Historical temporal trends in groundwater levels from British Columbia, Canada

Abstract

AbstractA time trend study of groundwater monitoring well levels was conducted in British Columbia, Canada. Trend data was available for a total of 210 groundwater monitoring well stations throughout the province with end-of-month water levels over the period of record. Significant temporal trends in groundwater levels were found at 67 stations (40.4% of all stations amenable to statistical examination, and 31.9% of all available stations). Of these 67 stations, 10 had increasing groundwater level trends and the remaining 57 had declining groundwater level trends. Thus, 34.3% of stations with a sufficiently long time series for analysis displayed declining groundwater level trends, while 6.0% have increasing trends, and 59.6% of these stations appear to have no significant temporal variation in groundwater levels. Geographic distinctions in groundwater level time trends are difficult to make owing to the unbalanced distribution of monitoring sites throughout the province. Based on percentages of total stations with a sufficiently long monitoring record for statistical analysis, it appears that the semi-arid Thompson/Nicola and Okanagan zones of British Columbia are most likely to have declining groundwater levels. Overall, a substantial proportion of groundwater monitoring wells in British Columbia - which have been operated with varying record lengths dating from recent installations to sites with records back to the 1950s - are exhibiting declining levels. At a significant number of other sites in the monitoring network, records are too short and/or poorly populated to facilitate statistical analysis.