INTRODUCTION

Interest in the limnology of montane lakes began decades ago, e.g., Strom (1931), Ruttner (1937), and Hutchinson (1937). Such pioneering efforts documented the short ice-free period of the lakes and their unproductive condition. In subsequent years a series of limnological studies contributed additional information to the fundamental understanding of the physical and chemical characteristics (water quality) of these lake systems (e.g., Pennak 1955; Pechlaner 1966, 1967, 1971; Loffler 1969; Stout 1969; James and Hubbick 1969; Reed 1970; Zutshi et al. 1980; Larson 1973, Larson et al. 1994; Mosello 1984; Mosello et al. 1991; Aizaki et al. 1987; Psenner 1989; Vass et al. 1989; Boggero et al. 1993; Gosso et al. 1993; and Kovacik and Stuchlik 1994). Collectively, these studies showed that the water quality of montane lakes during the ice-free period was influenced by basin geology, watershed vegetation, local climate, and lake depth.

In recent years, there has been a growing interest in characterizing the water quality of montane lakes at a coarser scale than the watershed unit. For groups of lakes distributed across montane landscapes, changes in lake water temperature, pH, alkalinity, and conductivity have been shown to be related to lake elevation (Anderson 1970; Zutshi et al. 1980; Vass et al. 1989; Stout 1993; Lukavsky 1994; Larson el at. 1995). Perhaps the best example of the relationship between elevation and water quality was provided by Nauwerck (1994), who showed that water temperature, pH, conductivity, and concentration of total phosphorus increased and concentration of nitrate-N decreased with decreasing elevation in montane lakes of northern Swedish Lapland. In the present study, we assessed the water quality of montane lakes distributed over an elevational range of 1651 m in a relatively limited geographical area that included alpine, subalpine, and forest vegetation zones, a relatively uniform geology, and sharp west-east climate gradient formed by the hydrologic divide (Lomnicky 1996). Our working hypotheses for data analyses were that: (1) increased lake temperature, pH, alkalinity, conductivity, and concentrations of nutrients would decrease with elevation; and (2) water quality would be influenced by lake depth and geology. The objectives of the study were to: (1) document the time of ice-out relative to lake elevation west of the hydrologic divide and describe how the west-east climate gradient affected this relationship for subalpine lakes; (2) assess how lake water quality was associated with lake elevation, and (3) assess how water quality differed between deep and shallow lakes, and between geologic types.