Mapping topsoil field-saturated hydraulic conductivity from point measurements using different methods

• Published in: Journal of Hydrology and Hydromechanics 2017-09, Vol.65 (3), p.264-275
• Main Authors: Braud, Isabelle, Desprats, Jean-François, Pierre-Alain Ayral, Bouvier, Christophe, Vandervaere, Jean-Pierre
• Format: Article
• Language: English
• Subjects: Equivalence; Extrapolation; Feasibility studies; Geographic information systems; Geographical information systems; Geological mapping; Geology; Hydraulic conductivity; Hydrologic models; Hydrology; Infiltration; infiltration methods; Land cover; Mapping; Measurement methods; Permeameters; Rain; Rainfall; Runoff; Scale (ratio); Soil; Soil properties; Soil texture; Soils; Statistical analysis; Statistical tests; Tension; Tests; Texture; Topsoil; topsoil field-saturated hydraulic conductivity
• ISSN: 0042-790X; 1338-4333; 0042-790X
• DOI: 10.1515/johh-2017-0017

Topsoil field-saturated hydraulic conductivity, [Kf[s]], is a parameter that controls the partition of rainfall between infiltration and runoff and is a key parameter in most distributed hydrological models. There is a mismatch between the scale of local in situ [Kf[s]] measurements and the scale at which the parameter is required in models for regional mapping. Therefore methods for extrapolating local [Kf[s]] values to larger mapping units are required. The paper explores the feasibility of mapping [Kf[s]] in the Cévennes-Vivarais region, in south-east France, using more easily available GIS data concerning geology and land cover. Our analysis makes uses of a data set from infiltration measurements performed in the area and its vicinity for more than ten years. The data set is composed of [Kf[s]] derived from infiltration measurements performed using various methods: Guelph permeameters, double ring and single ring infiltrotrometers and tension infiltrometers. The different methods resulted in a large variation in [Kf[s]] up to several orders of magnitude. A method is proposed to pool the data from the different infiltration methods to create an equivalent set of [Kf[s]]. Statistical tests showed significant differences in [Kf[s]] distributions in function of different geological formations and land cover. Thus the mapping of [Kf[s]] at regional scale was based on geological formations and land cover. This map was compared to a map based on the Rawls and Brakensiek (RB) pedotransfer function (mainly based on texture) and the two maps showed very different patterns. The RB values did not fit observed equivalent [Kf[s]] at the local scale, highlighting that soil texture alone is not a good predictor of [Kf[s]].