Temporal Variability of Thermal Refuges and Water Temperature Patterns in Relation to Changing Hydrometeorological Regimes

River temperatures in northern latitudes will increase under future climate change. This will have a negative impact on salmonid populations which are intolerant of high water temperatures.  In response to heat stress, salmonids thermoregulate in cold water units, termed thermal refuges.  However, the temporal variability of these units has never before been described.  We used multi-temporal airborne thermal infrared imagery to characterise the temporal variability of thermal refuges and water temperature patterns in the Rivière Ouelle, an Atlantic salmon river in Québec.  Data from hydrometeorological stations were used to explore the processes governing refuge variability over short and longer time scales.  Temporal variability in counts of lateral groundwater seeps correlated strongly with long duration hydrometeorological metrics associated with groundwater recharge, such as mean spring discharge (R² = 0.94, p < 0.01).  Conversely, thermal refuges resulting from cold water tributaries were more temporally stable.  Variability of larger-scale temperature patterns correlated best with short duration hydrometeorological metrics (eg. cumulative precipitation prior to each survey, R² = 0.90, p < 0.01).  In this paper, the first to link thermal refuge dynamics to hydrometeorological conditions, we discuss how changes to hydrometeorological regimes could influence the occurrence and persistence of thermal refuges in the future.