This paper takes a look at the setting up of and important work undertaken by the British government’s Hydraulics Research Station (HRS) in the 1940’s and 50’s. The research station, undertaking hydraulic research with the use of scale models for civil engineering projects, was set up by government in 1945. This was in response to a desire from both government and relevant interested bodies for a large-scale centre to undertake modelling work so as to assess various civil engineering strategies or discover the potential for them, besides harnessing and developing scientists/engineers for hydraulic modelling work in Britain and its Commonwealth and Empire. This paper firstly takes a look at the debates surrounding its setting up and the contextual and political issues involved in finding a suitable site for the laboratory, inparticluar the need for a suitable space where large-scale model work can be undertaken. Secondly, it examines the logics behind its architectural geographies before then, for the majority of the paper, through HRS’s model work on the Severn Barrage between 1945 and 1956, explores how this hydraulic model, calibrated to predict the future, was made, observed, encountered, contested, recalibrated, discussed over and contested among other things. This exploration will lead into discussions around issues of knowledge, temporality, movement, mimesis, materiality, scale, rythmn and turbulence among others and how material hydraulic simulations of future worlds are meant to ‘loop-back’ knowledge and become never through it.