Use of alternative water sources – One of the measures foreseen in PENSAARP 2030
If we look at the map of average annual rainfall in Europe, we see that Portugal is not in a bad situation, with variations throughout the country between 750 and 2000 mm, a situation that is further benefited by the fact that most Iberian rivers flow into our territory. But if we analyze the relationship between water demand and availability, we see that the situation is not so good.
Portugal has effectively a serious problem of water scarcity, which, according to recent studies, can be classified as high in the basins of the rivers Vouga, Liz, Cávado and Tejo, as severe in the rivers Sado, Guadiana, Ribeiras do Algarve and Oeste, and as extreme in the basin of the river Mira. This situation of water scarcity is naturally aggravated in years of drought, when demand is maintained, but supply is obviously more limited.
It is therefore important to ensure not only better management of water demand, through more rational and efficient use, but also better management of water supply, using alternative sources, such as treated wastewater.
In Portugal we currently collect about 640 million cubic meters of wastewater per year from the sewer pipes. The good news is that about 99% of this water is treated, thanks to the high investments made over the last two and a half decades. The bad news is that only 1.3% of these waters are reused. We are therefore wasting a significant amount of water and nutrients into rivers and into the ocean.
The reuse of wastewater can therefore assume a more important role in the management of our water resources, for internal uses of the management entity that produces it or for third-party uses, such as the agricultural and industrial sectors.
These uses may imply the need to reinforce the treatment that we do today and certainly requires its transportation to the places of consumption. This can be done directly with networks that allow the distribution of treated water, or indirectly with its discharge into an intermediate water medium, for example reservoirs, from where it is then removed for agricultural, industrial, or other uses.
To promote the reuse of wastewater in Portugal it would be important to re-evaluate the fiscal policy to introduce more incentive to this source of water, for example by making the water resources fee more impactful. Those who reuse would be excused from paying not only the rejection fee, but also the water abstraction fee, with a significant impact on their costs.
It would also be very important to change the current legislation on wastewater use, regarding indirect use through water, which is not covered in the current regulatory provisions. It would be useful to promote the development of technical documentation on the use of alternative water sources, their advantages, disadvantages, and best practices. It would also be important to develop awareness-raising for decision-makers about the use of alternative water sources, including reuse. From the perspective of scientific development, it is important to promote innovation on the use of alternative water sources and disseminate reference cases that motivate their multiplication.
One of the measures foreseen in the new Strategic Plan for Water Supply and Wastewater and Rainwater Management (PENSAARP 2030) is the use of alternative water sources, which includes the reuse of water.
Jaime Melo Baptista
Presidente da LIS-Water, Lisbon International Centre for Water
