long-term estimation of water losses through evaporation...
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International Journal of Civil & Environmental Engineering IJCEE-IJENS Vol: 16 No: 05 13
160905-7878-IJCEE-IJENS © October 2016 IJENS
I J E N S
Long-Term Estimation of Water Losses Through
Evaporation from Water Surfaces of Nasser Lake
Reservoir, Egypt Ali M. Hamdan* and Mohamed Zaki**
*Geology Department, Faculty of Science, Aswan University, Aswan, Egypt.
**Egyptian environment affairs Agency, Aswan, Egypt.
E-mail for the corresponding author: [email protected]
Abstract-- This work aims to long-term estimate water loss
through evaporation from an open water surfaces of Aswan High
Dam Reservoir (AHDR) using of local hydrological and
meteorological data collected from instrumented platforms at
nine locations: front of High Dam, Kohr Kalbshka, Wadi abud
north Allaqi, Almalka, Amada, Kohr Toshka, Toshka, Abu
Simple, and Argeen. Bulk Areodydimic method applied using
monthly available hydrometeorological data with longest data
record of the last 20 years (from water year 1995/1996 to
2014/2015). Water losses by evaporation vary from 12.004 ×
109m3 (in 1995/1996) to 15.53 × 109m3 (in 2007/2008) with an
average of 13.62 × 109m3/year. Water budget is another method
used to estimate evaporation losses for the past 5 decades (last 51
years) from 1964, after the construction of the High Dam and
before forming Nasser Lake reservoir till now. The relationships
between water losses by evaporation, lake water level, inflow
arriving the lake, and changes of the lake water storage were
detected and show many variations. Percentage of evaporation
relative to water storage in the lake vary from 3.55% to 20.26%,
with an average of 10.94%; and it ranges between 0.24% and
21.18% with average of 12.65% relative to the water income to
the lake.
Index Term-- Nasser Lake, evaporation loss, Bulk
Areodydimic, hydrometeorology.
1- INTRODUCTION Water distribution throughout the world is not homogeneous.
In many places, the majority of populace does not have
adequate amounts of fresh water. The industrial developments,
population growth, rising in energy demand, increasing the
quality of life standards, and agriculture irrigations have
resulted in the importance increasing for fresh water
resources. In arid and semi-arid regions, the evaporation water
loss from open-water reservoirs is one of the national
problems and it is a big problem throughout the World. Along
the world, evaporation loss values vary from reservoir to other
and change according to change in hydrometerological data. It
considered as one of the obscure components of the
hydrologic cycle as well as it is one of the main components in
both the water budgets and energy of lakes and a primary
process of water loss for most of them.
Many literatures estimate of the evaporation loss rates in many
parts using different methods. For example, the evaporation
losses calculated from open water reservoirs in South-East
Queensland (Australia), and it losses about 40% of their total
water storage capacity per year [1]. At Sparkling Lake,
northern Wisconsin (USA), the mean evaporation loss rate
estimated and it is 3.1 mm/day [2]. In tropical Africa lake
(Lake Ziway, Ethiopia), the evaporation rate is 4.87 mm/day
[3]. Using the energy budget method, evaporation from
Williams Lake (North Central Minnesota) varied from 2.82
mm/day to 2.19 mm/day [4]. In Okeechobee Lake (South
Florida), the evaporation estimated and it is 3.6 mm/day [5].
In Turkey, the total evaporation loss from water surfaces of
reservoirs and lakes estimated and it is 4.1 × 109 m
3/year from
reservoirs and 6.8 × 109 m
3/year, 2.7 × 10
9 m
3/year from lakes
[6]. Evaporation from the second largest lake in Japan
(Kasumigaura Lake) estimated for 2008 to 2012, the mean
annual E is 911 mm [7].
Many methods are used for evaporation losses estimation from
open water surfaces including: water budget methods (e.g. [8,
9, and 10]) and the bulk aerodynamic method such as (e.g. [2,
7, and 11]).
Aswan High Dam Reservoir (AHDR) consider as one of the
largest artificial water reservoirs of the world. It extends along
the Nile River, of which one-third about 150 Km (called
Nubia Lake) is in Sudan and two-thirds about 350 Km (known
as Nasser Lake) is in Egypt [12]. Nasser Lake lies between
latitudes 22o 00` to 23
o 58` N and longitudes 30
o 07` to 33
o 15`
E and lies in the extreme southern part of Egypt behind the
Aswan High Dam (Figure 1). This study worked on the
Egyptian part of the lake (Nasser Lake), where its surface area
is changing according to the annual amount of flood and the
water discharges from the lake.
