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ISSN:
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138
Art
i
c
le
Quality of surface waters of the San Pablo
-
Los Ríos river, for irrigaton
of agricultural crops
Vi
viana Sánchez
1
,*
y
Yessenia Sarango
2
1
Universidad
Estatal de Milagro, Ecuador, Milagro;
htps://orcid.org/0009
-
0006
-
6911
-
3646
2
Universidad
Estatal de Milagro, Ecuador, Milagro;
htps://orcid.org/0000
-
0001
-
7042
-
0623
;
ysarangoo@unemi.edu.ec
*
Correspondenc
e
:
vsanchezv@unemi.edu.ec
https://doi.org/10.70881/hnj/v3/n2/64
Abstract:
River pollution can be due to the influence of foreign materials,
garbage, biological or inorganic waste, among others, influencing the
suitability of
natural sources that can be used for agriculture, as is the case
of the San Pablo River. This research was focused on evaluating the surface
waters of the San Pablo River for irrigation of agricultural crops. The TULSMA
Book VI, Annex 1, in addition to th
e ICA
-
NSF calculation, was used as a
reference. Initially, samples were taken at four points along the San Pablo
and Santa Rosa Rivers, where activities that have a greater or lesser impact
on their pollution have been identified, which may influence their
quality. The
results of the physicochemical and microbiological analysis of the samples
indicate compliance with environmental regulations. The ICA
-
NSF quality
index showed values
for the river water with medium quality. This study will
allow proposals
to be made so that producers and residents of the area can
efficiently manage this resource, improve agricultural yields, and conserve
the water source and soil.
Keywords:
Water conservation, ICA
-
NSF, river water, index,
physicochemical parameters
Resumen
:
La contaminación de los ríos puede deberse a la influencia de
materiales extraños, basura, desechos biológicos o inorgánicos, entre otros,
influyendo en la aptitud de las fuentes naturales que pueden ser utilizadas
para la agricultura, como es el caso del
río San Pablo. Esta investigación se
enfocó a evaluar las aguas superficiales del río San Pablo para el riego de
cultivos agrícolas. Se utilizó como referencia el Libro VI, Anexo 1 del
TULSMA, además del cálculo del ICA
-
NSF. Inicialmente se tomaron
muestra
s en cuatro puntos a lo largo de los ríos San Pablo y Santa Rosa,
donde se han identificado actividades que tienen mayor o menor impacto en
su contaminación, las cuales pueden influir en su calidad. Los resultados de
los análisis fisicoquímicos y microbiol
ógicos de las muestras indican el
cumplimiento de la normativa ambiental. El índice de calidad ICA
-
NSF
mostró valores para el agua del río con calidad media. Este estudio permitirá
hacer propuestas para que los productores y pobladores de la zona manejen
e
ficientemente este recurso, mejoren los rendimientos agrícolas y conserven
la fuente de agua y el suelo
.
P
alabras claves
:
Conservación del agua, ICA
-
NSF, agua de río, índice,
parámetros fisicoquímicos
Cit
e
:
Sánchez, V., & Saran
go
-
Ortega, Y. (2025). Quality of
surface waters of the San Pablo
-
Los Ríos river, for irrigation of
agricultural crops.
Horizon
Nexus Journal
,
3
(2), 138
-
153.
https://doi.org/10.70881/hnj
/v3/n2/64
Received
:
02
/
03
/20
25
Revised
:
23
/
03
/20
25
Accepted
:
25
/
03
/20
25
Published
:
30
/
04
/20
25
Copyright:
© 202
5
by the
authors. This article is an open
access article distributed under
the terms and conditions of the
Creative Commons
Attribution
-
NonCommercial
4.0 International License
(CC
BY
-
NC).
(
https://creativecommons.org/lic
enses/by
-
nc/4.0/
)
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139
1. Introduction
The quality of water bodies such as rivers is deteriorating due to anthropic activities such
as: effluents generated in populated centers, industrial areas, primary sector activities,
and runoff (Jervez
et al
.
