Modelling the suitability of peatland restoration as a nature-based solution at the catchment scale : case of the Oulankajoki catchment

Abstract

Nature-based solutions (NBS) have the potential to effectively address societal challenges in a cost-effective manner. While landscape-level dynamics in the development of NBS, its effectiveness is often highly variable at the scale of catchments. This thesis investigates the impact of peatland restoration as a NBS on the Oulankajoki catchment in Northern Finland. The study aims to assess the effects of the restoration initiatives on hydrological processes and water quality in the catchment, addressing the ecological degradation caused by extensive peatland drainage. The research employs a semi-physical SWAT+ hydrological model to simulate the existing drained peatland networks, establishing a baseline scenario of the Oulankajoki catchment. Afterwards, four additional scenarios are simulated, representing distinct levels of peatland restoration from 25% to 100%. The methodology involves analysing changes in flow dynamics and water quality loading across these scenarios. The study also incorporates future climate projections using Representative Concentration Pathways (RCPs) to evaluate the impact of meteorological variations on restored peatlands. The key findings indicate that peatland restoration has a positive impact on hydrographic conditions: there is a rise in the flow rate and water storage across the catchment. The study has shown improved water quality through a reduction in harmful nutrient concentrations, such as nitrogen, in water bodies. This study therefore contributes to the understanding of how peatland restoration works as an NBS and provides valuable insights into environmental management and policy-making. The findings apply to similar boreal and temperate peatland catchments, providing a framework for assessing and implementing the approaches of peatland restoration to both mitigate climate change and enhance ecosystem health.