The shoreline of Nasser Lake reservoir at 180 m level is 7875
Km length and at 160 m level is 5416 Km. The surface area of
its entire reservoir at water level of 160 m is 3084 Km2, when
the reservoir is nearly full (at water level of 180 m) it has a
surface area of about 6276 Km2 [13]. The total capacity of the
Nasser Lake reservoir is 162.3 × 109 m
3 at the level 182 m. It
has an average depth of 25 m, maximum depth of 90 m,
average width of 10 km, and maximum width of 60 km [14].
Nasser Lake considered as the fresh and renewable water bank
of Egypt and it is important for drinking water, irrigation,
hydropower, and fishing.
A review of various studies on evaporation losses in Nasser
Lake as, the evaporation losses estimated at 2050 using data of
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I J E N S
3 raft stations due to the expected climate changes [15].
Annual evaporation stated for only period from1995 to 2004
based on data from three floating stations and it is 12.1 BCM
[16]. The evaporation calculated based on GIS and remote
sensing data in one month only (March 2002) and gave
evaporation values vary from 2.73 to 9.58 mm/day [17].
Evaporation losses estimated using data from only two raft
stations (one raft in 2011 and other in 2010) using neural
network and gave annual evaporation rate 7.64 mm/day [18].
Evaporation losses calculated in 2008 using remote sensing
(satellite imagery) and gave values vary from 12.5 to 16.3
billion m3 that year [19]. Evaporation estimated based on
remote sensing using Landsat images in only 2 years (from
October 1998 to October 2000), and gave evaporation value is
1.5 mm/day [20].
2- THE OBJECTIVE OF STUDY
Nasser Lake is located in an arid region so, estimation of
water that losses by the evaporation is quite interest and
essentially for determination of the water budget of Egypt.
Water shortage in the arid regions along the world is an
existing and future severe problem. Egypt has a limited budget
of 55 Bm3/year from basin of Nile River that has always been
stored in AHDR. So that, the main objective of the present
study summaries as:
- Long-term estimation of water losses through evaporation
from an open water surfaces of Aswan High Dam Reservoir
(AHDR) or Nasser Lake Reservoir applying Bulk
Areodydimic method using monthly collecting and
available hydrometeorological data with the longest data
record of the last 20 years (from water year 1995/1996 to
2014/2015) depend on local meteorological and
hydrological data collected from instrumented platforms
(floating weather stations) at nine locations on the lake
(Figure 1).
- Estimate evaporation loss applying another method (water
budget method) from AHDR for the last 51 years from
1964 (since construction of the High Dam and before
forming Nasser Lake reservoir) till now.
- More than study of evaporation loss, present work includes
studying the water budget, for the past 5 decades, in one of
the largest man made water reservoirs of the world
(AHDR), which considered as one of the main components
of studying the Egypt fresh water budget.
- The relationship between the evaporation losses from the
lake and the change in its water level values were
discussed. Also the relationship between E-values, the
inflow arriving the Lake (Vin), and the change of water
storage in Nasser Lake reservoir (S) were studied.
- It is necessary to study the percentage of E-values relative
to the water storage in AHDR; and relative to the water
income to the lake.
3- MATERIAL AND METHODS
To long-term estimate the amount of water lost by
evaporation from Nasser Lake, many hydrometeorological
and hydrogeological data were monitored and calculated for
different times and used many methods.
3.1- Meteorological Stations and Data sources
In the present work, the hydrometeorological data obtained
from the instrumented platform (floating weather stations)
which installed along Nasser Lake and carried out for
recording four meteorological parameters as follows:
1- Relative humidity (%).
2- Surface water temperature (°C).
3- Air temperature (°C).
4- Wind velocity (m/sec).
These data were recorded daily by (High and Aswan Dam
Authority) from which the average monthly was calculated
from the 9 raft meteorological stations. They have been
installed along the Nasser Lake, from the High Dam to the
southern borders of Egypt, in order to measure the
meteorological parameters. The obtained data were used for
long-term estimation of water evaporation losses. These 9
stations are described in the following (Figure 1):
1- Raft meteorological station in front of High Dam.
2- Kohr Kalbshka raft station (40 km from HD).
3- Wadi abud north Allaqi station (75 km from HD).
4- Almalka raft station (155 km from HD).
5- Amada raft station (185 km from HD).
6- Kohr Toshka raft station (230 km from HD).
7- Toshka raft station (240 km from HD).
8- Abu Simple raft station (280 km from HD).
9- Argeen raft station (331 km from HD).
The meteorological data were collected from the 9 raft
meteorological stations for the last 20 years from water year
1995/1996 to 2014/2015 were used for calculation of water
losses by evaporation using the Bulk Areodydimic method.
