Lake Nasser

This record is centred on Lake Nasser, the roughly 300-kilometre Egyptian portion between the High Dam and the Sudan border. Lake Nubia continues for about 196 kilometres through northern Sudan toward Dal Cataract. Publications often use “Lake Nasser” informally for both reaches, so every combined measurement below is labelled as applying to the full reservoir.^[2][4]

The page does not treat the approximately 2.4-million-km² catchment above the High Dam as part of the lake. Nor does it include the lower Nile, the older Aswan Low Dam downstream, or the separate Tushka Lakes west of the Nile valley. Those are connected features, not alternate boundaries of Lake Nasser.^[2][4]

Several dates describe different construction milestones. Reservoir closure and impoundment began in May 1964; Egypt's ministry says full storage began in 1968, the High Dam works were completed in 1970, and the formal inauguration followed in January 1971. None of those dates is a natural “formation age”: the basin is a twentieth-century flooded river landscape.^[1][2]

The dam closes the Nile at 23°58′ N, immediately south of Aswan. From there the reservoir trends south through Egyptian Nubia, crosses 22° N into Sudan, and narrows toward Dal Cataract near 20°27′ N. FAO gives overall longitude limits of 30°07′–33°15′ E. These limits orient an irregular water body; they are not a point coordinate and they include both national reaches.^[4]

At a published reference water level of 180 m above mean sea level, FAO's historical directory gives the full reservoir an area of 6,216 km²: 5,072 km² in Egypt and 1,144 km² in Sudan. It gives a maximum length of 496 km, a mean width of 12.5 km, a mean depth of 25.2 m, a maximum depth of 130 m, and stored volume of 156.9 km³. These are stage-specific legacy morphometric values, not a current shoreline survey; the source does not identify the vertical datum behind “mean sea level.”^[2]

A later bathymetric paper reproduces another historical table with 6,276 km² and 481.8 km at the same nominal 180-m stage. The roughly one-percent area difference and 14-km length difference are not reconciled by a common mapping method, so this page retains the internally consistent FAO set rather than averaging them. Egypt's ministry separately states 169 km³ at the designed maximum level of 183 m; that larger volume belongs to a higher stage and is not contradictory.^[1][2][3]

The deepest continuous line follows the former Nile channel. Side arms known locally as khors occupy tributary wadis and ravines that entered the pre-dam valley. Their tree-like plan is inherited drainage geometry: ridges became peninsulas, hilltops became islands, and low valley floors became long bays. Kalabsha and Allaqi are major eastern arms; Tushka is a broad western arm.^[3][4]

The shore is physically asymmetric. A 2016 bathymetric study describes the eastern margin as generally rockier and steeper and the western margin as flatter, more open, and often sandy. In its sonar-and-GPS surveys of five Egyptian khors, Tushka Khor extended about 34.5 km from its mouth and held shallow margins, a deeper former channel, and islands that appear or merge as stage changes. The example shows why one shoreline length or island count cannot be treated as permanent.^[3]

The dam created the water body but not the valley relief beneath it. River incision and older wetter phases had already cut the Nile corridor, gullies, wadis, and alluvial surfaces; impoundment then flooded the lowest connected ground. This sequence distinguishes Lake Nasser from a tectonic or volcanic lake basin.^[5]

Along much of the Egyptian western shore, Nubian Sandstone—sandstone beds with clay, siltstone, and shale interbeds—rests on an uneven Precambrian crystalline basement. Basement rocks crop out toward the south, while younger sedimentary units, Quaternary sand sheets, dunes, and wadi deposits occupy other sectors. West of the lake, the low-relief Nubian Plain rises toward the Sinn el-Kaddab limestone plateau and escarpment. These changes in rock resistance and relief help produce alternating sandy open margins, rock-bounded reaches, promontories, and incised khors; “Nubian Sandstone Aquifer” names the regional groundwater system, not the reservoir itself.^[5]

The Nile is the only sustained inflow and the normal outflow. Water arrives from Sudan after the White and Blue Niles meet at Khartoum and the Atbara joins farther downstream. FAO's basin review attributes the sharp flood-season inflow mainly to the Blue Nile and Atbara systems draining the Ethiopian Plateau, while the White Nile supplies a steadier year-round component from the equatorial lake region. Local khors can carry short-lived storm runoff, but rainfall beside the reservoir does not maintain it.^[4]

Water normally leaves through the High Dam into the regulated lower Nile. The reservoir therefore has an outlet and is not an endorheic, or closed, lake. Its level reflects upstream inflow, dam releases, changes in storage, evaporation, local inflow, and much smaller seepage exchanges with adjacent sandstone aquifers.^[1][5]

At very high stages a second pathway becomes active. Egypt's ministry states that the Tushka spillway begins discharging above 178 m toward a Western Desert depression about 250 km south of the dam. Satellite-based research documents overflow episodes in 1998–2002 and again from 2019 into the early 2020s; the resulting Tushka Lakes are temporary receiving basins outside Lake Nasser, not permanent arms of it.^[1][7]

Current slows abruptly where the Nile enters the southern end. Coarser material settles first near the reservoir head and through Lake Nubia; finer silt and clay travel farther into the Egyptian reach. FAO describes a riverine southern zone, a transition zone, and a more lake-like northern zone. This longitudinal sequence is more useful than saying simply that sediment settles “in the lake,” because deposition is strongly concentrated toward the inflow.^[4]

