Electrical conductivity as a tracer of changing peatland catchment response to climate warming

Montane peatlands are highly sensitive to climate change and disturbance, and their hydrological functioning strongly controls the transport of dissolved substances. Electrical conductivity (EC) serves as an integrative tracer of runoff generation processes and source contributions. This study analyzes long-term changes in EC-discharge (EC-Q) dynamics in response to climate warming and a multi-year drought in the Rokytka peatland, Central Šumava Mountains (Czechia) in response to climate warming and a multi-year drought. The drought is treated as a stress-test period that reveals the sensitivity and dominant response pathways of the system, indicating the likely direction of change as heat and drought intensify under climate warming.

We use a unique 20-year dataset of 10-minute measurements of discharge, EC, and meteorological variables. Runoff events were classified by antecedent wetness and event structure, and water circulation patterns were analyzed using event-scale EC-Q hysteresis loops characterized by loop direction and morphology. Events were further compared across seasons and major climatic and management phases.

Results show a pronounced shift after the onset of the warm and dry period in 2015–2018. Discharge regimes exhibit higher variability, more frequent extremes, and lower baseflow. Hydrographs became steeper, with shorter response times, faster rising and falling limbs, smaller event runoff volumes, and more asymmetric shapes. EC dynamics changed consistently: maximum EC values decreased, event-scale EC contrasts weakened, and EC returned more rapidly to baseline after events.

EC-Q hysteresis loops also changed markedly. Hysteresis indices decreased and separation between rising and falling limbs weakened, indicating reduced event-scale contrasts in solute sources and more uniform mixing. Loop direction shifted toward more frequent clockwise patterns after 2015, consistent with earlier flushing followed by dilution. Together, these changes point to faster runoff generation and altered solute mobilization under warmer and drier conditions.

The study demonstrates that long-term high-frequency EC monitoring provides a sensitive indicator of climate- and management-driven changes in peatland hydrology. EC-Q hysteresis analysis offers a powerful tool for diagnosing shifts in runoff generation, storage, and solute transport, and for evaluating the effectiveness of peatland restoration under a changing climate.