The water year start from August (began of flooding period)
and ended by July. These data. The surface water inflow (109
m3/year) arriving the Nasser Lake reservoir (Vin) and the
discharge downstream through Aswan and High Dams (Vout)
were measured by High and Aswan Dam Authority.
Diversions or seepage loss from lake water to adjacent Nubian
aquifer (109
m3/year) were calculated by [21]. The water
budget method applied using the available hydrological data to
calculate the evaporation losses from Nasser Lake reservoir
for the last 51 years from water year 1964/1965 till now
(2014/2015); i.e. after the construction of the High Dam
(1965-1971) and before forming Nasser Lake reservoir.
3.2- Methods of estimations
The most common procedures and methods which used for
computing the amount of evaporation losses depend on
theoretical analyses. Whereas others, as the present work,
based on the atmospheric elements and the
hydrometerological data applied below using for long-term
estimation of water losses through evaporation from water
surfaces of Nasser Lake Reservoir. Two methods used: a)-
Bulk Areodydimic method and b)- water budget method.
3.2.1- Bulk Areodydimic method
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I J E N S
Bulk Aerodynamic method considered as the most widely
used for evaporation losses determination from large
reservoirs and lakes. The calculations by this method were
applied using Harbeck equation [22]. The following formulas
and parameters were used for calculation:
a- Saturation vapor pressure (es) calculation
………………(1)
Where: es is the saturated vapor pressure at water surface
(kpa) and WST is the water temperature (oC).
b- Saturated vapor pressure of air calculation
……………(2)
Where: ESA is saturated vapor pressure of air (kpa) and AT is
air temperature (oC) at 2 m above water surface.
c- Actual vapor pressure calculation
…………..………….…(3)
Where: ea is the actual vapor pressure of the air (kpa) and RH
is the relative humidity.
d- Estimating evaporation from reservoir According to Harbeck equation [22], the evaporation from
Nasser Lake reservoirs estimated using the following
equation:
…………..…..……(4) Where: E is the evaporation losses (mm/hour and then
accumulated mm/day), U2 is the wind speed (m/sec) at 2 m
height above water surface, N is a coefficient related to the
reservoir surface area, ea is the is actual vapor pressure of the
air (kpa), and es is the saturated vapor pressure (kpa) at water
surface temperature.
3.2.2- Water budget method This method can provide a most acceptable estimation of
evaporation losses. All components used in this method are
accurately modeled and/or measured, which each of them is
often a difficult task, especially for water seepage losses [2].
The water balance as generally applied to the hydrologic cycle
is actually statement of the law of conservation of mass. It
based upon the hydrologic equation as following:
Inflow = Outflow + Storage …………....……(5)
This method depends on monitoring the change which can
occur in the reservoir content or water storage of the lake over
a certain period of time. Water inflow consist of water runoff
along basins, total water precipitation, diversions from outside
its basin into the lake, major channels inflow from outside
drainage basin, and groundwater inflow. Outflow consist of
water evaporation, groundwater flow from the reservoir,
diversions out of the water body, and major channel flow out
of the water body. Thus, the hydrological budget of the
reservoir and water balance equation can be expressed as:
Vin + Pr = E + Vout + S + D ……........……(6) Then, the equation no. (6) can be expressed in terms of E as:
E = Pr + Vin Vout S D …………....……(7)
Nasser Lake is located in subtropical and arid zone. According
to the meteorological data, the rainfall is nearly rare.
Therefore, the above equation can be re-written as:
E = Vin Vout S D ……...................……(8)
Where: E is evaporation volumetric rate of water from the lake
surface (109m
3/year). Vin is lateral inflow of surface water into
the water balance area, Vout is lateral outflow from the water
balance area, D is diversions or seepage loss from lake water
to adjacent Nubian aquifer, S is the change in water storage
of the lake, and Pr is direct precipitation on the lake water
surface.
4- RESULTS AND DISCUSSIONS
In the present work, the long-term estimation of water losses
through evaporation from water surfaces of Nasser Lake
Reservoir performed based on the hydrometerological data
and the atmospheric elements by applying two methods: 1-
Bulk Areodydimic method and 2- water budget method.
4.1- Calculation of water losses by evaporation using Bulk
Areodydimic method.
This method depends on immediate measurements of the
factors and elements which affecting the evaporation losses,
such as air and water temperatures, wind speed, and relative
humidity. In this work, to estimate the amount of water lost by
evaporation from Nasser Lake using Bulk Areodydimic
method, many hydrometeorological and hydrogeological data
were collected from the 9 raft meteorological stations
(instrumented platform floating weather stations) installed
along the Nasser Lake, from the High Dam to the southern
borders of Egypt (Figure 1).
