Visualisation of spatial uncertainty in hydrological modelling

Uncertainty in hydrological modelling is often associated with model structure or calibration coefficients, and little consideration is given to the visualisation of uncertainty in either input or output data. As hydrological modelling is often a component of landscape design, there is continuing interest in the visualisation of uncertainty in model inputs and outputs, which could include catchment size or landcover (spatial inputs), and the subsequent impact on uncertainty in model predictions (such as streamflow). In this paper, inputs and outputs associated with hydrological models are discussed in the context of spatial uncertainty and how this information may be presented to users by means of statistical and spatial visualisation techniques. A regional study in hydrological modelling is used to demonstrate the sensitivity to spatial uncertainty and its consequences. Tools and techniques are discussed for the visual presentation of uncertainty, with implications for land management and policy decisions. A description is given of an experimental software tool developed for visualisation of spatial uncertainty in hydrological landscape cross-sections, where depth-to-water-table is used as a predictor for dryland salinity. Uncertainty in the estimate of this depth is important to analysts and policy makers.