Trophic state and potential productivity assessment for Qaroun Lake using spatial techniques

Abstract

Qaroun Lake is one of the most important Egyptian lakes which, recently, have been exposed to severe degradation in water quality and fish productivity. In this manuscript, Carlson's trophic state index (CTSI) was used to evaluate the trophic state, while the trophometric index (TMI) was used to assess the potential productivity of Qaroun Lake. The present study is one of the initial attempts to investigate these indices in Qaroun Lake. To achieve this work, an integrated multidisciplinary approach was adopted integrating field investigation, geographic information system, and data analysis. CTSI combines three variables of water quality: chlorophyll-a (CHL-a), total phosphorus (TP), and transparency measured by Secchi disk depth (SDD). The result of overall CTSI showed the hypereutrophic state is represented by 62% and eutrophic state is represented by 38% of the total lake's area. Moreover, the calculated TMI indicated the average potential productivity value (PP) is 619 t. It can be concluded that the hypereutrophic is the dominant state in Qaroun Lake. The present study recommends the application of TMI model to evaluate and monitor the changes in Qaroun Lake's potential productivity in response to the changing environmental conditions and other biological pressures (e.g., Isopoda paraside).

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Environ Monit Assess (2023) 195:987
https://doi.org/10.1007/s10661-023-11504-2
RESEARCH
Trophic state andpotential productivity assessment
forQaroun Lake using spatial techniques
HagarM.Mohamed· MagdyT.Khalil·
AhmedM.El‑Zeiny· NehadKhalifa·
SamehB.ElKafrawy· WiamW.M.Emam
Received: 15 October 2022 / Accepted: 10 June 2023 / Published online: 25 July 2023
© The Author(s) 2023
Abstract Qaroun Lake is one of the most important
Egyptian lakes which, recently, have been exposed to
severe degradation in water quality and fish produc-
tivity. In this manuscript, Carlson’s trophic state index
(CTSI) was used to evaluate the trophic state, while
the trophometric index (TMI) was used to assess
the potential productivity of Qaroun Lake. The pre-
sent study is one of the initial attempts to investigate
these indices in Qaroun Lake. To achieve this work,
an integrated multidisciplinary approach was adopted
integrating field investigation, geographic informa-
tion system, and data analysis. CTSI combines three
variables of water quality: chlorophyll-a (CHL-a),
total phosphorus (TP), and transparency measured by
Secchi disk depth (SDD). The result of overall CTSI
showed the hypereutrophic state is represented by
62% and eutrophic state is represented by 38% of the
total lake’s area. Moreover, the calculated TMI indi-
cated the average potential productivity value (PP) is
619 t. It can be concluded that the hypereutrophic is
the dominant state in Qaroun Lake. The present study
recommends the application of TMI model to evalu-
ate and monitor the changes in Qaroun Lake’s poten-
tial productivity in response to the changing envi-
ronmental conditions and other biological pressures
(e.g., Isopoda paraside).
Keywords Carlson trophic state index·
Trophometric index· GIS· Fish yield·
Chlorophyll-a· Eutrophication
Introduction
Qaroun Lake is a closed saline basin in Egypt. It
has a great global significance since it compiled the
Rmsar convention and was designated as a natural
reserve in 1989 (NCS, 2006). Moreover, the local
importance is due to it is being the main source of
livelihood for the El Fayoum government. In 2014,
the lake’s contribution to the country’s total fish yield
from inland lakes was about 12.62% (4518 t) (CAP-
MAS, 2018) which decreased to 2.10% (832 t) in 2018
(CAPMAS, 2018). Napiórkowska-Krzebietke et al.
(2016) recorded Mugil cephalus and Solea spp as
dominant fish types, while Tilapia zillii and Engraulis
H.M.Mohamed(*)· S.B.E.Kafrawy
Marine Sciences Department, National Authority
forRemote Sensing andSpace Sciences (NARSS), Cairo,
Egypt
e-mail: HagarMahmoud102@yahoo.com
M.T.Khalil· W.W.M.Emam
Department ofZoology, Faculty ofScience, Ain Shams
University, Cairo, Egypt
A.M.El-Zeiny
Environmental Studies Department, National Authority
forRemote Sensing andSpace Sciences (NARSS), Cairo,
Egypt
N.Khalifa
National Institute ofOceanography andFisheries, NIOF,
Cairo, Egypt
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encrasicolus were found in the east and the middle of
the Lake. Qaroun Lake drainage system is consist-
ing of twelve drains; the main drains are El-Bats and
Al-Wadi (Mehanna, 2020; Zaher & Ibrahim, 2018).
