Geophysical and multi-criteria decision methods for delineating groundwater potential in coastal terrains: a study from Port Sudan

Why finding hidden water matters here

In large parts of eastern Sudan, rain is scarce, rivers are dry for most of the year, and more people are moving into cities fleeing conflict. Port Sudan, a fast‑growing coastal city on the Red Sea, now depends heavily on underground water to drink, cook, and support industry. Yet this water is mostly stored in cracks in hard rock and in narrow belts of sand and gravel, making it difficult and expensive to find by drilling alone. This study shows how satellite measurements of Earths gravity, combined with smart mapping and decision tools, can point to the most promising places to search for new wells in and around Port Sudan.

The challenge of water in a dry coastal city

Port Sudan lies between steep Red Sea Hills in the west and a low coastal plain in the east. With only about 200 millimeters of rain a year and very high evaporation, surface water is almost absent. People rely on groundwater stored in two main types of underground reservoirs: shallow alluvial deposits made of sand and gravel along dry riverbeds (wadis) and the coastal plain, and deeper fractured basement rocks made of ancient hard crystalline material. The shallow aquifers can yield good amounts of fresh water but are vulnerable to saltwater seeping in from the sea. The fractured rocks, common farther inland, hold less water and are hard to predict because the water is confined to narrow cracks and weathered zones.

Using gravity to see underground structures

Many of the breaks and cracks that guide groundwater lie deep below the surface and leave no visible trace that satellites or field mappers can easily see. To reveal them, the researchers turned to satellite gravity data, which record tiny changes in Earths pull caused by differences in rock density. After correcting these data for terrain effects, they separated deep, smooth background trends from shallow, sharper anomalies linked to local structures. By applying several edge‑detection filters and a technique called Euler deconvolution, they traced networks of hidden fractures and faults and estimated their depths. The result was a detailed map of lineamentslong, narrow zones where rocks are broken and potentially more able to store and transmit groundwater.

Weighing what controls where water can collect

Gravity alone cannot tell how much water a place can hold, so the team combined it with other factors that influence groundwater recharge. Using a method called the analytical hierarchy process, they asked: which features matter most for building a useful aquifer? Geology turned out to be the key, especially thick alluvial deposits with high porosity and permeability. Rainfall patterns, the density of fractures, the arrangement of streams, land use, and slope were also rated and mapped. Gentle slopes and low stream density were favored because they allow more rainwater to sink into the ground instead of running off. Tree‑covered land was considered more favorable than paved urban areas, which shed water quickly. Each factor was given a numerical weight and combined into a single index that classifies the landscape into low, medium, or high groundwater potential.

Testing the map against real subsurface data

To check whether their map was trustworthy, the researchers compared it with two‑dimensional models of the subsurface derived from the same gravity data, supported by information from local boreholes. These models showed how thick the alluvial layers are and how the hard basement rock surface rises and falls beneath them. Where the new map predicted high groundwater potentialmainly in the eastern coastal plains and along major wadisthe gravity inversion revealed deep, fault‑bounded basins filled with sand and gravel up to more than 25meters thick, ideal for storing water. In contrast, western areas marked as low potential corresponded to thin or absent sediment cover above rugged basement rock, implying small, unreliable supplies confined to fractures.

What this means for future wells and planning

For non‑specialists, the take‑home message is that it is possible to produce a reliable, city‑scale groundwater prospect map without drilling hundreds of test holes. By blending satellite gravity data, basic maps, and a transparent weighting of what makes a good aquifer, this study outlines where further, more detailed field work and well drilling should be focused around Port Sudan. The high‑potential zones in the alluvial plains are the best first targets, while basement areas in the west may still hold local supplies but require more careful, site‑specific checks. The approach is cost‑effective, repeatable, and suitable for other dry coastal regions facing similar water stress, helping planners move from guesswork toward evidence‑based groundwater development.

Citation: Mohammed, M.A.A., Daoud, A.M.A., Kazem, M.M. et al. Geophysical and multi-criteria decision methods for delineating groundwater potential in coastal terrains: a study from Port Sudan. Sci Rep 16, 5497 (2026). https://doi.org/10.1038/s41598-026-35127-y

Keywords: groundwater, Port Sudan, gravity mapping, aquifer, water scarcity