Surface and subsurface water contributions during snowmelt in a small precambrian shield Watershed, Muskoka, Ontario

Abstract

The rates and pathways of snowmelt runoff on Precambrian Shield watersheds are not fully understood. The results of a detailed field study and numerical analysis of these processes are presented for a small watershed located in Muskoka, Ontario, that has been gauged both chemically and physically since 1976 by the Ontario Ministry of the Environment as a part of its Acid Precipitation in Ontario Study. Field data show that in many areas, soils with very high hydraulic conductivities contributed significant amounts of subsurface flow to the hydrograph during and shortly after melt. Quickflow in the first phase of snowmelt was generated by a combination of saturation overland flow and saturated‐unsaturated subsurface stormflow from shallow side slopes; however, most of the total water volume was delivered via slower ground‐water flow. In the final phase of the melt period, the streamflow was mainly due to ground‐water flow recharged on a forested area and delivered over limited distances through shallow, highly permeable overburden materials. Quickflow peaks superimposed on this general trend could be accounted for mainly as surface runoff over ground‐water effluent areas mapped throughout the watershed. In support of ongoing hydrochemical studies by the Ontario Ministry of the Environment, these data and interpretations will aid in modifying and improving hydrologic submodels by adding to our understanding of water movement in acidified watersheds. © 1987 Taylor & Francis Group, LLC.