- A new research project is looking into the possibility of reflooding the Qattara Depression, a massive low-lying desert area in Egypt, to help counter sea level rise.
- Scientists forecast global sea levels will rise by at least 30 centimeters (12 inches) over present-day levels by the end of the century — and that’s a conservative prediction.
- Mongabay spoke with Amir AghaKouchak, the project’s leader, who says reflooding the Qattara Depression could also bring potential benefits to Egypt, including aquaculture, renewable energy and tourism.
- The idea remains in its infancy and would require the backing of the Egyptian government as well as a great deal of further study.
Sea levels are rising, threatening coastal areas, including cities, around the world. Due to climate change, the global ocean has already risen by 21-24 centimeters (about 8-9.5 inches) since 1880, and the rate is accelerating, according to the U.S. National Oceanic and Atmospheric Administration (NOAA). A new climate idea aims to slow this rise by moving seawater to reflood inland depressions.
The main causes of sea level rise are ice packs melting and the volume of water in the ocean expanding as Earth’s temperature increases due to human-caused climate change. Depending on the ferocity with which we cut greenhouse gas emissions, predictions of future sea level rise vary widely. According to NOAA, if we cap the global temperature rise at just 1.5° Celsius (2.7° Fahrenheit) above pre-industrial levels — nearly impossible at this point — the sea level would rise an additional 30 cm (12 in) by 2100. If emissions remain at the very high end of estimates, sea levels could rise by 200 cm (6.6 feet) by the end of the century, flooding many of the world’s coastlines and affecting tens of millions of people. There are even worse scenarios: if we lose much of Greenland’s ice sheet or the Thwaites Glacier in Antarctica — dubbed the Doomsday Glacier — the resultant rise in water level could affect billions.
A new research grant is looking at the idea of reflooding lowland depressions to alleviate the problem on the coasts, starting with the Qattara Depression, a massive low-lying desert area in western Egypt. Amir AghaKouchak, a professor of environmental and civil engineering at the University of California, Irvine, who focuses on climate extremes and solutions, is carrying out the research under a grant from the ARC Initiative, a climate change fund of the U.S.-based nonprofit Renaissance Philanthropy. AghaKouchak’s work with ARC could be groundbreaking. It is certainly ambitious, and likely to become controversial.
“Inland Sea Reflooding is the reconnection of large, below-sea-level basins to the ocean to create stable inland seas,” he told Mongabay by email. The initial flooding of the depression in Egypt, which at its lowest sits 133 m (436 ft) below sea level, could lower global sea levels by a few millimeters. Moreover, evaporation from the new inland sea would continue to curtail sea level rise over time, AghaKouchak says.
The new sea could potentially bring other benefits, according to AghaKouchak, such as renewable energy, aquaculture and even tourism.
Despite the unorthodox nature of the idea, it’s actually not new. The idea of flooding the Qattara Depression goes back to the late 1800s — and even inspired Jules Verne’s last novel, Invasion of the Sea. In the 1950s, even the CIA looked into the idea. Originally, the point was not to lower sea levels but to produce hydroelectric power, with possible side benefits such as desalination for freshwater and a new coastline for development.
Researching the idea doesn’t mean we’re actually going to reflood the Qattara Depression; many barriers remain, according to AghaKouchak. There would need to be adequate governance; compensation and justice for the sparse populations that currently live in the desert; environmental studies; and agreement within Egypt and the international community.
The Qattara Depression isn’t the only place we could reflood. Others include the Dead Sea, bordered by Jordan, Israel and the Israeli-occupied West Bank, and the Danakil Depression in Ethiopia. None of them are straightforward and all would likely be highly controversial, resting, as they do, amid the debate over whether geoengineering is an appropriate response to climate change, as well as complicated geopolitical relations.
Mongabay’s Jeremy Hance interviewed Amir AghaKouchak about this radical geoengineering, which he emphasizes should not be a substitute for reducing greenhouse gas emissions. The following interview was conducted over email and has been edited for length, clarity and style.