,
2022). Ecuador has an extensive hydrographic network,
originating mainly in the Andes Mountains with mouths in the Amazon River and Pacific
Ocean (Simbaña
-
Farinango et al. 2019). The territory of Ecuador is divided into 31
h
ydrographic systems, made up of 79 watersheds. These systems correspond to the two
watersheds, 24 drain towards the Pacific Ocean and represent 48.07% of the surface of
the national territory; and 7 drain towards the Eastern Region, which represents 51.41%
of the territory (Cisneros and Pacheco, 2010). The characterization of a river's water
quality consists of determining the extent, degree or intensity of contamination, which
may be of physical, chemical or biological origin, and the capacity of the syste
m to
naturally reestablish the characteristics or conditions it had before the presence of the
contaminant (Cajas et al
.,
2023).
The available volumes of freshwater for agricultural and urban
-
industrial use worldwide
have decreased considerably due to the e
xcessive use of surface and groundwater for
agricultural irrigation for food production of a constantly growing population (Quinteros
Carabalí et al, 2019). Contamination of the river is mainly due to the introduction of
materials foreign to its nature suc
h as: garbage, biological waste, fuels, wastewater,
which have caused the loss of biotic and abiotic resources, causing an ecological deficit
and mismatch in the food chain (
Prado
-
Vélez et al, 2023).
The Babahoyo River suffers
from progressive contaminatio
n due to various factors such as foreign chemicals,
microorganisms, waste from rice mills, sewage and others. Fundamentally, the water is
contaminated by human activity because the population is growing every year, and rice
mills are another important sour
ce of contamination because they daily deposit
thousands of contaminating wastes (garbage, chaff, plastics, etc.) (Moreira and Ramos,
2021). Evaluating the quality of water in family farming agroecosystems
-
which differ in
their production proposals
-
mak
es it possible to explore the effects of the forms of
appropriation of ecosystems and therefore the threats to the biocapacity and
sustainability of the systems, as well as the possibilities of proposals generated from
local ways of doing agriculture (trad
itional), and from modes that have at their base the
use of inputs from the environment based on ecological principles (organic), as opposed
to the proposal of conventional or modern agriculture (Guilcamaigua and Chancusig,
2019).
The territory of the sub
-
basin has been extensively intervened. Only 4.04% of the territory
(28,200 hectares) is protected as part of the Illinizas Ecological Reserve (with a total
area of 26,100 hectares, of which 23,700 are within the watershed) and three protected
forests (Mat
iaví
-
Salinas, Naranjapata and Cerro Guineales
-
Samama
-
Mumbes) (M
AATE, 2009). Almost half of the total area is suitable for irrigation, but the most
remarkable thing is that, in the vast majority of them, irrigation can be carried out without
restrictions (
CEDEGE and UNDP, 1983). In the San Pablo river basin, in the province of
Los Ríos, very few studies have been carried out to determine the quality of the river
water; it is important to determine the suitability of the river water, which is used to irrigat
e
crops in the area.
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The quality of irrigation water is conditioned by the salts (quantity and type) and
sediments that constitute it. It is of utmost importance to know its characteristics, since it
influences edaphic properties, increasing its salinity
and, consequently, affecting crop
yields. In this sense, salt tolerance is an agronomically important trait that is receiving
increasing attention among different research groups in the world (Masseroni et al,
2018). In Ecuador, it is observed that in the
last decades, the use of water for agriculture
intensified and products destined for agroexport were massified, in the eagerness to
increase the profits of large capitals (Guilcamaigua and Chancusig, 2019). Water quality
indices are tools that allow decisi
on
-
making to reduce the deterioration of water quality
by directly assessing variations in its quality parameters (Pérez et al, 2018). The ICA
-
NSF methodology is used to determine the quality of river water for human consumption,
using weighted weights in
its parameters, which has allowed it to be popularized in many
countries (Robledo
-
Hernández, 2022).
