Groundwater plays a major role in social and economic development and in human and ecosystem health. However, little is known about the potential impacts of climate change on this resource in Canada, namely if groundwater recharge is increasing or decreasing over time. This paper focuses on trend statistical analysis of historical series of baseflow and groundwater levels and their field significance as indicators of recharge. Monitoring wells are mainly located in the southern half of western Canada, where few gauging stations either are available or provide significant trends. Both data sets are thus complementary. Results show that most available groundwater level series have significant trends (80%), whereas most available baseflow series have not (3%–33%). However, groundwater level series usually show smaller slope magnitudes than baseflow series. Mixed trends are often observed across Canada for a given variable, period, or series length, although some regions can have marked trends. For instance, values below the 55°N latitude, and especially values in Atlantic Canada, show mostly downward trends (decreasing recharge). Values north of the 55° parallel often show upward trends. All groundwater level results are field significant at the 10% level, versus only 35% for baseflow results, but they show mixed results. Baseflow values show a majority of downward trends for annual values and the summer period for 40- and 50-year series, thus showing field significance, whereas mixed results are observed for 30-year series and the spring, fall, and winter seasons.

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