T.G. Northcote. 1998. Inland waters and aquatic habitats in Smith, I.M., and G.G.E. Scudder, eds. Assessment of species diversity in the Montane Cordillera Ecozone. Burlington: Ecological Monitoring and Assessment Network, 1998.

INLAND WATERS AND AQUATIC HABITATS

T.G. Northcote
Department of Zoology
The University of British Columbia
Vancouver, Canada
and
Elderstrand
10193 Giant's Head Road
RR2 S77B C2
Summerland, B.C.
VOH IZO
Canada

INTRODUCTION

The Ecological Stratification Working Group (1995) report and ecozone mapping did consider the importance of inland waters in distinction of ecoregions and ecoditricts as is evidenced by map notes

giving their definition and by inclusion of sections on freshwater molluscs, crayfish and fishes in its recent summary and assessment of species diversity, for the Mixedwood Plains Ecozone (Smith 1996). Nevertheless the major thrust of coverage to date has been terrestrial, so the request to prepare a chapter on inland waters of the Montane Cordfflera Ecozone (MCE) came as a welcome challenge to a limnologist who has spent nearly fifty years of his career working in that area.

Coverage of the inland waters of the NICE should include not only its large and small fresh waters but also its naturally saline waters as well as those now less than "fresh" because of various human activities. Therefore attention needs to be given to its lakes and reservoirs, its ponds, marshes and wetlands, its saline and meromictic lakes, and its flowing waters (rivers, streams, and springs including seasonally ephemeral ones).

Groundwater should also have been considered but could not because of time constraints. Only one of the five groundwater aquifers included in a recent review of B.C. water quality status (Anonymous 1996a) is in the MCE - that at Grand Forks, which ranked only fair because of high nitrate-nitrogen concentrations.

Though by no means one of the larger Canadian terrestrial ecozones (geographic areas that show relatively consistent character throughout in factors such as climate, geology and topography - Smith 1996), the MCE surely is the most diverse for all three of these factors (Ecological Stratification working Group 1995) so important in determining basic differences in regional limnology (Northcote and Larkin 1956). This ecozone includes sizable parts of at least nine major watersheds, five draining to the Pacific Ocean (Columbia, Fraser, Skeena, Nass, Stikine), two to the Arctic Ocean (Athabasca, Peace), and two draining to Hudson Bay (North and South Saskatchewan); see Fig. 1. Furthermore it also contains major portions of seven of the 12 limnological regions in British Columbia (Northcote and Larkin 1956, 1963) and six of the 13 lake basins recognized in Alberta (Mitchell and Prepas 1990); see Fig. 2. Parts of or the whole of at least six of the dozen or more large glacial and early postglacial lakes of British Columbia (Farley 1979) were located in the MCE. These also had important effects on its present aquatic biodiversity.

Of some 22,000 lakes conservatively estimated in British Columbia (Northcote 1964) about half lie in the MCE, as do nine of the ten largest unregulated natural lakes in the province, and all of the ten largest regulated lakes or reservoirs (Balkwill 1991). Many saline as well as meromictic lakes and ponds also are found in this ecozone (Northcote and Larkin 1963, Northcote and Halsey 1969). Ponds, marshes and wetlands harbour a rich abundance and diversity of aquatic blota and must be included in any serious coverage of such features.

There are at least 17 standing waterbodies with surface areas exceeding 100 km² in the MCE, the four largest of which have been formed by recent impoundment for hydroelectric generation (Fig. 3). Babine is the largest natural lake in this ecozone, and Quesnel the deepest (530 m; also the third deepest in the western hemisphere). Water levels of two other large lakes (Kootenay and Okanagan) are regulated to a minor extent by impoundment and several other major reservoirs in the upper Columbia River system undergo large fluctuations in water level under Columbia River Treaty regulations between Canada and USA.

This chapter will review the limnological features of inland water habitats within the MCE, consider how they support the underpinnings of an amazing range of aquatic biodiversity there, show causes for concern where they are threatened by various human activities, and suggest means for more effective conservation of their diversity.

TABLE OF CONTENTS