International perspectives on PUB and pathways forward: outcomes of the Perth PUB workshop

Hydrological prediction, where data are available, is relatively easily achieved, albeit subject to significant uncertainties. These uncertainties become crucial when attempting to predict the effects of change in a given catchment. However, the problem of ungauged catchments (by far, the majority) presents marked difficulties for hydrological prediction. Over recent decades there has been a continual decline in hydrological gauging networks, reducing the accuracy of hydrological prediction whilst increasing the uncertainty associated with the prediction and management of both water quantity and quality. Additional threats to water sustainability include encroaching anthropogenic impacts (such as land use change) and climate variability and change. The International Association of Hydrological Sciences (IAHS) has recently launched a new, exciting initiative, the IAHS Decade on Predictions in Ungauged Basins (PUB) (2003–2012), aimed at “formulating and implementing appropriate science programmes to engage and energize the scientific community, in a coordinated manner, towards achieving major advances in the capacity to make predictions in ungauged basins” (Sivapalan et al., 2003). Recognizing the great diversity of interests and expertise of hydrologists, and practical prediction needs, PUB has adopted a philosophy of plurality in terms of applications, hydro-climatic regions and prediction methods, yet it converges with a single-minded focus on the assessment, and eventual reduction, of predictive uncertainty. In line with the philosophy of plurality, and with a desire to energize hydrologists worldwide from the grass-roots level, PUB has resolved that the main engines of the research activities and progress will be PUB Working Groups, centred on applications, hydro-climatic regions, and/or modelling approaches, formed in a self-organizing manner, and cutting across traditional boundaries of specialization