The water courses that circulate in the city of Porto were, in the past, of great importance at a social and economic level, having served as poles of water supply to the populations and as a fundamental support in the irrigation of the cultivated fields. In fact, in the parish of Campanhã, in the 18th century, there were 76 mill wheels, distributed along the numerous water courses that ran through the parish, a symbol of the importance of this activity for economic development.

With the growth of the city and urban interventions, many of these water courses were progressively piped and used for the routing of wastewater (domestic and industrial), in some cases duly authorized and on a precarious basis and, in others, improperly. Thus, a break began to exist between the riverside areas and their urban surroundings, which culminated in a position of rejection by the populations, who became accustomed to living with their “backs turned” to the rivers and streams, which further aggravated their state of environmental degradation. The sharp growth of the urban fabric and the gradual occupation of water lines and adjacent areas introduced very significant changes in the urban hydrological cycle, which also manifested themselves in the loss of water quality.

Porto's rivers and streams are an example of the gradual artificialization of river ecosystems that cross an urban area of secular origin. It appears that currently around 75% of the water lines that cross the city are intubated.

Considering that rivers and streams and their respective banks constitute a system of continuous, interconnected and complex natural corridors, and due to the favorable conditions sheltering a large number and diversity of plant and animal species, riverside systems often outnumber the biological diversity of ecosystems surroundings.