the use of remote sensing and GIS for esimation of water loss from sharan lakes

Journal of African Earth Sciences xxx (2008) xxx–xxx

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Journal of African Earth Sciences

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The use of remote sensing and GIS for the estimation of water lossfrom Tushka lakes, southwestern desert, Egypt

Mohamed A. Bastawesy b, Fikry I. Khalaf a,*, Sayed M. Arafat b

a Faculty of Science, Port-Said, Suez Canal University, Egyptb National Authority for Remote Sensing and Space Sciences, Cairo, Egypt

a r t i c l e i n f o

Article history:Received 13 June 2007Received in revised form 11 March 2008Accepted 13 March 2008Available online xxxx

Keywords:Tushka lakesGISRemote sensingDEM

1464-343X/$ - see front matter � 2008 Elsevier Ltd. Adoi:10.1016/j.jafrearsci.2008.03.006

* Corresponding author. Tel.: +20 122472373; fax:E-mail address: [email protected] (F.I. Kha

Please cite this article in press as: BastaweSci. (2008), doi:10.1016/j.jafrearsci.2008.0

a b s t r a c t

As a result of the spill-over of the excess water from lake Nasser, the great reservoir formed by the AswanHigh Dam on the Nile, the Tushka lakes came into being within natural geological depressions in thesoutheastern part of the western desert of Egypt. By the end of 1998, the water of river Nile had enteredTushka depressions for the first time, once lake Nasser’s water level had exceeded 178 m above the meansea level. Intermittently, water continued to discharge into the depressions until the end of 2001 formingfour lakes; however, the lakes began to shrink because of the inconsistency of flooding levels.The behavior of hydrological regime of these lakes during the period 2002–2006 was assessed using anintegration of remote sensing and GIS techniques, which found that the total surface area of the lakes haddiminished from 1591 km2 to 937 km2, and their water volumes reduced from 25.26 billion m3 to12.67 billion m3. The study further revealed that the levels of the lakes surfaces had lowered by approx-imately 10 m over the course of those four years. This significant rate and volume of water loss can beattributed to both evaporation and infiltration. A comparison between the average annual evaporationrate at Tushka lakes and the calculated water loss revealed that most of Tushka lakes’ water is lostthrough evaporation with a very limited amount being percolated to the ground water. Assuming thatno further over flooding of the Nile will occur, these lakes will start to vanish in 2012 and disappear com-pletely by 2020, which will result in significant environmental impacts.

� 2008 Elsevier Ltd. All rights reserved.

1. Introduction

To protect the Aswan High Dam, the water level containedwithin its reservoir – lake Nasser – must not exceed 178 m abovethe sea level (a.m.s.l.), therefore, a 25 km long canal (spill-over ca-nal) was constructed back in 1978, on the western shore of lakeNasser (Khor Tushka), to direct the excess water, i.e. higher than178 m a.m.s.l., from lake Nasser to Tushka depression, making ita natural flood diversion basin. The Tushka lakes represent, seenfrom space, one of the most visible man-made changes on theearth’s surface (Fig. 1).

By November 1998, initial observations of satellite images re-vealed that the easternmost lake was increasing in size, by late1999, three additional lakes had formed in succession in the west-ward direction, with the westernmost lake forming sometime be-tween September 2000 and March 2001 (Fig. 2). Henceforth,within this paper, we will refer to these lakes, from east to westas L1, L2, L3 and L4.

Generally, with the changes in annual rainfall on the upstreamNile, it was found that the extent of these lakes fluctuated thus

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+20 66 3341303.laf).

sy, M.A. et al., The use of rem3.006

impacting the future development of the surrounding region. Afterthe excessive initial flooding in November 1998, surplus water in-flow to the Tushka depression was sporadic, and gradually came toa stop by the end of 2001. Since then the gradual decrease in thesurface and depth extents of the lakes became obvious. The de-crease was also manifested by the exposure of extensive dried wet-lands and sabkhas surrounding the lakes shorelines (Fig. 3).

Due to the lack of field monitoring of the lakes’ water levels, re-mote sensing represent a useful and efficient alternative techniqueand remote sensing images have been increasingly used to monitorand assess ongoing dynamic changes in large surface water bodieswithin dry lands and can provide useful estimates of the lake’swater budgets as well as annual rates of water loss (Drake and Bry-ant, 1994; Bryant, 1999; Bryant and Rainey, 2002; Castaneda et al.,2005; French et al., 2006). The use of this approach has been drivenby the increased availability of multi-temporal high and moderate-resolution satellite data, during the past three decades.

