the Degree Confluence Project


5.8 km (3.6 miles) SSW of Ciabbub Areddu, Semēnawī K’eyih Bahrī, Eritrea
Approx. altitude: 293 m (961 ft)
([?] maps: Google MapQuest OpenStreetMap ConfluenceNavigator)
Antipode: 16°S 141°W

Accuracy: 8 m (26 ft)
Quality: good

Click on any of the images for the full-sized picture.

#2: View looking northwest from the Confluence #3: JB in a view looking due north from the Confluence #4: Ouga in a view looking northeast from the Confluence #5: GPS display #6: The village of Gīnda #7: The paved road #8: Tracks in the plain #9: Acacia bushes #10: Desert pavement #11: A typically shattered rock #12: A view from the knoll close to the point in direction north #13: Map of the area

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  16°N 39°E  

#1: Looking down on the plain that contains the confluence point from the nearest hill (northeast of 16N 39E)

(visited by Johnathan Bascom and Ogbaghebriel Berakhi)

31-Mar-2005 -- We left Āsmara (7,340 ft/2,237 m), the capital of Eritrea at 6:45 a.m. Three of us - two geography professors from the University of Āsmara and a driver - headed down the eastern escarpment on the Massawa highway, encountering minimal traffic, but dozens of baboons. Atmospheric conditions were hazy by Eritrean standards when we stopped at the city of Gīnda before our final descent to eastern lowlands of Eritrea. Gīnda lies above 800 meters (2,500 feet) and thus, is part of the wetter "greenbelt" of Eritrea. This zone is commonly thought of as one of the best places to live in Eritrea.

At the bottom of Eritrea's eastern escarpment lies the small town of Gahtēlay, located at the junction of the Gahtēlay River and the Massawa-Āsmara road (Gahtēlay, a Saho word that means "returned river", refers to the ephemeral nature of the Gahtēlay River). The village serves a truck stop before the challenging climb up to the capital city. Its arid climate typifies the country's coastal zone. At Gahtēlay (spelled Gahtielay on the map) we left the Massawa highway and turned north onto a newly constructed highway. The first 27 kilometers of the Gahtēlay-Āfabēt road are now paved. It runs along the flatlands parallel to the escarpment. The road is prone to flashflood washouts in the dry arroyos, so new washout bridges are currently being reconstructed. The paved road continues northward beyond the town of Sh'eb (spelled Sh'eb-Mensheb on the map), at 15°51.000'N 39°05.127'E. Several kilometers north of Sh'eb - and near the 39N 16E confluence point - the road suddenly turns due west. From that bend on, the road surface changes from asphalt to gravel.

In the late morning, we made an initial foray on foot, hiking westward from the paved road several hundred meters. Hiking was made more difficult by the fact that we were moving across small plains paved with small boulders and loose scree material. After 20 minutes of hiking, we returned to the truck and decided to try again later in the day to reach the confluence point from a different vantage point.

Next we drove a circle route north of the 16N 39E point to see the spate irrigation system featured in that area. (Spate irrigation systems are found throughout the arid Middle East. Those in eastern Eritrea were most likely first introduced by immigrants from Yemen.) Having driven a dry riverbed back to the Āfabēt-Gahtēlay road, we began to search for a passable track that would take us off-road and closer to the confluence point. Our second try was fruitful. We located the beginnings of a track, whereby the 4-wheel drive truck got us a kilometer closer to the goal. At the edge of a steep hill that fell away into a dry streambed, the truck could go no further, so we proceeded on foot with our GPS in hand at approximately 1:50 p.m. (The truck was parked at 16°00.483'N 39°00.723'E)

Using the GPS to negotiate our way southwest (taking occasional readings and then setting our sights on a bearing point several hundred meters ahead), we worked our way to the confluence point of 16N 39E. Arrival time was 2:35 p.m. on 31 March 2005.