The 9 raft meteorological stations recorded daily relative
humidity (%), wind velocity at height 2 m above water surface
(m/sec). water temperature (°C), and the air temperature at 2
m above water surface. The meteorological data were
collected for the last 20 years from water year 1995/1996 to
2014/2015 to calculate E-values using this method through
applying the Equations (nos. 1 to 4) (Table 1 and Figure 2).
Many parameters were computed before calculating the E-
values as: a)- Saturated vapor pressure of air (ESA), b)-
Saturation vapor pressure (kpa) at water surface temperature
(es), and c)- Actual vapor pressure of the air (ea).
The E-values (Table 1) vary from year to anther and range
between 12.004 × 109 m
3 (calculated during 1995/1996) and
15.53 × 109 m
3 (estimated in 2007/2008) with an average of
13.62 × 109 m
3/ year. Along the study reservoir, the daily total
evaporation was best described as a function of the vapor
pressure difference between the water surface and atmosphere,
as well as it affected by the horizontal wind speed.
The relationship between the calculated values of water losses
by evaporation from Nasser Lake and the change in its water
level values from 1995 to 2015 shows a slightly direct relation
(Figure 3). The calculated evaporation loss values by applying
the Bulk Areodydimic method is changeable. The E-values
increase from 1995/1996 to 1998/1999 then start to decrease
till the water year 2005/2006. After that time, the evaporation
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losses increase to water year 2007/2008 then decrease again
(2009/2010), after that E-values change irregularly (up and
down) in recent years.
Fig. 1. Location map of the hydrometerological floating station along Nasser Lake
Comparing between the change of E-values in summer,
autumn, winter, and spring from water year 1995/1996 to
2014/2015 are shown in Figure (4). At the same year, the
water losses by evaporation from Nasser Lake are not
stable, but vary from month to other. Evaporation rates
show an attribute of annual cycle with highest values at
summer, where the air temperature at 2 m above water
surface (AT), the water temperature (WST), the saturated
vapor pressure of air (ESA), and the saturated vapor pressure
at water surface (es) at the study area have high values at
July, August, and September months. These parameters are
directly affected to the E-values.
Autumn and spring come after summer, in E-values, due to
present moderate values of the mentioned parameters.
Finally, the low E-values estimated in winter at January,
February, and March months because the previous
parameters have low values comparing with other months
along the same year.
0.40.60.81.01.21.41.61.8
AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN JUL
Evap
ora
tio
n (
10
9 )
Monthly evaporation loss (from 1995/1996 to 1999/2000)
1995/1996 1996/1997 1997/1998 1998/1999 1999/2000
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Fig. 2. Monthly average of water losses by evaporation for period from 1995 to 2015.
Table I
Water losses by evaporation (109m3) using hydrometerological data calculated by applying the Bulk Areodydimic method from 1995 to 2015.
1995-
1996
1996-
1997
1997-
1998
1998-
999
1999-
2000
2000-
2001
2001-
2002
2002-
2003
2003-
2004
2004-
2005
August 1.183 1.347 1.589 1.587 1.352 1.574 1.609 1.449 1.311 1.432
September 1.122 1.286 1.469 1.56 1.425 1.465 1.74 1.481 1.442 1.439
October 1.25 1.265 1.422 1.578 1.504 1.565 1.746 1.43 1.231 1.23
November 0.923 0.774 0.99 1.086 1.233 1.077 1.16 0.945 1.14 1.13
December 1.005 0.762 0.979 1.056 0.974 1.059 1.019 0.787 0.91 0.913
January 0.741 0.991 0.916 0.969 1.03 0.887 1.008 0.603 0.769 0.819
February 0.668 0.871 0.892 0.913 1.025 1.002 0.64 0.798 0.71 0.66
March 0.732 0.935 0.973 1.007 0.984 0.903 0.796 0.952 0.913 0.835
April 0.902 0.976 1.024 1.06 0.98 1.127 1.023 1.137 0.986 0.891
May 1.087 1.224 1.175 1.4 1.275 1.214 1.099 1.257 1.14 1.112
June 1.146 1.352 1.314 1.349 1.354 1.266 1.193 1.266 1.412 1.152
July 1.245 1.383 1.396 1.443 1.457 1.335 1.286 1.653 1.263 1.145
Minimum 0.668 0.762 0.892 0.913 0.974 0.887 0.64 0.603 0.71 0.66
Maximum 1.25 1.383 1.589 1.587 1.504 1.574 1.746 1.653 1.442 1.439
Average 1.001 1.097 1.178 1.251 1.216 1.206 1.193 1.147 1.102 1.063
Total 12.004 13.166 14.139 15.008 14.593 14.474 14.319 13.58 13.227 12.758
0.40.60.81.01.21.41.61.82.0
AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN JUL
Evap
ora
tio
n (
10
9)
Monthly evaporation loss (from 2000/2001 to 2004/2005)
2000/2001 2001/2002 2002/2003 2003/2004 2004/2005
0.40.60.81.01.21.41.61.82.0
AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN JUL
Evap
ora
tio
n (
10
9 )
Monthly evaporation loss (from 2005/2006 to 2009/2010)
2005/2006 2006/2007 2007/2008 2008/2009 2009/2010
0.40.60.81.01.21.41.6
AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN JUL
Evap
ora
tio
n (
10
9 )
Monthly evaporation loss (from 2010/2011 to 2014/2015)
2010/2011 2011/2012 2012/2013 2013/2014 2014/2015
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I J E N S
Table I
Continue.
