When we talk about swimming in open waters, you could say the same ideas come to our minds: visibility, temperature, currents,… but it is also true that the accompanying adjectives will always depend very much on where are we going to swim. When swimmers from Galicia, particularly those swimming in the Rías Baixas, are asked what the swimming conditions to swim in these waters are like, the answer will be clear, using a platitude, very typical Galician: “It depends…”
Actually, , beyond clichés, this is how things really are. The number of different responses is not only due to our swimming inside a estuary or in open sea, because even inside a estuary it will depend on whether we swim on the eastern or western side, close to the shore, along its major axis or crossing it, or whether the wind is blowing from the South or from the North.
There are two major factors that stand out above the rest and when swimming in the waters of the Rías Baixas and make the real difference when comparing these waters to others in the Iberian Peninsula: currents and temperature.
For those reading this text, it may come as a surprise to learn that, in the summer, the water in the inner parts of the estuaries is usually quite colder than in the Atlantic Ocean or the Cantabrian coast. This means it may range from 15ºC to 20ºC, the average temperature being around 18ºC. Moreover, it can go down two or three degrees in just a couple of days and then take almost a couple of weeks to bounce-back to the original temperature. That is why we answer… it depends on when we are asked about the water conditions.
The reason for this odd behaviour of the superficial temperature is the so-called oceanic upwelling, a phenomenon that takes place in a hardly a handful of other places in the world, and is the source of the fish wealth in the estuaries. The superficial water in the estuaries is substituted by a much deeper and colder oceanic water that is also very rich in nutrients that supports the primary and secondary production and the ecological biodiversity. The upwelling takes place when the wind blows from the North, predominant during summer, and when the Azores anticylone is present in high latitudes, but it does not remain in the same place during the entire season.
Because of this, for instance, during the summer of 2013 from mid July to early August the water in the Ons island was around 21º C and in less than a week fell down to 15º C due to the winds from the North. However, during the summer of 2014 the water temperature was always below 18º C and only reached 20º C in September and remained like that until October. So, if you ask what the temperature of the water the day of the competition will be, we have no choice but to answer …”It depends”.
The second characteristic of these waters is the superficial water currents. In contrast with what happens in the Mediterranean, the tidal range in Galicia is quite significant, about 3.5 meters, meaning that the process of renewal of water in the estuaries takes around 6 hours. This causes the development of superficial currents, that add on top of those caused by the wind. The two of themogether can reach 1 m/s (3,6 km/h) in the Ons Island. It may not look like a lot, but if you think about how it takes you to swim 3000 metres in a swimming pool against that current it doesn’t seem to be so little, does it?. Imagine how little progress you would make against that current. Fortunately, with a normal soft wind regime (North or South), which is usually the case for the dates of the competition, there will be lateral, not frontal, currents that will not be stronger than 0.4 m/s. As we discussed for the temperature, it all depends….
But if you ask us about the beauty of the place in which you are going to swim, our answer will be unanimous: it is really beautiful!!! Bear in mind that you will leave from the beach of a national park, which cannot just be an ordinary national park when in the Ons Island, just a few metres from the departure, there is a place named Hell´s hole (Buraco do inferno) or when the Cies Islands were considered by the Romans as the Islands of the Gods.
When this year you swim the first 7 km in the Atlantic Ocean you could think that you are going over the remains of some of the 32 shipwrecks catalogued in the National Park and then, for the next 6 km, you will enjoy a spectacular and diverse coastline with many beaches and cliffs, with a rich sea bed with all sorts of flora and fauna. If you are lucky, dolphins may greet you before your arrival.
With or without currents, with more or less cold, we guarantee that it will be an unforgettable experience, although, well, that depends, doesn’t it?
Eugenio Fuentes, Metereology enthusiast and advanced swimmer in open waters.
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