Over the last twenty years, most European cities have had to face a new and unforeseen phenomenon, a reduction in the consumption levels of urban technical networks (and in particular water systems). The reasons for this phenomenon are numerous, from technical improvements of domestic appliances and deindustrialisation to changes in behaviours of users and the development of policies promoting sobriety and moderation in the use of natural resources. This is however a symptom of a larger process rather than a process per se. Indeed, declining consumption levels reveal the slow decay of the traditional model of management of urban networks, which has long relied on increasing demand associated with perpetual extension of the network. The erosion of this model is forcing network operators to confront a new form of vulnerability, which I term infrastructural vulnerability, the effects of which touch all components of a network, from users to pipes through operators and regulators. The thesis argues that this changing consumption regime is no single interlude, but rather constitutes the emergence of a new mode of network management. As such, it can be interpreted as an infrastructural bifurcation, i.e. a radical and durable transformation of network management as a means of adaptation to this regime of shrinking demand. To deal with this challenge, urban technical network operators have had to adapt and decided to transform both their business model and their territorial base. In order to grasp the rationales of these changes, I opted for a methodology involving being embedded for several months within two local firms facing this issue of diminished consumption with differing levels of intensity. The first is a multi-utility in the eastern part of Germany (Städtische Werke of Magdeburg), while the second is a water and sanitation operator in the south of Spain (EMASESA in Sevilla).My approach combines contributions from Science and Technology Studies (STS), urban political ecology and work on urban shrinkage to reveal that an emerging model of network management is yet to be fully stabilised, but that common adaptation strategies can be observed in both the cases. These strategies are not limited to technical adjustments or tariff increases to compensate the losses due to non-consumed volumes. The transformation in management model relies not only on major technical changes (such as downsizing, resizing or recentralisation of the network), but also on organisational shifts and new relations and arrangements between users and operators. Network operators have thus modified their role to become more than only suppliers of fluids. Their new business model has consequently reoriented production of value towards the development of services for users and the downstream part of the sector. This shift has a spatial dimension, as operators are also experiencing a form of rescaling of their management. The search for new economies of scale to preserve the stability of their socio-technical systems pushes them to extend their functional territories. This leads to potential conflicts with the local actors of the absorbed territories, but also to new forms of territorial solidarity and spatial redistribution. Systemic transformation thus sketches out a new geography of urban technical networks which advances work on local infrastructure firms and on network evolution by integrating the neglected configuration of a shrinking demand regime