2005-
2006
2006-
2007
2007-
2008
2008-
2009
2009-
2010
2010-
2011
2011-
2012
2012-
2013
2013-
2014
2014-
2015
August 0.966 1.355 1.628 1.468 1.49 1.361 1.217 1.35 1.338 1.377
September 0.978 1.433 1.836 1.753 0.96 1.433 1.11 1.47 1.337 1.345
October 1.011 1.674 1.363 1.725 0.78 1.305 1.337 1.37 1.185 1.303
November 0.908 1.294 1.628 1.041 1.18 1.156 1.088 1.31 1.106 1.155
December 0.912 1.115 1.119 0.557 0.86 1.249 0.909 1.16 0.884 0.947
January 0.93 0.853 0.899 0.886 0.53 1.076 0.805 0.77 0.732 0.813
February 0.849 0.686 0.863 0.723 0.57 0.657 0.748 0.79 0.905 0.698
March 1.025 0.957 0.978 0.802 0.89 1.067 0.858 0.79 0.958 0.881
April 1.05 1.038 1.029 1.178 0.98 0.963 0.93 0.98 1.152 1.006
May 1.169 1.103 1.155 1.139 1.19 1.236 1.082 1.137 1.17 1.157
June 1.203 1.19 1.417 1.542 1.19 1.312 0.994 1.205 1.277 1.249
July 1.205 1.246 1.615 1.649 1.5 1.366 1.075 1.391 1.309 1.396
Minimum 0.849 0.686 0.863 0.557 0.53 0.657 0.748 0.77 0.73 0.698
Maximum 1.205 1.674 1.836 1.753 1.5 1.433 1.337 1.47 1.34 1.396
Average 1.017 1.162 1.294 1.205 1.010 1.182 1.013 1.144 1.113 1.11
Total 12.206 13.944 15.53 14.463 12.12 14.181 12.153 13.723 13.36 13.328
Fig. 3. Relation between water losses by evaporation and lake water level.
Fig. 4. Comparing between the change of E-values in summer, autumn, winter, and spring.
4.2- Calculation of water losses by evaporation using water
budget method
All water balance equations are principally based on the
difference between water outflow and water inflow over a
period of time for the hydrologic system of a reservoir and
must equal the change in water storage. The water balance or
the hydrological budget of the Nasser Lake, as well as the
water losses by evaporation, can be calculated from different
parameters using Equation no. 8 (seepage loss from lake water
to adjacent Nubian aquifer, change in water storage, and
inflow of and outflow from the lake). The imaginary of water
budget of Nasser Lake reservoir is shown in Figure (5). This
method can be assessed for any period of time, for any of
hydrologic cycle subsystem, and for any basin area. It can
apply to check all storage and flow components involved with
quantitatively estimation. It can serve to calculate with
160
165
170
175
180
11.0
12.0
13.0
14.0
15.0
16.0
wa
ter
leve
l m
eva
po
ratio
n(1
09)
Evaporation loss (BCM) Lake water level
0.2
0.7
1.2
1.7
2.2
Evap
ora
tio
n (
10
9 )
Summer Autumn Winter Spring
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sufficient accuracy the one unknown component of the
balance equation, concerned that the other components are
known.
The discharge downstream through Aswan and High Dams
(Vout) and the surface water inflow arriving the Nasser Lake
reservoir (Vin) were measured by High and Aswan Dam
Authority. Diversions or seepage loss from lake water to
adjacent Nubian aquifer (109 m
3/year) were calculated from
[21]. The available hydrological data used to calculate the
losses from Nasser Lake reservoir by the water budget method
for the last 51 years from water year 1964/1965 till now
(2014/2015), i.e. after the construction of the High Dam
(1965-1971) and before forming Nasser Lake reservoir.