It receives a massive amount of wastewater reaching
450 mm3/year from agricultural sector, sewage water,
and excessive nutrient salts from aquaculture drain-
age dominating the southern part of the lake (Elsayed
etal., 2021). Consequently, the lake’s aquatic environ-
ment is highly contaminated by inorganic and organic
contaminants (El-Zeiny et al., 2019; El Agawany
etal., 2021).
Eutrophic phenomena is arisen in Qaroun Lake
from the discharge of drainage water into the enclosed
lake’s body. The increased nutrient level will increase
the rate of phytoplankton growth. Thus, they exceed
standard levels which produces high chlorophyll con-
centration and prevents the sunlight from entering the
bottom of the lake causing the transparency factor to
decline. High bacterial populations, followed by high
breathing rates, cause the loss of living organisms
and the release of organic matters. The organic mat-
ter is normally bound to bottom sediments, including
different forms of phosphorus. Hypereutrophic has
a significant impact on fish productivity in the lake
(Alprol etal., 2021).
Carlson trophic state index (CTSI) is developed
by Carlson (1977) to classify the lake productivity
into different categories; oligotrophic, mesotrophic,
eutrophic, and hypereutrophic that aid in manage-
ment plans (Alprol etal., 2021; Carlson & Havens,
2005). The trophic state index (TSI) formula is based
on three parameters, i.e., total phosphorus TP, chlo-
rophyll-a (CHL-a), and water transparency (SDD)
that finally form CTSI. Geographic Information Sys-
tem (GIS) helps to generate thematic maps for TSI
(CHL), TSI (TP), TSI (SDD), and CTSI. Globally,
this index is used to assess the lakes eutrophication
by many researchers, i.e., Sruthy etal. (2021), Al-
Khafaji and Al-Taee (2022), and Yan etal. (2022),
and in Egypt, successful attempts were done by
Donia and Hussein (2004), Darwish etal. (2021) and
Hasan (2021). Stakeholders could easily monitor and
assess the eutrophic situation in the lakes to start
executing a suitable plan.
Estimating the real fish yield (fish productivity) for
water bodies is consuming time and is highly costly
(Onumah et al., 2020). As an alternative way, the
potential productivity (PP) can be estimated through
the changes in the morphometry, water quality data,
and biological parameters. Recognizing the potential
productivity of lakes is an essential step for good sus-
tainable management. It depends mainly on the deter-
mination of the gap between estimated and real yield
(Crul, 1992; Tesfaye & Getahun, 2021 and Mohamed
etal., 2022). Among the potential productivity mod-
els, this manuscript applied the trophometric index
(TMI) which has been adopted to assess PP by Lara
etal. (2009) on eight reservoirs in the Mediterranean
Lakes with model statistical description R2 > 0.8;
P < 0.01. Trophometric index is an indirect method to
measure the lake’s potential productivity through the
combination of morphometry represented in depth,
area, perimeter, and volume, chemical factors repre-
sented in electrical conductivity (EC) data and bio-
logical factors (CHL-a) (Milligan etal., 2020).
The combination between GIS and field data could
provide a rapid or a large-scale understanding of lake
changes and in developing management strategies for
the lake (Papastergiadou et al., 2008; Emam, 2016;
El-Zeiny et al., 2019; Elkafrawy et al., 2020). Fur-
thermore, the package of GIS could help to achieve
the desired purpose by converting the tabulated data
to thematic maps to detect the highly affected areas
giving an earlier alarm (Hussian etal., 2019).
The main aims of this approach are to quantify and
qualify the eutrophic state in Qaroun Lake through
mapping the TSI for (CHL-a), (TP), and (SDD)
parameters to produce the CTSI map by using the
geostatistical analyses, and the second aim is to apply
the trophometric index to Qaroun Lake to evaluate its
potential productivity. Both CTSI and TMI are spe-
cific indices developed to evaluate and understand the
productivity of the lake.
