Water in Portugal is a theme that brings great challenges. But Portugal is not a country poor in water resources when compared to other European countries, according to Gonçalo Matias, president of the Francisco Manuel dos Santos Foundation.
In medium terms, and by inhabitant, the amount of water that flows through our water courses, the so -called “annual flow”, is superior, for example, to that of Greece, France, Italy or Spain.
We remember that one cubic meter corresponds to a thousand liters of water: Portugal has about seven thousand cubic meters of water per inhabitant, which is a value far above 2,500 cubic meters considered as a reference value, below which a country becomes vulnerable to water scarcity.
The point is that the Mediterranean climate that encompasses Portugal is characterized by having a very variable precipitation.
First, variable in territorial terms. For example, in the north of the country the average annual rainfall is about five times higher than the interior of Alentejo.
But precipitation is also very variable in temporal terms. In the drier years, the precipitation level is a third of the recorded in the most wet years. And it has a very sharp seasonality.
Precipitation varies in terms of the territory and also from year to year. How does it vary throughout the same year? Do climate change have anything to do with it?
As we see in the graph, during the year, almost 85% of average annual precipitation in mainland Portugal occurs between October and April. After this period, it descends significantly and is practically null from May to September in the south of the country.
Climate change
It is true that climate change has already had an impact and should continue to have it.
Climate change has led to a reduction in precipitation, but, moreover, increased temperature also leads to greater water evaporation. This translates into the reduction of the so-called “water flow”, the amount of water we have available.
The most serious scenarios for the future point to 40% reductions of this availability until the end of the 21st century, when compared to the historical period.
It is also important to remember that most of the Portuguese continental territory is located in international watersheds that are shared with Spain, a country that faces the same challenges as water management and even more sharply.
Portugal has a long history of agreements with Spain about water sharing, namely the Albufeira Convention, whose terms were updated in 2024. However, we have a weakened position because we are downstream in all shared watersheds, which puts us a little at the mercy of the Spanish side management.
The unstable precipitation
Is this variable precipitation that limits water availability in some areas of the country?
Yes, the variability and asymmetry of precipitation condition water availability and the ability to respond to regular needs, especially in periods and drier regions.
In mainland Portugal, half of the water captured annually exists on the surface (such as rivers and ponds), while underground origins provide the other half.
This distribution varies along the territory, namely according to the existence of more or less geological areas capable of storing groundwater, the so -called
Aquifers. But this almost equal distribution between surface and underground waters is common to many other countries in the world. Especially in the south of the country, there are great weaknesses to meet water needs, both current and future.
And it is expected until these weaknesses increase as a result of climate change and increased water demand.
To respond to this problem, Portugal has been building dams throughout its history and especially from 1950.
For example, taking into account the precipitation of these last weeks, at this time the vast majority of the country’s reservoirs, which are the large reservoirs of freshwater formed through the construction of dams, has water above 80% of the capacity.
Almost all watersheds on the continent are above average and storage capacity at 92%.
Water storage in reservoirs contributes to alleviation the difficulties in water availability, particularly in the drier periods. But it is a solution that causes economic and environmental costs, and is subject to physical limits.
What is Portugal’s ability to store water in reservoirs?
Portugal is close to Spain at the levels of storage capacity in reservoirs, with about 1135 cubic meters per inhabitant, more than twice the average of the European Union, which surrounds the 435 cubic meters. Slightly ahead of Portugal is Greece and the top of this ranking is occupied by Sweden and Finland, with triple the capacity of Portugal and Spain.
Construction of new dams and better exploitation of underground resources are possible ways to increase water availability in the drier periods, but this bet is reaching its limit, taking into account the already installed storage capacity and the intense exploration of aquiferous systems, ie groundwater.
Thinking about building new dams or interconnecting them should therefore be very well studied, requiring a comprehensive cost-effective analysis, to take into account, on the one hand, construction, operation and maintenance costs and, on the other hand, the environmental costs of the different alternatives.
