Water budget analysis of small forested boreal watersheds: comparison of Sphagnum bog, patterned fen and lake dominated downstream areas in the La Grande River region, Québec.

A water budget analysis (precipitation (P), surface runoff (Q), evapotranspiration (ET) and storage variations (ΔS)) was completed over a 3-year span for two Sphagnum bogs, three patterned fens and two shallow lakes all located in the La Grande River watershed in central Québec. The high variability of P from 2005 to 2007 during summer and fall (July to October) allowed us to produce water budgets over a large spectrum of wetness conditions at seasonal and event timescales. Bogs and fens (not lakes) have the intrinsic ability to keep the water table near the surface most of the time, which affects Q. Fens and lakes showed a similar hydrological behavior when compared to bogs, in spite of differences in Q and ΔS variability due to the typical vegetation structure of fens. This structure also tends to produce sharper rises of Q when compared to lakes that have overall smoother hydrograms. The dominant water budget term for bogs, fens and lakes was ΔS, Q and ET, respectively. Finally, an adaptation of the Penman-Monteith equation was successfully used to estimate potential ET. This revised method is based on peatland vegetation identification that provides a simple weighing factor for stomatal resistance. [ABSTRACT FROM AUTHOR]