Material andmethods
Study area
Lake Qaroun is located in the North African Sahara
Desert. It is a natural lake in the middle of Egypt, def-
initely in the lowest north-west region of El-Fayoum
Depression. It is situated in an arid region between
latitudes 30°24′ and 30° 49′ E and latitudes 29° 24′
and 29° 33′ N (Fig.1). The elevation of Lake Qaroun
is located between − 43 and − 45 m below the sea
level. Furthermore, the average water depth of the
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lake is 4.2 m since the Lake is surrounded by resi-
dential and agricultural areas from the east and the
south, while desert is common at the north. Fresh
water enters Lake Qaroun through a drainage net-
work. It has two main drains (El-Bats and Al-Wadi)
and a number of secondary drains (Fig.2). It receives
about 450 mm3 each year as a mixture of untreated
industrial, sewage, agricultural, and domestic efflu-
ents from El-Fayum Province (Barakat et al., 2013;
El-Zeiny etal., 2019).
Methodology
The methodology adopted in the present paper
depended on two main inputs: field data and satel-
lite images. Each data set was subjected to several
and successive processes, which are summarized in
Fig.3. Each step in the flow chart will be described in
detail in the following sections.
Sampling and analysis
Water samples were collected from ten different sites
during November 2018, February 2019, March 2019,
and June 2019. The sampling sites are well distrib-
uted in Qaroun Lake. All water samples were sent to
the laboratory for further analysis (EC and TP) fol-
lowing APHA (1992).
Transparency was measured using a white enam-
eled Secchi disk depth (SDD). Chlorophyll-a determi-
nation was performed in the other exact volume of the
500-ml water sample which was filtered on the same
day of collection using GF/C filters. The filters were
kept in a deep freezer until analysis. Chlorophyll-a
in the phytoplankton cells retained on the filters was
extracted by using 90% acetone and measured spec-
trophotometrically at 630, 645, 665, and 750 nm
wavelengths (Strickland & Parsons, 1972).
The results of the field data were organized in an
Excel sheet in order to be imported into ArcGIS 10.5.
Fig. 1 Location map of the study area: A African continent where Egypt is located; B location map of Egypt showing the boundary
of the study area at the north of the western desert; C close up view of Lake Qaroun indicating the sampling sites
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Some statistical analyses were computed as a mini-
mum, maximum, average, and Ln value (natural loga-
rithm) for further use in indices measurements.
Index calculation
Calculating the TSI CTSI for lakes is calculated
based on some water quality parameters represented
in CHL-a (μg/L) concentration, total phosphorus TP
(μg/L), and water transparency (m). Yet, CTSI ranged
from 0 to 100 to assess the trophic state in Lake
Qaroun and is classified as driven from (Carlson &
Simpson, 1996) (Table1).
The following equations were utilized together to
describe TSI:
(1)
TSI(CHL − a) = 9.81 ln(CHL− a) + 30.6
(2)
TSI(SD) = 60 −14.41 ln(SD)
(3)
TSI(TP) = 14.42 ln(TP) + 4.15
where ln is natural logarithm.
Calculation ofthePP The trophometric index was
developed by Lara etal. (2009). The trophometric
index accommodates seven variables: area (Km2),
volume (m3), average depth (m), VOAP (area/depth)
(Eq.5), EC (mS/cm), CHL-a (μg/L), and perimeter
Pe (m) (Eq.5).
Multiplying inputs into the model helps to
increase its accuracy. The inputs of the trophomet-
ric index consist of IF (Eq.5), VOAP (Eq.6), EC,
chlorophyll-a, and VOAP (volume of water to area
percent), which is the volume percentage of water
with sufficient oxygen to sustain fish life (Wootton,
1990; AKKUŞ & Mustafa, 2019).
where
(4)
CTSI = TSI() + TSI(TP)+ TSI(CHL − a)
3
(5)
TMI = IF ∗ VOAP ∗
ln EC ∗
ln CHL − a
ln Pe
Fig. 2 Hill shade of Qaroun Lake and its vicinities illustrating El Fayum depression and the drainage system
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Then, Eq. 8 was used to calculate the potential
productivity in kg/ha.
To convert the calculated potential productivity
to tons, use.
