Description of the unsaturated soil hydraulic database UNSODA version 2.0

Quantifying water flow and chemical transport in the vadose zone typically requires knowledge of the unsaturated soil hydraulic properties. The UNsatu rated Soil hydraulic DAtabase (UNSODA) was developed to provide a source of unsaturated hydraulic data and some other soil properties for practitioner s and researchers. The current database contains measured soil water retent ion, hydraulic conductivity and water diffusivity data as well as pedologic al information of some 790-soil samples from around the world. A first MS-D OS version of the database was released in 1996. It has been applied in num erous studies. In this paper, we describe the second version (UNSODA V2.0) for use with Microsoft Access-97((R)1). The format and structure of the new database have been modified to provide additional and more convenient opti ons for data searches, to provide compatibility with other programs for eas y loading and downloading of data. and to allow users to customise the cont ents and look of graphical output. This paper reviews the structure and con tents of the database as well as the operations that can be performed on th e different data types in UNSODA V2.0, The use and application of the new d atabase are illustrated with two examples. The retrieval of data is briefly illustrated, followed by a more detailed example regarding the interpolati on of soil particle-size distribution data obtained according to different national definitions of particle-size classes, The interpolation procedure, which is based on finding similar particle-size distribution curves from a large European data set, also performed well for soils that originate from other geographical areas. (C) 2001 Elsevier Science B.V. All rights reserv ed.