Surface-groundwater exchange between a wetland, sandur, and lava field in southeastern Iceland

Abstract

In May 2019, over 50 springs were identified at a sandur-lava field–wetland complex in Southeast Iceland and a subset was selected for further investigation including monitoring water levels, discharge, and water chemistry. Between May and September 2019, springs at the study site had relatively stable water levels and temperatures (4–5 °C), although heavy rains (>10 mm) corresponded with increased water levels and/or temperatures at some springs. Together, the water level, temperature, and stable isotope data suggest that the springs at the study site are fed by older groundwater from an aquifer that is recharged by precipitation. Spikes in water level indicated that at least one spring at the edge of the sandur also received floodwater and shallow subsurface flows from the glacial-fed Brunná River. One wetland spring was further monitored over the water year (October 2019 to October 2020). Like other springs, water levels and temperatures remained relatively stable, fluctuating with inputs of precipitation. Longer-term studies will be needed to gain an improved understanding of seasonal spring vulnerability to climate change and their role in the functioning of a coastal wetland in Southeast Iceland.