Efficiency of buffer zones in nutrient load reduction under climate change conditions (Nurzec River, eastern Poland)

• SWAT model simulations tested effectiveness of buffer zones (2–20 m wide) • Buffer zones reduced TN by 27–55% and TP by 19–37%, depending on buffer width. • Impact of climate change on nutrient loads have been tested under RCP4.5 and RCP 8.5 scenarios. • Effectiveness of these zones under climate change can reach 66% TN and 30% TP. Buffer zones are considered as the most common measures aimed at reducing nutrient loadings into aquatic environments. Assessment of their effectiveness, especially under climate change scenarios, is crucial for planning future mitigation measures, and implementation of the Water Framework Directive. The goal of this study was to evaluate the potential effect of buffer zone implementation in the Nurzec River catchment (eastern Poland) under current and future climate conditions. Nutrient loads were modelled with the use of the SWAT model (Soil & Water Assessment Tool), and simulated influences of four buffer zone widths (2, 5, 10, and 20 m) using an inbuilt SWAT model option (FILTERW). All variants were examined using climate change scenarios (RCP4.5 and 8.5) in three-time horizons (2026–2050, 2051–2075, and 2076–2100), resulting in 35 individual model settings. Implementation of buffer zones in the study area reduced nutrient loads by approximately 27–55 % and 19–37 % for total nitrogen (TN), and total phosphorus (TP), respectively, depending on the increase of buffer width. These values correspond with a reduction of 396.7 and 18.6 tons per year of TN and TP, respectively. Moreover, our results show that climate change will have an ambiguous impact on nutrient loads (TN decrease and TP increase). Despite these differences, we forecast that the effectiveness of the implemented buffer zones will be maintained at 66 % and 30 % for TN and TP, respectively. Even more important in our research is the detailed information on the effectiveness of the described research, which is a significant step forward in the use of model analyses of water quality.