Robert A. Metcalfe

Estimation of Continuous Streamflow in Ontario Ungauged Basins: Comparison of Regionalization Methods

Regionalization, a process of transferring hydrological information [i.e., parameters of a conceptual rainfall-runoff model, namely, the McMaster University-Hydrologiska Byrans Vattenbalansavdelning (MAC-HBV)] from gauged to ungauged basins, was applied to estimate continuous flows in ungauged basins across Ontario, Canada. To identify appropriate regionalization methods, different regionalization methods were applied, including the spatial proximity [i.e., kriging, inverse distance weighted (IDW), and mean parameters], physical similarity, and regression-based approaches. Furthermore, an approach coupling the spatial-proximity (IDW) method and the physical similarity approach is proposed. The analysis results show that the coupled regionalization approach as well as the IDW and kriging produce better model performances than the remaining three. Further investigations show that the coupled-regionalization approach provides slightly better performances than the other two spatial proximity methods. In addit...

Semi-distributed water balance dynamics in a small boreal forest basin

Information on water balance dynamics is an essential component of studies of the role of the boreal forest in surface-atmosphere interactions and climate change. The water balance of a small boreal forest basin in northern Manitoba was examined using a semi-distributed approach to assess basin sensitivity to climate change, provide a framework for distributed hydrological modelling, and explore data aggregation and micro-to-meso scaling of hydroclimatological variables. Black spruce forest with a highly variable canopy density was the main land cover in the basin. Spring snowmelt dominated basin runoff, while summer outputs were largely via evaporation. Annual differences in spring runoff were controlled by variations in snow water equivalent, rainfall timing and magnitude, thaw depth, and antecedent water content in surface stores and upland soils. Water storage in small wetlands and ephemeral surface depressions in the open-canopy black spruce forest and its subsequent loss via evaporation was a fundamental component of the basin water balance. However, its role could be overlooked by inappropriate spatial lumping of landscape units when scaling-up variables or in the production of depressionless digital terrain models. Hydrological consequences of climate warming in this part of the boreal forest include: (i) increased evaporation following spring snowmelt in open black spruce areas; (ii) decreased surface and soil water storage on basin slopes; and (iii) reduced streamflow response to spring runoff and summer and fall rainstorms.

A statistical model of spatially distributed snowmelt rates in a boreal forest basin

Spatial variation in snowmelt rates in the boreal forest can be explained by diAerences in canopy density. Canopy density, represented as gap fractions (GF), controls both the amount of short-wave radiation reaching the snowpack surface and wind speed over the snow surface, which in turn regulates sensible and latent heat fluxes. Reductions in shortwave, sensible and latent heatfluxes outweigh any increased contributions from longwave radiation from the canopy. DiAerences in the total energy available for melt do not translate to equally proportional changes in melt rates under diAerent canopy densities. As available energy increases, the melt rate increases with decreasing canopy density and the form of the relationship can vary depending on climatic conditions. A good relationship between ground-based GF measurements and a canopy closure index derived from Landsat TM provides the spatial fabric for the distribution of snowmelt rates that show comparable patterns of snow ablation during years of very diAerent climatological conditions. This physically meaningful method of determining the spatial variability of snow ablation and subsequent meltwater delivery to the soil interface is particularly useful for providing insight to the heterogeneous active layer development in permafrost regions of the boreal forest and the implications for runoA processes. #1998 John Wiley & Sons, Ltd.

Assessing the effects of dams and waterpower facilities on riverine dissolved organic matter composition

An extensive study was performed in boreal rivers across northern Ontario Canada, to examine the responses of dissolved organic matter (DOM) in rivers altered by hydroelectric waterpower operations. This was tested through three study components: a control-impact component comparing differences upstream and downstream of waterpower facilities (WPFs); a longitudinal component examining responses downstream; and a temporal component comparing the diurnal variations between two disparate rivers. Parallel factor analysis was used to examine how the inherent characteristics of the DOM pool changed between rivers. All rivers were located in heavily forested watersheds with low-level human land use. The main factor differentiating rivers was the presence or absence of WPFs. In a few instances, we identified larger relative differences in the nutrients moving downstream of the WPFs and some diurnal variation between an altered and reference river. However, the overall outcome from each study component was that the presence of WPFs had very little influence on DOM. We related these results to riverine hydrology, as well as a potential relationship between DOM and temperature. In the boreal forest of northern Ontario, catchment characteristics may exert the strongest influence on DOM composition.

Dynamic Modelling of the Impact of Climate Change and Power Flow Management Options using STELLA: Application to the Steephill Falls Reservoir, Ontario, Canada

This paper presents a dynamic modelling framework for evaluating the impact of climate change and flow management options on a hydroelectric power reservoir. The model couples the HBV (Hydrologiska Byrns Vattenbalansavdelning) rainfall-runoff model to a generic reservoir routing model. The efficacy of the model was tested on the Steephill Falls hydropower facility located in the Magpie River watershed in Northern Ontario. Both the impact of climate change and future energy demands were evaluated. Using a statistical downscaling approach, future climate under Intergovernmental Panel on Climate Change (IPCC) A1B and A2 emission scenarios was projected from the Canadian Global Circulation Model 3 (CGCM3). Both scenarios suggest a significantly increasing trend in air temperature (p < 0.001) corresponding to a 1.7C increase by the middle of the century and a 2.9C to 3.7C increase by the end of the century relative to the baseline period (19702000). The model performed well in simulating the inter-annual seasonal dynamics of the reservoir. Plausible climate-induced increase in runoff input into the reservoir might be counterbalanced by increased drawdown caused by increasing energy demands and water users, resulting in increased pressure to adjust lower reservoir rule curves, in-stream flow requirements downstream, or a combination of both.

Tools to Support the Implementation of Environmentally Sustainable Flow Regimes at Ontario's Waterpower Facilities

A strategy for establishing ecologically relevant flow regimes for highly regulated rivers in Ontario is described. Generation of daily flow time-series is used to re-construct natural flow regimes at ungauged sites with waterpower facilities and estimate various ecologically relevant flow characteristics. The flow generation is accomplished by spatial interpolation of observed historical streamflow records and makes extensive use of flow duration curves. Software was developed to automate the flow generation procedure and the analysis and display of flow characteristics. The software makes extensive use of regional spatial databases and GIS facilities and is emerging as a standard tool for calculating environmental flow requirements in regulated rivers in Ontario and as a support system for water management decisions.