The objective is to evaluate the water quality of the San Pablo river by applying the
TULSMA and considering the ICA water quality index,
to determine phys
ical, chemical
and biological parameters for the characterization of water for irrigation of agricultural
crops. In addition to analyzing the suitability of the water in terms of its physical, chemical
and biological properties, to be used for crop irrigat
ion;
taking as a reference for sampling
several points along the San Pablo and Santa Rosa rivers, where it has been possible
to identify activities that may influence the quality of the river as there are discharges that
may affect to a greater or lesser d
egree to its contamination.
2. Materials and Methods
Each sampling point was identified with a code and geographic coordinates using a
Global Positioning System (GPS). The research work was carried out during the month
of November 2021, with the
specialized service of an accredited laboratory for sampling
and physical, chemical and microbiological analysis.
Study area
This research was carried out in the area of Babahoyo
-
San Pablo River. A descriptive
exploratory study was developed in the water
body, starting with the collection of
samples at points that offered ease of access, safety, representativeness and a
permanent flow of water.
The field work began with sampling in the bodies of water, at the determined study points
(point 1: Water of the
river near the Amelia farm, before joining the crystal river; point 2:
Santa Rosa River
-
near the "El Beldaco" farm; point 3: San Pablo River near the
Technical University of Babahoyo; point 4: San Pablo River
-
4 de mayo sector). This, in
order to obtai
n current information on water quality in the study area.
Sample analysis:
The samples were analyzed once they arrived at the laboratory to
guarantee the results of the analyses, considering the sample preservation controls at
the time of being transferred
to the laboratory once taken at the sampling points. For the
research carried out, the parameters for the analysis of the samples were chosen taking
as a reference the TULSMA
-
Book VI Annex 2, Table 3, as well as the Water Quality
Index (WQI), developed
in 1970 by the National Sanitation Foundation (NSF).
Parameters of water quality levels for irrigation, among the selected parameters are:
hydrogen potential (pH), temperature, dissolved oxygen % saturation (DO), total
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dissolved solids (TDS), turbidity, bi
ochemical oxygen demand (BOD5), nitrites, nitrates,
sulfates, fecal coliforms (Cajaleón, 2020).
Criteria for determining water quality
-
environmental regulations:
The areas and
sampling points were chosen based on the research criteria established in the
national
regulations, water quality criteria for agricultural or irrigation use (section 5.1.3 of
TULSMA).
Criteria for determining water quality ICA
-
NSF:
The assessment of water quality can
be understood as the evaluation of its chemical,
physical, and biological nature in relation
to natural quality, human effects, and possible uses. To simplify the interpretation of
monitoring data, there are water quality indices (WQI) (
Robledo
-
Hernandez, 2022)
. The
evaluation of water quality should con
sider representative indicators that guarantee a
comprehensive analysis of the water resource, allowing actions to be taken for its
management and control through the different water purification processes; one of the
most widely used tools are the water q
uality indexes (ICA) (Méndez
-
Zambrano et al,
2020). Once the results of the analysis of the water samples were obtained, the Water
Quality Index (WQI), developed by the National Sanitation Foundation (NFS) of the
United States, was calculated, which consid
ers several parameters such as pH,
temperature, dissolved oxygen, biochemical oxygen demand total dissolved solids,
turbidity, nitrates, phosphates and fecal coliforms (Méndez
-
Zambrano et al., 2020).
This information was obtained by means of formulas, for
which the data obtained from
the analysis of the samples taken at the points previously established for the study are
required. Initially, we worked with the curves already established to obtain the Q values,
which decreases as the contamination of the wat
er body increases. To determine the Q
values, we worked with the graphs established by Brown (1970), which correspond to
each parameter analyzed (Granizo & Toa, 2020). The index was calculated by applying
the formula proposed by the NSF, which is based on
the weighted arithmetic average of
9 variables, through the equation (Caho
-
Rodríguez and López
-
Barrera, 2017).
퐼퐶퐴
−
푁푆퐹
=
∑
푖
=
푛
푖
=
푙
푄
푖
∗
푊
푖
Where:
Qi corresponds to the scale factor of the variable, depends on the magnitude of the
variable and is ind
ependent of the other variables.
Wi, represents the importance factor or weighting of variable i with respect to the other
variables that make up the index (Freire et al, 2020).