The main objective of this paper is to estimate the rate and theextent of water loss from the Tushka lakes during the period 2002–2006 and predict approximately their potential changes over thenext 10 years. In addition, changes in the aerial extent and the vol-ume of water within these lakes are further discussed and their po-tential environmental impacts are assessed.

ote sensing and GIS for the estimation of water loss ..., J. Afr. Earth

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Fig. 1. Location map of the Tushka lakes.

2 M.A. Bastawesy et al. / Journal of African Earth Sciences xxx (2008) xxx–xxx

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2. Study area

The Tushka depression is located in the southwestern desert ofEgypt, approximately at 250 km southwest of Aswan, between lat-itudes 22�300–23�450 N and longitudes 30�00–31�300 E (Fig. 1). Untilfairly recently, little has been published on the physiography ofthis remote and desolated area, however, since the constructionof the Aswan High Dam, the interest of geologists and hydrogeolo-gists has been aroused, inciting them to study the area expected tobe flooded by lake Nasser waters (Issawi, 1971, 1978; El Ramly,1972; El Shazly et al., 1977; Klitzch, 1978, 1984; Klitzch and Le-jal-Nicol, 1984; Kim and Sultan, 2002). Recently, the Environmentand Climate Research Institute of the Egyptian Water ResearchCenter carried out an integrated environmental assessment of thenewly developed Tushka lakes (Environment and Climate ResearchInstitute, 2007).

2.1. Climate

The Tushka area is located within the hyper-arid zone whereprecipitation occurs once every two or three decades. Data ob-tained from the Tropical Rainfall Measuring Mission (TRMM) showthat the Tushka area has received less than 20 mm of total rainfallfrom September 1999 to September 2006 (Fig. 4). This area is char-acterized by very hot summers and cold winters and the air tem-perature ranges in summer between 49.5 �C and 27.3 �C and inwinter between 30 �C and 15 �C, while relative humidity ranges be-tween 43% and 18% in summer and between 43% and 10% in winter(Egyptian Meteorological Authority, 1996). Meteorological mea-surements taken within the Tushka area, during 2006, revealedthat the monthly average air temperature measured at 2 m abovethe Tushka lakes’ water surface, ranges between 31.4 �C and32.9 �C in summer (August), while in winter (January) it fluctuatedbetween 14.1 �C and 20.7 �C (Table 1). The monthly mean of rela-tive humidity ranges between 32% and 58%. The monthly averageof the rate of evaporation, as measured during the period 2003–2005, reached between 115 mm in winter and 300 mm in summerwith an overall average of 189.7 mm per month (Table 2) (Environ-ment and Climate Research Institute, 2007).

2.2. Geomorphology

The surface of the Tushka depression is nearly flat in its easternside and is interrupted with sand dunes and low hills in its western

Please cite this article in press as: Bastawesy, M.A. et al., The use of remSci. (2008), doi:10.1016/j.jafrearsci.2008.03.006

part (El Shazly et al., 1977). The depression is bordered at the northby Sinn El Kaddab Eocene limestone plateau and at the south bythe Nubian pediplain. The border of the depression nearly con-forms to contour line 200 m a.m.s.l. The Sinn El Kaddab plateaurises several hundred meters a.m.s.l. (+400 m) and is encircled byseveral small structural scarps which form a conspicuous topo-graphic feature and are parallel to the dominant regional E–Wfaulting system. Several rock-cut pediments surround the depres-sion, and from wide flat terraces stretching from the Sinn El Kad-dab scarp foot and extending for several kilometers with a gentleslope towards the depression.

The Nubian pediplain is an extensive erosional surface with avery gentle slope towards the north. Individual conical and flattopped hills are commonly scattered over this pediplain. A pro-nounced extensive belt of barchan-type sand dunes crosses thewestern part of the depression in a N–S direction.

The area is dissected by a network of drainage lines, partiallymasked due to the recent aridity and the active aeolian processes.However, well marked drainage occurs in the eastern part of thearea and flows eastwards to lake Nasser (e.g. wadi kurkur, wadikalabsha, and wadi Tushka). Using Shuttle Radar Topography Mis-sion (SRTM) data, Ghoneim and El-Baz (2007) delineated the an-cient Tushka mega-watershed, which is presently covered bydesert sand surface, and they came to the conclusion that the Tush-ka basin is a closed hydrological system independent of the Nilehydro-system.

