Effect of land use on soil erosion in a small watershed in Emilia –Romagna Region

The study of the environmental impact of soil erosion due to water runoff is important to protect soil quality and fertility. In order to estimate erosion at a watershed scale, discharge and sediment content in a stream draining a small watershed were studied. The Centonara watershed (197 ha), located in a hilly area South East of Bologna, Italy, has been monitored for water and suspended sediment discharge since 1994. Meteorological and hydrological data have been recorded continuously with the use of an ISCO flow meter and water samples have been collected from the stream in order to estimate transported sediment. Several thematic maps were produced (slope, pedological, geolithological and morphological). In each agricultural season, the land use (tillage, crop, chemical treatment, fertilisation, etc.) was mapped (1:5000). Seasonal soil losses from the watershed, due to soil particles transported by water, were measured and related to the precipitation’s characteristics and to the different agricultural soil use and management. The results showed large yearly variability of the amount of transported sediment and a relation with the agronomic land use and management. In particular, the annual erosion of the watershed was related to the percentage of grass (meadows and set-aside) covered surface. The quantity of suspended and dissolved sediments and the electrical conductivity of water were found to be dependent on the season and the flow rate.