Sorocaba River regime is directly bounded to rainfall, as
expected. Beside, the discharge at Itupararanga Reservoir
is approximately 12 m³/s in 50% of the time (Figure 3),
being this value slightly smaller than the monthly aver-
age discharge into Itupararanga Reservoir, i.e. 12.7 m³/s
Figure 1. Simplified geological map of the Alto Sorocaba basin and location of sampling points in the Itupararanga Reser-
Figure 2. Monthly average rainfall and discharge into Itu-
pararanga Reservoir between 1960 and 2004.
Figure 3. Permanence curve of discharge into Itupararanga
Reservoir between 1960 and 2004.
Copyright © 2013 SciRes. JWARP
3. Sampling and Analytical Techniques
To define the sampling points in the reservoir, an explora-
tory field trip to visit was made to check the level of an-
thropogenic influence. After this stage, to assess the quality
of water in the spatial scale, was chosen 20 sampling points
for collecting surface water samples evenly distributed
throughout the Itupararanga Reservoir and 2 points for a
vertical sampling, to assess the profiles of water column
(P1 and P2), this points were located one near the beginning
and one in the end of the reservoir (Figure 1).
To the assessment of the quality of water in the reservoir
timescale, there were two collection campaigns in different
seasons, one during the wet season (01/24/2007 and 01/
25/2007) and another in dry season (08/01/2007 and 08/
02/2007). To collect samples of surface water, containers
(high density polyethylene) were previously prepared to
receipt of samples. For the sampling of vertical profiles,
were used a bottle of Van Dorn. Water transparency was
measured with Secchi Disc to assess the disappearance
On-site collection, all water samples (surface or vertical
profile) were characterized by following variables: water
temperature (Temp, ˚C), pH, electrical conductivity (EC,
S/cm) and dissolved oxygen (DO, mg/L). The equipment
used for these measurements were YSI, YSI 556 model.
The pH electrode is combined type and patterns of high
purity were used for calibration of pH 4.00 (4.005 ±
0.010 at 25˚C ± 0.2˚C) and 7.00 (7.000 ± 0.010 at 25˚C ±
0.2˚C). The conductivity meter was calibrated using a
standard solution of KCl (1.0 mmol/L) of known conduc-
tivity, i.e. 147 μS/cm at 25˚C.
All samples were stored properly preserved and brought
to the Laboratory of Environmental Geochemistry at
UNESP-Sorocaba. In the laboratory each sample was
divided into two aliquots for quantification of total pho-
sphorus (TP) and chlorophyll-a (Cl). The first aliquot
was measured the total phosphorous concentration, in
this laboratory, using the method of acid digestion with
potassium persulfate through the spectrophotometer DR-
2800 Hach Company. The second aliquot was transported
to the Laboratory of Limnology at USP-São Paulo, fil-
tered and Chlorophyll-a was determined according to
Wetzel and Likens [4].
Trophic State Index (TSI) characterization of the Itu-
pararanga Reservoir was calculated according to Carlson
modified, used as default in São Paulo State [5], which it
is composed for Trophic State Index to total phosphorous
—TSI(TP) and Trophic State Index to chlorophyll-a—
TSI(Cl). With the results, it was possible to evaluate the
Trophic State Index of the Itupararanga Reservoir as
oligotrophic (TSI < 44), mesotrophic (44 < TSI < 54),
eutrophic (55 < TSI < 74) e hypereutrophic (TSI > 74)
[5]. The statistical tests among the parameters analyzed
were evaluated using Pearson Correlation Test and the
spatial distribution of the Trophic State Index was ob-
tained through the software Surfer for Windows.
4. Results and Discussion
Tables 1 to 4 present the results obtained in this work to
spatial and temporal water quality characterization of the
Itupararanga Reservoir. The results for the Pearson Cor-
relation Test are presented in Tables 5 and 6. Figures 4
and 5 show the temperature, pH and dissolved oxygen
and total phosphorous and chlorophyll-a profiles, respec-
The depth of the Secchi Disk was 4 and 8 m at points
P1 and P2, respectively, in the first sampling, 01/24/2007,
indicating that the aphotic zones are below 5 and 9 m.
Already during the second stage of sampling (01/08/
2007), the depth of the Secchi Disk was 9 m to 10 m,
with a photic zone of 10 and 12 m for the points P1 and
P2, respectively. With these results it was possible to iden-
tify the trophic zone for both sampling sites increased
50% (P1) and 33% (P2) for the driest period. This dif-
ference can be attributed to a larger input of suspended
sediment entering the Itupararanga Reservoir in the rainy
season due to the laminar erosion and, consequently,
reducing waters clarity and the photic zone.