2.3. Geology

The exposed rock units in Tushka area extend from PrecambrianEra to Quaternary Era (El Ramly, 1972). However, the depression ismostly underlied by the impervious Paleocene Esna Shale (El Sha-zly et al., 1977). The Precambrian is represented by low-lying expo-sures of the basement rocks which are unconformably overlain byPalaeozoic and Mesozoic successions. The lower part of these suc-cessions is made of undifferentiated conglomerate, sandstone andshale (Gilf Formation), while the middle part is made of coarsepebbly sandstone (Abu Simbel Formation), fine sandstone andshale (Abu Ballas Formation), and the sandstone of El Borg Forma-tion. All are Upper Jurassic–Lower Cretaceous age. The upper partof the succession is formed of interfingering sandstone and mud-stone (Nubia Formation), which extensively dominates the surfacegeology of the study area, and represents the main ground wateraquifer. It attains variable thickness, ranging from few meters to


Fig. 2. An enhanced Landsat mosaics showing the evolution of Tushka lakes during the period from 1998 to 2000. Notice the number of the lakes.

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300 m. The Nubia is overlain by karstified Tertiary limestone (Kor-kor, Garra and Dungul), other few are locally capped by Dakhlashale and clay of Upper Cretaceous age (Kim and Sultan, 2002).

The Tushka depression lies within the seismically active NubianSwell, where faulting is pronounced throughout the entire studyarea. Two major fault systems cut across the area, trending east–west and north–south. The former, the Kalabsha, is an active faultsystem.

2.4. Ground water

The Palaeozoic and Mesozoic successions form productive aqui-fers and contain fossil ground water that was recharged during wetpalaeoclimatic periods (Aly et al., 1993; RIGWA, 1998). The regio-nal ground water flow is from southwest to northeast (Ball, 1927).


Six ground water basins occur within and around Tushka depres-sions, these are Nubia, Plateau, El Shab, El Kharga, Umm Shagher,and El Dakhla (Environment and Climate Research Institute,2007). However, the two main ground water basins in the areaare Nubia in the east and Dakhla in the west. Kim and Sultan(2002) have indicated that the surface water level of lake Nasseris generally higher than the ground water level near the lake,and they have estimated a net recharge from lake Nasser in theeastern aquifers as 5.3 � 1010 m3 during the period 1970–2000.

The salinity of the ground water generally increases from<1000 ppm in the east to >3000 ppm in the west. Ground waterwell monitoring during the period November 1999–November2000 indicated that the level of ground water within the Tushkalakes’ area had not been changed, while the area close to lake Nas-ser has changed significantly (Environment and Climate Research


Fig. 3. Field photo shows the dried up fringes partially covered by salt crust, lake 4.

Table 1The average monthly of air temperature (�C) in Tushka area (Environment andClimate Research Institute, 2007)

1999 2000 2001 2002 2003 2004 2005

January 17.9 16.8 20.7 14.1 16.3 16.9February 17.7 16.6 16.8 18.7 17.2 19.9March 21.4 19.1 22.7 21.8 21.6April 24.3 25.9 26.3 25.6 25.6 25.7 26.1May 29.3 28.3 28.8 28.1 29.9 30.1 28.8June 30.9 30.6 29.6 30.5 31.7 31.0July 32.0 32.4 32.1 32.8 32.2 32.7 32.1August 31.4 32.9 32.8 32.9 32.0 32.5September 30.4 30.7 30.9 30.6 29.6 30.5October 27.7 25.3 25.8 27.8 28.0 27.5November 22.7 21.5 21.1 22.8 21.6December 19.1 17.5 17.2 17.5


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Institute, 2007). This supports the aforementioned Kim and Sultan(2002) conclusion and suggests that the ground water aquiferswithin Tushka depression are isolated.

3. Data and methods

Water loss modeling for the Tushka lakes required various typesof data from different sources. Three ASTER images dated February2002 and four SPOT-4 images for February 2006 were acquired andprocessed to delineate lakes surface areas. The images were recti-fied into Universal Trans-Mercator (UTM), zone 36.

