Comparison of the Hydrological Budgets and Detailed Hydrological Responses in Two Forested Catchments

Detailed hydrological budgets for two mature forested catchmentsshow very similar inputs and vegetational throughputs (throughfalland stemflow) for both Norway and Sitka spruce. Stream outflow,equivalent to 1707 mm, is comparable both with measured rainfallinputs (2250 mm) or rainfall in combination with throughfalland stemflow (1826 mm). Soil throughflow from the differingsoil profiles follows similar patterns, in both soil types withinitial flow response at depth (>50 cm). This may increasetowards a maximum for some horizons, and, depending on inputamounts, be followed by a transfer of flow up through the profile.Hydrological responses and their effect on soil temperatureswere again similar at both sites, with no obvious anomalieswhich would explain the resultant differences in stream chemistrybetween these catchments. The observed changes in surface waterchemistry must therefore be primarily due to vegetational orsoil induced chemical processes combined with observed differencesin hydrological fluxes.