Ground Water: 

The availability of water in shallow aquifer is relatively small because of over abstractions of ground-water and it mainly depends on the rainfall which is low and might differ from one year to another.

Surface Water:

Surface water is one of the conventional resources and the availability of surface water is limited and temporary because of low rate of rainfall and high evaporation rates.

Waste Water:

Energy consumption is one of the biggest issues confronting wastewater plants, mainly the process of filtering wastewater and the impact of sludge disposal.

Reverse Osmosis (RO):

Beside the huge energy consumption, contributing to the emission of greenhouses gases, another problematic is that the membranes must be rinsed and chemically cleaned periodically. High maintenance costs.

MEB or MSF :

Energy consumptions is one of the biggest issues. Valuable gases and petroleum is used to keep these plants running. Emission lots of greenhouses gases.

Stormwater:

Storm water picks up and carries numerous pollutants from air, in particular urban areas. Low precipitation phenomena

Foreigners control the private water sector in Portugal​

Of the seven largest private groups in the sector, only one is controlled exclusively by Portuguese companies, which is:  Aquapor

Altogether, these seven private water supply concessionaires in Portugal achieved a turnover of 258,8 million euros in 2016.
Indáqua, which holds about 30% of the market share of this business, promises to invest more in the domestic market in the next years to consolidate and even strengthen this position. 

The desalination system market is highly fragmented, as the market share is divided among several companies. 

In Portugal exists only one desalination plant which is located in Porto Santo, in Madeira (Portugal´s island), which was a pioneer and since 2005 produces about 6900 m3 of drinking water per day for a total of 5000 inhabitants, via revers osmosis.

Some other companies are dedicated exclusively for distribution and marketing of water treatment systems, like for example:

- Cleanpur

- Watertech

- Watercare