The water losses by evaporation from Nasser Lake which
calculated by the water balance method using Equation (no. 8)
are shown in Table (2) and Figure (6). The E-values vary from
0.29 (109 m
3) estimated in 1964/1965 to 20.89 (10
9 m
3)
calculated in 1975/1976 with an average of 8.701 (109
m3/year). The surface water inflow arriving the Nasser Lake
reservoir (Vin) reached its maximum in 1964/1965 and
1975/1976 (119.51 and 101.95 (109 m
3) respectively). The
minimum (Vin) is 41.45 (109 m
3) recorded in 1984/1985. The
average of (Vin) is 70.52 (109 m
3/year).
The change in water level values in Nasser Lake from
1964/1965 to 2014/2015 (Table 2) and the calculated values of
water losses by evaporation from lake at the same period of
time were used to determine the relationship between them
(Figure 6). It shows a slightly direct relation. It can be seen
that, the evaporation loss values from Nasser Lake as
calculated by this method is not consistent. Whereas, the water
losses by evaporation increase in the period from 1964/1965
to 1975/1976 then start to decrease till the water year
1987/1988. After that time, the evaporation losses increase
significantly to water year 1998/1999 then start to decrease
again in recent years.
This inconsistency in the evaporation losse values of Nasser
Lake as shown in Figures (6 and 7) is related to the annual
change of its water budget which is affected by many
hydrological parameters (seepage loss from lake water, the
change in water storage, and volume of water inflow of and
outflow from the lake reservoir). The annual change in water
storage in Nasser Lake reservoir (S) also considered as one
of the important component for assessing of the water budget
or estimation the water balance, as well as in calculating
values of the evaporation losses. It calculated using the
volume of water storage in the Lake every year for the last 51
years from 1964/1965 till now (Table 2). The average annual
change in water storage in Nasser Lake reservoir (S) is 2.04
(109m
3/year), while the minimum is -21.48 (10
9 m
3) calculated
in 1984/1985 and the maximum is 35.11 (109 m
3) detected in
1988/1989.
The relationship between the change of water storage in the
lake (S), water losses by evaporation (E) using this method,
and the inflow arriving the lake (Vin) were examined for the
last 51 years (Figure 7). It is a slightly direct relation between
the three variables along Nasser Lake reservoir.
Fig. 5. The imaginary of water budget of Nasser Lake reservoir.
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Fig. 6. Water losses by evaporation using water budget method and their relation with lake water level.
Fig. 7. Relationship between the water losses by evaporation (E), the volume of water inflow (Vin), and the change in the water storage (S) of the Lake (109
m3/year).
4.3- The percentages of water lost by evaporation
4.3.1- E-values relative to water storage in the lake
It is necessary to know the percentage of the water storage
in the Nasser Lake reservoir (fresh and renewable water
bank of Egypt) relative to water loss by evaporation as a
main component for determination the water budget of
Egypt. The estimated percentage of the water storage in the
lake relative to water lost by evaporation were examined as
shown in Figure (8). The maximum water storage in the lake
reaches 125.72 billion cubic meters recorded in 2000/2001,
while the minimum value is 3.33 (109 m
3) estimated in
1964/1965 and contains average 85.52 billion cubic meters
from fresh water (Table 2). The obtained percentage values
vary from 3.55% (recorded during year 1992/1993) to
20.26% (appeared during year 1965/1966), with an average
of 10.94% (Table 2).
4.3.2- Percentage of E-values relative to the water income
to the lake
Also it is very important to calculate the percentage of water
loss by evaporation relative to water income to the lake
(Figure 9). The percentage of evaporation loss relative to Vin
or total of (E + Vout + S + D) were calculated from
equation 9 or 10 (Table 2).
…(9)
…………..….(10)
The average of this percentage is 12.65% and the maximum
percentage value is 21.18% detected at 1976/1977 while the
minimum values recorded at the first three years from
forming Nasser Lake reservoir.
110
130
150
170
0
5
10
15
20
25
wat
el le
vel
m
Evap
ora
tio
n L
oss
es (
BC
M)
Evaporation loss Water level Linear ( Evaporation loss)
0
5
10
15
20
25
-40
-20
0
20
40
60
80
100
120
140
Evap
ora
tio
n L
oss
es (
BC
M)
Vin
an
d C
han
ge in
wat
er s
tora
ge (
BC
M)
Inflow arriving the Lake Change in water storage of the Lake Evaporation loss
International Journal of Civil & Environmental Engineering IJCEE-IJENS Vol: 16 No: 05 21
160905-7878-IJCEE-IJENS © October 2016 IJENS
I J E N S
Fig. 8. Percentage of water lost by evaporation relative to the water storage in the lake
Table II
Water losses by evaporation (109 m3) from Nasser Lake reservoir along period of time from 1964/1965 to 2014/2015 as calculated by the water budget method.