Confluence Point Overview

The confluence point is situated in the northern half of the coastal strip that has an average width of 24-40 kilometers. The coastal plain is tectonic in origin; it forms part of the Rift Valley and, as such, is bounded by the Great Escarpment in the West and the Red Sea Basin to the East. Huge sediment supply - brought by erratic ephemeral mountain torrents/streams, sheet and gully flows, and slope processes - have spread over the foothills and plains throughout the Quaternary Period, resulting in talus, alluvial and colluvial deposits that range from 0 to more than 50 meters in thickness.

Ecologically, the northern lowland is located in the Coastal Eco-geographical Zone, which is characterized by a semi-desert to real desert ecology. Annual rainfall barely reaches 200 mm, while potential evapo-transpiration rates can be as much as ten times greater than the total rainfall. Given less than a 30-day growing season in the winter months, by late March the confluence area was almost devoid of ground cover.

Vegetation cover ranges from barren landscape to woodland vegetation mostly acacia species, interspersed with relatively dense riverine woody vegetation along ephemeral streams and wadis. Soils, in general, are poorly developed - groups of aridosoles consisting mainly of xerosols, lithosols and solonchaks.

Against this eco-geographical background, some specific descriptive features of the confluence point and its immediate environ could be added. The very sparse vegetation cover, which is made up of extremely few and scattered low acacia bush and scrub, some clumps of hardy grass, testifies to the meager rainfall regime in the coastal plain, which also leaves the very dry ground surface exposed to high-severe wind erosion. The surface material, which is made up of pebbles, gravel and boulders was originally brought and deposited by sheet flood. These sediment deposits have been repeatedly reworked by fluvial and aeolian process. Selective erosion and transportation by sheet flow and wind has removed the finer particles like clay, silt and fine sand leaving the surface strewn with coarser materials and boulders. At places, the gravel and pebbles are re-arranged and fitted together by the constant jostling of the wind and cemented together by cementing minerals drawn up by capillary action, to produce desert pavement typical of arid environments. The hot temperatures, which dominate this arid environment, play a role reshaping the surface material as well. Strong thermal variations, both diurnal and seasonal, result in contraction and expansion, which especially acts upon larger surface material. Boulders, such as the one seen below, eventually split, often with sharp knife-like edges.

Such a bare and dry ground surface (lithosols at most) is practically useless for agriculture. During short rains though, some fast growing grass species and the tiny leaves of the acacia shrubs and scrub give temporary respite for a few grazing and browsing animals. Given significant constraints on rainfall - annual precipitation ranges from 250 to 400 mm - this region is primarily the domain of pastoralists. Most rain is delivered in the months of January and February, which with cooler temperatures prompts a flush of new vegetation for camels, cattle, goats, and sheep. Hence, herding paths crisscross the landscape, including one that seemed to lead directly to the confluence point.

Searching for the confluence point in the scorching afternoon was draining. The wind, instead of consoling us, gave a burning sensation on our faces, for it seemed to have come from a dying flame. Here on the coastal plain, average temperatures in March range between 28 and 31 °Celsius. Afternoon temperatures are even higher. One has to consume a lot of water to compensate for the rapid loss of body moisture due to excessive evaporation and transpiration, so we made our way back to the truck by way of a small knoll, where we could gain some elevation perspective on the confluence point and the surrounding area below.

We returned to the truck at 3:15 p.m., having relished the opportunity to contribute to the global Degree Confluence Project. This foray marked a successful documentation of the 2nd confluence point registered in Eritrea. The first one was one degree further south - 15N 39E - registered on 28 December 2003.

 All pictures
#1: Looking down on the plain that contains the confluence point from the nearest hill (northeast of 16N 39E)
#2: View looking northwest from the Confluence
#3: JB in a view looking due north from the Confluence
#4: Ouga in a view looking northeast from the Confluence
#5: GPS display
#6: The village of Gīnda
#7: The paved road
#8: Tracks in the plain
#9: Acacia bushes
#10: Desert pavement
#11: A typically shattered rock
#12: A view from the knoll close to the point in direction north
#13: Map of the area
ALL: All pictures on one page