Table 1. Quality of surface water in the Itupararanga Res-
ervoir in wet period: 01/24/2007.
Point EC
(˚C) pH
(g/L) TSI
1 60.00 26.707.00 5.20 0.18 8.49 62
2 60.00 27.307.20 7.00 0.20 27.8169
3 60.00 27.907.50 8.10 0.14 9.23 60
4 60.00 27.107.60 8.60 0.19 13.9065
5 70.00 27.907.50 8.30 0.15 6.38 59
6 70.00 28.907.50 7.70 0.15 6.22 59
7 60.00 27.207.60 8.40 0.14 4.95 57
8 70.00 27.907.50 8.10 0.11 4.14 55
9 70.00 27.207.70 7.70 0.11 2.11 51
10 70.00 27.207.50 7.10 0.10 2.11 51
11 70.00 28.207.50 7.30 0.09 1.75 49
12 70.00 26.607.60 7.60 0.09 1.62 49
13 70.00 28.007.60 7.40 0.10 0.67 45
14 70.00 27.507.60 7.70 0.11 2.48 52
15 70.00 28.507.50 7.80 0.09 1.19 47
16 70.00 26.307.70 7.90 0.09 1.27 47
17 70.00 28.307.70 7.80 0.11 0.83 47
18 70.00 27.507.70 7.90 0.11
0.51 44
19 70.00 26.807.70 7.90 0.08 0.84 44
20 50.00 26.607.60 8.00 0.07 0.99 44
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Table 2. Quality of surface water in the Itupararanga Res-
ervoir in dry period: 08/02/2007.
Point EC
(˚C) pH
(g/L) TSI
1 60.00 12.40 6.605.00 0.20 5.50 60
2 70.00 14.80 6.906.80 0.23 18.1067
3 60.00 15.70 7.507.90 0.16 5.66 59
4 70.00 15.90 7.408.00 0.19 8.92 62
5 70.00 16.00 7.408.10 0.16 8.33 61
6 70.00 16.30 7.408.10 0.15 9.59 61
7 70.00 16.80 7.507.80 0.14 9.44 61
8 70.00 17.00 7.408.00 0.11 8.88 59
9 70.00 16.00 7.607.60 0.10 9.39 58
10 70.00 17.10 7.707.80 0.10 4.82 55
11 70.00 16.80 7.408.10 0.10 4.86 55
12 70.00 17.00 7.407.50 0.10 4.95 55
13 70.00 17.00 7.507.60 0.11 4.49 55
14 70.00 16.90 7.407.50 0.10 5.07 55
15 70.00 16.80 7.607.50 0.09 5.10 55
16 70.00 17.10 7.407.40 0.11 4.61 55
17 60.00 16.90 7.507.70 0.12 4.29 55
18 70.00 16.90 7.407.60 0.11
3.93 55
19 60.00 16.80 7.407.60 0.08 3.19 51
20 60.00 16.30 7.507.60 0.07 3.16 50
Table 3. Results of water profile in the Itupararanga Reser-
voir in wet period: 01/24/2007.
(˚C) pH
(g/L) TSI
Profile P1
0.00 70.00 16.30 7.40 8.10 0.15 9.5961
2.00 70.00 16.00 7.40 7.90 0.18 12.5864
4.00 70.00 15.30 7.50 6.90 0.20 14.4165
6.00 70.00 15.20 7.10 6.60 0.17 12.9764
8.00 70.00 15.00 7.00 6.40 0.11 13.5461
10.00 70.00 14.50 6.50 4.50 0.08 4.4753
Profile P2
0.00 65.00 17.10 7.40 7.40 0.11 6.3457
2.00 65.00 16.50 7.50 7.20 0.13 7.6659
4.00 65.00 16.30 7.70 6.80 0.18 11.0063
6.00 65.00 15.90 7.50 6.40 0.14 8.2160
8.00 65.00 15.80 6.70 6.00 0.10 6.8256
12.00 65.00 15.00 6.50 4.10 0.07 4.0951
Table 4. Results of water profile in the Itupararanga Res-
ervoir in dry period: 08/02/2007.
