Spatial structure of soils and hydraulic properties in desert piedmonts of interspersed bare soil and shrub mosaic is important in understanding large scale evapotranspiration and other hydrological processes important to desert environments and ecosystems. This study investigates the implications of distinct soil hydraulic properties structures of under canopy and interspace on hydrological processes in a desert environment. The impact on the large scale evapotranspiration of spatial variability of desert shrubs coverage is investigated with different ranges of shrub coverage and correlation lengths for the shrub distributions. Given the distribution of the shrub coverage, two distinct fields for the soil hydraulic parameters are generated. The first field is the under canopy soil hydraulic parameters, and the second one represents the interspace soil hydraulic parameters. These two fields are combined to produce one complete spatial distribution for the soil hydraulic parameters. The hydrological process is then calculated for the local scale and then aggregated to represent large scale evaporation and transpiration.

Results/Conclusions

Results demonstrate that spatial variability of soil hydraulic properties affects water partition at small scale. The structure of spatial shrub distribution has moderate impact on field scale partition of transpiration and evaporation when shrub coverage is sparse. The ratio of shrub transpiration and total evapotranspiration at large scale increases between precipitation events and slightly drops immediately after rain. It indicates evaporation in interspace and shrub transpiration operate at different temporal scales. The evaporation process for sparse shrub coverage environment responds in short pulses while shrub transpiration has slightly longer temporal response.