more on Lake Chad

From NASA’s earth observatory, Dust Storm in the Bodele Depression:

Today, Lake Chad seems like little more than a muddy puddle surrounded by increasingly dune-streaked wetland (tan stripes across the green vegetation)… But between 5,000-10,000 years ago, a much larger lake extended across the area, a low-lying basin… Today, part of the former lake bed, the Bodele Depression, is probably the largest single source of wind-blown dust in the world. In the image, a dust storm is whipping across the Bodele…softening the orange sands of the Sahara into a pale tan.

Of hydrologic significance, in more recent times (in the past century), the lake used to flow into the Bodele Depression by way of the Bahr-el-Ghazal, as indicated by the Encyclopedia Britannica (see Online Encyclopedia entry on Lake Chad, with the caveat that I have yet to investigate the legitimacy of this source):

Beyond the south-east corner of the lake is a depression known as the Bahr-el-Ghazal (not to be confounded with the Nile affluent of the same name). This depression is the termination of what is in all probability the bed of one of the dried-up Saharan rivers. Coming from the Tibesti highlands the Bahr-el-Ghazal has a south-westerly trend to Lake Chad. Near the lake the valley was formerly swampy, and at high-water the lake overflowed into it. There was also at one time communication between the Shari and the Bahr-el-Ghazal, so that the water of the first-named stream reached Chad by way of the Bahr-el-Ghazal.

Sprol – Worst Places in the World

One of the reasons water is of such importance nowadays is that it is fairly low–let’s say rock bottom–on Maslow’s hierarchy of needs yet is threatened more and more in terms of quantity and quality (although there have been many success stories in more recent years involving the cleanup of rivers, improved environmental management practices, etc. at least in certain parts of the world).

Sprol points out the worst of the worst–the “Worst Places in the World”, many of which involve areas of heavily contaminated surface water. More specifically:

Sprol shows the visual macroscopic effects of the decisions and behavior of our society. Since previous generations have not had the advantage of this perspective it is our obligation to use it wisely.

Here are the Sprol entries mentioning “rivers” or “water”

note & disclosure: the WWF advertisement on Sprol.com and my involvement with WWF have no relation and are purely coincidental.

Lake Chad (Western Africa)

Name: Lake Chad
Location: Western Africa (at the meeting of Chad, Cameroon, Niter and Nigeria)

Lake Chad is the final sink of a large endorheic basin (see the first image below) and can be considered more of a wetland rather than a lake, the second largest wetland in Africa. Lake Chad has been reported on a number of times in recent years due to it’s significant decrease in area over the past 45 years.

• NASA’s Goddard Space Flight Center (Feb. 27, 2001): A Shadow of a Lake: Africa’s Disappearing Lake Chad
  
• and the related NASA’s Earth Observatory: Africa’s Disappering Lake Chad (the source for the second image below)
• USGS EARTHSHOTS: SATELLITE IMAGES OF ENVIRONMENTAL CHANGE (Jan. 12, 2001): Lake Chad, West Africa: 1963, 1973, 1987, 1997 (the source for the first image below)
• BBC News (April 14, 2006): Slow Death for Africa’s Lake Chad
• National Geographic (April 26, 2001): Shrinking African Lake Offers Lesson in Finite Resources

In general, there are many websites dedicated to information about various aspects of the lake, both documenting its demise, reversing its demise, and giving current information on the natural resources of the basin for both exploitation and conservation purposes.

Here is an excerpt from the USGS Earthshots site:

The lakebed is flat and shallow, so small changes in depth mean huge changes in area. Even in normal times, Lake Chad was no more than 5-8 meters deep. It may be more accurate to think of it as a deep wetland. Considered this way, Lake Chad was once the second largest wetland in Africa, highly productive, and supporting a diversity of wildlife.

(source url: http://earthshots.usgs.gov/LakeChad/LakeChadnorthAfricaAVHRR.jpeg, accessed Aug. 30, 2006)

(source url: http://earthobservatory.nasa.gov/Newsroom/NewImages/Images/landsat_chad.jpg, accessed Aug. 30, 2006)

Chelif River (Algeria)

Name: Chelif River
Location: Northern coast, Algeria
Algeria is not known for its rivers. Just the opposite: four fifths of Algeria is desert. It is not that there are no rivers whatsoever, it’s just that most of those that do occur are either relatively short in both space and time. A map of the country reveals that there are, in fact, numerous discernible oueds (oued is French for wadi) scattered throughout. Only in those parts of the Sahara that are sand dune through and through, areas such as Grand Erg Occidental, Grand Erg Oriental, Erg Issaouane, and Erg Iabes do the oueds disappear entirely. (The Oxford English Dictionary defines an erg as “a type of desert area in the Sahara consisting of shifting sand dunes” and an oued = wadi or wady as “a ravine or valley which in the rainy season becomes a watercourse” or “the stream or torrent running through such a ravine”.)