Since the reflectance of water is nearly zero in the reflectiveinfrared bands, and the majority of land covers are of higher reflec-tance, the images histograms of the study area ordinarily display adouble peaked curve. Therefore, the dual histogram thresholdmethod was used to discriminate between the lakes and surround-

Fig. 4. Map shows the TRMM total rainfall for the Tushka area from Septe


ings (Moore, 2000). Uncertainty may arise as there are mixed andtransitional zone pixels between land and water residing betweenthe peaks, and it is difficult to find the exact value of threshold.Nonetheless, the threshold was fixed to all images in order to min-imize the errors in the lakes surface area estimation at the differentgiven dates (Fig. 5).

Topographic maps of scale 1:100,000, that were surveyed priorto the formation of the lakes, were digitized and a digital elevationmodel (DEM) was generated to simulate lakes bed bottom topogra-phy and surroundings (Fig. 6). The DEM is of 20 m resolution andwas interpolated in ArcInfo Topogrid’s module using digitized con-tours, drainage networks and spot heights layers. The choice ofdata sources and generation techniques is very critical to the qual-ity of a DEM (Weibel and Heller, 1991; Burrough and McDonnell,1998).

The quality and reliability of the produced DEM was examinedboth visually and analytically. Using available field measurementsof lake level a logical query on the DEM was undertaken to derivelake surface areas and configurations at given elevations (a.m.s.l.).

mber 1999 to September 2006 (source: www.giovanni.gsfc.nasa.gov).


http://www.giovanni.gsfc.nasa.gov

Table 2The average monthly pan evaporation (mm) during the period September 2003–December 2005 (Environment and Climate Research Institute, 2007)

Month Rate of evaporation

Year 2003September 300October 270November 225December 195

Year 2004January 165February 150March 180April 195may 220June 230July 280August 300

Year 2005January 125February 115March 114April 144may 162June 152July 107August 151September 221October 230November 187December 126


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The DEM-simulated lakes were then directly overlaid on theircounterparts from the co-incident 2002 and 2006 satellite images.A high degree of coincidence was observed between the simulatedand observed lakes surface areas and configurations (Fig. 7). Vol-umes of the stored water in the lakes at given levels were calcu-lated from the DEM using mathematical functions from the GridModule in Arc Info.

4. Results

Analysis of the DEM revealed that the lakes surfaces at eachstage equated to different elevation levels, where the levels of lakesL1, L2, L3, and L4 in 2002 were at 153, 151, 141, and 140 m a.m.s.l.,respectively, and were reduced in 2006 to 143 m for L1, 131 m forL3 and 130 m for L4. However, the rate of drop in the lake surfacelevels during the period 2002–2006 was fairly consistent; and wasrecorded as approximately 10 m over the 4 years. Therefore, thecalculated annual water level drop was 2.5 m.

The reduction in the water level of the lakes was accompaniedby the appearance of large sabkha fringing the four lakes. The esti-mated total surface area of Tushka lakes in 2002 was 1591 km2 dis-tributed as follows: L1 = 449 km2, L2 = 20 km2, L3 = 265 km2 andL4 = 807 km2. In 2006, the surface areas of these lakes were greatlyreduced and reached a total of 937 km2. At this stage, L2 was com-pletely dried up, and surface areas of L1, L3 and L4 were estimatedat 286 km2, 101 km2, and 550 km2, respectively (Table 3).

The spatial analysis functions on bathymetry DEM were used inthe summation of depths within each lake when its surface is stand-ing at different elevation levels. For example, L1 surface area in 2002was represented by 1,220,500 pixels that range in depths up to32.6 m, and the estimated water volume was 6.78 � 109 m3. Itwas reduced in 2006, where it was represented by 715,000 pixelsand the maximum depth reached approximately 22 .6 m, and there-fore, the stored water volumes were greatly reduced to 3.45 � 109

m3. Overall, the calculated water volumes in L1, L2, L3, and L4 forthe year 2002 were 6.78 � 109, 0.044 � 109, 2.21 � 109, and


16.23 � 109 m3, and were 3.45 � 109, zero, 0.44 � 109, and8.78 � 109 for the year 2006 m3, respectively (Table 3).

Assuming that there will be no further flooding and the annualrate of drop in the Tushka lakes surface level will be maintained at2.5 m, a GIS-based scenario was established to predict the futuresurface areas, configurations and storage of these lakes. Fig. 8 showsthe DEM simulation of L1 in 2006 in addition to the prediction of itsfuture shape and depths. Overall, it is predicted that L3 (the middleone), L1 (the eastern one), and L4 (the western one) will be dried upin years 2012, 2014 and 2020, respectively (Figs. 9 and 10).

