Evaluation of stream gauge density and concept of virtual gauges in Northern Ontario watersheds for hydrologic and hydraulic modeling

Elizabeth Philip and Jim McLaughlin, Ministry of Natural Resources and Forestry, Peterborough, ON, Canada


A balanced stream-gauge network consists of two elements: geographic sampling and time sampling. As the name reflects, geographic sampling is the process of determining the rate and volume of streamflow for different streams and at different locations on the same stream. Time sampling is for a point location of the stream reach and determines the variations of the rate and volume of streamflow with time. The basis of design of a stream gage network is the establishment of base stations to serve as fixed points for the time sampling factor, and secondary gauges to operate for relatively shorter period for geographic sampling. Once a secondary gauge establishes a correlation with the base gauge, then the secondary station acts as a virtual gauge. Further, the secondary station is transferred to another stream reach for optimizing the hydrological information in space and time. The concepts of stream gauge density and virtual gauges provides the minimum network and length of record to avoid serious deficiencies in hydrologic and hydraulic modelling.

The objective of this study was two fold, first to evaluate the Water Survey of Canada’s HYDAT stream gauge density of Northern Ontario watershed systems based on World Meteorological Organisation (WMO), 2008 guidelines. The second objective was to introduce the concept of virtual gauges described above into the stream network. The discontinued gauges are the virtual gauges and Reference Hydrometric Base Stations (RHBN) are the base stations. Monthly mean streamflow was re-constructed for 9 discontinued gauges up to 2015 reducing the extent of unmet data needs. The data re-constructed was also tested using the coefficient of determination and suitability for modelling. This improves the cost efficiency of the network and optimizes the hydrologic information for the land use planning initiative of Far North. 

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