(6)
IF = Area
volume
(7)
VOAP = Area
depth
(8)
PP(Kg∕ha = −54.191 +67.63 ∗ TMI
Satellite images and GIS
Satellite image acquisition
A high-resolution Sentinel-2B MSI scene was used for
carrying out the morphometric analysis, including the
lake boundary and perimeter during 2018–2019 for
Lake Qaroun (tile number: 35) with pixel size 10m. The
scene was freely downloaded from the Copernicus Open
Access Hub website. The database was built from the
number of thematic layers that were provided with the
UTM Zone 35 projection systems with WGS 84.
Geospatial analysis
Extraction of Qaroun Lake’s boundary The nor-
malized difference water index (NDWI) introduced
by McFeeters (1996) to detect and map surface water
(9)
PP(tonnes) = PP(kg∕ha)∗0.405 ∗55340
1000
Fig. 3 A flowchart showing
the methodology adopted in
this study
Table 1 Category of Carlson trophic state index
Category Range
Oligotrophic 0–30
Mesotrophic 30–50
Eutrophic 50–70
Hyper‑eutrophic 70–100
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from multi-spectral remote-sensing images (Eq.10).
Calculating the lake’s area could be done through the
NDWI, which is a successful index for surface water
extraction from the satellite image. Moreover, NDWI
has simple, fast, and good achievements through the
water indexes that are used for recognizing the water
bodies (Jiang etal., 2014). This technique is based on
the difference in the absorption and reflection of light
between the water and other features in different fre-
quency bands, as described in the following equation.
where the green band average range is 0.56μm. The
near-infrared (NIR) reflectance range is 0.84μm.
The created geodatabase for the extracted lake bound-
ary will be ready to use the information recorded in the
attribute table to give area (km2) and perimeter (km).
Generating thematic maps The geographic location of
each sample was detected using the Global Positioning
System (GPS) linked to the measured parameter values in
an Excel sheet. The Excel file was subsequently imported
into GIS and interpreted using ArcGIS 10.5 in combina-
tion with the boundary layer of Lake Qaroun. The kriging
interpolation was carried out for the following outputs:
TSI (SD), TSI (TP), TSI (CHL-a), and CTSI. The con-
cept of Kriging interpolation is to use a limited set of sam-
pled data points to estimate the value of a variable over
a continuous spatial field (Oliver & Webster, 1990). In
addition, the ordinary kriging approach has been proven
that kriging interpolation is the best interpolation method
for the water parameters (Huchhe, 2016). Then, using the
raster to polygon tool, the classified raster to polygon was
used in order to extract the area of each class. Finally, the
percentage of each class is calculated through Eq.(11).
Results
In situ characterization of water quality
The average water parameter analysis for Lake Qaroun
during 2018–2019 is presented in Table 2. Chloro-
phyll-a levels ranged from 51.9 to 335.8 (µg/L) during
(10)
NDWI = (NIR − gr een)
(NIR + green)
(11)
class% = class area
Total Lake ar ea
×
100
the period of the study, with an annual average 156.9
(µg/L). On the other hand, the average annual value
of total phosphorus was 102.2µg/L, with a minimum
value of 55 µg/L and a maximum annual value of
295.4 µg/L. The transparency of Qaroun water fluc-
tuated from 0.2 to 0.8 m, and the average value was
0.4m, while the EC mean value is 45.7 µS/cm, mini-
mum of 30.1 µS/cm, and a maximum of 53.5 µS/cm.
Morphometric results
Three images of Sentinel-2B MSI scene for Febru-
ary, March, and June were used to extract Qaroun
Lake boundary and perimeter through applying the
NDWI model. However, data for autumn were taken
from Mohamed etal. (2022). The result of the mor-
phometric data required to achieve this work were
231 km2 for area and 146.1m for perimeter.
Evaluation of CTSI
A Carlson trophic state index was conducted on
Qaroun Lake to classify its trophic state. The applied
CTSI is represented in Table3. The overall CTSI is
the average values derived from each module: TSI
(CHL-a), TSI (TP), and TSI (SDD) (Table3).