5. Discussion

The Tushka spillway canal and the lakes within Tushka depres-sion represent a system that was designed to save the Aswan HighDam and the downstream of the Nile river during periods of theriver flooding. These man-made lakes represent storage of a hugeamount of fresh water which has subsequently been subjected tovery high rates of evaporation. The massive floods of the Nile riverduring 1998, 1999, 2000 and 2001 resulted in their gradual nour-ishment. Thereafter, the cessation of water flooding from lake Nas-ser resulted in the shrinking of the lakes’ area.

Satellite images acquired in 2002 and 2006 along with bathym-etry DEM generated from topographic maps surveyed prior to thelakes existence were used to delineate the changes in their surfaceareas and water volumes. An annual rate of water loss is estimatedat 2.5 m for the period 2002–2006, and this has resulted in thereduction of the Tushka lakes’ areas from 1591 km2 to 937 km2

and the stored water volumes from 25.26 � 109 m3 to12.67 � 109 m3. Therefore, the amount of the water lost during thisis about 12.59 � 109 m3.

Our estimate of water volumes in the Tushka lakes is much differ-ent from other earlier work. For example, Yan et al. (2003) estimatedthat a total of 8.47 � 109 m3 of water has been diverted from lakeNasser to the Tushka depression from 1998 to 2001. They con-structed a DEM from Stereo ASTER level 1 scenes, but ASTER waslaunched in December 1999, and this means that considerableamount of water was already in the Tushka lakes (Fig. 2) and the AS-TER-DEM certainly underestimate the Tushka lakes water budget.

Since there is no human exploitation of water from Tushkalakes (with the exception of very minimal activity around L1),the estimated rate and volume of water loss can be attributed toboth evaporation and/or infiltration. Field measurements of theaverage monthly evaporation rate during the period September2003–December 2005 suggest that the annual average water lossby evaporation may be estimated as 2.276 m, (i.e. a total of9.104 m in the four years between 2002 and 2006). These measure-ments are correlatable with those of Sadek et al. (1997), who re-ported annual evaporation rates that vary from 2.1 m to 2.6 m atthe Aswan High Dam reservoir.

This amount represents approximately 91% of the total amountof the water lost during 2002–2006 as calculated by the differencein the water level (10 m in the same four years). Therefore, the ex-pected amount of water to be lost by evaporation is estimated at91% of the total water loss. This suggests that less than 10% ofthe lost water (less than 1.25 � 109 m3) may have been rechargedto the ground water aquifer underlying the lakes. The nature of thelakes bed, impervious shale, could be responsible for such limitedrecharge. Such conclusion is partially supported by the rechargepattern of the ground water aquifers in the study area.

It should also be noted that the dense vegetation cover of thewetlands that surround these lakes are responsible for some of thiswater loss by the evapotranspiration. Therefore, the amount ofwater that may have been infiltrated to the ground water aquiferscould be far less than the aforementioned estimation.


Fig. 6. DEM of the Tushka area prior to the formation of lakes.

Fig. 5. Tushka lakes surface area change from 2002 (top) to 2006 (bottom).


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Please cite this article in press as: Bastawesy, M.A. et al., The use of remote sensing and GIS for the estimation of water loss ..., J. Afr. EarthSci. (2008), doi:10.1016/j.jafrearsci.2008.03.006

Fig. 7. Lake 1 image in 2002 (left) and the DEM-simulated configuration and bathymetry for the lake in 2002 (right).

Table 3Changes in area (km2) and water volume (109 m3) on the Tushka lakes during theperiod 2000–2006

Area (KM2) Volume (billion m3)

2002 2006 2002 2006

Lake 1 499 286 6.78 3.45Lake 2 20 0 0.044 0Lake 3 265 101 2.21 0.44Lake 4 807 550 16.23 8.78Total 1591 937 25.264 12.67

Fig. 8. Estimated shapes and bathymetry for L1 in

0

2

4

6

8

10

12

14

16

18

2002 2006 2008 2010 2012 2014 2018 2020

Year

Vo

lum

e (1

09 m3 )

Lake 1

Lake 3

Lake 4

Fig. 9. Stored water volumes derived using data sets between 2002 and 2006.


