Estimation of areal soil moisture by use of terrain data

In this study measured soil moisture is related to primary and secondary to pographical attributes within two small-scale drainage basins. The study si tes are the Buddby and the Dansarhallarna drainage basins within the NOPEX area. The primary topographic attributes slope, aspect, plan and profile cu rvature, and the secondary topographic attribute, the wetness index, are de rived from a 5 m resolution digital elevation model. The relationship with measured soil moisture in the Buddby basin is investigated by linear regres sion analysis. Based on mean plot measurements for the whole measurement pe riod two different models were established, resulting in a high R-2 value. The best model was achieved with slope, profile curvature and aspect as reg ression variables. The models obtained were further used to regionalise the results into basin scale at both Buddby and Dansarhallarna. This demonstra ted a soil moisture pattern different from the pattern resulting from the w etness index. Finally, models were established, based on two different date s or field campaigns. The results showed a good agreement with the observed soil moisture values, and a higher R-2 value was obtained when using the w etness index for the medium wet period compared to the wettest period. Furt her analysis is needed to verify the physical significance of the results a nd their suitability for hydrological modelling.