Constructing a saturated hydraulic conductivity map of Spain using pedotransfer functions and spatial prediction

Currently, most of the research focused on general pedotransfer functions (PTFs) has been generated under humid climatic conditions. Nevertheless, this article proposes an estimation of pedotransfer functions for a great variety of climatic and physiographic conditions, with a predominance of soils developed under semi-arid conditions, such as those occurring in Spain. The results obtained, in spite of the variety of measuring methods of the variables used, show that it is possible to estimate saturated hydraulic conductivity values for soils from sand content data. These are compared with results obtained from the application of other authors' PTFs. This is an important support to the present attempts at establishing soil inference systems. The PTFs obtained have increased the number of profile points in networks with saturated hydraulic conductivity data, allowing the transformation of point data to a continuous saturated hydraulic conductivity surface. To reach this goal, three methods have been applied: that of Batjes, inverse distance weight and kriging interpolation, with the latter giving the best results. Finally, a saturated hydraulic conductivity map with a spatial resolution of 1 x 1 km for the Spanish part of the Iberian Peninsula has been generated. The resulting map showed a good spatial fit after being compared with lithological distribution, which confirms the applicability of the method for future hydrological applications. (C) 2004 Elsevier B.V. All rights reserved.