Kevin Shook

An evaluation of snow accumulation and ablation processes for land surface modelling

This paper discusses the development and testing of snow algorithms with specific reference to their use and application in land surface models. New algorithms, developed by the authors, for estimating snow interception in forest canopies, blowing snow transport and sublimation, snow cover depletion and open environment snowmelt are compared with field measurements. Existing algorithms are discussed and compared with field observations. Recommendations are made with respect to: (a) density of new and aged snow in open and forest environments; (b) interception of snow by evergreen canopies; (c) redistribution and sublimation of snow water equivalent by blowing snow; (d) depletion in snow-covered area during snowmelt; (e) albedo decay during snowmelt; (f) turbulent transfer during snowmelt; and (g) soil heat flux during meltwater infiltration into frozen soils. Preliminary evidence is presented, suggesting that one relatively advanced land surface model, CLASS, significantly underestimates the timing of snowmelt and snowmelt rates in open environments despite overestimating radiation and turbulent contributions to melt. The cause(s) may be due to overestimation of ground heat loss and other factors. It is recommended that further studies of snow energetics and soil heat transfer in frozen soils be undertaken to provide improvements for land surface models such as CLASS, with particular attention paid to establishing the reliability of the models in invoking closure of the energy equation. #1998 John Wiley & Sons, Ltd.

Snowmelt resulting from advection

Snowmelt can be estimated by applying an energy balance to a control volume of snow. A major problem with this method is the difficulty of obtaining accurate estimates of the turbulent transfers of sensible and latent heat. This paper uses a modified form of the Penman-Monteith equation, a combined aerodynamic-energy balance approach for calculating evaporation from vegetative surfaces, to estimate the energy available for snowmelt during large-scale advection. The modification requires knowledge of k, the ratio of the energy used for melting to the net energy available for phase changes (vaporization and melting). Comparisons between the melt flux determined by the Penman-Monteith equation and estimates derived from field measurements suggest a value of k in the range of 0.90-0.99. The modified Penman-Monteith equation is used in a detailed simulation of melting of a shallow prairie snow cover. This simulation incorporates the effects of a small-scale advection of energy from bare ground to adjacent patches. It is demonstrated that the contributions by large- and small-scale advective energy transfers to melt depend on the interactions between snow-covered area and meteorological variables.

The 2005 flood events in the Saskatchewan River Basin: Causes, assessment and damages

In June 2005, the headwater tributaries of the Saskatchewan River Basin in the western Canadian province of Alberta were struck by four heavy rain events. Runoff from the rainfalls resulted in three floods which extended from Alberta through the provinces of Saskatchewan and Manitoba, causing at least four deaths and property damages of CAD

The effects of the management of Lake Diefenbaker on downstream flooding

400 million.

R-functions for Canadian hydrologists: a Canada-wide collaboration

The impact of management of Lake Diefenbaker, Saskatchewan, the Canadian Prairies’ largest reservoir, on downstream flooding is examined over three large inflow events in 2005, 2011 and 2013. The reservoir stores inflows for water supply, recreational and ecological purposes and preferentially releases water in mid-winter for hydroelectricity generation. It can also have an important role in downstream flood mitigation. The analysis shows great uncertainty in inflows due to ungauged local inflows, and substantial errors in the mass balance of the reservoir associated primarily with high inflows. The management of the reservoir has been challenged by declining spring inflows since the 1960s with a trend for increasing minimum annual reservoir elevations over time. Management of the reservoir has undergone changes since 2011 to lower the minimum elevation so as to achieve the 1 July target level, resulting in very different effects on flooding in 2005, 2011 and 2013. In all years, the management of the reservoir reduced the maximum flooded area upstream of Saskatoon and the integrated flooded duration and area. In 2005 the area of flooding upstream of Saskatoon was reduced for all durations and in 2013 for durations shorter than 5 days, but in 2011 it was increased for durations between 5 and 20 days. Flooding on the Saskatchewan River, i.e. downstream of the confluence of the North and South Saskatchewan Rivers, was increased in 2011 due to the delay in the timing of the peak flow induced by reservoir operation. Elimination of downstream flooding in these years would have required continuous adjustment of outflows to optimize storage, which itself requires modelling the inflow hydrograph. Future operation of the reservoir should adopt such optimization and modelling, whilst considering the impact of non-stationarity due to climate change.

SMALL‐SCALE SPATIAL STRUCTURE OF SHALLOW SNOWCOVERS

R is an open-source statistical language that is supported by a large user community with many benefits for use in watershed analysis. R has been used widely in the Canadian research community and Canadian researchers have contributed numerous R packages with specific applications (e.g. seas, GEVcdn, RHtests, tidyhydat, FlowScreen). Here a new R package, CSHShydRology, is introduced that combines functions developed by hydrologists across Canada.