Analysis of Inter-Storm Period Soil Moisture Dynamics

Abstract

Soil moisture temporal dynamics is the result of the interaction between the stochastic climate forcing and the buffering effect operated by the soil volume, depending on its hydraulics properties. To address an analysis of the soi moisture temporal variability, a number of input and output processes to the representative soil volume have to be modeled. Overall, at the point scale, input process corresponds to the effective rainfall occurrences whereas the output process correspond to the losses function represented by the evapotranspiration, sub-surface and deep percolation fluxes. The number and relative complexity make troublesome both the processes schematization and the interpretation of soil moisture dynamics.In this study, observed soil moisture data, recorded over a 3 years period, have been explored to assess and characterize the dominating processes at an experimental site, locate in Southern Italy, Campania region, with reference to inter-storm periods, when the soil water balance is only driven by the losses fluxes. About thirty inter- storm events, including five or more days, have been selected and the soil moisture depletion process has been explored. Soil moisture depletion over the experimental site occurs following a negative exponential law. The rate of soil water content reduction appears to be different over the seasons, with the highest rate occurring during the spring season, perhaps reflecting the higher vegetation water consumption during this particular period of the year. Initia soil water content seems also to affect the inter-storm dynamic, being the rate of depl tion lower for low initial soi moisture contents. Multilevel recorded data also allowed the investigation of the importance of soil depth, with a depletion process rate being much more smoother in the deeper soil layer.