Analysis of near-surface soil moisture spatial and temporal dynamics in an experimental catchment in Southern Italy.

Management of water resources in basins under Mediterranean climate is based on the knowledge of the complex interaction among rainfall, evapotranspiration, streamflow discharge, and changes in water storage. Understanding the spatial and temporal evolution of such relations is a key issue for obtaining reliable applications of hydrological models. In this study we identified the water dynamics involved in the catchment-scale water balance within a sub-humid area in Southern Italy. To meet this objective, precipitation and evapotranspiration were retrieved through data recorded by a weather station whereas water discharge was monitored at the water reservoir delimited by an earth dam in the outlet of the Alento River 102.5 km2 catchment. The landuse is dominated by pasture, orchard and grassland and the main terrain attributes have been calculated from a 5 m DEM. Six hillslope transects have been delineated along hillslopes in order to capture soil variability. Surface soil water content has been monitored with a portable TDR device along the aforementioned transects with a spatial interval of 50 m in 10 field campaigns, from October 2004 to January 2005. Mediterranean climate is characterized by dry summers with strong water deficit and wet winters with replenishment of the water reservoir. In the dry season, soil water content has high temporal instability and is mainly influenced by the aspect and tangential curvature. On the other hand during the wet season, near saturation conditions of soil surface are able to diagnose rapid streamflow response since rainfall events generate runoff and subsurface later flow. Soil water content is more stable and shows a significant correlation with the slope and the wetness index.