Evapotranspiration From a Mountain Peatland: Potential Impact of Diminishing Snow Cover on Water Yield

ABSTRACT

Peatlands store large volumes of water, playing an important role in catchment hydrology, and thus regional water cycles. Water from peatlands is released both as streamflow and via evapotranspiration (ET) to the atmosphere. ET is linked to snow cover through recharge and water availability; however, the direct impact of snow cover on ET has received little research attention. We hypothesised that snow cover has the potential to influence rates of ET from a mountain peatland. This influence may be susceptible to the impacts of climate change, including a predicted decrease in snow cover in coming decades. Here, we used eddy covariance to quantify rates of ET in an Australian mountain peatland over 5 years (mid‐2017 to mid‐2022), comparing ET between periods with and without snow cover. Across the 5‐year study, ET showed significant year‐to‐year variation and in years 1, 3 and 5, distinct seasonality across the year. In contrast, Years 3 and 4 (2019–2020 and 2020–2021) did not show strong seasonality in ET. Net radiation and vapour pressure deficit were significant, nonlinear environmental drivers of ET, while soil water content was not significant, indicating that limitations in energy rather than water availability drove rates of ET in this ecosystem. When accounting for differences in net radiation and VPD, rates of ET were still, on average, 13.2% lower during periods of snow cover compared to periods without snow. Overall, our results suggest that predicted decreases in snow cover arising from increasing global temperatures will lead to higher rates of water loss via ET from Australian mountain peatlands, with potential consequences for ecosystem function, including catchment water regulation.