Turning deserts into sea: Qattara Depression, in Egypt’s Western Desert
The idea proposes creating new inland seas inside large desert depressions located below sea level, allowing seawater to flow inland and remain there permanently. The objective of the proposal is to investigate whether redirecting seawater into large desert depressions located below sea level could create stable inland basins able to store substantial volumes of water, contributing to a measurable slowing of sea level rise, while also generating local environmental and socio-economic opportunities.
One of the most studied cases is the Qattara Depression in Egypt’s Western Desert, a vast basin that lies more than 130 meters below sea level and was once connected to the sea millions of years ago. Researchers, including climate scientist Amir AghaKouchak from the University of California, Irvine, are exploring whether reconnecting such depressions to the Mediterranean through canals or tunnels could create stable inland seas. In arid climates, strong evaporation would help maintain continuous inflow, turning these basins into long-term reservoirs that remove hundreds of cubic kilometres of water from the oceans. On a global scale, this would translate into sea level reductions measured in millimetres, a marginal but not meaningless contribution in a climate context where every fraction matters.
Why the Qattara Depression draws scientific attention
The Qattara Depression is considered a particularly interesting case because it combines several rare conditions. Its large surface area, extreme aridity, and relative proximity to the Mediterranean make it technically conceivable to study controlled reflooding scenarios. Unlike many other below-sea-level basins, Qattara is vast enough to host a significant volume of water, while its desert climate would naturally favour evaporation over time, sustaining a continuous inflow from the sea.
A complementary idea, not a climate solution
Researchers are careful to stress that inland sea reflooding is not a solution to climate change, nor an alternative to cutting greenhouse gas emissions. Its potential contribution to slowing sea level rise would be limited. However, in a context where coastal risks are increasing worldwide, even marginal contributions are being examined as part of a broader portfolio of adaptation and mitigation strategies. The value of the proposal lies as much in its exploratory nature as in its possible outcomes.
Environmental risks beneath the surface
The most critical concern raised by scientists is the risk of salinization of soils and freshwater aquifers. Many desert regions, despite their dry surface, host underground reserves of freshwater that sustain oases, agriculture, and local communities. In sandy deserts, highly permeable soils can allow saline water to migrate vertically and laterally, potentially contaminating aquifers that formed over thousands of years and recover extremely slowly once salinized.
How research addresses salinization and groundwater impacts
For this reason, inland sea reflooding is approached with extreme caution. Current research focuses on detailed hydrological and hydrogeological modelling, designed to simulate salt transport in soils and aquifers over long time horizons. Scientists are exploring controlled engineering solutions such as staged filling, hydraulic barriers, basin lining, and continuous monitoring systems. The objective is to confine seawater within the depression and ensure that evaporation, rather than infiltration, remains the dominant process.
When salinity is already part of the landscape
Researchers also distinguish between depressions connected to active freshwater systems and those that are already saline by nature. In Egypt, the Fayum Depression offers a useful reference. Its saline lakes, such as Lake Qarun, have persisted for centuries under relatively stable hydrological conditions. While Fayum is not directly comparable to Qattara, it shows that inland saline water bodies can exist over long periods when interactions with freshwater aquifers are limited.
Potential local benefits and new opportunities
Beyond global sea level considerations, the proposal attracts interest for its potential local and regional impacts. These could include renewable energy generation during the filling phase, opportunities for saline aquaculture, tourism development, and the creation of new aquatic ecosystems. In some scenarios, changes in local humidity and microclimatic conditions are also being explored, although these effects remain highly uncertain and site-specific.
Between innovation and precaution
Inland sea reflooding remains a research concept rather than an engineering plan. Its scale, irreversibility, and long-term consequences require a high level of scientific evidence, environmental assessment, and governance. As AghaKouchak and other researchers emphasize, the role of science is not to promote quick fixes, but to provide solid data so that societies and governments can make informed decisions.
Whether inland seas will ever become reality remains uncertain. What is already clear is that such ideas push climate thinking beyond conventional boundaries, forcing us to confront the deep connections between oceans, deserts, groundwater, and human systems.
Turning deserts into sea: Qattara Depression, in Egypt’s Western Desert
