Abstracts
Trends in Groundwater Levels in Eastern Canada
Yves Michaud1, Christine Rivard, Joëlle Marion, Alfonso Rivera and René Lefebvre
1Natural Resources Canada
ymichaud@rncan.gc.ca
Groundwater plays a major role in the water cycle since it is the largest reservoir of fresh water on earth. In Canada, 30% of the population relies on groundwater for their drinking-water supply. In eastern Canada, this percentage reaches 50 to 100%, depending on the province. The renewal of this resource and thus the amount of groundwater available for consumption in a specific region is dependant upon climatic conditions, groundwater uses, evapotranspiration and runoff. It is established that an increase in temperature causes increased evaporation and evapotranspiration, which in turn may decrease aquifer recharge. Climate changes and its influence on recharge variations, may have an impact on groundwater levels in aquifers, and groundwater availability. A research project was designed then to assess the potential impacts of climate change on groundwater in Quebec and the Atlantic Provinces. This aims to understand the relationship between climate and groundwater levels. By using historical data sets of groundwater levels, temperature, precipitation and river discharge, this research project attempted to characterize the relationship between climate and groundwater levels over time and geographical regions. The database developed for the project includes information from 95 wells, 169 stream gauging stations on rivers and 68 meteorological stations reaching close to 7 millions entries. Time series coming from wells that are both influenced or not influenced by pumping, cover periods of 15 to 30 years, while climatic and river discharge data are available for up to 100 years.
Results from these data show that both temperature and precipitation seem to increase since the beginning of the twentieth century, while the annual recharge is either stable or gently decreasing over time. Significant rapid responses to precipitation can be seen in unconfined granular aquifers while time lags in the order of several years are noticed for aquifers in different geological contexts. Therefore, seasonal and long-term fluctuations (over decades) of up to 6 m have been recorded in some locations. These results provide a preliminary assessment of the relationship between climatic factors, anthropogenic activities enhanced by greater demand for potable water during warm and dry periods and the fluctuation of groundwater levels. For eastern Canada, it seems that the groundwater resource is not particularly at risk when you foresee the projections from GCM and you compare with the actual groundwater use, but these trends appear to suggest that the lowering of the groundwater table is directly link to an increase of evapotranspiration, runoff (which is related to land use), and pumping. Future projections seem to imply that private well owners with shallow wells and small rivers, creeks or humid environments are the first one at risk.
2005-04-05 |
 |