ALBERT

Description: The estimation of catchment-scale soil properties, such as water storage capacity and hydraulic conductivity, is of primary interest for the implementation of distributed hydrological models at the regional scale. This estimation is generally done on the basis of information provided by soil databases. However, such databases are often established for agronomic uses and generally do not document deep weathered rock horizons (i.e. pedologic horizons of type C and deeper), which can play a major role in water transfer and storages. Here we define the Drainable Storage Capacity Index (DSCI), an indicator that relies on the comparison between cumulated streamflow and precipitation to assess catchment-scale storage capacities. DSCI is found to be reliable to detect underestimation of soil storage capacities in soil databases. We also use the streamflow recession analysis methodology defined by Brutsaert and Nieber in 1977 to estimate water storage capacities and lateral saturated hydraulic conductivities of the non-documented deep horizons. The analysis is applied to a sample of twenty-three catchments (0.2 km 2 – 291 km 2 ) located in the Cévennes-Vivarais region (south of France). For a regionalisation purpose, the obtained results are compared to the dominant catchment geology and present a clear hierarchy between the different geologies of the area. Hard crystalline rocks are found to be associated with the thickest and less conductive deep soil horizons. Schist rocks present intermediate values of thickness and of saturated hydraulic conductivity, whereas sedimentary rocks and alluvium are found to be the less thick and the most conductive. These results are of primary interest in view of the future set up of distributed hydrological models over the Cévennes-Vivarais region. This article is protected by copyright. All rights reserved.