Evaluation of and improvements in predictive uncertainty: contributions from the top-down modeling working group (TDWG)

The Top-Down modeling Working Group (TDWG) is one of several international working groups within the Prediction in Ungauged Basins (PUB) initiative of the International Association of Hydrological Sciences (IAHS). The focus of the TDWG is on building models based on the information that can be extracted from data, and supported by theoretical understanding and hypotheses regarding the behaviour of the system. This paper gives a summary of some of the activities of the TDWG over the first five years of the lifespan of PUB (2003~2012), including an overview of the top-down approach to model development, datasets that are freely available to members of the hydrological community, development of new model approaches (e. g. model emulation and surface water-groundwater interactions), methods for estimating parameter values at ungauged sites, and modeling in the presence of uncertainty. Projects initiated by the TDWG are also outlined.