VERTICAL WATER CONTENT DISTRIBUTION IN THE UNSATURATED SOIL BY TDR MEASUREMENTS AT SHALLOW DEPTH

The water content in the surface soil is a key factor in soil physic, meteorology, agronomy, and of coursehydrology and environmental water management. Nowadays the soil water content can be measuredusing Time Domain Reflectometry (TDR) technique. Long series of TDR data are here presented; theywere measured in different soils: fine sand at the Lido beach (Venice, Italy), silty loam at an alpine valley(Val d’Ossola) between Switzerland and Lago Maggiore (Italy), loam at a suburban area close to Milan(Italy), silty clay loam at the campus of the University of Modena (Italy). An algorithm based on the massbalance equation has been derived, and used with soil moisture readings, to compute the loss or gain ofwater of a soil column of unitary cross section and known height. So, the soil water content (in the first 1-2m) and the rain gauge data allow estimating evaporation or infiltration according to atmosphericconditions. A new theoretical procedure to solve the linearized Richards equation for arbitrary initial andboundary conditions is under development.