Drivers of hydrological response for distinct wetland complexes in a high latitude alpine watershed

Abstract

Alpine wetlands provide important hydrological and ecological services, and in rapidly warming northern environments are at risk as frozen ground thaws and evaporation increases. The hydrological role of wetlands is highly variable depending on the season and their position in the landscape. Despite their extensive presence, there is limited understanding of cold, alpine wetlands due to logistical challenges. The objective of this research is to evaluate water table dynamics and seasonal water sources for two distinct wetland complexes in the Wolf Creek Research Basin (WCRB), Yukon: a valley-bottom wetland and a high-elevation isolated wetland. This study used hydrometric data and stable water isotopes to track the seasonal evolution of water table depth and source waters. Results showed that in high-elevation isolated wetlands, ponds were restored in the spring after snowmelt and then experienced progressive drying with open water areas never returning to spring extent. Pond waters were continually enriched and evaporated throughout the season suggesting little lateral inputs, and as the temperature warmed, exchanges were largely vertical with considerable water lost to evaporation. In the valley bottom wetland, water levels remained high throughout the year as the water was supplied continuously to the wetland from upland areas. While there were some small reversals in flow through the base of the wetland, stable isotopes suggest the continued supply of depleted meltwater throughout the course of the year. Implications from this suggest that isolated ponds in WCRB are susceptible to drying under climate warming as a longer snow-free season will increase evaporation and the window for drainage. In contrast, the valley-bottom wetlands are less vulnerable due to their position in the landscape and the presence of beaver ponds that impound water.