(˚C) pH
(g/L) TSI
Profile P1
0.00 70.00 16.307.40 8.10 0.15 9.5961
2.00 70.00 16.007.40 7.90 0.18 12.5864
4.00 70.00 15.307.50 6.90 0.20 14.4165
6.00 70.00 15.207.10 6.60 0.17 12.9764
8.00 70.00 15.007.00 6.40 0.11 13.5461
10.0070.00 14.506.50 4.50 0.08 4.4753
Profile P2
0.00 65.00 17.107.40 7.40 0.11 6.3457
2.00 65.00 16.507.50 7.20 0.13 7.6659
4.00 65.00 16.307.70 6.80 0.18 11.0063
6.00 65.00 15.907.50 6.40 0.14 8.2160
8.00 65.00 15.806.70 6.00 0.10 6.8256
12.0065.00 15.006.50 4.10 0.07 4.0951
Table 5. Relationship among all parameters obtained for
surface waters from Itupararanga Reservoir (P 0.01).
Wet period
EC Temp pH DO TP Cl
EC 1.00
Temp 0.38 1.00
pH 0.35 –0.01 1.00
DO 0.05 0.15 0.56 1.00
TP –0.350.08 –0.32 –0.21 1.00
C-a –0.45–0.03 –0.31 –0.17 0.85 1.00
Dry period
EC Temp pH DO TP C-a
EC 1.00
Temp 0.38 1.00
pH 0.23 0.55 1.00
DO 0.35 0.41 0.53 1.00
TP 0.01 –0.73 –0.48 –0.40 1.00
C-a 0.38 –0.34 –0.35 –0.05 0.81 1.00
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Temperature ( C)
Depth (m)
Wet period
Temperature ( C)
Depth (m)
Dry period
DO (mg/L)
Depth (m)
Dry period
DO (mg/L)
Depth (m)
Wet period
Depth (m)
Dry period
Depth (m)
Wet period
Figure 4. Temperature, pH and dissolved oxygen profiles in the Itupararanga Reservoir.
Total phophorous (mg/L)
Depth (m)
Wet period
Depth ( m)
Chlorophyll-a (
Wet period
Depth (m)
Dry period
Total phophorous (mg/L)
Depth (m)
Dry period
Chlorophyll-a (/L)
Figure 5. Total phosphorous and chlorophyll-a profiles in the Itupararanga Reservoir.
The electrical conductivity depending on temperature
and amount of dissolved ions present. The electrical
conductivity parameter does not determine specifically
which ions are present in a given sample of water, but
can contribute to possible recognition of environmental
impacts that occur in the drainage basin. The conductivity
values are presented fairly constant throughout the reservoir
and in the vertical profiles in both seasons, ranging between
60 and 70 μS/cm.
This same behavior was also found by Mariani [6] for
Riacho Grande Reservoir, which is the compound that
supplies the Billings, located in the metropolitan area of
São Paulo. Studies such as Calijuri et al. [7], Bicudo et al.
[8] and Mariani [6] conducted in eutrophic reservoirs
especially for industrial and domestic sewage, showed
values above 150 μS/cm for electrical conductivity in
these reservoirs. Thus, the results of electrical conductiv-
ity can be considered low for surface water, indicating
that the Itupararanga Reservoir still has good quality of
Temperature is a determining factor in driving the
reactions that affect the chemical, physical and biological
processes and thus have an enormous influence on bio-
logical activity and growth of aquatic organisms. With
the temperature change, algae and photosynthetic micro-
organisms may distance themselves from the water sur-
face by migration or even death. It is observed that in the
rainy season, water temperature at the surface is consi-
derably greater than in the dry season, i.e. variation be-
tween 26.30˚C to 28.90˚C and 12.40˚C to 17.10˚C,
respectively. In the dry period is noted an increase of
about 4˚C between point 1 and 20, due to collection start
the morning with cooler temperatures, and end in the
afternoon, with heating this shell throughout the day due
to higher solar radiation.
According to Tundisi [9], the stratification of the water
column must be greater in summer, which can be found
in both vertical profiles studied, i.e., stratification of about
3.5˚C and 2.0˚C during wet and dry periods, respectively.
Moreover, for both profiles, the higher temperature were
characterized in samples collected near the surface, as
also found for the Rio das Pedras Reservoir [10]. In other
studies performed in Brazilian reservoirs, usually the
lowest temperature are characterized on the water surface,
due to air temperature and intensity of local wind, as was
the case of the Rio Paranapanema Lake/SP [11], Jurumirim
Reservoir/SP [12], Lobo Reservoir/SP [13] and Riacho
Grande Reservoir/SP [6].
