The Waters of Salto — What They Are, What They Do, and Who They Are For

Words by Mathias Nicola · August 2026

It is eight in the morning and the air is cool. You lower yourself slowly into a wide open-air pool, and the water — 36 degrees, silky, smelling faintly of minerals — rises around you. Within minutes, the knees that have been aching since winter loosen. The shoulders drop. The breathing slows. You have not taken a pill. You have not done anything, really, except get in the water. And yet something is clearly happening.

This is not a spa brochure. This is chemistry — and now, for the first time, it has been fully documented. In 2026, the first Vademecum of Thermal Mineral Waters of Uruguay was published, the result of a collaboration between the Universidad de la República (CENUR Litoral Norte, Salto) and the School of Medical Hydrology of the Universidad Complutense de Madrid. For the first time, the thermal waters of Uruguay — and in particular those of Salto — were subjected to the same rigorous hydrochemical and therapeutic analysis applied to the great European spa traditions. The conclusion is clear: these waters work. And now science can say exactly why.

Who comes here — and why

The hottest pool at Termas del Daymán is the one that has always been recommended for rheumatism, and children are kept out of it because of the heat: nobody lasts more than a few minutes in that water. It is my favourite, the one I always go to. Around it there is a smaller, cooler pool for families, and that is where you see children playing and parents with their babies.

The last time I was there I went at about nine in the morning and had one of the other pools to myself for more than an hour. And every time I go I make a point of standing a few times under the chorros, the open-air showers, and letting the water hit my shoulders, my back and my head. I drink it as well, since the water is potable.

Many of the people in the hot pool are not on holiday in any trivial sense. They come back every year — some several times a year — because they have learned, through experience, that the waters of Salto do something for them that nothing else quite replicates. The Vademecum now confirms what they already knew in their bodies.

According to the document, the thermal waters of Salto — Daymán, Arapey, Agua Clara, Club Remeros — are classified as weakly to moderately mineralised, with temperatures above 35°C at the source and up to 46°C. Their dominant ions are bicarbonate and sodium. These properties produce, in clinical terms: muscle relaxation, peripheral vasodilation, analgesic and sedative effects, and modulation of the autonomic nervous system. In plain language: they ease pain, reduce inflammation, calm the nervous system and help you sleep.

What the waters are good for

The Vademecum lists therapeutic indications across multiple medical specialities. For the visitor who wants to know whether this is relevant to them, here is what the science says:

Joint and muscle conditions. Osteoarthritis, chronic back pain, fibromyalgia, tendinopathies, muscle stiffness, recovery after injury or surgery. The thermal water reduces joint load through buoyancy, applies heat deep into the tissue, and eases the kind of stiffness that accumulates over years. For older travellers whose knees or hips have been making travel feel difficult, this is the specific promise of Salto.

Respiratory conditions. Rhinitis, chronic sinusitis, pharyngitis, chronic bronchitis and asthma, always outside the acute phases. The Vademecum lists these waters for them through bathing, steam and inhalation. Its general chapter also notes a growing interest in persistent respiratory symptoms after viral infections, post-COVID among them.

Skin conditions. Eczema, dermatitis and psoriasis in their stable phases, and dry skin. The Vademecum notes that these waters are well tolerated by sensitive skin, and lists them too for the skin after cancer treatment, where they help with hydration and comfort.

Stress, anxiety and sleep. This is perhaps the most universal indication. The combination of high temperature and low mineralisation favours deep relaxation, less stress and better night rest, and the Vademecum lists these waters for chronic stress, mild anxiety and adjustment disorders. These are documented outcomes of bathing in the hot springs, not marketing claims.

Metabolic conditions. This one comes from the Vademecum's general chapter rather than from its pages on Salto: bathing, when integrated into a structured programme of diet and physical activity, has shown positive effects on lipid profiles, insulin sensitivity and weight management, and there is emerging interest in the role of mineral waters in the gut microbiota. For the Salto waters themselves, the document points instead to healthy ageing, fatigue, mobility and recovery after sport.

Where the water comes from

The thermal waters of Salto emerge from the Guaraní Aquifer System — one of the largest underground freshwater reserves on Earth, stretching beneath Uruguay, Argentina, Brazil and Paraguay. The heat comes from the high geothermal gradient of the region and from the basalts that seal the aquifer and keep that heat in. The wells reach the water at different depths: 1,070 metres at Club Remeros, 1,200 at Agua Clara, 1,300 at Arapey and 2,204 at Daymán, the deepest of them all, which is why the water comes out hottest there, at up to 46 degrees. It arrives at the surface already mineralised, with a profile shaped by geology and time.

A practical note for the visitor

The hot springs of Salto cover the whole range. The municipal termas of Daymán and Arapey are open to everyone, unhurried, and used for leisure as well as for treatment: people come to enjoy themselves, to spend a day in hot water, often with the whole family, and the therapeutic side is there for whoever needs it. At the other end, Termas del Arapey has two all-inclusive resorts, Arapey Thermal and Altos del Arapey, the latter a five-star with an eighteen-hole golf course, its own well feeding its pools, an airstrip for light aircraft and a heliport. The main centres — Termas del Daymán, Termas del Arapey, Agua Clara and Termas de Salto Grande — are open year-round. Club Remeros is a private club: its hot spring pools are for members, not for the general public. Several of the centres operate from early morning. Agua Clara, for example, opens at 8:00 AM and offers hydrotherapy showers, massage beds and on-site medical cover alongside its four pools. The water park at Daymán, Acuamanía, is a separate place from the municipal termas, with its own entrance fee, and it is not open all year.

For the traveller arriving with a chronic condition, with post-operative fatigue, with the accumulated weight of years in a body that has simply been asked to do too much — Salto does not offer a cure. What it offers is something quieter and, in many ways, more valuable: time in water that the science now confirms is genuinely good for you, in a place where nobody is in a hurry, and where the act of getting better is treated as something worth taking seriously.

“To think of water as a simple hydrating element is to diminish its true value. Medicinal mineral waters are a complex system in which the water acts as a vehicle for essential elements, allowing them to reach the body naturally.”
— María Lorena Vela, “El agua como agente terapéutico: no todas son iguales”, in Vademécum de Aguas Minerales Termales del Uruguay, Balnea 12, 2026, p. 127

Once you are in the water, nobody is going to hurry you out.