The parameters to be analyzed and their NSF Weight (W) values are shown belo
w in
Table 1
.
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Table 1.
Parameters to be analyzed
Parameter
NSF Weight (W)
pH
0.11
Temperature
0.1
Dissolved oxygen
0.17
Biochemical Oxygen Demand
BOD5
0.11
Total Dissolved Solids
0.07
Turbidity
0.08
Nitrates
0.1
Phosphates
0.1
Fecal
Coliforms
0.16
Source: Granizo and Toa, 2020
According to the result obtained from the application of the formula for the calculation of
the ICA
-
NSF, the results are analyzed with the help of the classification scale of the water
quality index ICA
-
NSF
(Ta
ble 2)
, according to Méndez
-
Zambrano et al
.
(
2020).
Table 2.
ICA classification proposed by Brown
Description
Range
Excellent
91
-
100
Good
71
-
90
Regular
51
-
70
Mala
26
-
50
Very bad
0
-
25
Note:
This table shows the ICA quality index
proposed by Mendez
-
Zambrano et al.
(2020).
3. Results
3.1 Analysis of physicochemical results
Not all the parameters evaluated at the sampling points are included in the regulations,
but they are considered important for the calculation of the
ICA
-
NSF quality index, such
as temperature, OD % saturation, TDS, turbidity, BOD5 and nitrates, as shown in the
table of analysis results of the river water samples at the four different monitoring points
against the Ecuadorian environmental regulations e
stablished in the TULSMA, as shown
in Table 3 (Cuvi and Ruiz, 2022). The results obtained show that the four sampling points
comply with the Ecuadorian environmental regulations; it can be observed that
parameters such as pH, nitrites and sulfates comply w
ith the quality criteria.
The
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temperature decreases in a not very significant way from one sampling point to another.
M3 has the lowest reading in relation to the other points, with a value of 28.4°C.
Table 3
Table of sample analysis results.
Parameter
Un
it
Results
Quality
criteria
M1
M2
M3
M4
Hydrogen potential, in situ
U of pH
7,59
7,49
7,54
7,16
6
-
9
Temperature, in situ
ºC
30,00
29,40
28,40
28,80
---
In situ dissolved oxygen, %
saturation
%
72,50
69,90
72,90
67,10
---
Total dissolved
solids (TDS)
mg/l
88,00
76,00
84,00
104,00
---
Turbidity
NTU
9,22
15,80
13,60
26,10
---
Biochemical Oxygen
Demand (BOD5)
mg O2/l
5,85
2,76
2,67
3,54
---
Nitrites
mg/l
0,10
0,07
0,08
0,14
0,5
Nitrates
mg/l
0,16
0,23
0,21
0,22
---
Sulfates
mg/l
9,00
9,00
9,00
12,00
250
Fecal coliforms
MPN/100
ml
161,00
110,00
41,00
200,00
1000
Note:
This table shows the average of the results obtained from the physicochemical
analysis, for the four sampling points, compared to the environmental regulations in
force,
admissible quality criteria for water intended for agricultural use, which are
presented in Table 3 of Annex 2 of Book VI of the TULSMA (Prepared by the company).
The results of the field measurements indicate that the variability of pH between the
four
sampling points is negligible, since the values range from 7.16 to 7.59, with the greatest
variability being at point M4, and between points M1 M2 and M3 the bias is smaller; these
are neutral pH values with a slight tendency towards alkalinity (Table
4). Regarding
nitrites, among the 4 sampling points, M2 and M3 register values below 0.1 mg/l while
M1 and M4 are 0.1 and 0.4 mg/l, the four points present results that are well below the
quality criteria complying with the regulations (table 5).
Finally,
in regard to sulfates, the concentrations do not vary considerably among the
points sampled, with M4 having the highest concentration of 12 mg/l, even so, these
values are below the quality criteria established by the regulations Table 6).
The values obt
ained for fecal coliforms vary at each point, remaining below the quality
criteria and complying with regulations. We observe that at points M1 and M4 there is an
increase in values of 161 and 200 NPM/100ml, respectively, due to the fact that these
are mor
e populated sectors, causing an increase in the organic load (Table 7).
