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Rise and Demise of the New Lakes of Sahara Missouri University of Science and Technology Scholars' Mine Geosciences and Geological and Petroleum Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works Engineering 01 Apr 2008 Rise and Demise of the New Lakes of Sahara Mohamed G. Abdel Salam Missouri University of Science and Technology, [email protected] Ahmed M. Youssef Sayed Arafat Mohamed Alfarhan Follow this and additional works at: https://scholarsmine.mst.edu/geosci_geo_peteng_facwork Part of the Geology Commons Recommended Citation M. G. Abdel Salam et al., "Rise and Demise of the New Lakes of Sahara," Geosphere, vol. 4, no. 2, pp. 375-386, Geological Society of America (GSA), Apr 2008. The definitive version is available at https://doi.org/10.1130/GES00142.1 This Article - Journal is brought to you for free and open access by Scholars' Mine. It has been accepted for inclusion in Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works by an authorized administrator of Scholars' Mine. This work is protected by U. S. Copyright Law. Unauthorized use including reproduction for redistribution requires the permission of the copyright holder. For more information, please contact [email protected]. Rise and demise of the New Lakes of Sahara Mohamed G. Abdelsalam* Department of Geological Sciences and Engineering, Missouri University of Science and Technology, 129 McNutt Hall, 1400 N. Bishop, Rolla, Missouri 65401, USA Ahmed M. Youssef Department of Geology, Faculty of Science, Sohag University, Sohag, Egypt Sayed M. Arafat National Authority for Remote Sensing and Space Sciences (NARSS), 23 Joseph Brows Tito Street, El-Nozha El-Gedida, P.O. Box 1564, Alf Maskan, Cairo, Egypt Mohammed Alfarhan Department of Geosciences, University of Texas at Dallas, 2601 North Floyd Road, Richardson, Texas 75083, USA ABSTRACT lakes decreased to ~800 km2 with an average the crest and ~980 m at the bottom. Six tunnel loss of ~17 km2/month. If this trend contin- inlets are used for discharge control and water Multispectral remote sensing data and dig- ues, the New Lakes of Sahara will disappear supply to power plants. An escape spillway is ital elevation models were used to examine completely by March 2011. The spatial distri- provided at the western side to permit excess the spatial and temporal evolution of the New bution of the New Lakes of Sahara is strongly water discharge if water exceeds the 182 m Lakes of Sahara in southern Egypt. These controlled by morphologically defi ned east-, maximum capacity of the dam. lakes appeared in September 1998, when north-, northeast-, and northwest-trending The water level of Lake Nasser reached water spilled northwestward toward the faults. The water recharge of the Nubian ~178 m by 1978, but the lake receded to ~158 m Tushka depression due to an unusual water aquifer by the New Lakes of Sahara is insig- in 1987 due to severe drought in Ethiopia and rise in Lake Nasser induced by high precipi- nifi cant; much of the lakes’ area is above an Sub-Saharan Africa in the mid 1980s (Collins, tation in the Ethiopian Highlands. Five lakes impermeable formation. 2002). In the early 1990s water level began to were formed in local depressions underlain rise again, and reached ~182 m in 1997 due to by an impermeable Paleocene shale and chalk Keywords: New Lakes of Sahara, Western Des- above-average precipitation in the Ethiopian formation. The lakes developed through ert, Egypt, Nubian aquifer. Highlands (Kim and Sultan, 2002). By 1998 three stages. (1) A rise stage occurred from water level exceeded 182 m and water began September 1998 to August 2001; the area cov- INTRODUCTION to fl ow northwestward through the Tushka Val- ered by the lakes reached ~1586 km2. In this ley toward the Tushka depression, forming the stage the rate of water supply far exceeded Egypt relies completely on the Nile River New Lakes of Sahara (Fig. 3). the rate of water loss through evaporation. for its water supply because it is located in Since their formation, only a few presenta- This stage was characterized by an early arid and semiarid zones with ~100 mm/yr tions have addressed the spatial and temporal phase (August 1998–August 1999) when precipitation (Fig. 1). Almost all of the Egyp- evolution of the New Lakes of Sahara and the area covered by the lakes increased by tian Nile water, which totals ~84 × 109 m3/yr their potential infl uence on the rechargeabil- ~75 km2/month. This was followed by a late (Abu Zeid and El-Shibini, 1997), comes from ity of the Nubian aquifer. Yan et al. (2003) phase (August 1999–August 2001), in which the highlands of Ethiopia and Sub-Saharan used multitemporal resolution data to estimate area increase averaged ~28 km2/month. (2) Africa through the Blue Nile and the