Long-term simulations of Nature-Based Solutions effects on runoff and soil losses in a flat agricultural area within the catchment of Lake Massaciuccoli (Central Italy)

Nature-Based Solutions (NBSs) are implemented worldwide to mitigate the impact of industrial agriculture on sediment and nutrient losses; however, their effectiveness depends on site-specific features such as surficial hydrology, soil permeability and erodability. This study analyzed the effects of vegetative buffer strips (VBSs) and winter cover crops (CCs) in a land reclamation area of the Catchment of Lake Massaciuccoli (Central Italy) by modelling water and soil dynamics at a very detailed scale, using a novel approach based on high-resolution input data. To this aim, SWAT+ was applied on digital terrain models (DTMs) from close-range photogrammetry, land-cover mapping, real crop rotations and a detailed calendar of farming practices. NBSs behaviour was investigated in two test areas, namely the Studiati and the Gioia areas, with uniform geomorphological settings but different soil types and annual crop rotations. NBS effects were compared with a baseline control scenario (without NBSs) and assessed under future climate conditions (RCP 4.5 and RCP 8.5). Specifically, VBSs and CCs showed different capabilities in mitigating runoff and sediment losses, and their combination provided maximum effectiveness. For the current climate scenarios, the implementation of VBSs produced a reduction of runoff depth of about 41% and 64% in the Studiati and Gioia areas, respectively, whereas showing a limited with the CCs implementation. Under the future climate conditions, similar patterns were observed, even if predicting significantly lower runoff depths. The sediment loss reduction was in the order of 79% and 64% in Studiati and Gioia areas, respectively. Concerning soil and water dynamics, the study remarked that slight topographic irregularities on flat morphologies can trigger concentrated flows responsible for high runoff and sediment losses. Furthermore, the differences in soil texture and organic matter content affected soil erodability rate on a local scale, driving the consistency of NBS mitigating effects. Future climate changes scenarios, exhibiting higher temperature and rarer but more concentrated rainfall events, emphasize the impact of different soil types. Results observed at a very local scale, with a spatialization of a few square meters - which clearly relates to the types of crop rotations, NBSs and soil distribution - noticed that SWAT+ is a suitable tool to aid farmers in cropping systems management and design.