Ecohydrological feedbacks increase water storage, streamflow and resilience of natural peatlands

Peatlands are hypothesized to enhance water storage, sustain baseflow, and mitigate drought impact at the landscape level. The importance of ecohydrological feedbacks for the peatland water cycle and the interaction with surrounding landscapes is, however, poorly understood. This thin scientific basis hinders effective land- and water management and understanding peatland restoration impacts on regional hydrology. We developed the PECOSIM model (PEatland ECOhydrology and Streamflow SIMulator) to quantify the impact of three ecohydrological feedbacks on streamflow and water storage: (1) the transmissivity feedback (2) elastic storage and (3) water table depth (WTD) - evapotranspiration feedback. Validation with seven years of hourly observations from Degero Stormyr, an oligotrophic fen in northern Sweden, confirms strong model performance for growing season WTD and streamflow (Kling Gupta Model Efficiency: 0.88 and 0.87). Using PECOSIM we show the synergy of all ecohydrological feedbacks quadruples growing season streamflow (66 mm vs 16 mm without feedbacks) and maintains a shallower, more stable WTD (0.13 m vs 0.55 m). Without feedbacks, 'active' streamflow generating storage during the growing season was absent (0 mm), whereas the feedbacks together provide 63 mm streamflow generating storage. The three feedbacks additionally sustain streamflow and storage regimes under water stress, boosting drought resilience of natural peatlands and their surrounding landscape. This study provides scientific support for the crucial role of ecohydrological feedbacks in natural peatlands and highlights their function as nature-based solution by increasing water storage and baseflow. Degradation of natural peatlands will diminish feedback efficiency, and compromise peatland ecosystem services vital for sustainable water management.