Mongabay: How are you connected to ARC?
Amir AghaKouchak: I am a faculty member at the University of California, Irvine. My work focuses on climate extremes, compound hazards, water resources and climate solutions. I collaborate with ARC on the inland sea reflooding concept, providing the climate, hydrology and risk analysis needed to evaluate feasibility, benefits and trade-offs.
Mongabay: Can you explain what inland sea reflooding is and how it could help lower sea level rise globally due to climate change?
Amir AghaKouchak: Inland sea reflooding is the reconnection of large, below-sea-level basins to the ocean to create stable inland seas. Many candidate sites were once marine embayments or shallow seas that became isolated by tectonics, sedimentation or shoreline change, and later dried. Because these basins sit below sea level, gravity can move water inland through canals or tunnels. The refilled basin then functions as a long-term seawater sink. The initial impoundment removes a defined volume from the ocean, lowering global mean sea level by a small amount. Ongoing evaporation over the inland sea sustains a net ocean-to-basin transfer as long as the connection is maintained. Of course, a fraction of that evaporation later returns to open oceans, but a fraction will also contribute to inland rains. The effect of any single basin is modest, but a portfolio of suitable basins could provide a measurable, durable contribution alongside emissions reductions and coastal adaptation.
Mongabay: You’re currently studying the idea with the Qattara Depression in Egypt as an example. Why did you choose the Qattara Depression? What makes it a prime location for this potential geoengineering?
Amir AghaKouchak: Qattara is one of the world’s largest land depressions below sea level, with extensive area, hot arid climate and proximity to the Mediterranean. Those attributes matter. Large area increases the volume that can be stored during the initial fill. Hot, dry conditions mean high evaporation, which sustains a continuing ocean-to-basin transfer. Being relatively close to the Mediterranean reduces conveyance distance and allows gravity-fed designs, which lowers energy requirements during construction and operation.
Graph of potential targets for inland sea reflooding. Image courtesy of Amir AghaKouchak.
Mongabay: How would such an area be flooded? How much would it lower our seas?
Amir AghaKouchak: In practical terms, reflooding would use a sea-level intake on the Mediterranean connected by a canal or tunnel system to Qattara’s interior. Flow would be regulated for stability, energy opportunities during the initial fill, and environmental safeguards. Based on the depression’s footprint and depth profile, a first-order estimate is that fully filling Qattara to a designed operating level could remove on the order of a few hundred to roughly 1,000 cubic kilometers [240 cubic miles] of seawater from the global ocean. Spread over the area of the world’s oceans, that corresponds to a global mean sea level reduction of a few millimeters, with continued millimeter-scale additional drawdown over time due to evaporation if inflow is sustained. These numbers are deliberately conservative and depend on final design elevations, staging and environmental constraints.
Mongabay: The idea of flooding this particular depression has been around for more than a century. Why do you think climate change might actually make this happen?
Amir AghaKouchak: Two things have changed. First, the problem has changed. Sea level rise is accelerating and intensifying coastal risk, creating demand for complementary solutions that work alongside decarbonization and coastal adaptation. Second, our tools have changed. We now have far better climate projections, satellite and ground observations, geotechnical methods and environmental safeguards. That allows us to evaluate legacy ideas with modern science and governance, quantify trade-offs, and consider limited pilots or phased implementations rather than all-or-nothing megaprojects.
Mongabay: What are the main challenges and benefits?
Amir AghaKouchak: Challenges [include] large-scale earthworks in a sensitive desert environment, potential impacts to groundwater and dust dynamics, salinity management, habitat loss in the inundation zone and dealing with unexploded ordnance in parts of the Western Desert. Some of the candidate sites include local communities, and any change to their environment should be properly coordinated with them. Also, there are long-term obligations to monitor, operate, and mitigate environmental effects, plus license and financing.
