Nile Hydrology Preliminary Research Anthony Makana Paris

General Facts Length: 6700 km Length: 6700 km Total Catchment Area: 3 million km2 Total Catchment Area: 3 million km2 Average Runoff – 30 mm Average Runoff – 30 mm Major contributors of total flow – East African lake region, Ethiopian Highlands Major contributors of total flow – East African lake region, Ethiopian Highlands Main Tributaries – White Nile, Blue Nile and Main Nile Main Tributaries – White Nile, Blue Nile and Main Nile Wide band of Latitude – 4 o S to 32 o N Wide band of Latitude – 4 o S to 32 o N

Flow Patterns White Nile & Atbara Seasonal White Nile & Atbara Seasonal –July – Oct. peak White Nile fairly constant White Nile fairly constant

Flow Patterns Seasonal Contributions Seasonal Contributions

Sectional View

Elevations

The Lake Victoria Basin –Inflows Rainfall – 1151 mm, 122 km 3 /yr Rainfall – 1151 mm, 122 km 3 /yr Tributary – 276 mm, 22.4 km 3 /yr Tributary – 276 mm, 22.4 km 3 /yr –Evaporation – 1116 mm, 107 km3/yr –Outflow – 311 mm, 39.8 km 3 /yr –Characteristics Provides a relatively steady baseflow. Provides a relatively steady baseflow.

The East African Lakes below Lake Victoria Lakes -- Albert, Kyoga, Edward Lakes -- Albert, Kyoga, Edward Inflows Inflows –Rainfall – 10.3 km3/yr –Tributary – 10.6 km3/yr Evaporation – 16.3 km3/yr Evaporation – 16.3 km3/yr Outflow – 45 km3/yr Outflow – 45 km3/yr Characteristics Characteristics –Outflow contribution to Nile dominated by lake Victoria. –Dramatic variation in flow level historically

The Bahr el Jebel & the Sudd –Rainfall – 871 mm –Evaporation – 2150 mm –Characteristics Most complex of the Nile reaches due to having many seasonal inflows. Most complex of the Nile reaches due to having many seasonal inflows. Permanent swamp land, seasonal flood plains that are inundated Permanent swamp land, seasonal flood plains that are inundated High levels of evaporation and transpiration from vegetation (ex papyrus). High levels of evaporation and transpiration from vegetation (ex papyrus). Little seasonal variation with annual outflow about half the inflow. Little seasonal variation with annual outflow about half the inflow. Jonglei Canal Jonglei Canal –Reduce evaporation losses in Sudd

The Bahr el Ghaal Basin –Characteristics Ouflow to the White Nile is almost negligible (~3%) Ouflow to the White Nile is almost negligible (~3%) Upper basins have relatively high rainfall, but the river flows spills over into flood plains resulting in almost total lost to evaporation. Upper basins have relatively high rainfall, but the river flows spills over into flood plains resulting in almost total lost to evaporation. Sediment loads of these rivers if greater than lake-fed Bahr el Jebel Sediment loads of these rivers if greater than lake-fed Bahr el Jebel Higher potential for alluvial channels. Higher potential for alluvial channels.

The Sobat Basin & Machar Marshes –Characteristics The regime of Sobat and its tributaries is complex. The regime of Sobat and its tributaries is complex. Most of the runoff develops in the mountains and foothills of Ethiopia. Most of the runoff develops in the mountains and foothills of Ethiopia. Pibor drains a wide area of plains, but only contributes significantly in times of high rainfall. Pibor drains a wide area of plains, but only contributes significantly in times of high rainfall. Provides about half of the flow for the White Nile. Provides about half of the flow for the White Nile. Relatively same outflow as the Sudd. Relatively same outflow as the Sudd. Relatively little is known about he hydrology of the basin area, due to the river straddling the border of Sudan and Ethiopia. Relatively little is known about he hydrology of the basin area, due to the river straddling the border of Sudan and Ethiopia. The system is reasonably self-contained with water stored in the channel and flood plain during high flow periods, returning to the channel when the flow recedes, losses to evaporation and soil moisture recharge. The system is reasonably self-contained with water stored in the channel and flood plain during high flow periods, returning to the channel when the flow recedes, losses to evaporation and soil moisture recharge.

The White Nile below Malakal –Characteristics Drops 13 m over 840 km Drops 13 m over 840 km Tributary inflows are sporadic and small Tributary inflows are sporadic and small Flood plain storage results in delay of outflow and increased loss to evaporation. Flood plain storage results in delay of outflow and increased loss to evaporation. The Jebel Aulia dam further raised upstream river levels after June 1937 The Jebel Aulia dam further raised upstream river levels after June 1937 Irrigation and evaporation have led to increased losses. Irrigation and evaporation have led to increased losses. Outflow is delayed to supplement the Blue Nile in low flow season due to the dam Outflow is delayed to supplement the Blue Nile in low flow season due to the dam Sudd provides the baseflow component Sudd provides the baseflow component Sobat basin contributes the seasonal component Sobat basin contributes the seasonal component

The Blue Nile and its Tributaries Characteristics Characteristics –Provides the greater part of flow of the Main Nile (~60%) –Limited information is known about its hydrology, especially in its upper basin within Ethiopia –Geography  Begins in Ethiopian Plateau  Elevations of m, peaks of 4000m  Very broken and hilly, grassy uplands, swamp valleys, and scattered trees.  Deep ravines and canyons (~1300m at places)  Lake Tana  1800m  Surface Area – 3000 km2  Blue Nile leaves and travels through series of cataracts.  Travels through the Sudan Plains  Slopes westwardly from about 700 m  Covered with Savannah or thorn scrub

The Blue Nile and its Tributaries  Major Tributaries  Below reservoir  Rahad  Dinder  Similar basins to lower Blue Nile, highly seasonal  Above reservoir  Dabus – wetland area of 900 km2  Didessa – smaller swamps  Drains southwestern & humid portion of the Ethiopian basin, contributes significantly to total flow  Reservoir Storing  Roseires Dam (2.4 km2)  Sennar Dam (0.5 km2) –Largest Sediment load (especially during the flood season)  ~140- million tonnes per year

The Atbara & Main Nile to Wadi Halfa –Convergence of White Nile and Khartoum –Atbara Only major tributary after Khartoum Only major tributary after Khartoum Most seasonal of all tributaries Most seasonal of all tributaries Drains northern Ethiopia (68,800 km2) and mountains north of Lake Tana (31,400 km2) Drains northern Ethiopia (68,800 km2) and mountains north of Lake Tana (31,400 km2) –Topography Sabaloka gorge 80 m north of Kartoum Sabaloka gorge 80 m north of Kartoum Arid plain dotted with low hills and rock outcrops Arid plain dotted with low hills and rock outcrops

The Main Nile in Egypt –Characteristics Major issues are storage and water use Major issues are storage and water use No flows are generated below the Atbara confluence No flows are generated below the Atbara confluence Aswan High Dam Aswan High Dam –Storage of flood water –1/3 lost to reservoir evaporation –Allows increased water availability for irrigation & hydroelectric –Annual release decreased, but provides a steady yield downstream.