The pH is a measure of balance between of hydroxyl
(OH) and hydrogen ions (H+), being used to identify
whether a solution is acidic, neutral or basic. With respect
to pH, there is close relationship between plant and animal
communities and aquatic. On communities, the pH is
directly involved in the processes of cell membrane
permeability, thereby interfering in the ionic transport
within the cell, and between organisms and the environ-
ment. The criteria to protect aquatic life that set the range
of pH should be ranging from 6 to 9, as established in
Brazil for surface water Class II [1]. All pH values ob-
tained for the Itupararanga Reservoir in horizontal and
vertical scaling are proposed within this range.
The higher pH values, both at horizontal or vertical
scales, occurred during the rainy season. In horizontal
scale, it is observed that the lower pH values in both
samples were always obtained between points 1 and 2,
being these values close to the Sorocaba River before it
enters the Itupararanga Reservoir, where has a charge of
domestic effluents.
In the other sampling points there was small variation
in pH values remained between 7.50 and 7.70 and 7.40
and 7.60 for wet and dry seasons, respectively. The in-
crease in pH may be due to photosynthetic activity oc-
curring in the Itupararanga Reservoir, which removes
CO2 and 3
, and tamper with the carbonate buffer
system. Vertical scale for both sites and sampling periods,
it is possible to observe a slight stratification in pH,
which remained practically constant in the first meters of
water column, with a gradual decrease until the deeper
sites, located in the aphotic zone. The lower pH values in
the regions close to the bottom of the reservoir are expected
due to chemical oxidation of organic matter by anaerobic
bacteria, as already observed in Riacho Grande Reservoir
Among the dissolved gases in water, oxygen is one of
the most important parameter to dynamic characteriza-
tion of aquatic ecosystems. The main sources of oxygen
to water are the atmosphere and photosynthesis. On the
other hand, the losses are due to consumption by the
decomposition of organic matter (oxidation), exchanges
in the atmosphere, respiration of aquatic organisms and
oxidation of metal ions, such as iron and manganese.
Samples collected in both sampling periods indicates the
dissolved oxygen concentration in horizontal and vertical
scale values were above 5.0 mg/L, minimum value
established by CONAMA 357 to Class II waters [1]. The
exception was for the sampling points in vertical scale
located in the aphotic zone, where the dissolved oxygen
values were always below 5.0 mg/L.
The lowest levels of dissolved oxygen in both horizontal
and vertical scale occurred in the dry season, in the
points 1 and 2 due to decomposition of organic matter
from the domestic wastewater of Ibiúna. After this region,
the dissolved oxygen values increase along the reservoir,
being this fact attributed to photosynthetic activity.
The values of dissolved oxygen concentration in vertical
scale decrease with depth. According to Tundisi [9] and
Lampert and Sommer [14], in many cases, a decreasing
gradient of temperature causes a decreasing gradient of
Copyright © 2013 SciRes. JWARP
dissolved oxygen. Statistical tests of correlation between
temperature and dissolved oxygen (r = 0.75 (P1), and r =
0.90 (P2), in wet period and r = 0.95 (P1), and r = 0.94
(P1), in dry period, Table 6) indicate that the temperature
must control the concentration of dissolved oxygen in the
vertical scale Itupararanga Reservoir, as already described
for the Rio das Pedras Reservoir [10]. Moreover, the
dissolved oxygen values characterized the sampling points
located in the photic zone in both sampling periods in-
dicate no anoxia at the bottom of the reservoir.
Trophic State Index (TSI)
Phosphorus is an essential element for the metabolism of
living beings, which acts as the energy storage (ATP)
and the structuring of the plasma membrane, composed
of phospholipids. The amount of chlorophyll-a is directly
related to the phytoplankton biomass, and consequently
with the total production of the lakes. In terms of total
phosphorus and chlorophyll-a, all samples were higher
for phosphorus and lower to clorophyll-a in relation to
allow by CONAMA 357 for Class II waters [1], which
indicates the maximum concentration for both parameters
Table 6. Relationship among all parameters obtained for
water profiles from Itupararanga Reservoir (P 0.01).