Table 2 The average values of water parameters used in this
study
TP total phosphorus, CHL-a chlorophyll-a, SDD Secchi disk
depth, EC electrical conductivity
Sample no. TP (µg/L) CHL‑
a(µg/L) SDD (m) EC (µS/cm)
1295.4 92.7 0.2 30.06
279.9 116.4 0.4 42.67
374.7 174.0 0.4 44.0
482.0 334.2 0.4 48.7
569.3 335.8 0.5 49.6
661.2 173.6 0.5 52.5
7186.7 145.7 0.2 30.1
866.3 77.8 0.7 52.6
956.9 62.6 0.8 53.0
10 55.2 51.9 0.6 53.5
Average 102.8 156.5 0.5 45.7
Minimum 55.2 51.9 0.2 30.1
Maximum 295.4 335.8 0.8 53.5
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The spatial distribution maps of the resultant
maps are illustrated in Figs. 4 and 5 and Table 4
showing the percentage of each trophic class. The
spatial distribution of TSI (TP) showed an obvious
hypereutrophic state near the main drains EL-Bats
and EL-Wadi drain, representing 21% of the total
lake area, while eutrophic state is dominant (79%)
as shown in Fig. 4A. The spatial distribution of
TSI (CHL-a) showed hypereutrophic areas at the
east and the m4iddle of Qaroun Lake, amounting
91% of the total lake area. However, the eutrophic
state appeared in the western part of the lake and
represents19% of the total lake area (Fig.4B). TSI
(SDD) hypereutrophic state was the dominant class
representing 67%. The eutrophic state was 33%
around samples 8 and 9 west of the lake (Fig.4C).
The overall CTSI showed the hypereutrophic state
with 62% dominating the lake and the eutrophic
state with 38% at the west around samples numbers
8, 9, and 10.
Potential productivity TMI
The variables required assess and map TMI are
described in Table5. The average potential productivity
for the four seasons was estimated using an equation
from Lara etal. (2009).
Discussion
Trophic state of Qaroun Lake
Eutrophic is a common phenomenon in inland lakes
(He et al., 2021). Qaroun Lake’s trophic state has
IF = 230.8
10
TMI =
0.24 ×54%×3.68 ×
5.05
4.98 ;
PP(kg∕ha) =
54.191
+
67.63
×1.3;
PP(tons) = 34.4 ×0.405 × 56,340
1000
PP(tons) = 652t.
Table 3 The average TSI (TP), TSI (CHL-a, and TSI (SDD), and CTSI (Carlson & Havens, 2005)
Sample
no.
TP
(µg/L)
TSI
(TP)
CHL-a
(µg/L)
TSI
(CHL-a)
SD
(m)
TSI
(SD)
CTSI
1295 84 93 74 0.21 82 80
280 66 116 77 0.33 76 73
375 66 174 80 0.34 76 74
482 67 334 83 0.29 78 76
569 65 336 82 0.36 75 74
661 63 174 81 0.45 71 72
7187 79 146 78 0.24 81 79
866 64 78 73 0.73 65 67
957 62 63 71 0.76 64 66
10 55 62 52 69 0.59 68 66
TP total phosphorus, TSI trophic state Index, CHL-a chlorophyll-a, SDD Secchi disk depth
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been previously discussed in many ecological stud-
ies as a eutrophic lake or highly eutrophic state. They
attributed the eutrophic state of the lake to receiving
excess nutrients, which increases the chlorophyll-
a concentration rates. Additionally, Qaroun Lake
is located within an arid to hyperarid region that is
characterized by high temperatures and thus high
evaporation rates with stable water movement (Abu-
Ghamja et al., 2018; Goher et al., 2018; Ibrahim
etal., 2021). On the other hand, a trophic level index
(TLI) of Qaroun Lake was carried out for specific
sites by Napiórkowska-Krzebietke etal. (2016) which
revealed that the status of the lake is a hypereutrophic
state in most of the sampling sites. However, in the
current study, the calculated trophic state of the lake
was missing the oligotrophic and mesotrophic states.