Hydrogen potential pH.
For the pH variable, we worked with an estimated 12 data, where the values are in a
range of 7.15 to 7.59
U of pH. As shown in Table 4 below.
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Table 4
Analysis r
esults for pH
-
U of pH.
M1
M2
M3
M4
1
7,58
7,49
7,53
7,16
2
7,59
7,49
7,54
7,15
3
7,59
7,48
7,54
7,16
Prom
7,59
7,49
7,54
7,16
Note:
This table shows the average of the results for hydrogen potential pH obtained
from the
physicochemical analysis, taking the average for 3 samples at each of the four
sampling points (own elaboration).
Nitrites
For the nitrite variable, we worked with an estimated 12 data, where the values are in
the range of 0.07 to 0.14 mg/l, as shown in Ta
ble 5.
Table 5
Analysis results for biochemical nitrite demand mg/l.
M1
M2
M3
M4
1
0,10
0,07
0,08
0,14
2
0,10
0,06
0,08
0,13
3
0,09
0,07
0,07
0,14
Prom
0,10
0,07
0,08
0,14
Note:
This table shows the average of the results for nitrites
obtained from the
physicochemical analysis, taking the average for 3 samples at each of the four
sampling points (own elaboration).
Sulfates
For the sulfate variable, we worked with an estimated 12 data, where the values are in
the range of 9.00 to 12.00 m
g/l
(Table 6).
Table 6
Analysis results for sulfates mg/l.
M1
M2
M3
M4
1
9,01
9,00
9,00
12,01
2
8,99
9,00
8,99
12,00
3
9,01
8,99
9,01
12,00
Prom
9,00
9,00
9,00
12,00
Note:
This table shows the average of the results for sulfates obtained from the
physicochemical analysis, taking the average for 3 samples at each of the four sampling
points (own elaboration).
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The relationship between population and these parameters is directly proportional, i.e.,
in those areas with a higher population density and a
n inadequate sanitation system, the
results are slightly affected, presenting a higher organic load in the receiving waters and,
therefore, with slightly higher values of BOD5 and fecal coliforms at points M1 and M4
compared to points M2 and M3.
Results fo
r fecal coliforms.
For the fecal coliform variable, we worked with an estimated 12 data, where the values
range from 41 to 200 NMP/100 ml
(Table 7).
Table 7.
Analysis results for fecal coliforms NMP/100 ml.
M1
M2
M3
M4
1
161,00
110,00
41,00
200,00
2
161,00
110,00
41,00
200,00
3
161,00
110,00
41,00
200,00
Prom
161,00
110,00
41,00
200,00
Note:
This table shows the average of the results for fecal coliforms obtained from the
physicochemical analysis, taking the average for 3 samples at each of the
four sampling
points (own elaboration).
Water quality index ICA.
In addition, the quality index was determined using the ICA
-
NSF methodology used in
the United States.
퐼퐶퐴
−
푁푆퐹
=
∑
푖
=
푛
푖
=
푙
푄
푖
∗
푊
푖
The data obtained from the calculation of the
ICA
-
NSF quality index for the samples of
the four different points selected for the study were 57.64 for the sample of the first point,
59.64 for the sample of the second point, 62.76 for the sample of the third point and
56.02 for the sample of the fourt
h point; these values indicate that the quality index of
the four points is in the medium category, It should be noted that the value of phosphate
content was not included for each sample analyzed, which would represent a weighting
that would increase the
AQI value, thus
obtaining
a more
significant and representative
index
of the degree of contamination and the water quality rating could have a more
acceptable value on this rating scale.
The ICA water quality index was obtained considering the values obtai
ned in the
physicochemical analysis at each sampling point, which is shown in Tables 8, 9, 10, 11.
Table 8.
ICA
shows at
point 1: Water from the river near the
Amelia farm
, before joining the crystal
river.
