H2Oceans & rivers: water of the Algarve

It’s the reason almost everybody visits the Algarve. You dive in it, swim in it, surf in it, splash in it and laze in it on an inflatable plastic dolphin. You use it to fuel you water pistol and take some pictures when it looks amazingly good but actually feels freezing. But apart from that, what do we know about the H2O in Portugal’s south? Where does the water come from, what’s the average temperature, how salty is it? Enjoy the Algarve investigates.

See the original article in Enjoy the Algarve – magazine July 2016

Water has always played an important role in Portugal’s history. A seafaring nation, in the 15th century, sailors gathered their sextants, climbed into their boats and set off into the ocean to develop a maritime trade. In the past, water even decided where in the countryside villages were established. As fertile soil was only found near rivers, agricultural settlements like Carriços were built on top of nearby hills, leaving the good ground for the likes of tomatoes and lettuce. Not many new towns have been constructed lately, but houses close to the sea or river are still worth more than their landlocked counterparts. The role of water has changed, but its importance hasn’t. H2O has become the Algarve’s number one tourist attraction, from water parks to the over 200km of Atlantic coastline.

Atlantic-Med mix

The Atlantic Ocean is of course the Algarve’s main body of water. It’s the world’s second largest ocean, covering about 22% of the Earth’s surface. But the water reaching our shores actually comes from two different oceans; the Atlantic, which comes from the south, and the Mediterranean ocean from the east. Those two meet at the Gibraltar Strait (south of Spain, see the picture below by ESA astronaut Tim Kopra), where the difference in temperature and salinity causes an area with two shades of blue (the Mediterranean water is heavier and saltier). Visit the area on a nice day and you’ll be able to see the different colours.

On average, the Atlantic is the saltiest major ocean, with salinity levels ranging from 3.3 to 3.7% by mass. However, this varies with latitude and season; in the Portuguese seaside waters it’s about 3.5% (35 parts per 1000). In other words: we don’t recommend drinking it. This salinity also has its advantages such as, of course, the sea salt, which in the Algarve is harvested in salinas in Castro Marim, Fuseta and Olhão.

Bye bye towel

Another characteristic of the ocean is the tidal movement. You know, that annoying thing which happens when you’ve parked your towel close to the water edge as you’re visiting Praia da Rocha in the middle of August and it was the only place left. Leave five minutes to get an ice-cream and there’s no need to worry about sand on your towel anymore as it has all washed off. In the Algarve we have semidiurnal tides, which means that low and high tide both happen twice a day. Founder of the first RYA sea school in Portugal Martin Northey explains the Atlantic tides extensively on the Algarve Daily News website: contrary to other places such as the Bay of Fundy in Canada, where the difference between high and low water can exceed 15 metres, the tidal range in Portugal is only up to 3 metres. (Still, that’s enough to wash away your flip flops pretty fast if you don’t pay attention).

Seawater temperatures range from 12˚C in winter time to 25˚C in the summer. Usually, the water is warmer in the south and cooler in the west. In other words: if you fancy hot water, you should be bathing in Vila Real de Santo António instead of in Monte Clérigo. August and September are the best months to swim if you’re not keen on freezing your balls off, but do realise that the sea in south Portugal never reaches Caribbean temperatures. Then again, being heated up for an entire summer (with some support of the North Atlantic current as can be seen in the image below by Andrew Ryzhkov) can make swimming in shallow lagoons a pleasant affair even in early November (at least, that’s what we at Enjoy the Algarve thought last year).

Maldives of the Algarve

But there’s way more to the mixture of hydrogen and oxygen molecules in the south of Portugal than just the Atlantic Ocean. Groundwater for example, which in the Algarve is mainly used for irrigation. (Interested in Portugal’s groundwater situation? Check out this EASAC report). And rivers, from the over 700km long Rio Guadiana, which separates us from Spain in the east, to the Rio Seixe, which forms the natural border with the Alentejo, in the northwestern part of the Algarve. Together they transport billions of litres of water and make for calm, family-friendly riverside beaches such as Praia Fluvial in Alcoutim.

Then there are the barragens, water reservoirs, and the fontes, natural springs that run through the centre of many Algarvian villages, including Alte and Estômbar to name just two. Were those fontes originally providing the town with water for washing, nowadays they are mostly inhabited by ducks and have more of a let’s-meet-up-and-have-a-picnic function. It seems that a stream of water is almost as quintessential for a successful Sunday afternoon BBQ with the entire Portuguese family as piri piri chicken is. By the way: washing your clothes in the river is now frowned upon.

Other special places are the Ria Formosa lagoon (see picture below by Marijke Verschuren), also called ‘Maldives of the Algarve’, and the estuary of the Ria Alvor. Both are an important source of seafood such as clams, cockles and mussels. The Ria Formosa is a shallow lagoon, with an average depth of 1.5m, up to 3.5m in the channels. About 55km long and 6km wide, stretching all the way from Faro to Cacela Velha, it consists of five sandy barrier islands which make for an extremely pretty view, especially when seen from above. Six inlets allow for a large tidal exchange of water with the Atlantic, but the inner channels of the lagoon range from brackish (in winter) to hypersaline in summer time because of the salt pans. (Want to know more about the Ria Formosa? Check out this 

scientific publication by Alice Newton and Stephen M.Mudge).

Not too many streptococci

Over all, the quality of the water in the south of Portugal is pretty good. This year, another three Algarve beaches have been awarded a blue flag status, raising the amount to a total of 88 for 2016. (Picture below by stavros1 shows the blue flag beach Praia da Rocha Baixinha). The Blue Flag is a certification by the Foundation for Environmental Education (FEE), meaning that the beach meets stringent criteria which also include water quality. Water at Blue Flag beaches must be free from sewage and is therefore continuously monitored for the presence of three types of bacteria; total coliform, faecal coliform and faecal streptococci.

These bacteria levels should be pretty low (below 500/100ml for total coliform, below 100/100ml for faecal coliform and below 100/100ml for faecal streptococci to be precise), although marginally higher levels are allowed a few times during the season. Also the physical-chemical parameters have to be monitored, which basically means the water should be free of oil film or odour, the pH should be between 6 and 9 and there shouldn’t be any floatables in it. No, they don’t mean inflatable pool toys, it’s things like bottles, glass or rubber that are forbidden.

Some people fear that the scheduled oil drillings in the Algarve will negatively influence the water quality, especially if controversial drilling techniques such as fracking are used. It’s unclear yet if all the planned drillings will go ahead, but just to be on the safe side, better make the most of the water this summer, when it’s still clean. Oh, and try to keep it unpolluted please, after all, it’s a main source of life.


See the original article in Enjoy the Algarve – magazine July 2016

Posted in Features.