It ranged between eutrophic and hyper-eutrophic
state, occupying 38% and 62% of the surface area of
Fig. 4 The distribution
maps of A TSI (TP), B TSI
(CHL-a), and C TSI (SD)
along Qaroun Lake during
2018–2019
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the whole lake respectively. Based on the calculated
trophic state for each sampling site in the study area,
a clear 2D map for the spatial distribution of the TSI
(TP), TSI (CHL-a), TSI (SDD), and CTSI has been
created using the potential of GIS. Investigation of the
TSI (TP) map shows that the zones of hyper-eutrophic
state appear closer to the two discharge points rep-
resented by the two main drains that are connected
to Qaroun Lake (i.e., El Bats; El Wadi). This is due
to the fact that phosphorus enters the natural water
resources from external sources, particularly agri-
cultural drainage wastes (Mahmoud, 2015). The
Fig. 5 Distribution of overall CTSI along Qaroun Lake during 2018–2019
Table 4 The calculated area of trophic state for each of TSI (CHL-a), TSI (TP) and TSI (SDD), and CTSI
Area (Km2)Area (%)
Trophic stateHyper-EutrophicEutrophicHyper-EutrophicEutrophic
TSI(CHL-a)210 21 91% 9%
TSI(TP)49 181 21% 79%
TSI(SD)154 77 67% 33%
TSI(CTSI)142 88 62% 38%
TP total phosphorus, TSI trophic state index, CHL-a chlorophyll-a, SDD Secchi disk depth
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agriculture drains in Egypt are loaded with excessive
amount of pesticides, which carry a high amount of
TP (Matter et al., 1992). Phosphorus is an essential
element for accelerating the phytoplankton growth
(Saputra et al., 2017). Exceeding the concentration
of phosphorus will seriously increase the growth of
phytoplankton, leading to the appearance of a hyper-
eutrophic state (Saetang & Jakmunee, 2021).
Consequently, the examination of the gener-
ated spatial distribution map of TSI (CHL-a) shows
that most of the surface area of the lake falls within
the hyper-eutrophic state covering 91% from the
total area of the lake. The chlorophyll levels ranged
between 51.9 and 335.8 µg/L which exceeded the
standard chlorophyll-a levels for the lake’s water,
where the normal levels are ranging between 4.49
and 69.50 μg/L (Saeed & Mohammed, 2012). It is
worthy mentioned that the chlorophyll levels are pro-
portionally increasing during the last 8 years where
in 2008, the average chlorophyll-a concentration was
201.5µg/L, while in March 2015, the recorded CHL-a
average reaches its maximum value 336μg/L show-
ing a blooming phenomenon (Hussein et al., 2008;
Zaher & Ibrahim, 2018). High CHL-a concentra-
tions give alarm to increase lake eutrophication where
chlorophyll-a is positively correlated to enriched
nutrient concentrations which forms a blooming, poor
water quality and the presence of harmful species of
algal. Carlson (1977) confirmed that the best indica-
tor in assessing trophy is chlorophyll a.
Finally, transparency will be affected due to
the vigorous growth of phytoplankton. Using TSI
(SDD), the hyper-eutrophic state was 67%. The
transparency factor in Qaroun Lake is low due to
the direct discharges of two main drains carrying the
suspended particles (e.g., fertilizers and, fish farm-
ing outputs, the disposal of untreated sewage, and
agricultural effluents) to the lake. The combination
of the three modules of trophic states (TP, CHL-a,
and SSD) derived the CTSI map showing the over-
all eutrophic state as 38% and the hyper-eutrophic
state as 62%. The negative impacts of hyper-eutrophic
are arisen from the decline in oxygen level in shal-
low lakes which create dead zones that change the
ecosystem, decrease biodiversity, and have a dra-
matic effect on the fish productivity of the water body
(Fathi & Flower, 2005; Khalil etal., 2017; El-Zeiny
etal., 2019). On the other hand, in a nearby lake in
the study area (Wadi El Rayan Lakes), only the TSI
(CHL-a) from the parameters of CTSI was applied
to detect the trophic sate for the two lakes. The study
revealed that the first lake is mesotrophic, while the
second Wadi El Rayan lake is oligotrophic according
to Konsowa (2007) which presented normal levels of
trophic state that may be attributed to the absence of
draining system reaching water bodies, keeping them
in normal conditions.