Parameter
Result
Units
Q
-
value
Wi
Subtotal
pH
7,59
U of pH
94
0,11
10,34
Temperature
30,00
°C
9
0,10
0,9
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OD
72,50
%
73
0,17
12,41
TDS
88,00
mg/l
85
0,07
5,95
Turbidity
9,22
NTU
78
0,08
6,24
BOD
5,85
mg O2/l
50
0,11
5,50
CF
161
MPN/1000 ml
40
0,16
6,40
Nitrates
0,16
mg/l
99
0,10
9,90
Water quality index Pt. 1:
57,64
Note:
This table shows the results obtained from the physicochemical analysis, the
corresponding Q value from the graphs established by Brown (1970)
-
NSF quality
function, and the water quality index
AQI after applying the formula, for sampling point
1: river water near the "Amelia" farm before joining the crystal river.
Table 9
ICA sample
taken
at point 2: Santa Rosa River
-
near the "El Beldaco" farm.
Parameter
Result
Units
Q
-
value
Wi
Subtotal
pH
7,49
U of pH
93
0,11
10,23
Temperature
29,40
°C
9,5
0,10
0,95
OD
69,90
%
70
0,17
11,90
TDS
76,00
mg/l
85
0,07
5,95
Turbidity
18,80
NTU
69
0,08
5,52
BOD
2,76
mg O2/l
75
0,11
8,25
CF
110
MPN/1000 ml
44
0,16
7,04
Nitrates
0,23
mg/l
98
0,10
9,80
Phosphates
---
---
---
0,10
---
Water quality index Pt. 2:
59,64
Note:
This table shows the results obtained from the physicochemical analysis, the
corresponding Q value from the graphs established by Brown (1970)
-
NSF quality
function, and the ICA water quality index after applying the formula, for sampling point 2:
Santa Rosa River
-
near the "El Beldaco" farm.
Table 10
ICA sample taken at point 3: San Pablo River near the Universidad Técnica de
Babahoyo.
Parameter
Result
Unit
s
Q
-
value
Wi
Subtotal
pH
7,54
U of pH
94
0,11
10,34
Temperature
28,40
°C
10
0,10
1,00
OD
72,90
%
74
0,17
12,58
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TDS
84,00
mg/l
86
0,07
6,02
Turbidity
13,60
NTU
72
0,08
5,76
BOD
2,67
mg O2/l
74
0,11
8,14
CF
41
MPN/1000 ml
57
0,16
9,12
Nitrates
0,21
mg/l
98
0,10
9,80
Water quality index Pt. 3:
62,76
Note:
This table shows the results obtained from the physicochemical analysis, the
corresponding Q value from the graphs established by Brown (1970)
-
NSF quality
function, and the
ICA water quality index after applying the formula, for sampling point 3:
San Pablo River at the height of the Technical University of Babahoyo.
Table 11
ICA sample taken at point 4: San Pablo River
-
sector 4 de mayo
Parameter
Result
Units
Q
-
value
Wi
Subtotal
pH
7,16
U of pH
91
0,11
10,01
Temperature
28,80
°C
10
0,10
1,00
OD
67,10
%
66
0,17
11,22
TDS
104,00
mg/l
85
0,07
5,95
Turbidity
26,10
NTU
56
0,08
4,48
BOD
3,54
mg O2/l
68
0,11
7,48
CF
200
MPN/1000 ml
38
0,16
6,08
Nitrates
0,22
mg/l
98
0,10
9,80
Water quality index Pt. 4:
56,02
Note:
This table shows the results obtained from the physicochemical analysis, the
corresponding Q value from the graphs established by Brown (1970)
-
NSF quality
function, and the water quality index
AQI after applying the formula, for sampling point
4: San Pablo River
-
sector 4 de mayo.
When calculating the AQI
-
NSF of the average of the results of the parameters of the
four monitoring points, a value of 59.73 was obtained for the General Water Qua
lity
Index, this value, reviewing Table 2, indicates that this water source is of "Medium"
quality, taking into consideration that the value of phosphate content was not included
for each sample analyzed, which would represent a weighting that would increa
se the
value of the AQI and therefore it is estimated that the water quality rating could have a
more acceptable value on this rating scale. As shown in Table 12 and 13, the AQI was
obtained from the average of the values obtained in the physicochemical an
d NSF
analysis.
