The Greek historian Herodotus described Egypt as ‘the gift of the Nile’. Stretching for 6,695 kilometres (km), the Nile is the second longest river in the world and covers an area of about 2.9 million km2. The river has one of the largest catchment areas in the world. The Ethiopian Plateau provides 86% of the Nile’s flow (Blue Nile 59%, Sobat 14% and Atbara 13%), while the contribution from the Equatorial Lakes region amounts to 14% (White Nile). Around 55.5 billion cubic metres per year (BCM/yr), or 97% of Egypt’s renewable water resources, are received from the 1,660 BCM/yr of water that falls inside the Nile Basin. The remaining supply comes from groundwater, residential wastewater, rainfall and desalinated water. About 85% of the Nile waters that reach the Aswan High Dam come from the Blue Nile, Atbara and Sobat, all of which rise in Ethiopia. Approximately 15% of the Nile waters is made up of the White Nile, which draws its water from Lake Victoria and its tributaries.
Because rainfall is scarce, Egypt relies on the Nile for its water needs, and the vast majority of the population lives close to the river. The impact of climate change on the Nile’s flow may be the reason for incidences of both flood and drought in Egypt. As the Nile’s sources are located outside the Egyptian border, so Egypt will not be able to develop and execute plan to alleviate the consequences of climate change on the Nile basin without have agreement with other basin countries.
Egypt’s renewable groundwater is primarily pumped from the Nile Valley reservoir (which has reserves of around 200 BCM) and the Delta region reservoir (with reserves of about 400 BCM). This water is actually a component of the Nile’s water resources.
An estimated 7.2 BCM of water is collected annually from these aquifers, with the delta aquifer accounting for 6.1 BCM (85%). According to the Groundwater Research Institute, this is less than the safe extraction limit of 7.5 BCM.
Figure 1. Water resources in Egypt.
The quality of this groundwater is also superb, with salinity ranging from 300 to 800 parts per million (ppm) in the delta’s southern parts. It is estimated that the withdrawals from these reservoirs approached about 7.5 BCM after 2017 .
Non-renewable groundwater reservoirs can be found in the deep Eastern Desert and Western Desert as well as the Sinai Peninsula. The most important reservoir is the Nubian Sandstone Aquifer system (NSAS) in the Western Desert, whose stock is believed to be around 40,000 BCM, and which runs across north-eastern Africa, including Egypt, Sudan, Libya and Chad. This reservoir is regarded as one of the most important sources of fresh groundwater that is not available for use in Egypt because of the water’s availability at great depths, which raises the costs of lifting and pumping. As a result, only 0.6 BCM of water is currently extracted per year, enough to irrigate approximately 63,000 hectares in the Owainat region. The annual extraction rate is expected to increase to around 2.5-3 BCM/yr as a safe and cost-effective withdrawal limit.
Egypt is almost devoid of rain, except for on the north coast, where rain falls at an average yearly rate of 50-250 millimetres (mm). On the north-east coast, the rain increases towards the east, averaging 150 mm in Arish while reaching about 250 mm in Rafah.
Considering the normal winter precipitation rates, the volume of rainwater that falls over the northern parts of Egypt (an area of about 200,000 km2) is approximately 5-10 BCM/yr. Of this amount, 1.5 BCM flows over the surface, and a large part of it is returned by evaporation and transpiration to the atmosphere. The rest seeps into the ground to be added to the groundwater recharge. The water that flows over the surface from the streams of the valleys is lost in the sea.
The amount of rain falling on the Sinai Peninsula, distributed over its various water basins, as well as the amount of rain that flows on the surface and exits from the water basins towards the sea, is 131.67 million cubic metres (MCM) annually, representing 5.25% of the total rainfall.
It should be highlighted that the average annual rainfall in the country is approximately 8 BCM, with 200-300 MCM/yr harvested in Sinai, the north coast, and the eastern Red Sea mountain.
Reuse of agricultural water
Reused agricultural drainage water is one of the main sources that will be used in the future to enhance water resources availability. This water includes leakage losses from the irrigation and drainage network. It is considered to be low-quality water because of its high salinity (ranging from 700 to more than 3,000 ppm) and its mixing with drain water, which is often polluted.
To reduce environmental risks associated with the reuse of this type of water, it is necessary to effectively treat the water from sub-drains or main drains before mixing it with fresh water.
Reuse of treated wastewater
Treated wastewater can be used for irrigation purposes if appropriate health requirements are met. The annual amount of treated water increased from 0.26 BCM/yr in the early 1990s to about 0.6 BCM/yr in 2000, eventually reaching about 3.7 BCM in 2017. It is used to irrigate non-food crops for humans and animals and to cultivate trees in the desert to produce wood. The focus is on treating this water and separating agricultural drainage from sewage to avoid the risks of chemical waste to public health and the environment.
Despite seawater’s high salinity, which may reach 35,000 ppm, desalination is an effective technique to obtain high-quality drinking water in coastal areas where there are no alternative water resources. The price of desalination depends, as is well known, on the type of energy and technology employed, as well as the size of the project. Nevertheless, even at the lowest cost currently feasible, saltwater desalination is still an expensive endeavour.
Egypt currently has 90 seawater desalination plants in operation, with a total capacity of 1.3 BCM, costing 0.4 billion dollar. Seventy-six units have been constructed and are completely operational, with a daily capacity of 850 × 103 m3. By 2050, there will be 14 functioning plants with a total daily capacity of 450 × 103 m3. The Egyptian government aims to provide 6.4 × 106 m3 per day of fresh water using the desalination technique. However, the increasing water scarcity and high cost of obtaining it from traditional sources on the one hand, and scientific progress in discovering non-traditional sources of energy and low-cost technological methods on the other, may lead to an expansion of seawater desalination in the future.
 Herodotus, 2006.An account of Egypt by Herodotus, being the second book of his histories called Euterpe. (G. C. Macaulay, Trans.), G.C. Macaulay, Editor.
 Negm, A.M., Sakr, S., et al., 2019, An overview of groundwater resources in Nile Delta aquifer, in Groundwater in the Nile Delta, A.M. Negm, Editor. Springer International Publishing: Cham. 3-44.
 Elsaie, Y., Soussa, H., et al., 2022.Water desalination in Egypt; literature review and assessment. Ain Shams Engineering Journal: 101998.