Runoff from orchard floors—micro-plot field experiments and modeling

Hydrologic response patterns of three ground treatments (resident vegetation, bare soil and ripped resident vegetation) were investigated. An in situ, micro-scale, plot retention-tank system was employed and used in conjunction with a kinematic wave model [Seasonal changes in infiltration and soil water storage in conventional and alternative agricultural systems, MS Thesis, University of California, Davis (2000)] to calculate surface water runoff hydrographs via the orchard floor-specific infiltration function. The model optimized Green and Amptʹs infiltration function on the suction at the wetting front until the endpoint of the cumulative runoff hydrograph matched observed runoff volumes. Our approach aimed to minimize data collection in the field and was found useful in the evaluation of different ground treatments as well as in evaluating their ability to reduce runoff under dry and wetted conditions. Infiltration for ripped resident vegetation was approximately an order of magnitude greater than that for bare soil. Resident vegetation yielded intermediate results. However, under elevated soil water conditions (degree of saturation greater than 0.80), differences between response patterns of resident vegetation and bare soil markedly decreased.