The Winter Environmental Continuum of Two Watersheds

Benoit Turcotte,Brian Morse

doi:10.3390/w9050337

Abstract

This paper examines the winter ecosystemic behavior of two distinct watersheds. In cold-temperate regions, the hydrological signal and environmental parameters can fluctuate dramatically over short periods of time, causing major impacts to aquatic habitats. This paper presents the results of the 2011–2012 winter field campaign in streams and rivers near Quebec City, QC, Canada. The objective was to quantify water quantity and quality parameters and their environmental connectivity from headwater creeks above to the larger rivers below over the entire freeze-up, mid-winter and breakup periods with a view toward exploring the watershed continuum. The paper presents how aquatic pulses (water level, discharge, temperature, conductivity, dissolved oxygen and turbidity, measured at seven sites on an hourly basis along channels of different sizes and orders) evolve through the aquatic environment. Ice conditions and the areal ice coverage were also evaluated (on a daily time step along each instrumented channel). Some findings of the investigation revealed that water temperatures remained well above 0 °C during winter in headwater channels, that dissolved oxygen levels during winter were relatively high, but with severe depletions prior to and during breakup in specific settings, that high conductivity spikes occurred during runoff events, that annual turbidity extremes were measured in the presence of ice and that dynamic ice cover breakup events have the potential to generate direct or indirect mortality among aquatic species and to dislodge the largest rocks in the channel. The authors believe that the environmental impact of a number of winter fluvial processes needs to be further investigated, and the relative significance of the winter period in the annual environmental cycle should be given additional attention.

Highlights

The term “aquatic ecosystem” is commonly used, but what is really known about how a watershed works as a system, especially during the cold season? Life subsists under the ice cover of cold regions’river systems
Continuous aquatic environment monitoring in the presence of ice has seldom been done; the potentially dynamic river ice breakup period generates aquatic habitat constraints that have not been accurately investigated despite the relative importance in the annual hydrological cycle; and the ecological impact of common and less common river ice processes is often only superficially described
Openings in the suspended ice cover at Sites M2–M4 remained visible throughout winter, often downstream of low order tributaries

Summary

Introduction

From a spatial point of view and scientists and engineers have sampled multiple sites simultaneously, the headwater-to-large-channel dynamics of ice-affected river systems has not been sufficiently documented. This is defendable from a biological point of view since project managers are often emphasizing specific aquatic habitats and channel morphologies. The succession of cold and mild air temperature spells during winter, the latter potentially accompanied by rain that can generate river ice breakup events, produces hydrological pulses that can significantly impact aquatic parameters at varying time and space scales. The hydrological impacts of dynamic river ice formation and breakup events are synthesized in [7,10]

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Conclusion