AVERAGING SCHEMES OF HYDRAULIC PROPERTIES IN LARGE SCALE HETEROGENEOUS SOILS

Soil hydraulic properties at large scale (e.g., large climate model grids) are critical for land–atmosphere interaction and general circulation models as well as other applications in representing hydrologic processes. This study investigates the use of soil hydraulic properties applicable to large scale hydrologic processes in a landscape with heterogeneous soil hydraulic properties. The focus is on the flux exchange between the vadose zone and atmosphere. The specific objectives are to investigate: 1) the appropriateness of commonly used hydraulic parameter averaging schedules in representing the large scale near surface flux, and 2) evolution of hydraulic property averaging schemes with time frame of large scale hydrological processes. Large scale average flux behavior in the heterogeneous soils is quantified through multiple simulations of local scale process and aggregation. The various averaging schemes of soil hydraulic parameters are used to simulate the flux exchange, which is then compared to the large scale average flux. The difference of flux is examined in terms of variances and correlations of local scale hydraulic parameters, and various other conditions such as surface boundary conditions.