USING PRAIRIE POTHOLE ANALOGUES TO UNDERSTAND THE HYDROLOGICAL RESPONSE OF CLOSED LAKE SYSTEMS

The water level in close lakes without perennial outflow streams is a sensitive indicator of climatic fluctuations. This is in contrast to open lakes, where the water-level fluctuation is buffered by the negative feedback mechanism provided by the dependence of surface outflow on the water level. Since many closed lakes are located in arid and semi-arid regions, where the amount of precipitation is limited, they often provide critical habitat for migratory waterfowls and other aquatic fauna and flora. For these reasons, it is important to understand the hydrological response of closed lake systems to climate change in the past and future. However, it is difficult to identify the factors causing the observed changes in the water level of large lakes having large drainage basins, due to heterogeneous landcover, soil, geology, and climate within the basin, all responding differently to a given meteorological (e.g. precipitation) or anthropogenic (e.g. landuse) forcing. Prairie potholes are closed systems, but have much smaller drainage basins than closed lakes. The recorded water-level trends of prairie potholes in the past several decades were similar to the trends of lager closed lakes, suggesting that the examination of prairie pothole hydrology may provide valuable insights into the hydrology of closed lakes. The water balance of prairie potholes are strongly influenced by the amount of snowmelt runoff, evaporation from the water surface, and transpiration by the riparian vegetation. Using the field data collected in the St. Denis National Wildlife Area in Saskatchewan, Canada, we will examine how these hydrological processes are affected by the timing and amount of precipitation and by landuse changes.