This paper revisits a widely cited study of the Boyne catchment in the east of Ireland that attributed a change in streamflow during the mid-1970s to increased precipitation linked to a shift in the North Atlantic Oscillation. Using the method of Multiple Working Hypotheses we explore a wider set of potential drivers of hydrological change. Rainfall-runoff models are employed to reconstruct streamflow to isolate the effect of climate taking account of both model structure and parameter uncertainty. The Mann–Kendall test for monotonic trend and Pettitt change point test are applied to explore signatures of change. Different to earlier work, arterial drainage and the simultaneous onset of field drainage in the 1970s and early 1980s were inferred to be the predominant driver of change within the Boyne. There is evidence that a change in precipitation regime is also present, albeit to a lesser extent. This new explanation posits that multiple drivers acting simultaneously were responsible for the observed change. This work highlights the utility of the Multiple Working Hypotheses framework in moving towards more rigorous attribution, which is an important part of managing unfolding impacts on hydrological systems.