The Atlas Mountains to the north, however, produce a number of rivers flowing northward into the Mediterranean Sea. The Chelif River (also spelled Chéliff or Sheliff) is one such river, and is the longest and most important river in Algeria. The photo below, an old photo of the Chelif Bridge, was the only decent photo I could find of with the river. I have borrowed it from the website of the village of Aïn Tédélès, located just inland from the mouth of the Chelif River, a few miles northeast of Mostaganem (itself about halfway between Algiers and the Algeria-Morroco border).

The following entry from the Encyclopædia Britannica Online is about as dry as the river itself, yet still gives a decent basic overview:

Its farthest tributary, the Sebgag River, rises in the Amour ranges of the Saharan Atlas Mountains near Aflou. Crossing the Hauts Plateaux for most of the year as a chain of marshes and muddy pools, the river loses most of its water but is replenished by a stream near Chabounia, the Nahr Ouassel River. The Chelif then turns abruptly north to rush through a deep gorge in the Tell Atlas Mountains between Ksar el-Boukhari (formerly Boghari) and Djendel (formerly Lavigerie). Below Oued Chorfa (formerly Dollfusville) the river swings to the west, flowing for about 145 miles (230 km) parallel with the coast in a depression (the Chelif plain) between the Dahra Massif, Mount Zaccar Rherbi, and the Tell Atlas. The river reaches the Mediterranean about 8 miles (13 km) north of Mostaganem.

The Chelif is unnavigable throughout its 450-mile (725-kilometre) length, and its flow is irregular, the maximum being November to March. The Chelif plain receives only moderate, undependable rainfall (average, 16 inches [400 mm] annually), and evaporation is intense. The lower reaches of the river’s basin are, however, cultivated with the aid of irrigation. Three main dams have been constructed on the Chelif system at Ksar el-Boukhari (1932), Ech-Cheliff (formerly El-Asnam; 1932), and El-Khemis (1939). Cereals, oranges, and grapes are the principal crops, and there is minor cultivation of cotton around the town of Ech-Cheliff.

Citation:
“Chelif River.” Encyclopædia Britannica. 2006. Encyclopædia Britannica Premium Service. 25 Aug. 2006 <http://www.britannica.com/eb/article-9022758>.

Idhān Awbārī (Western Libya)

Name: Idhān Awbārī
Location: Western Libya
Calling Idhān Awbārī a river would be misleading, but not entirely untrue, as you could possibly call Idhan Awbari a river of sand. At least, if you removed the sand and poured in water, you would have a great river flowing, quite probably, into the Mediterranean, as the Nile does today. Being an expansive tract of sand, a part of the greater Sahara Desert, it does not flow. However, from above, from a satellite’s eye view, it appears a great lake nonetheless. Replace it with ice and you would call it a glacier or ice field (although in this part of the world a glacier wouldn’t last long at all). These great dunes are connected to water in another very fundamental way in that their defining characteristic is the very absence of water. These are the sorts of places that make one realize just how important water is (not that anybody debates this point).

The desert from this vantage point is at a scale that would hardly be recognisible were you to actually visit this place yourself. Do a quick search for Idhān Awbārī and you quickly realize that it is a very archetypal desert. You find photos of this area as representations of the ideal desert: huge sandy dunes rising from the earth as far as the eye can see, without a single sign of life at all. That’s not to say that water cannot be found deeper beneath the surface here. I am not sure how great the precipitation is here, but judging from the geomorphologic features (i.e. the shape of the land) of the area, it seems likely that there might actually be quite a bit of water much farther down.

On a technical note, the reason I focus on this is its significance in mapping water courses. Obviously, because of the loose sand, any water on the surface forms not even a wadi. But even still, it is important when mapping the potential water courses over the desert to have reliable data. The data I am working with has a problem in that over certain land types the radar used to detect it simply does not return with a strong enough signal. This is often the case in instances of sand over a hard subsurface such as rock, such as you find here. As such, the elevation data that I have for this area is quite poor in quality.