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Table 12
ICA for the average values of all samples.
Parameter
Average
Results
Units
Q
-
value
Wi
Subtotal
pH
7,45
U of pH
92
0,11
9,13
Temperature
29,15
°C
11
0,10
1,10
OD
70,60
%
74
0,17
12,58
TDS
88,00
mg/l
85
0,07
5,95
Turbidity
16,93
NTU
68
0,08
5,44
BOD
3,71
mg O2/l
70
0,11
7,70
CF
128
MPN/1000 ml
44
0,16
7,04
Nitrates
0,21
mg/l
98
0,10
9,80
Overall water quality index of the average:
59,73
Note:
This table summarizes the results obtained from the
physicochemical analysis, the
corresponding Q value from the graphs established by Brown (1970)
-
NSF quality
function, and the ICA water quality index after applying the formula; it represents the
average values of all the samples taken for the investigat
ion.
Table 13.
NSF water quality index results at each monitoring point.
Sampling points
Location
ICA
-
NSF
Ranking
Item 1
Water from the
river near the
Amelia farm,
before joining
the crystal river.
57,64
Media
Item 2
Santa Rosa
River
-
near the
"El Beldaco"
farm
59,64
Media
Item 3
San Pablo
River near the
Universidad
Técnica de
Babahoyo
62,76
Media
Item 4
San Pablo
River
-
4 de
mayo sector
56,02
Media
Note:
This table summarizes the results obtained after applying the formula for
calculating the NSF water quality indexes at each monitoring point.
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4. Discussion
The main objective of this research work is to evaluate the quality for irrigation of
agricultural crops of the surface waters of the San Pablo river basin, located in the
city
of Babahoyo, this was done through the physical, chemical and microbiological analysis
of water samples from the natural source studied; the results obtained provided us with
important information regarding water quality compared with environmental re
gulations
Book Vi, Annex 1, Table 3. Admissible quality criteria for water intended for agricultural
use, it was possible to conclude that the variables of pH, nitrites, sulfates and fecal
coliforms are within the ranges or values established by the regula
tions, so it is
concluded that the water at point 1: Water from the river near the Amelia farm, before
joining the crystal river, point 2: Santa Rosa River
-
near the "El Beldaco" farm, point 3:
San Pablo River near the Technical University of Babahoyo, an
d point 4: San Pablo
River
-
4 de mayo sector, comply with Ecuadorian environmental regulations.
Considering that the concentrations of CF in the water taken at point 1 (waters near the
Amelia farm) and at point 4 (San Pablo river in the sector of the 4 de
mayo citadel), are
values that increase significantly in relation to point 2 (Santa Rosa river, near the "El
Beldaco" farm) and point 3 (San Pablo river near the Technical University of Babahoyo),
this increase in the results is related to the fact that t
hese points are very close to the
influence of the inhabitants of the city of Babahoyo, at point 4 and at point 1 near the "El
Beldaco" farm, This increase in the results is related to the fact that these points are very
close to the influence of residents
of the city of Babahoyo. At point 4 and point 1, near
the El Beldaco farm, there is a certain amount of settlement of people, which is attributed
to the possible discharge of domestic wastewater into the river without any prior
treatment; even so, the val
ues obtained are within the maximum permissible limit,
making it possible to use them for irrigation purposes in the area's crops.
The pH is in values between 7.16 and 7.59 U of pH, this is a good indication of water
quality, since together with the temper
ature and dissolved oxygen, it influences the
stability of biological processes, therefore this favors the development of microorganisms
involved in the process of degradation of organic matter, as well as in the process of
photosynthesis of plants and alg
ae which contribute to the amount of oxygen available.