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These results are very alarming, especially when consideringthe near future predication of the lakes behavior, they will startto vanish staring the year 2012 and will be completely disappearedin the year 2020, assuming that no over flooding of the Nile occurs.Therefore, a valuable water resource in a hyper-arid region is beinglost without any action to make full use of it except very limitedagricultural and fish culture activities on the retreating shores ofthe eastern lake. It is hoped that the results of the present studymay encourage decision makers to think of a rational measure tosave this valuable resource. The present work demonstrates that

2006, 2010 and 2014 (left, middle and right).

0

100

200

300

400

500

600

700

800

900

2002 2006 2008 2010 2012 2014 2018 2020

Year

Are

a (k

m2 )

Lake 1Lake 3Lake 4

Fig. 10. Prediction of lakes surface area using data sets between 2002 and 2006.



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the use of satellite data and GIS techniques in the prediction of thetemporal changes in the quantity of these water masses is an effi-cient tool, especially when the remote location and the extensivearea coverage of these lakes are considered.

However, it should be noted that some limitations wereencountered in the development of the designed GIS model. Asthe DEM was interpolated from topographic maps contoured at10 m interval and with scattered elevation points, it is not surpris-ing that extracting the lake boundaries will not exactly matchthese portrayed from satellite images. This little discrepancy canbe attributed to the density, magnitude and frequency of the sam-pled elevation values, i.e. contours, and spot heights recorded onthe topographic map. The vertical accuracy of the DEM is measuredby integer meters, since the spot heights and contours values areintegers. On the other hand, the lake level is regularly measuredin the field, with an accuracy of centimeters by the Egyptian WaterResources Research Center expeditions. However, this inevitableand minor discrepancy between lake surface area and level estima-tion from DEM and satellite images is slightly influencing the anal-ysis. The coincidence of lake surface areas simulation from theDEM and their counterparts on satellite images exceeds 98% whenthe DEM-estimated lake elevation levels errors are less than 1 mfrom the field measurements.

The continuous loss of water from these lakes by evaporationwill have significant environmental impacts, among these are totalloss of wetland ecosystem, increase in the lake water salinity, dete-rioration of the fisheries industry, and the occurrence of dust stormsthat developed within these lakes; the dried bottom sediments andthe associated salt crust will be subjected to the wind action.

About 652 km2 of wetland ecosystem that use to fringe the lakeshas been dried up and its dense vegetation cover with the associatedfauna was lost. The salinity of the lake’s water has drastically in-creased; the concentration of the total dissolved solids is more than1000 ppm (Environment and Climate Research Institute, 2007),while that of lake Nasser is about 142 ppm. This may adversely im-pact the aquatic fauna and flora as well as the fringing wetlands.

The occurrence of these huge lakes has encouraged investors todevelop a fisheries industry, and considerable number of fishermenmigrated from the coastal lagoons of the Nile Delta to these lakes.The authors have visited several locations on the shores of theselakes where fish catch was landed. The shrinkage of the lakes areaand the increase of their water salinity may adversely impact thisindustry.

The bottom sediments of the dried wetland and the associatedsalt crust, which covers vast areas, will be subjected to the windaction. This will result in the deflation of the fine grained sedimentand the abundant occurrence of dust storms by the active north-westerly winds, while the sand fraction will be saltated and formmigrating sand dunes and sand sheets. The deflation of the finegrained sediment will increase the suspended particulates in thearea atmosphere and may eventually degrade the atmosphericquality within the south Valley Development Project area whichis located to the east of the lakes. This may also have adverse im-pacts on humans, animals and plants due to the transport of thesalt particulates. These salt particulates may cause corrosion prob-lem to the metal structures.

6. Conclusion

Remote sensing images and DEM analysis were integrated to as-sess the recent surface hydrological and environmental changes ofTushka lakes, and the following has been concluded:

� Due to their location in a hyper-arid zone, Tushka lakes are sub-jected to a high rate of evaporation and results in an annual loss


of about 2.5 m of their water column. Only 10% of this amount isrecharged to the ground water aquifers beneath the lakes.

� It is predicted that these lakes will start to vanish in 2012 andwill completely disappear in 2020, assuming that no over flood-ing of the Nile will occur.

� The continuous loss of water from these lakes by evaporationwill have significant environmental impacts. Among these aretotal loss of wetland ecosystem that used to fringe the lakes,increase in the lake water salinity, deterioration of the fisheriesindustry and the occurence of dust storms that developed withinthese lakes. The dried bottom sediments and the associated saltcrust will be subjected to the wind action.

� It is strongly recommended that measures must be taken tomaximize the benefits of this huge amount of water resourcesbefore being totally lost via evaporation.

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