This paper revisits a widely cited study of the Boyne catchment in eastIreland that attributed greater streamflow from the mid-1970s to increasedprecipitation linked to a shift in the North Atlantic Oscillation. Using themethod of multiple working hypotheses we explore a wider set of potentialdrivers of hydrological change. Rainfall–runoff models are used toreconstruct streamflow to isolate the effect of climate, taking account ofboth model structure and parameter uncertainty. The Mann–Kendall test formonotonic trend and Pettitt change point test are applied to exploresignatures of change. Contrary to earlier work, arterial drainage andsimultaneous onset of field drainage in the 1970s and early 1980s are nowinvoked as the predominant drivers of change in annual mean and high flowswithin the Boyne. However, a change in precipitation regime is also presentin March, thereby amplifying the effect of drainage. This new explanationposits that multiple drivers acting simultaneously were responsible for theobserved change, with the relative contribution of each driver dependant onthe timescale investigated. This work demonstrates that valuable insightscan be gained from a systematic application of the method of multipleworking hypotheses in an effort to move towards more rigorous attribution,which is an important part of managing emerging impacts on hydrological systems.
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