Oued Assaq (Western Sahara)

Name: Oued Assaq (Wadi)
Location: Western Sahara
I’ve come across the wadi Oued Assaq, located toward the central coast of Western Sahara. The most interesting Google hit (among less than one page of results) comes from Chasing the Lizard’s Tail by Jens Finke (Chapter 6: The Western Sahara), during his bicycle journey across the Sahara.

About fifty or sixty kilometres south of Boujdour I came to an area of wind scarred ruins, interlaced with barbed wire and anonymous mechanical contraptions that were scattered around. As far as could make out, this was the abandoned settlement of Aoufist [though it may have been Hassi Aouziouah - curse my map!]. Here, an earlier part of the Moroccan defensive wall drops down all the way to the coast. The beach to my right was barred with wire, concrete and mounds of rubble. From Aoufist, all maps were ignored again as the road started up the valley of the dead River Assaq, where in the year 1500, the Spanish who had wanted to construct a fort at its mouth were massacred by local tribes. The river hasn’t flowed for decades. The land hereabouts consisted of bizarrely eroded tufa – a porous rock made of calcium carbonate deposited from ancient springs that crumbled like meringue if ever I touched it.

Obviously, one of the defining features of a desert is its lack of significant quantities of water. Indeed, Finke begins his chapter on the Western Sahara with the only quote of thirteen chapters that explicitly mentions water:

[A people] who never enjoy fresh water
And whom the grass of the fields inadequately supplies,
A country you may say ill disposed to bear any fruit,
Where the birds consume iron in their bellies,
A land suffering extreme want of everything…
—Luis Vaz de Camões, Os Lusíadas 6, 1572

Wadi Howar (Sudan)

Name: Wadi Howar
Location: Northern Darfur, Sudan (part of the greater Nile River basin),
v. Times Atlas of the World 10th Comprehensive Ed. Plate 83, N3

Further along in my virtual travels, I come across an ancient river now called the Wadi Howar, located in present-day Northern Darfur. The question for me is, do I include it as part of the Nile River basin? I have decided on yes, since were there water pouring into it, with only minimal evaporation and groundwater seepage, it would definitely flow into the Nile. This, from ARKAMANI Sudan Journal of Archaeology and Anthropology, ON THE TRACKS OF THE EARLY HERDSMEN, by Rudolph Kuper:

The Wadi Howar, a barren river of a 1000 km length, has been of special importance as a settlement area and commerce artery at the border to the Sahel. It leads from the Ennedi-Mountains in the Chad to the Nile in the south Dongola and obviously kept its importance as a mayor contact zone between inner Africa and the Nile valley until recently. The 400 km long lower reaches from Djebel Rahib eastwards to the Nile have not even been marked on the newest maps yet. The proof that the Wadi Howar was a series of at least episodically interlinked lakes up to the 2nd millennium BC was only found during the last years. This gave a new basis to all the considerations on the connections of the cultures of the Nile valley to inner Africa.

And, of course, there are these photos of Wadi Hawar National Park from David Haberlah.

Fw: New water-related sites added to the World Heritage List

Excerpt from:
UNESCO WATER PORTAL WEEKLY NEWSLETTER No. 148: HUMID TROPICS
21 July 2006

NEWS

New water-related sites added to the World Heritage List

The World Heritage Committee held its 30th session, in Vilnius , Lithuania , on 8 to 16 July 2006. Among the cultural properties inscribed on the World Heritage List on this occasion were several water related sites.

For instance the aflaj irrigation system in Oman includes 3,000 such systems still in use today. Aflaj is the plural of falaj in classical Arabic, which means to divide into shares and equitable sharing of a scarce resource to ensure sustainability and remains the hallmark of this irrigation system. Archaeological evidence suggests that irrigation systems existed in this extremely arid area as early as 2,500 BC.

The Old Town of Regensburg with Stadtamhof in Germany has been an influential trading town since the 9th century AD. Located on the Danube River , it has preserved a notable number of historic structures spanning some two millennia, including its 12th century AD stone bridge.

The Vizcaya Bridge in Spain straddles the mouth of the Ibaizabal estuary west of Bilbao . It was completed in 1893 and was the first bridge in the world to carry people and traffic while allowing for navigation thanks to a high suspended gondola.

:: Read more http://whc.unesco.org/en/newproperties/

The UNESCO Water Portal Weekly Newsletter archives (starting at issue N° 85) are available online at: http://www.unesco.org/water/news/newsletter/