{{Short description|River in Ethiopia}} {{Infobox river | name = Gilgel Abay | image = Gilgel Abay during flood.jpg | image_caption = Gilgel Abay at BIkolo, during flood | map = Lake tana and rivers.svg | map_caption = Map of Lake Tana, showing rivers flowing into it | other_name = Lesser Abay | native_name = {{native name|am|ግልገል አባይ}} | mouth_coordinates = {{coord|11.798679|N|37.125324|E|display=inline, title}} | country = Ethiopia | state_type = Region | state = Amhara | region_type = Zone | region = West Gojjam | source1_coordinates = {{coord|11.01147|N|37.15229|E}} | source1_location = Near Gish Abay | source1_elevation = {{cvt|2454|m}} | mouth = Lake Tana | mouth_location = {{cvt|12.5|km}} SE of Kunzila | mouth_elevation = {{cvt|1786|m}} | length = {{cvt|154.5|km}} | progression = Lake Tana → Blue Nile → Nile → Mediterranean Sea | river_system = Nile Basin | etymology = Literally "Lesser Nile" | basin_size = {{cvt|3887|km2}} | basin_population = 1,220,000 | width_max = {{cvt|71|m}} }}

The '''Gilgel Abay''' (Amharic: ግልገል አባይ, Gǝlgäl Abbay), or '''Lesser Abay''', is a river of central Ethiopia. Rising in the mountains of Gojjam, it flows northward to empty into south-western Lake Tana in a bird's-foot delta. Tributaries of the Gilgel Abbay include the Ashar, Jamma, Kelti and the Koger. It was regarded as the true source of the Nile for a long time and the Jesuit priest Pedro Paez visited it in 1618. The name Gilgel Abbay means Lesser Nile, as Abbay is the name for the Blue Nile.

== Characteristics == It is a meandering river, with a catchment area of {{cvt|3887|km2}}. It is 71 meters wide near its mouth, with a slope gradient of 0.7&nbsp;m/km. The average diameter of the bed material is 0.37&nbsp;mm (sand).<ref name="hani">{{cite journal |last1=Hanibal Lemma |first1=and colleagues |title=Bedload transport measurements in the Gilgel Abay River, Lake Tana Basin, Ethiopia |journal=Journal of Hydrology |date=2019 |volume=577 |article-number=123968 |doi=10.1016/j.jhydrol.2019.123968 }}</ref>

== Sediment transport == The river carries annually 22,185 tonnes of bedload and 7.6 million tonnes of suspended sediment to Lake Tana.<ref name="hani"/>

== See also == * List of Ethiopian rivers

== References == {{reflist}}

== Further reading == * S. Uhlenbrook, Y. Mohamed, and A. S. Gragne, "Analyzing catchment behavior through catchment modeling in the Gilgel Abay, Upper Blue Nile River Basin, Ethiopia." Hydrol. Earth Syst. Sci., 14, 2153–2165, 2010 *Hydrologic Impact of Land-Use Change in The Upper Gilgel Abay River Basin, Ethiopia; TOPMODEL http://www.itc.nl/library/papers_2010/msc/wrem/gumindoga.pdf

Category:Tributaries of Lake Tana Category:Rivers of Ethiopia

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