Water year
Flow
arriving
the Lake
(109 m
3)
Water
storage in
the Lake
(109 m
3)
Change
of water
storage in
the Lake
(109 m
3)
Discharge
downstre
am from
HAD
(109 m
3)
Nasser
Lake
water
level (m)
Water
seepage
loss
(109 m
3)
Water
losses by evaporation
(109 m
3)
Percent of evaporation
loss/total
Vin or
total Vout
Percent of evaporation
loss/water
storage in
the Lake
1964/1965 119.51 3.33 2.42 116.76 117.89 0.044 0.29 0.239% 8.58%
1965/1966 81.06 4.60 1.27 78.80 119.02 0.058 0.93 1.150% 20.26%
1966/1967 70.88 14.54 9.94 58.77 133.73 0.058 2.11 2.98% 14.52%
1967/1968 92.84 29.26 14.72 72.17 133.73 0.062 5.89 6.34% 20.12%
1968/1969 71.06 39.97 10.71 53.12 145.54 0.052 7.18 10.10% 17.96%
1969/1970 70.36 46.43 6.46 54.85 151.1 0.052 9.00 12.79% 19.38%
1970/1971 79.38 61.36 14.93 55.36 153.83 0.060 9.03 11.38% 14.72%
1971/1972 77.49 69.82 8.46 55.96 159.68 0.059 13.01 16.79% 18.63%
1972/1973 52.71 57.24 -12.58 55.24 162.49 0.062 9.99 18.95% 17.45%
1973/1974 75.88 66.70 9.46 56.30 158.2 0.062 10.06 13.25% 15.08%
1974/1975 81.76 80.60 13.90 55.80 161.71 0.065 12.00 14.67% 14.88%
1975/1976 101.95 108.37 27.77 53.22 165.6 0.068 20.89 20.49% 19.28%
1976/1977 67.10 105.05 -3.32 56.14 172.42 0.067 14.21 21.18% 13.53%
1977/1978 76.41 108.84 3.79 61.78 171.7 0.061 10.78 14.11% 9.90%
1978/1979 72.70 111.30 2.46 59.72 172.52 0.057 10.46 14.39% 9.40%
1979/1980 55.93 103.12 -8.18 56.71 173.04 0.049 7.35 13.14% 7.13%
1980/1981 66.01 102.49 -0.63 56.60 171.27 0.046 9.99 15.14% 9.75%
1981/1982 67.34 99.15 -3.34 59.00 171.13 0.041 11.64 17.28% 11.74%
1982/1983 50.09 81.03 -18.12 58.73 170.36 0.035 9.45 18.86% 11.66%
1983/1984 57.87 72.94 -8.09 57.06 165.87 0.039 8.86 15.31% 12.15%
1984/1985 41.45 51.46 -21.48 56.28 163.6 0.030 6.62 15.97% 12.86%
1985/1986 63.76 53.70 2.24 55.52 156.37 0.031 5.97 9.36% 11.12%
1986/1987 52.83 47.26 -6.44 55.27 157.23 0.026 3.97 7.52% 8.41%
1987/1988 48.26 40.67 -6.59 52.89 154.65 0.032 1.93 4.00% 4.74%
1988/1989 96.36 75.78 35.11 53.39 151.7 0.036 7.82 8.12% 10.32%
1989/1990 59.96 73.52 -2.26 54.00 164.41 0.042 8.18 13.64% 11.12%
1990/1991 58.03 69.52 -4.00 53.80 163.77 0.034 8.20 14.12% 11.79%
1991/1992 64.93 74.23 4.71 54.25 162.5 0.028 5.94 9.15% 8.01%
1992/1993 71.26 87.06 12.83 55.30 163.98 0.040 3.09 4.34% 3.55%
1993/1994 74.75 96.05 8.99 55.47 167.45 0.040 10.25 13.71% 10.67%
1994/1995 77.68 108.00 11.95 55.50 169.64 0.041 10.19 13.12% 9.43%
1995/1996 65.54 109.97 1.97 55.50 172.34 0.045 8.03 12.24% 7.30%
0%
5%
10%
15%
20%
25%
0
50
100
150
E% r
elat
ive
to w
ater
sto
rage
V. W
ater
sto
rage
(B
CM
)
Water storage in the Lake (BCM) E% relative to water storage in the lake
International Journal of Civil & Environmental Engineering IJCEE-IJENS Vol: 16 No: 05 22
160905-7878-IJCEE-IJENS © October 2016 IJENS
I J E N S
1996/1997 78.93 123.80 13.83 55.97 172.76 0.048 9.08 11.51% 7.34%
1997/1998 61.86 120.00 -3.80 55.58 175.48 0.044 10.04 16.22% 8.36%
1998/1999 88.26 120.00 0.00 71.44 174.75 0.046 16.77 19.01% 13.98%
1999/2000 83.13 125.41 5.41 67.06 174.75 0.042 10.62 12.77% 8.47%
2000/2001 73.72 125.72 0.31 61.98 175.79 0.041 11.39 15.45% 9.06%
2001/2002 76.00 124.92 -0.80 68.13 175.85 0.053 8.62 11.34% 6.90%
2002/2003 65.54 122.03 -2.89 57.14 175.7 0.045 11.25 17.16% 9.22%
2003/2004 49.15 106.68 -15.35 57.71 175.14 0.042 6.75 13.73% 6.33%
2004/2005 54.61 95.84 -10.84 56.95 172.06 0.046 8.45 15.48% 8.82%
