The Effect of Storage on Runoff from a Headwater Subarctic Shield Basin

Abstract

ABSTRACT. Canadian Shield runoff production processes have been investigated, but research is needed beyond the hillslope scale to determine the influences on the volume and timing of runoff from headwater basins to higher-order streams. Such research will permit an understanding of the magnitude of climate change impacts at the watershed scale, where changes in the hydrologic regime are felt most by water resource users. To this end, water budget terms were measured over different portions of a headwater lake basin north of Yellowknife, Northwest Territories, during the spring snowmelt of 1998 to determine the relative importance of each component as water moved through the basin. Evaporation made up 16% and runoff 70% of the snowmelt from upland areas. Upland ponding of water during the melt increased the evaporative loss. Headwater lake storage deficits are very important in the timing and volume of runoff that is transmitted downstream: 53% of basin meltwater went to meeting the storage deficit in the lake so that only 7% of the meltwater was routed out of the basin. These results imply that topology of shield headwater basins, notably the location of lakes and antecedent water levels in lakes, are important in determining the runoff response. As storage deficits in surface waters will cause changes over space in runoff response and timing, it may be inappropriate to consider the snowpack or rainfall volume in isolation when forecasting runoff volume. These results are important for water management and hydrological modeling applications of northern shield basins.Key words: Canadian Shield, Northwest Territories, runoff, snowmelt, water management RÉSUMÉ. On a étudié les processus qui entraînent la production de ruissellement sur le Bouclier canadien, mais il faut envisager la recherche d'un point de vue plus global que l'échelle des versants, afin de déterminer les facteurs qui influencent le volume et la périodicité du ruissellement provenant des bassins d'amont vers des cours d'eau d'ordre plus élevé. Une telle recherche permettra de mieux saisir l'importance des retombées du changement climatique à l'échelle du bassin hydrographique, où les changements dans le régime hydrologique sont le plus ressentis par les usagers des ressources en eau. À cette fin, on a mesuré le bilan hydrique sur plusieurs sections d'un bassin lacustre d'amont au nord de Yellowknife, dans les Territoires du Nord-Ouest, durant la fonte des neiges au printemps de 1998, pour déterminer l'importance relative de chaque élément, à mesure que l'eau traversait le bassin. L'évaporation représentait jusqu'à 16 p. cent et le ruissellement 70 p. cent de la fusion nivale venant des hautes terres. À ces endroits, l'accumulation d'eau dans des dépressions durant la fonte augmentait la perte due à l'évaporation. Les déficits dans les réserves lacustres d'amont ont une influence majeure sur le rythme et le volume du ruissellement qui passe en aval: 53 p. cent de l'eau de fonte du bassin allait compenser le déficit des réserves du lac, de sorte que...

Storage dynamics and streamflow in a catchment with a variable contributing area

“…These areas, while capable of generating runoff, were disconnected from and had no access to the basin outlet. This behaviour has been documented earlier in landscapes comparable to the Baker Creek catchment (Spence, 2000;Mielko and Woo, 2006). Contributing area to the outlet of Lower Martin Lake was always less than the active area except at the wet and dry extremes.…”

Shallow soil moisture – ground thaw interactions and controls – Part 1: Spatiotemporal patterns and correlations over a subarctic landscape

“…Other examples include Park (1979) who found modelling soil moisture values by landscape typology yielded more accurate water balances than by using one single, lumped value. Runoff generation from headwater subarctic Shield basins is also greatly influenced by landscape topology (Spence, 2000;Spence and Woo, 2006). Comparably, it has been found water distribution in other landscapes is correlated with landscape position or surface form (e.g.…”

Hydrological processes and streamflow in a lake dominated watercourse

“…This may be particularly significant on the Canadian Shield where lakes dominate watercourses. Both Spence (2000) and Mielko and Woo (2006) observed lakes in first and second order streams with storage demands prior to the spring freshet. This storage delays the transfer of run-off from hillslopes until lakes fill to their outlet elevations and spill.…”