Hydroclimatic influence of seismic line disturbances based on field measurements and modelling across Alberta, Canada

Abstract

Geologic exploration for petroleum has resulted in a dense network of seismic lines—linear clearings—across the boreal forest, yet their effects on hydrometeorological conditions remain understudied. With a focus on peatland ecosystems, this study used a combination of field-based measurements and hydrological modelling (CoupModel) to investigate the impact of seismic lines on wintertime hydrometeorological conditions, summertime evapotranspiration (ET), and the annual water balance for study sites in Alberta, Canada. Winter assessments revealed that photosynthetically active radiation (PAR) was 1.8 times higher on seismic lines than in the adjacent forest understory, with greater negative net radiation (i.e., high outgoing radiation for the ground surface) also observed. Wind speeds on seismic lines during the unfrozen period were significantly elevated, 8 times higher at an east-west site and 7 times higher at a north-south site, compared to the adjacent undisturbed peatlands. Soil temperatures remained above freezing for seven days longer on the lines, suggesting thermal insulation effects caused by the deeper snowpack observed on the seismic lines. Snowpack dynamics captured by time-lapse photography across upland and peatland sites showed a 5 cm higher maximum snow depth on seismic lines, and a 3 cm greater average snow depth, though the latter was not statistically significant. Snow depth declined more rapidly on seismic lines, but with maximum depth reached five days later, snow-free conditions occurred one day later despite an ablation duration five days shorter than in undisturbed areas. Actual ET (AET) from the ground layer on seismic lines in peatlands was 59% and 14% higher than adjacent areas based on lysimeter and chamber measurements, respectively. Soil temperature, PAR, and plant composition were key drivers of chamber-based AET, while lysimeter-based AET was mainly influenced by PAR and wind speed. Potential ET (PET) was 51% higher on seismic lines, raising the Priestley-Taylor coefficient (α) from 0.61 to 0.73. While not directly measured, tree transpiration estimates from the literature were applied, which revealed that seismic line AET still surpassed that of adjacent areas with an intact tree cover by 31%. Comparing 1-D simulations for on and off seismic line conditions for peatlands from a process-based hydrological model (CoupModel) supported field-based findings, indicating higher soil moisture, temperature, and shallower groundwater depths on seismic lines. The simulated AET was 6% higher on the lines, largely driven by moss evaporation, which compensated for lost canopy transpiration. Despite higher ET, increased precipitation that reaches the ground surface and lateral flow led to 5 mm more water storage on seismic lines. Model sensitivity analysis revealed that an increase in soil compaction substantially elevated runoff, drainage, soil moisture, and storage. The seismic line had a greater difference in conditions from offline areas when peatland canopy LAI was greater; the undisturbed condition with higher LAI resulted in higher transpiration, and cooler soils. Overall, the findings illustrated that seismic line clearing results in measurable local changes in hydrological conditions; future research should explore the impact of seismic lines on the catchment scale to better understand the cumulative impact of these disturbances on hydrological processes in boreal ecosystems.