Benefits [include] a persistent sink that modestly offsets sea level rise, opportunities for renewable energy during the filling phase, new blue-economy activities such as managed aquaculture and salt or mineral recovery, dust suppression compared with bare [sands], and potential co-benefits for local employment, research and ecotourism if designed carefully.
Mongabay: What kind of governance would be required to actually deploy an idea like this? Would it only require Egypt’s consent?
Amir AghaKouchak: Egypt’s consent and leadership are essential because the project is within Egyptian territory. Beyond national approvals and a rigorous environmental and social impact assessment, best practice would include international consultation and transparency due to the global framing and potential transboundary ecological, climatic or maritime considerations. Engagement with multilateral environmental agreements, regional neighbors, Indigenous and local communities, scientific advisory panels, and independent monitoring would be crucial. Basically, a nationally led, internationally informed governance model with binding safeguards.
Mongabay: Do people live in the area? If so, how many and what would happen to them?
Amir AghaKouchak: The Qattara Depression itself is sparsely populated, but there are communities and nomadic users across the Western Desert and around oases and transport corridors. Any plan must map current land use, heritage sites and seasonal livelihoods; avoid or minimize displacement; and, where unavoidable, follow international standards for compensation, resettlement and livelihood restoration. Early, sustained consultation and benefit sharing are nonnegotiable.
Mongabay: Obviously, this would destroy the existing ecosystem. What could we lose
Amir AghaKouchak: This area used to be under seawater [around 5 million years ago] and because of that the soil is saline and there are limited flora and fauna. But inundation would eliminate some desert habitats including existing flora and fauna, and could affect groundwater-dependent ecosystems at the margins. This is why more in-depth ecological, environmental and social studies are necessary before we can move forward with any of the sites, including Qattara.
Mongabay: Creating an inland sea would create a new ecosystem. What could we expect in terms of benefits for wildlife and Egypt itself?
Amir AghaKouchak: A managed hypersaline to marine-salinity water body can create novel aquatic and coastal habitats that support birdlife and fisheries adapted to those conditions. With smart zoning, you can set aside conservation areas, regulate aquaculture, and design shorelines to promote biodiversity. For Egypt, there are potential benefits in jobs, research, education and carefully governed tourism. None of this is automatic. It depends on clear objectives, water-quality management and rigorous enforcement.
Mongabay: Are there other areas in the world that could be reflooded to lower sea level rise?
Amir AghaKouchak: Yes. A small number of large, below-sea-level depressions near the coast could, in principle, be candidates. Examples often discussed include the Dead Sea basin via Mediterranean or Red Sea links, parts of the Danakil Depression, and selected basins with short, feasible connections to the ocean. Each case is unique and must pass environmental, social, economic and geopolitical tests.
Mongabay: Can you tell us about some of the most promising?
Amir AghaKouchak: We prioritize sites using a simple screen: large area below sea level, proximity to the coast for gravity inflow, arid climate to sustain evaporation, low conflict with communities and heritage, and manageable engineering corridors. Qattara scores well on those criteria. The Dead Sea and Danakil score high on proximity and aridity, but involve complex transboundary governance and sensitive ecosystems. Preliminary multicriteria assessments help identify “no-go” sites early and focus attention on the few places where benefits may outweigh risks.
Mongabay: Given the scale of the climate crisis and the rate at which the seas are rising, do you think this will really be something we may need to do?
Amir AghaKouchak: Reflooding is not a substitute for other solutions such as cutting greenhouse gas emissions or for protecting and restoring coasts. It is best viewed as a complementary, limited-scale option that can contribute millimeters of relief while delivering local co-benefits if done responsibly. Whether we should do it depends on careful case-by-case analysis, social license and strong governance. Our job is to provide the evidence so that decision-makers and communities can weigh the real trade-offs, not the hypotheticals.
Banner image: Soda schweinfurthii, a desert subshrub, native to arid regions from Egypt to the Arabian Peninsula. Image by Krzysztof Ziarnek, Kenraiz via Wikimedia Commons (CC BY-SA 4.0).
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