Long-Term Estimation of Water Losses Through Evaporation ...ijens.org/Vol_16_I_05/160905-7878-IJCEE-IJENS.pdf · through evaporation from an open water surfaces of Aswan High Dam

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

mailto:[email protected]



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



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



I J E N S

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



I J E N S

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


Evap

ora

tio

n (

10

9)


2000/2001 2001/2002 2002/2003 2003/2004 2004/2005

0.40.60.81.01.21.41.61.82.0


Evap

ora

tio

n (

10

9 )


2005/2006 2006/2007 2007/2008 2008/2009 2009/2010

0.40.60.81.01.21.41.6


Evap

ora

tio

n (

10

9 )


2010/2011 2011/2012 2012/2013 2013/2014 2014/2015



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



I J E N S

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.



I J E N S

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



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



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



I J E N S

High and Aswan Dams Authority for providing

meteorological data and their cooperation throughout the

research.

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Long-Term Estimation of Water Losses Through Evaporation ...ijens.org/Vol_16_I_05/160905-7878-IJCEE-IJENS.pdf · through evaporation from an open water surfaces of Aswan High Dam