Ethiopia's Water Resources

• About 71% of the Earth's surface is covered by water, mainly seas and oceans.
• 97.5% of water is alkaline water in seas and oceans.
• 2.5% of water is fresh water, with 68.7% deposited in glaciers.
• 30.1% of the total water is groundwater, 0.8% in permafrost, and 0.4% in surface waters.
• Lakes, rivers, the atmosphere, soils, and wetlands are considered surface waters.
• Ethiopia's landscape includes highlands, rugged terrain, and low plains.
• Diverse topography and higher rainfall result in larger volumes of ground and surface water.
• Approximately 0.7% of Ethiopia's land is covered by water.
• Surface water potential is estimated at 124.4 billion cubic meters (BCM).
• Ethiopia is known as the water tower of Eastern Africa.

Major Drainage Systems of Ethiopia

• A drainage system channels water through a well-defined path which consists of a main river and its tributaries.
• River systems start at a source or headwater and end at a mouth.
• Drainage systems include stream channels and adjacent land slopes.
• River basin patterns are determined by topographical structures, like outward sloping plateaus, the Rift Valley's inward-sloping escarpments, and faults/joints.
• Ethiopia has three main drainage systems: Western, Southeastern, and Rift Valley.

Western Drainage Systems

• The largest system that drains 40% of the country, carrying 60% of the annual water flow.
• The catchment area aligns with the westward sloping part of the western highlands and lowlands.
• It includes four major river basins: Tekeze, Abay, Baro-Akobo, and Ghibe (Omo).
• The Ghibe (Omo) flows southward.
• The Abay, Tekeze, and Baro rivers flow westward and join the Nile, which ends at the Mediterranean Sea.
• The Abay is the largest river in terms of discharge and coverage.
• The Abay River basin covers 199,812 km2, including parts of Amhara, Oromia, and Benishangul-Gumuz regions, and carries 65% of the region's annual water flow.
• Rising from Lake Tana, the Abay flows approximately 1,450 km and joins the White Nile in Khartoum, Sudan.
• More than 60 streams drain the Abay within elevations of 500 - 4261 meters above sea level.
• The largest stream is Ghilgel Abay (Little Abay).
• The Abay flows eastward, bends 180 degrees, cuts a gorge, and emerges in the west.
• The Tekeze River and its tributaries drain 82,350 km2 of land between 536-4517 meters above sea level and carry 12% of the annual water flow.
• Erosion resulted in tablelands, plateau blocks, and isolated mountain groups in the Tekeze basin, which has two main tributaries: Angereb and Goang
• The Tekeze River is called Atbara in Sudan and is a tributary of the Nile.
• The mean annual flow from the Tekeze basin is 8.2 billion metric cubes (BMC).
• The Baro-Akobo and Ghibe/Omo rivers drain the wettest highlands in southern and southwestern Ethiopia, carrying 17% and 6% of the annual water flow, respectively.
• The Ghibe/Omo river basin drains 79,000 km2 with an estimated mean annual flow of 16.6 BMC.
• The Baro River flows across a marshy land and the Baro Akobo river basin covers an area of 75,912 km2, including parts of Benishangul-Gumuz, Gambella, Oromia, and SNNPR.
• The mean annual flow from the Baro-Akobo river basin is 23.6 BMC.
• The Baro and Akobo form the Sobat River in South Sudan, and the Ghibe/Omo River empties into Chew-Bahir at Lake Turkana.

Southeastern Drainage Systems

• The system covers the southeastern part of Ethiopia, drained mainly by the Wabishebelle and Ghenale rivers
• They slope southeastward across large, water-deficient plains, with major highlands including the Arsi, Bale, Sidama, and Harerghe plateaus
• They cross into Somalia, and carry 25 % of Ethiopia's annual water flow.
• The Ghenale covers 171,042 km2, including parts of Oromia, SNNPR, and Somali regions
• It has fewer tributaries but carries more water than the Wabishebelle and reaches the Indian Ocean.
• The Wabishebelle's basin flow is estimated at 5.8 BMC between 171-4385 meters above sea level
• It is called the Juba River in Somalia and has a catchment area of 202,697 km2
• The Wabishebelle is the largest river in terms of catchment area, covers Oromia, Harari, and Somali regions
• It is the longest river in Ethiopia, with mainly left-bank tributaries; it doesn't reach the Indian Ocean, flowing parallel to the coast where its water disappears into the sands.