White water storage in the lakes until 2003 and their A steady-state stage occurred from August Nile, respectively, where precipitation reaches possible recharge contribution to the Nubian 2001 to August 2003, during which the area ~1800 mm/yr (Fig. 1). For decadal manage- aquifer. El-Bastawesy et al. (2007) used digital covered by the lakes remained relatively ment of the Egyptian Nile water, Egypt built elevation models (DEMs), extracted from air- unchanged and water lost through evapo- the Aswan High Dam, which was completed borne photogrammetic data acquired before ration was continuously replaced by water in 1968. To the south, the dam created Lake the lakes were formed, to estimate water loss. supply from Lake Nasser. (3) A demise stage Nasser, which is ~500 km long, and ~12 km Chipman and Lillesand (2007) used Moder- occurred from August 2003 to April 2007, wide on average (Fig. 2; Said, 1993). This lake ate Resolution Imaging Spectroradiometer during which water supply from Lake Nasser covers an area of ~6000 km2 and stores ~163 (MODIS) and Advanced Very High Resolu- stopped completely and water was continu- × 109 m3 of water. The Aswan High Dam is tion Radiometer (AVHRR) images, Shuttle ously evaporating. The area covered by the ~2325 m long,~111 m high, and ~40 m wide at Radar Topography Mission (SRTM) DEMs, *[email protected] Geosphere; April 2008; v. 4; no. 2; p. 375–386; doi: 10.1130/GES00142.1; 9 fi gures; 1 table. For permission to copy, contact [email protected] 375 © 2008 Geological Society of America Downloaded from https://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/4/2/375/3338675/i1553-040X-4-2-375.pdf by Missouri S & T Library Periodicals user on 08 October 2018 Abdelsalam et al. 30N DATA AND METHODS Mediterranean Sea Rainfall in mm/year Multidate (September 1998–April 2007) Figure 2 > 1800 Landsat Thematic Mapper (TM) and Enhanced 1200 - 1800 Thematic Mapper Plus (ETM+), the Advanced 25N Spaceborne Thermal Emission and Refl ec- 800 - 1200 tion Radiometer (ASTER) data, SRTM DEMs 400 - 800 (Table 1), and previously published geological information were used in this study. Bands 2, 4, 100 - 400 and 7 of Landsat TM and ETM+ data are used < 100 20N to outline the areal extent of the New Lakes of Egypt Sahara and to generate a time series for the evo- lution of the lakes between August 1998 and April 2007 (Fig. 4). For this, a one-class (water) parallelepiped supervised classifi cation is used Red Sea 15N to reduce the commission error (error arises from the incorrect inclusion of pixels represent- ing land cover other than water). The accuracy of supervised classifi cation in detecting small Eritrea water bodies and wetlands in dry regions can 10N sometimes be low due to variation of spectral signatures as a function of ecological conditions Sudan (Gond et al., 2004). However, it is expected here that the accuracy of parallelepiped classifi cation will be signifi cantly high because of the sharp 5N difference between the spectral signatures of water within the New Lakes of Sahara (which absorbs bands 2, 4, and 7) compared to the sur- Ethiopia rounding Sahara sand (which refl ects bands 2, 4, and 7). This is evident in the 7–4-2 Landsat TM and ETM+ images in which the New Lakes 0 of Sahara (black) can be clearly distinguished from the surrounding sand of the Sahara Desert Democratic (white to light brown). In addition, the accu- Republic Kenya racy of the supervised classifi cation is evaluated of Congo through the computation of the lake’s perimeter 5S Uganda to lake area ratio. This ratio is between 0.66 Indian and 0.31 for all lakes (Fig. 4), indicating a high Rwanda Ocean accuracy of results of supervised classifi ca- tion. Scan Line Corrector (SLC)–off mode is Burundi Tanzania selected for Landsat ETM+ data acquired after 10S 25E 30E 35E 40E 45E 50E 31 May 2003 to avoid image distortion caused by malfunctioning of the SLC since that date. Results of the supervised classifi cation are sub- Figure 1. Map of the Nile River system showing annual precipitation. Box shows location sequently used to calculate the area of each lake of Figure 2. as well as the total area of all lakes. The change of area covered by the New Lakes of Sahara is presented as a function of time (Fig. 5). A linear regression modeling is implemented to and laser altimetry data from the ICESat Geo- the New Lakes of Sahara using multidate remote predict the life expectancy of the lakes (Fig. 6). science Laser Altimeter System (GLAS) to sensing data and DEMs. We present time slices A 7–3-1 ASTER mosaic is draped onto the estimate surface area and water volumes of the of the evolution of the lakes since their forma- STRM DEMs to create three-dimensional (3D) New Lakes of Sahara until September 2005.
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