Portugal’s Reservoirs Slip Toward Summer Lows, Raising Algarve Worries

Foreign residents who spent last winter watching swollen rivers spill onto quaysides may be surprised to hear that Portugal’s reservoirs are already sliding toward their seasonal lows. National water-monitoring data released this week show an overall picture that is still comfortable by historical standards, yet a handful of southern basins are once again flirting with drought. In practical terms, that means expats in Lisbon can water their rooftop herbs without guilt, while small-town gardeners in the western Algarve should keep one eye on coming utility bills.

Why reservoir levels matter when you live here

Portugal relies on 200-plus albufeiras to smooth out a Mediterranean climate where rain falls hard in winter and disappears in summer. Those stored reserves feed municipal taps, irrigate the fruit that stocks market stalls, and drive turbines that keep electricity prices comparatively low. Foreigners often underestimate how quickly supplies shrink between May and September, especially south of the Tejo, where hotter weather accelerates evaporation. The national water institute (SNIRH) therefore publishes monthly snapshots. The August read-out shows that 36 % of monitored reservoirs remained above four-fifths of capacity, while only 4 % dipped below two-fifths—reassuring figures that nonetheless hide sharp regional contrasts.

Winners and strugglers in the late-summer scoreboard

Basins threaded through the wetter North and Interior once again topped the table. The Douro stood at 88 % full and the Guadiana at 85 %, buoyed by both spring downpours and regulated inflows from Spain under the Albufeira Convention. The Vouga, Cávado and Tejo hovered just below 80 %, more than enough to meet urban, industrial and hydro-power demand. At the other end of the scale, the western Algarve’s Ribeiras do Barlavento held just 48 %, the Sado 52 %, and the coastal Mira 55 %. Although still above emergency thresholds, each of those basins now sits below its own 30-year August average, meaning any dry autumn could force restrictions.

Barlavento’s roller-coaster year

If you bought a villa near Lagos last summer you may remember tanker trucks shuttling water to parched golf courses. At that point Barlavento reserves had collapsed to a record 17 % of capacity. Heavy January storms lifted the figure past 60 %, but a scorching, tourist-packed summer erased much of that gain. Climate scientists blame a combination of higher evaporation rates, intense irrigation for avocado and citrus groves, and growing urban demand. Local councils have already hinted that outdoor pools registered as "+extra-large" could face filling limits unless September storms arrive on cue.

Engineering a buffer: from desalination to dam facelifts

To end this boom-and-bust cycle the government has rolled out the Plano Regional de Eficiência Hídrica do Algarve, anchored by a €108 M seawater desalination plant in Albufeira. Scheduled to open in 2027 with an initial output of 16 million m³, the project faces court appeals over land expropriation and environmental clearance, yet officials insist ground works will begin next spring. In parallel, construction crews are already sealing leaks in the Bravura dam and converting the Silves-Lagoa-Portimão irrigation grid into a pressurised, low-loss network. Feasibility studies for two new reservoirs—Foupana and Alportel—are pencilled into the national strategy Água que Une, giving the Algarve an eventual three-pronged safety net: stored river water, desalinated seawater and treated wastewater for crop spraying.

Reading the skies: what forecasters predict for 2025-26

Meteorologists at IPMA expect an autumn that is warmer than average and neither particularly wet nor dry, followed by a mild but rainier winter, with most downpours concentrated north of Coimbra. That pattern historically leaves the Mondego, Mira and Sado basins exposed, because the frontal systems that drench Porto often fizzle before reaching the Alentejo plain. The models do show a burst of December rainfall that could recharge soil moisture across central Portugal, yet even that scenario would do little for the lower Alentejo and western Algarve, where run-off is fast and aquifers shallow. In short, the basins already below par cannot count on nature alone.

What foreigners should keep in mind

Property owners south of Lisbon should watch municipal websites for tiered water tariffs that penalise heavy summer consumption. Rural entrepreneurs eyeing kiwi orchards or glamping sites must build contingency storage into business plans, because trucking water is expensive and sometimes banned during peak shortages. Conversely, hydro-dependent electricity prices tend to soften when the Douro and Guadiana are as high as they are now, a small but welcome bonus for anyone signing a fixed-rate energy contract. Finally, if you are scouting real estate, remember that a hillside plot with a private borehole is only as reliable as the nearest basin’s long-term health—and in Portugal’s deep South, that health increasingly hinges on desalination plants and modernised dams, not on the next rainy week.