Recent Pockmark activity in Lake Banyoles (NE Spain) severely affected by changes in climate and land use

Abstract

Study region Two giant pockmarks in Lake Banyoles (NE Spain) have been surveyed over the last 35 years. The giant pockmark ‘B1’ has maintained an ‘eruptive’ mode with permanent groundwater discharge, whereas, the giant pockmark ‘B2’ has displayed alternating quiescent and eruptive phases.

Study focus Interannual variability of lake-subsurface groundwater discharge in both pockmarks and the main lake aquifer level correlates with changes in the accumulated rainfall during the previous 10 months in the north-east of Spain. In the eruptive phase, the lutocline, marking the top of suspended sediments, is warmer than the ambient lake water and generates a turbid hydrothermal plume.

New hydrological insights for the Region: Results show that the permanent hydrothermal plume at pockmark B1 is no longer penetrating the lake's background stratification due to the loss of plume buoyancy. The available data demonstrate that current climate change coupled with a depletion of groundwater resources has strongly impacted the hydrogeology and limnology of the main pockmark of the lake and also the distribution of suspended sediment in the water column.