Hydraulic installations were an essential element of Roman streets, both those built to be visible, especially public fountains (whether utilitarian or monumental), and the "hidden" installations, largely in the form of conduits that ensured water supply or drainage in the cities. Their study is essential, not only to understand the urban water cycle of which they form part, but also to analyse the evolution of the streets themselves. Several were part of the original urban design and were therefore designed and built together with the streets. Others were added by private or public initiative in response to changes in urban planning.

The aim of this paper is to present, through a selection of case studies, an overview of the hydraulic installations associated with the city streets of Lusitania, one of the three provinces into which the territory of Hispania was divided during the High Empire. The provincial capital, Augusta Emerita (Mérida), one of the most important and best-studied cities of Roman Hispania, offers the most information on all types of hydraulic infrastructures. In other cities, knowledge is more fragmentary. Nevertheless, the preserved remains reveal the existence of these installations in their road spaces, such as fountains and water supply pipelines, as can be observed, for example, in Aeminium (Coimbra), Conimbriga (Condeixa-a-Velha) and Olisipo (Lisbon). Sewer networks were also widespread.

This global approach shows that, although hydraulic installations were essential in the urban landscape of Lusitania, there were differences depending on the degree of urban development, their geographical conditions, and the local building materials and techniques.