4.3 Nitrite values at all points are very low, ranging between 0.07 mg/l and 0.14 mg/l, this
is due to the fact that it is very unstable in the environment as it goes through the
nitrification and den
itrification process. The four sampling points comply with
environmental regulations for the nitrite parameter. Sulfates can be considered, together
with chlorides, as components of high pollutant risk since they contribute to water salinity
(Campos, 2022)
. The analyzed samples contain quantities lower than the maximum
permissible limits established by Ecuadorian environmental regulations, 250 mg/l, so that
by presenting values between 9.00 mg/l and 12 mg/l of sulfates, the established quality
standards are
met.
The values of biochemical oxygen demand are between 2.67% at point 3 (San Pablo
river at the height of the Technical University of Babahoyo) as a minimum value and with
a maximum value of 5.85% at point 4 (San Pablo river, sector 4 de mayo), this
cor
responds to the amount of dissolved oxygen in the water, which is necessary for the
aerobic oxidation of organic substances present in the water, therefore, it is an indicator
of the general quality of water and organic pollution
(Cajaleón, 2020)
. Organic
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contamination would cause in plants an accumulation of the same in the roots or
extremities of vegetables, and this will have repercussions on consumers.
Dissolved oxygen is found in a range of values between 67.10% and 72.90%, which we
can consider as an
indicator of water quality since, if there are very low or zero levels of
dissolved oxygen, this would indicate a possible high contamination, septic conditions of
contaminating organic matter or intense bacterial activity (consumption of dissolved
oxygen
) and this would affect the respiration processes, photosynthesis processes and
the preservation of aquatic life
(Bustos, 2019)
. Temperature is a factor that conditions
the behavior of the internal components of water, according to (Cajas et al, 2023).
Tem
perature affects the solubility of gases, which is important, since an increase in
temperature decreases the solubility of oxygen in the water, and also affects the
sedimentation rate of solids.
In the results obtained, the temperature presents
considerabl
e values between 28.80 and 30.0 °C.
The values obtained for temperature, dissolved oxygen, total dissolved solids, nitrates,
biochemical oxygen demand, and turbidity could not be validated with the environmental
regulation Book VI, Annex 1, Table 3. Admiss
ible quality criteria for water intended for
agricultural use, since it does not consider them as critical variables to be considered in
accordance with their use.
5
. Conclusions
When analyzing the results of the investigation, it can be seen that at point
4, the results
show a difference in the values corresponding to total dissolved solids, turbidity and fecal
coliforms, this is because this sample was taken in the San Pablo river, sector 4 de mayo,
This is due to the fact that this sample was taken in th
e San Pablo river in the 4 de Mayo
sector, which is part of the urban area of the city, an area influenced by residents who
use the water source for their daily cleaning activities, in addition to the fact that several
lubrication plants and a gasoline di
stributor are located very close to the sampling point.
These have their water treatments prior to sending their effluent to the receiving water
body, which contributes to the fact that although the values are higher than those of the
other three points, t
hey comply with environmental regulations regarding fecal coliforms,
pH, nitrites and sulfates.
In each of the sampling points, the water quality index ICA
-
NSF was determined, with
which it can be established that in the four points the water quality is in
the "regular"
category, in general the parameters used for this quality criterion do not have a great
influence on the result, the result obtained is influenced by the absence of the phosphate
value, for this reason it is inferred that if we had these val
ues, the water quality index
could be in the "good" category.
Author Contributions:
Conceptualization,
VL
-
SV
. and
YB
-
SO
.; methodology,
VL
-
SV.
a; software,
VL
-
SV.
; validation,
VL
-
SV. and YB
-
SO
.
; formal analysis,
VL
-
SV
.; research,
VL
-
SV. and YB
-
SO
;
resources,
VL
-
SV. and YB
-
SO
; writing the original draft,
VL
-
SV.
;
writing, revising, and editing,
VL
-
SV.
; visualization,
VL
-
SV.
; supervision,
VL
-
SV.
All
authors have read and accepted the published version of the manuscript.
Funding:
This research has not
received external funding.
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Acknowledgments:
Special thanks to Milagro State University for their support
throughout this research.
Data availability statement:
Data are available upon request to the authors of
correspondence:
vsanchezv@unemi.edu.ec
Conflict of interest:
The authors declare that they have no conflict of interest.
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