Temporal variation in depth to water table and hydrochemistry in three raised bogs and their laggs in coastal British Columbia, Canada

Abstract. The laggs of three raised bogs in coastal British Columbia were studied in 2010–2012 to determine the temporal variation in depth to water table and hydrochemistry. The lagg is an integral, but rarely studied, part of a raised bog that helps to maintain the water mound in the bog and provides a buffer for runoff from adjacent mineral areas. Depth to water table measurements in 25 piezometers displayed similar annual fluctuations, with the highest water table in winter and the lowest at the end of summer. The smallest fluctuations in depth to water table were recorded closest to the bog centre, and the largest fluctuations in the laggs and adjacent mineral soil sites. Removal of a mature forest stand on one of the study transects resulted in a "watering-up" of the lagg site; the mean water level between August and November increased by 8 cm from 2010 to 2011, and by up to 27 cm during the driest time of the year. pH, pH-corrected electrical conductivity, and Na⁺ and Mg²⁺ concentrations varied little during the study period, whereas Ca²⁺, K⁺, Cl⁻, and DOC concentrations and acidity were more variable.