Estimation ofthepotential productivity using TMI
In the current study, the average annual potential pro-
ductivity (PP) based on trophometric index (TMI)
was 652 t during 2018–2019. Indeed, the advan-
tage of the potential productivity model is that it
could clarify the gap between the actual yield (832
t) reported from CAPMAS (2018) and the estimated
Table 5 The values of variable in TMI
CHL-a chlorophyll-a, EC electrical conductivity
(1) Mohamed etal. (2022). VOAP (volume of water to sustain life in area percent) was estimated by multiplying the total area of
each reservoir by the depth at which the oxygen is equal to 3.0mg L)1, considered by Wootton (1990) as the tolerance limit for the
survival of fish
Parameters Nov 2018 Feb 2019 Mar 2019 Jun 2019 Average
Area (km2) 228 1231.2 230.2 230.9 230.8
Perimeter (m) 139 150.5 147.2 147.5 146.1
Volume × 108 (m3) 9.804110.034 9.991 10.021 10.0
CHL-a (µg/L) 124.4 101.1 293.6 106.8 156.5
EC (mS/cm) 49.6 36.46 35.29 38.79 40.0
Average depth14.3 4.3 4.3 4.3 4.3
VOAP 53% 53.70% 53.50% 57.70% 54%
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PP (652 t). The accuracy of the applied model for
estimating potential productivity is 80% of the actual
yield indicating an acceptable level of accuracy. The
advantage of the TMI is the contribution of seven
vital variables to identify the productivity giving
more reliable results and estimations.
In closure, it can be mentioned that the low
actual productivity of the lake is greatly affected
by the detected hyper-eutrophication state resulting
from the environmental related impacts of untreated
discharges (sewage and agriculture). Moreover, it is
necessary to restore this closed basin to maintain a
suitable environment for the living organisms and
work on the sewage treatment before discharging
into the lake.
Conclusion
The present study achieved the multidisciplinary inte-
gration of insitu measurements, environmental indi-
ces, and GIS to assess the spatial distribution of the
lake’s trophic state. Moreover, it focused on apply-
ing models such as CTSI to assess the trophic state
of the lake and the TMI to assess potential productiv-
ity. According to CTSI, TP was the main factor for
the trophic state of the lake. The degree of annual and
potential productivity from the trophometric index
(TMI) indicated an acceptable accuracy for estimat-
ing Qaroun Lake yield that can widely be used in sus-
tainable management plans. On the other hand, it is
necessity to work on raising the lake potentiality and
decreasing the level of pollution reaching the lake
particularly nutrients levels.
Accordingly, it is highly recommended to pay
more attention to Lake Qaroun as a closed system
exposed to excessive pollution that threatens produc-
tivity, i.e., loss of species diversity and quantitatively
changes (i.e., decrease in fish production). Provid-
ing triple wastewater treatment plants is a must to
improve drains water quality and consequently restore
Lake Qaroun.
The present study provides the decision maker
with the necessary thematic layers and spatial analy-
ses that is necessary for future planning and produc-
tivity improvement. The current multidisciplinary
integration achieved satisfactory results and is appli-
cable in similar settings.
Acknowledgements The authors acknowledge NARSS for
support provided during field survey/lab analyses and USGS
for providing Sentinel images to the present study.
Author contribution All authors contributed to the study con-
ception and design. Material preparation, data collection, and anal-
ysis were performed by Hagar M. Mohammed, Magdy T. Khalil,
Ahmed M. El-Zeiny, Sameh B. El Kafrawy, Nehad Khalifa, and
Wiam W. M. Emam. The first draft of the manuscript was written
by Hagar M. Mohammed and Ahmed M. El-Zeiny, and all authors
commented on previous versions of the manuscript. All authors
read and approved the final manuscript.
Funding Open access funding provided by The Science,
Technology & Innovation Funding Authority (STDF) in coop-
eration with The Egyptian Knowledge Bank (EKB).
Availability of data and materials All data generated or
analyzed during this study are included and available in this
article.
Declarations
Ethics approval Not applicable
Consent to participate Not applicable.
Consent for publication The author warrants that the work
has not been published before in any form and is not under con-
sideration by another publisher, that the persons listed above are
in the proper order, and that no author entitled to credit has been
omitted, and generally that the authors have the right to make
the grants made to the publisher complete and unencumbered.
The author also warrants that the work does not libel anyone,
infringe anyone’s copyright, or otherwise violate anyone’s stat-
utory or common law rights.
Competing interests The authors declare no competing interests.
Open Access This article is licensed under a Creative Com-
mons Attribution 4.0 International License, which permits
use, sharing, adaptation, distribution and reproduction in any
medium or format, as long as you give appropriate credit to the
original author(s) and the source, provide a link to the Crea-
tive Commons licence, and indicate if changes were made. The
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the permitted use, you will need to obtain permission directly
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http:// creat iveco mmons. org/ licen ses/ by/4. 0/.
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