Rift Valley Drainage System

• Characterized by low rainfall, high evaporation, and a small catchment area.
• The drainage area is restricted by outward-sloping highlands that start at the escarpment's edge.
• Drainage is confined to the escarpment slopes and Rift Valley floor.
• The only major river basin is the Awash has a catchment area of 114,123 km2 and an average annual discharge of 4.9 billion cubic meters.
• The Awash originates from the Shewan plateau in central Ethiopia and flows 1250 kms and covers parts of the Amhara, Oromia, Afar, Somali, Dire Dawa, and Addis Ababa City Administration.
• The Awash is the most utilized river in the country.
• Streams flow in all directions, and the Awash flows northeast.
• It ends in a maze of small lakes and marshy areas, the largest of which is Lake Abe on the Ethio-Djibouti border.
• The Afar drainage sub-basin has practically no stream flow due to little rain, high temperature, and very high evaporation.
• Lake Afrera and Asale are the only main surface waters, formed by tectonic activities.
• The southern part of the Rift Valley sub-basin has lakes and small streams and a fault depression.
• Small streams drain from mountain slopes and supply water to lakes, like the Meki and Katar Rivers flowing into Ziway, the Bilate into Abaya, and the Segen into Chew Bahir.
• Lakes Ziway and Langano drain into Lake Abijiata through small streams like: Lakes Ziway streams. of Bulbula, and Langano streams Horocolo

Ethiopian Water Resources

• Ethiopian rivers form 12 major watersheds that separate the Mediterranean Sea from Indian Ocean drainage systems.
• Most rivers originate in the highlands and cross the Ethiopian boundary.
• Catchment Area (km²), Annual Volume (BMC), Terminus/Mouth, and their Major tributaries

Characteristics of Ethiopian Rivers

• Ethiopian rivers originate from highlands above 1500 meters above sea level
• Majority are trans-boundary.
• Rivers have extreme seasonal fluctuations
• The wet results in higher runoff, full rivers, bursting banks, destroying small bridges and roads, and flooding.
• Dry seasons lead to mere trickles of water or rivers drying up.
• Rivers have rapids and waterfalls and cut steep-sided valleys and deep gorges.
• Rivers have steep slopes and serve as international and domestic administrative boundaries.

Ethiopian Lakes are in the Rift Valley System

• Ethiopia is rich in lakes
• Most of Ethiopia's lakes resulted from tectonic activity during the Quaternary period of the Cenozoic era
• Most are in the Rift Valley System and formed on faulted depressions, clustered in a linear pattern.
• Lake Tana, the largest lake in Ethiopia, occupies a shallow depression in the highlands and formed from sinking and lava flow between Gojjam and Gonder massifs.
• Ethiopia has crater lakes like Bishoftu, Wonchi, Hayk, and those atop Mount Zikwala.
• Lake Ashenge (Tigray)is formed in a tectonic basin.
• Man-made lakes include Koka, Fincha, and Melka Wakena which dammed for hydroelectric power projects.
• Cluster of lakes are lined up within main Ethiopian rift.
• Lake Abaya is the largest of all the lakes in the system.
• The southern tip of the Rift Valley forms the marshy land called the Chew Bahir
• Shala and Ziway which are drained by Segan and Woito? are the shallowest and deepest ones in the central Ethiopian Rift.
• Climate and geophysical conditions impact groundwater resources leading to groundwater potential estimation between 2.6 - 6.5 BMC
• Studies show Ethiopia's groundwater potential ranges between 12-30 BMC.

Water Resources Potentials and Development in Ethiopia

• Ethiopia's underground water potential isn't fully used.
• Opportunities can transform water resources into social and economic benefits.
• Ethiopian rivers have hydro-electric potential of about 45000 megawatts.
• The first plant generating hydroelectric power was installed on Akaki River (Aba Samuel) in 1932
• Many dams are being constructed to meet energy goals, with the Grand Ethiopian Renaissance Dam (GERD) being the country's largest aiming for 6400 megawatts.
• The Gilgel Gibe III hydropower project now generates 1870 megawatts.
• Ethiopia currently has 14 operational hydroelectric power plants like Lake Aba Samuel, Koka, Tis Abay, Awash, Melka Wakena, Sor, Fincha, Gibe/Omo, Tana Beles and Tekeze, generating ~4000 megawatts of energy.
• Besides domestic consumption, Ethiopia exports electricity to neighboring countries.
• Problems related to hydroelectric power use include seasonal flow fluctuations, climate change impacts, and erosion from highlands leading to sedimentation in reservoirs.
• Ethiopia's rugged terrain limits the use of rivers for irrigation and transportation.
• Highlands have steep slopes, rapids, waterfalls, while lowlands have high demand for irrigation.
• Ethiopia has 5.3 hectares of land potential for irrigation
• The Bare-Akobo and Genale Dawa river systems have the most potential.
• Most hydro-electric reservoirs are multi-purpose and expected to contribute to irrigation except for a select few (60%+ is for Rift Valley Drainage System)
• Ethopian Rivers are not suitable for transportation, except the Baro River, which is navigable.
• Ethiopian Lakes are suitable for use as transportation, namely Lake Tana and Lake Abaya.
• Most Ethiopian lakes have fishing potential, producing close to 31.5 tons per year; Lake Tana leads with 8,000-10,000 tons per year
• Lake Chamo's annual fish production is ~4,500 tons each year, with 60+% of supplies come from Rift Valley lakes now at risk because of sedimentation, Species (ex: water hyacinth), over-exploitation, and lakeside investment expansion
• There are diverse birds and other aquatic life in the lakes. and are home to natural wildlife that require a high scientific significance
• Hot springs and scenic river gorges enhance the recreational and tourist appeal.