Wet period (P1)
EC Temp pH DO TP Cl
EC 1.00
Temp 0.13 1.00
pH 0.09 0.40 1.00
DO 0.46 0.75 0.59 1.00
TP 0.24 0.51 0.83 0.51 1.00
C-a –0.39 –0.25 0.90 0.43 0.791.00
Wet period (P2)
EC Temp pH DO TP C-a
EC 1.00
Temp 0.19 1.00
pH 0.11 0.53 1.00
DO 0.50 0.90 0.51 1.00
TP –0.29 0.12 0.92 0.43 1.00
C-a –0.51 –0.32 0.74 –0.02 0.861.00
Dry period (P1)
EC Temp pH DO TP C-a
EC 1.00
Temp 0.31 1.00
pH 0.34 0.41 1.00
DO 0.51 0.95 0.49 1.00
TP 0.32 0.33 0.89 0.78 1.00
C-a –0.22 0.31 0.72 0.58 0.741.00
Dry period (P2)
EC Temp pH DO TP C-a
EC 1.00
Temp 0.21 1.00
pH 0.31 0.45 1.00
DO 0.44 0.94 0.47 1.00
TP 0.54 0.47 0.88 0.41 1.00
C-a –0.36 0.01 0.80 0.12 0.751.00
as 0.030 mg/L.
The highest values of total phosphorus in horizontal
and vertical scale were quantified in the dry season. In
horizontal scale for both sampling periods, the highest
values of this parameter are among the sampling points 1
and 9, being the highest values found in sampling point 2.
After this region, the values of total phosphorus decreases
in downstream direction, indicating that the Itupararanga
Reservoir acts as a restraint of substances than those who
flock to it, possibly due to sedimentation, absorption and/
or complexation of these substances. Regarding the
distribution of total phosphorus in vertical scale, could be
observed a well-marked stratification for both sampling
periods, with higher values being quantified up to four
meters deep, with a subsequent gradual decrease to the
deep zones of the Itupararanga Reservoir.
In the dry period there was greater chlorophyll-a con-
centration along the Itupararanga Reservoir in horizontal
and vertical scale, indicating greater population of algae
in the reservoir. Chlorophyll-a vertical profiles show
eutrophic patterns environments, with lower concentrations
in regions of greater depth. Statistical tests indicates a strong
correlation between total phosphorus and chlorophyll-a
for surface waters in the Itupararanga Reservoir in both
sampling periods (r = 0.85 and 0.81 in wet and dry
periods, respectively, Table 5), suggesting that the be-
haviors of these parameters must be correlated. It was
also possible to find a correlation between total phosphorus
and chlorophyll-a in the both vertical profiles and samp-
ling periods (r = 0.79 (P1) and r = 0.86 (P2) in wet period
and r = 0.75 (P1) and r = 0.74 (P2) in dry period, Table 6).
According to the TSI, the Itupararanga Reservoir was
classified as mesotrophic and eutrophic in wet and dry
periods, with a better quality of water in the Itupararanga
Reservoir found in the wet season. As shown in Figure 6,
Wet per
Dry period
04812 16 20 k
Figure 6. Trophic State Index (TSI) in the Itupararanga Res-
ervoir in wet and dry period.
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the points with higher values of TSI in the Itupararanga
Reservoir, in both sampling periods, where observed
mainly among the sampling points 1 up to 4, causing
excessive growth of aquatic autotrophs, making harder
the navigation in this section due to green algae blooms.
This fact is directly linked to the Sorocaba River,
which before discharging in the Itupararanga Reservoir,
suffers severe environmental impacts, affecting their qua-
lity. The Ibiúna city does not possess effluents treatment
planning, and, disposes almost 100% of domestic and
industrial effluents into the Una River. The Sorocabuçu
and Sorocamirim rivers do not pass through any urban
center. However, these rivers receive diffuse pollutants
due to the vegetables crops (cabbage, lettuce, potatoes,
and tomatoes, among others) and presence of small vil-
lages along its length and livestock [15]. Finally, there is
an improvement in quality of water after the sampling
point 4, mainly in wet period.
There are two explanations for the increase in the TSI
value in dry period, as already evidenced in Ponte Nova-
Alto Tietê [16] and Rio Grande-Billings Complex [6].
The first explanation is due to rapid eutrophication of the
Itupararanga Reservoir caused by the land use of the
Upper Alto Sorocaba basin. The second explanation is
the algae persistence in this reservoir, which were proli-
ferated and spread throughout the summer. However, the
chlorophyll-a concentration must decrease until the next
summer together with the water temperature of the Itu-
pararanga Reservoir. Only a more detailed study with a
monthly sampling during one or two complete hydrologi-
cal cycles can confirm which of the hypotheses should be
5. Acknowledgements
The authors thank CAPES for the scholarship to F. J. M.
Pedrazzi, and the Ibiúna municipally police and SOS Itu-
pararanga for the operational support during this study.
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