Soil moisture modelling - Conception and evolution of the VSMB

The Versatile Soil Moisture Budget (VSMB), including the background leading to its development in the ''early days'' meaning around 30 yr ago, is described. National and international efforts before that rime created a healthy climate for the development of agrometeorology in Canada and the pioneering work in soil moisture and crop-weather modelling. Events in the early days leading to a concerted endeavour of soil moisture modelling included: (i) a small group of highly qualified professionals from different disciplines, as well as support staff, had been established under the guidance of a ream leader at the then Plant Research Institute (PRI); ii) a Canada wide crop-weather study had produced daily climatological and crop data at nine Canada Department of Agriculture establishments over 10 yr (1953-1962); iii) a computer became available to PRI staff (IBM 1620 with 16K); and (v) several sub-models providing the necessary input to the soil moisture model were at various stages of development (e.g. the ''latent'' evaporation and the biometeorological time scale sub-models). This paper presents an overview of the development of the VSMB using standard climatological data for generating daily soil moisture estimates under crops. Its concept, design and widespread applications in Canada and abroad are discussed. A more detailed analysis is left to the other presentations at this Symposium.