| Inter-storm streamflow, or baseflow, is commonly assumed to be generated directly from groundwater discharge to the stream network. In moderate-relief terrain of New England, wetlands are important in stream function. The assumption that streamflow is generated from groundwater discharge from a headwater catchment containing 11% wetland or pond area coverage was tested using stable isotopes of water. Binary end-member mixing analysis showed that 18 to 30% of streamflow at the catchment outlet (less than 50% at 95% confidence) was generated from groundwater; the remainder was derived from outflow from an upstream wet meadow. Results from the wet meadow water and isotopic mass balance suggest <27% of meadow outflow was accommodated by groundwater inflows. Increasing isotopic enrichment correlates more strongly with stream length within wetlands (p = 0.005) than catchment wetland area (p = 0.04); ranking catchments by the same metric also distinguishes catchments by their relative average run-off. |
