Semi-distributed water balance dynamics in a small boreal forest basin
1999
Metcalfe, R.A. | Buttle, J.M.
Information on water balance dynamics is an essential component of studies of the role of the boreal forest in surface-atmosphere interactions and climate change. The water balance of a small boreal forest basin in northern Manitoba was examined using a semi-distributed approach to assess basin sensitivity to climate change, provide a framework for distributed hydrological modelling, and explore data aggregation and micro-to-meso scaling of hydroclimatological variables. Black spruce forest with a highly variable canopy density was the main land cover in the basin. Spring snowmelt dominated basin runoff, while summer outputs were largely via evaporation. Annual differences in spring runoff were controlled by variations in snow water equivalent, rainfall tinting and magnitude, thaw depth, and antecedent water content in surface stores and upland soils. Water storage in small wetlands and ephemeral surface depressions in the open-canopy black spruce forest and its subsequent loss via evaporation was a fundamental component of the basin water balance. However, its role could be overlooked by inappropriate spatial lumping of landscape units when scaling-up variables or in the production of depressionless digital terrain models. Hydrological consequences of climate warming in this part of the boreal forest include: (i) increased evaporation following spring snowmelt in open black spruce areas; (ii) decreased surface and soil water storage on basin slopes; and (iii) reduced streamflow response to spring runoff and summer and fall rainstorms.
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