Publication Date:
1995-02-01
Description:
C. H. TAYLOR Methodological issues associated with isotopic hydrograph separations (IHSs) in built‐up environments are explored using results from the 1990 spring melt in a suburban basin in Peterborough, Ontario, Canada. The hetrogeneous nature of suburban environments complicates the selection of appropriate isotopic signatures for event and pre‐event waters. Near‐stream groundwater δ18O sampled from wells was poorly mixed, such that the pre‐event water signature was best characterized by δ18O in pre‐melt baseflow or discharge from a headwater spring. The event water signature during snowmelt can be characterized using δ18O in the pre‐melt snowpack, surface runoff samples or meltwater from lysimeters. However, the use of snowpack δ18O may be inappropriate in suburban basins where meltwater from thin snowcover may exhibit pronounced responses to δ18O in rainfall contributions. Intensive sampling of the spatial variability of runoff or meltwater δ18O may be required to characterize the average event water signature adequately. Rainfall δ18O provided an appropriate event water signal during a large rain on snow event, and differences between this IHS and one generated using an event water signature that included meltwater contributions from snow‐covered surfaces were within the uncertainty attributable to the analytical error in δ18O values. Event water supplied 55‐63% of the peak discharge and 48‐58% of total runoff from the basin during the melt, which is consistent with the fraction of the basin that has been developed. These results contrast with IHSs conducted in forested basins that suggest that stormflow is dominated by pre‐event water contributions. Copyright © 1995 John Wiley & Sons, Ltd
Print ISSN:
0885-6087
Electronic ISSN:
1099-1085
Topics:
Architecture, Civil Engineering, Surveying
,
Geography