What sectors spend the most water?
Agriculture is the great user of water and this happens in both Portugal and Spain. At national level, when we look at the distribution of water use, it is clear that agriculture is responsible for more than three quarters of the volume of water captured and is used in watering.
As for the other sectors, following agriculture comes the use of water by the population – the so -called urban use, which represents 15% of the total. The following is the industry, albeit with significantly lower needs than agriculture.
But there is a wide variation within the territory itself in the use that is made by the agricultural sector.
On the continent, agricultural lands represent 40% of the territory surface, but only 15% of this agricultural area is watering.
In fact, most crops are rainfall, which means that production depends exclusively on rainwater, using soil moisture without the need for artificial irrigation. Regadio areas have a variable distribution in the country.
The watersheds with larger watered areas are the Tagus and Ribeiras do Oeste, Sado and Guadiana, which coincide with the driest regions.
In mainland Portugal, there are currently 560,000 hectares of agricultural area that has to be watered, – to realize the dimension well, a hectare corresponds to a soccer field – and there are projects and pretensions to increase this value significantly.
If, on the one hand, agricultural production by irrigation allows greater added value crops and greater income stability of agricultural companies, its increase will put more pressure on water resources.
How much is this agricultural area – which has to be watered – has it increased in recent years?
Between 2009 and 2019, the watering area increased by about 100,000 hectares, especially in Alentejo, where more than 89,000 hectares began to be watered in the Alqueva influence zone. The trend of increasing the watered areas should remain and more approved or over 75,000 hectares of irrigation, to be developed in the next decade.
The point is that, in addition to increasing the watering area, also changed the type of crops that occupy this area. The surface of permanent irrigation crops increased by 118,000 hectares, especially the vineyard and olive groves. And in percentage terms, the
Small berry fruits (such as blackberries, raspberries or blueberries) and rija bark fruits (such as almonds, nuts or pistachers) were the fastest growing crops.
By expanding the watering and permanent crops (such as olive or almond), the flexibility is lost that annual crops (such as cereals or vegetables) allow, because they can not even be cultivated in drier years, adjusting to water availability.
What regions live a shortage of water?
Water scarcity is defined as a chronic situation in which the search for water is of the same order of magnitude as water availability. This means that the offer approaches demand. And in these cases there is a risk of human activities and ecosystems can be compromised.
The southern Portugal suffers from water shortages. These asymmetries are clear when we look at the so -called water scarcity index, which we see on the map, an indicator adopted by the European Union, to quantify the scarcity of water in the watersheds.
While in the region of Minho and Lima the scarcity level is less than 10%, in the south of the country around 60%. Also the ratio between the volume of water used and the availability of water is 60% in Alentejo and Algarve, when the national average is 45%.
In the case of the Algarve, water availability per inhabitant is less than 1000 cubic hectimeters per year, seven times less than the average of mainland Portugal.
How to deal with water scarcity?
There are several important measures that can help in this challenge. One of them is the short -term reduction of physical water supply losses, which surround the 20% to 30% in urban areas and even exceed 40% in the agricultural sector.
For this it is necessary to improve some distribution networks, especially in smaller municipalities, and invest in the improvement of watering channels between capture and agricultural portion, which is where there is a larger volume of water use and also higher losses.
It would also help invest in support for some farmers to modernize their traditional irrigation systems.
Another measures is the diversification of water supply, for example through the reuse of wastewater and the desalination of seawater. Only 1.2% of the wastewater treated are reused and there is a single desalination center, which is in Porto Santo, other than being built in Albufeira, Algarve.
It is also important to think of greater control of water demand, assuming that not all pretensions of use can be satisfied if it is less productive or less useful to society. And it is also lacking to bet on improved knowledge about water resource management, which is an area that has been sub -financed.
In short, the solution to the challenge of water scarcity in Portugal is in an integrated management of water resources, putting into practice these solutions simultaneously, so as not to compromise the sustainability of ecosystems from now on.