Historical ILEC records show the same pattern: through the early impoundment period, most measured alluvium accumulated in the approximately 185-km reach from Akasha in Sudan to Adindan at the border. Its 1965/66–1977/78 series also records far more suspended sediment entering than leaving the reservoir in every listed year, though those dated values should not be projected as a constant modern rate.^[6]

In summer, solar heating can stratify the water column, leaving warm surface water above cooler deep water. FAO reports that this layering weakens or breaks down in autumn and winter as surface cooling and floodwater arrival promote mixing. Conditions differ between the deep trunk channel and shallow sheltered khors, so a whole-reservoir mixing label does not imply uniform water temperature everywhere.^[4]

FAO classifies the reservoir region as subtropical, hot, and very dry desert. Rain beside the lake is sparse and irregular; strong sunshine, dry air, high summer temperatures, and persistent northerly winds drive evaporation across the open surface. An early lake-based study using 1970–71 meteorological surveys and both heat-budget and bulk-aerodynamic methods estimated mean evaporation at about 7.4 mm per day, or roughly 2.7 m per year, at an average lake stage of 175 m. It is a period-and-method estimate, not a fixed annual loss for every water level and climate year.^[4][8]

Stage changes translate directly into map changes. FAO's historical inventory gives 3,057 km² at 160 m but 6,216 km² at 180 m for the full reservoir: a 20-m rise more than doubles mapped water area because it floods broad khors and low valley margins. By comparison, deep channel reaches change less in width. This is why area, width, shoreline length, mean depth, and island count must always carry a date or reference stage.^[2][3]

Read the system from south to north: runoff from the Ethiopian Highlands and equatorial lake region combines in the Nile network; the Main Nile enters Lake Nubia in Sudan; the reservoir broadens into Lake Nasser in Egypt; water converges on the High Dam; and regulated discharge continues through the Nile Valley, delta, and Mediterranean Sea.^[4]

The shoreline lies within the Sahara, and the adjoining Nubian Desert contains the Wadi Allaqi drainage that meets an eastern khor. Return to the lake hub, or compare Lake Volta, another African reservoir whose branching plan follows a submerged drainage network under a very different climate.

1. Egyptian Ministry of Water Resources and Irrigation, The High Dam and Aswan Reservoir (accessed 30 August 2026). Official source for storage chronology, the 183-m designed maximum level and 169-km³ capacity, and the 178-m Tushka spillway threshold. The page does not state a vertical datum.
2. Food and Agriculture Organization of the United Nations, Source Book for the Inland Fishery Resources of Africa, Volume 3: Egypt—Nasser/Nubia Reservoir (CIFA Technical Paper 18/3, 1991; directory data citing Entz and other specialist sources). Source for national naming, impoundment milestones, catchment-above-dam scope, and stage-specific 160-, 180-, and 183-m measurements. These are legacy inventory values, not live observations.
3. Abd Ellah, R. and El-Geziry, T., “Bathymetric Study of Some Khors in Lake Nasser, Egypt”, Lakes, Reservoirs and Ponds 10(2), 139–158 (2016). Source for Egyptian Lake Nasser's approximate 300-km extent, the old Nile channel, eastern–western shore contrast, dendritic khors, stage-sensitive islands, the five-khor GPS/sonar survey, and the alternative historical 180-m morphometry.
4. van Zwieten, P. A. M. et al., Review of Tropical Reservoirs and Their Fisheries: The Cases of Lake Nasser, Lake Volta and Indo-Gangetic Basin Reservoirs, FAO Fisheries and Aquaculture Technical Paper 557 (2011), pp. 39–49. Source for endpoint coordinates, two-reach lengths, riverine-to-lacustrine zoning, upstream flow sources and seasonality, bottom sediment, desert climate, evaporation context, thermal stratification, and stage history.
5. Hamdan, A. M., Selim, S. A., and Abdallah, M. M., “Interactions between the surface water and groundwater in the western shoreline of Lake Nasser, Upper Egypt”, Arabian Journal of Geosciences 6, 77–84 (2013). Source for the western shore's geomorphic units, Nubian Sandstone succession, Precambrian basement, desert deposits, faults, and measured lake–aquifer interaction.
6. International Lake Environment Committee Foundation, World Lake Database: Aswan High Dam Reservoir (historical record based on Egyptian Water Research Center and published studies; accessed 30 August 2026). Source for the dated 1965/66–1977/78 sediment budget and early-impoundment deposition between Akasha and Adindan. Its undated headline dimensions are not used here where more clearly staged FAO values are available.
7. Elhaddad, H. et al., “Optimization of floodwater redistribution from Lake Nasser could recharge Egypt's aquifers and mitigate its excessive floods”, Communications Earth & Environment 5, 385 (2024). Source for satellite-observed 1998–2002 and 2019–2022 overflow episodes, maximum-stage context, Tushka Lakes, and their position in depressions west of the Nile Valley.
8. El-Bakry, M. M., El-Hussaini, A., and Metwally, M., “Estimation of evaporation from the lake of the Aswan High Dam (Lake Nasser) based on measurements over the lake”, Agricultural Meteorology 23, 293–308 (1981). Source for the heat-budget and bulk-aerodynamic methods, 1970–71 survey period, 175-m average stage, and 7.4-mm/day annual mean evaporation estimate.