The Analysis of Seasonally Varying Flow in a Crystalline Rock Watershed Using an Integrated Surface Water and Groundwater Model
Creators: name: Normani, Stefano D.
name: Randall, Jeffrey E.
name: Sykes, Jon F.
name: Normani, Stefano D.
Publisher: name: XVI International Conference on Computational Methods in Water Resources
Year: 2006

description: Minimal scientific knowledge is available to describe the interaction of surface
water and groundwater flow systems within watersheds in the crystalline rock setting
of the Canadian Shield.  The surface water and groundwater flow in a small watershed
are investigated using the fully coupled groundwater / surface water model
HydroGeoSphere.  The watershed has an area of 6.92 square kilometers and contains
multiple lakes, including Bass Lake (the largest lake) with a surface area of 0.94
square kilometers and a maximum depth of 9.0 meters.  The surface water drainage
system includes wetlands, small streams, and beaver dams while the topographic relief
has a range of 50 meters.  

A bathymetric survey was completed and lake circulation patterns were determined for
Bass Lake within the watershed using RMA2.  The overburden is thin with granite
bedrock outcrops occurring at numerous locations throughout the basin.  The
conceptual model for the subsurface system includes the surface sediments while three
categories are used to characterize the bedrock: moderately fractured rock (MFR),
sparsely fractured rock (SFR), and fracture zones (FZ).  These categories are
consistent with those used in the characterization of the crystalline rock at the
Atomic Energy of Canada Limited (AECL) Underground Research Laboratory near Lac du
Bonnet, Manitoba.  

ArcView GIS was used to facilitate data synthesis, analysis, and visualization.  Data
layers include orthophotos and digital Ontario Base Maps.  Hydrologic data for the
basin includes 2 rain gauges and a continuous water level recorder for Bass Lake. 
Additional climate data were obtained from nearby meteorological stations.  The
HydroGeoSphere model is based on the FRAC3DVS three-dimensional groundwater model and
the MODHMS surface water simulator.  HydroGeoSphere was used to investigate and
calibrate the parameters for groundwater and surface water flow in the basin for a
spring to fall time period.  Model output is compared to the observed continuous
hydrologic record.

The simulation results are compared to expected trends and observed field data.  The
groundwater heads and flow vector fields show groundwater movement in expected
directions with reasonable flow velocities, while the subsurface saturation levels
confirm that the evapotranspiration component is withdrawing groundwater during plant
transpiration.  Surface water depths and locations of water accumulation are
consistent with known and collected field data, while surface water flows and
velocities are in the expected ranges and directions.  Simulated Bass Lake surface
elevations compared very well to observed data-logger water elevations.  Low overland
friction values produced the most accurate Bass Lake elevations, with high overland
friction values slightly overestimating the Bass Lake water level throughout the
simulation period.  The integrated surface water-groundwater model HydroGeoSphere
faithfully reproduced the observed conditions and physical processes of the Bass Lake
model domain.