In many physically based hydrological models, there is the requirement to specify the suction-moisture curve of the soil system. This paper shows that where the suction moisture curve is known, then a model can be derived to predict groundwater rise. Secondly, it is shown that with only mapped soils data, relationships exist that allow suction-moisture curves to be predicted. This prediction scheme is incorporated into a forecasting model for ungauged catchments and results are presented to show the potential validity of the scheme for operational forecasting.