2005/2006 60.51 91.87 -3.97 57.50 169.59 0.045 6.93 11.46% 7.55%
2006/2007 88.03 113.20 21.33 59.09 168.65 0.055 7.55 8.58% 6.67%
2007/2008 84.15 120.26 7.06 68.86 173.42 0.053 8.18 9.72% 6.80%
2008/2009 68.89 112.60 -7.66 62.79 174.8 0.053 13.71 19.90% 12.17%
2009/2010 52.97 96.70 -15.90 58.04 173.3 0.050 10.78 20.35% 11.15%
2010/2011 70.65 101.70 5.00 58.23 169.79 0.050 7.37 10.43% 7.25%
2011/2012 59.32 92.73 -8.97 59.14 174.14 0.042 9.11 15.35% 9.82%
2012/2013 80.25 104.74 12.01 59.95 173.4 0.046 8.24 10.27% 7.87%
2013/2014 67.98 105.30 0.56 60.42 173.1 0.048 6.95 10.22% 6.60%
2014/2015 69.37 104.79 -0.52 61.17 170.4 0.049 8.67 12.50% 8.27%
Fig. 9. Percentage of water lost by evaporation relative to the water income to the lake
5- CONCLUSIONS
long-term estimation of water losses through evaporation from
water surfaces of Nasser Lake Reservoir performed by
applying two methods. Bulk Areodydimic method used to
estimate evaporation losses the last 20 years from 1995/1996
to 2014/2015 through collecting hydrometeorological and
hydrogeological data from 9 raft meteorological stations
installed along the Lake, from the High Dam to the southern
borders of Egypt. The rate of evaporation using this method is
13.62 × 109 m
3/ year and evaporation losses vary from 12.004
× 109 m
3 (calculated during 1995/1996) to 15.53 × 10
9 m
3
(estimated in 2007/2008). At the same year, the water losses
by evaporation are not stable and show highest values at
summer, where (AT), (WST), (ESA), and (es) have high values
at July, August, and September months.
The water budget method applied to calculate the evaporation
losses for the last 51 years from 1964/1965 till now
(2014/2015). The E-values as calculated by this method vary
from 0.29 (109 m
3) estimated in 1964/1965 to 20.89 (10
9 m
3)
calculated in 1975/1976 with an average of 8.701 (109
m3/year). The relationship between water losses by
evaporation and the change in water level of the lake shows a
slightly direct relation with some changes and fluctuations.
The relationship between the change of water storage in the
lake (S), the evaporation losses (E) using water budget
method, and the inflow arriving the lake (Vin) were examined
and show a slightly direct relation between the three variables.
The estimated percentage of the water storage in the lake
relative to water lost by evaporation were examined and its
values vary from 3.55% (recorded in 1992/1993) to 20.26%
(detected in 1965/1966), with an average of 10.94%. Also, the
percentage of evaporation losses relative to water income to
the lake calculate. The average of this percentage is 12.65%
and the maximum value is 21.18% detected at 1976/1977
while the minimum values recorded at the first three years
from forming Nasser Lake reservoir.
6- ACKNOWLEDGMENT
The authors would like to acknowledge and very grateful to
0%
5%
10%
15%
20%
25%
0
20
40
60
80
100
120
140
E% r
elat
ive
to w
ater
inco
me
Flo
w A
rriv
ing
the
Lake
(B
CM
)
Flow Arriving the Lake(BCM) E% relative to water income to the lake
International Journal of Civil & Environmental Engineering IJCEE-IJENS Vol: 16 No: 05 23
160905-7878-IJCEE-IJENS © October 2016 IJENS
I J E N S
High and Aswan Dams Authority for providing
meteorological data and their cooperation throughout the
research.
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