The physical effects of a large river (Thompson River) entering a deep, intermontane lake (Kamloops Lake, British Columbia) suggest that, depending upon its temperature relative to that of lake water, river water moves through the lake as a surface overflow, an intermediate depth interflow, or a near-bottom underflow. Circulation is further influenced by the earth's rotation so that the incoming river flows preferentially along the right-hand shoreline of the lake. Convective overturn in autumn and spring is influenced by cabbeling, which occurs than 4°C and one colder, combine to form a whenever two parcels of water, one warmer mixture whose temperature is at or near 4"~.
Kamloops Lake in central British Columbia is a deep, intermontane lake fed by the strong and seasonally variable flows of the Thompson River. Considerations of lake-river interaction, supported by physical and geological evidence, suggest that sediment transport and deposition within the lake is controlled by three interdependent but distinct processes: delta progradation at the lake-river confluence which results in delta topset and foreset bedding; sediment density surges originating along the delta face which result in turbidite sequences lakeward from the base of the delta; and dispersal by the interflowing river plume which, due to Coriolis effects, results in a higher sedimentation rate and greater fraction of coarser material along the right-hand side (Northern Hemisphere) of the lake in the direction of flow. has its present morphology, and the sediment density surges are generated. Although none of these processes are unique to river-dominated lakes, a recognition of their combined effects proves extremely useful in understanding sediment distributions, and in interpreting geological data for economic or environmental applications.Our study is based on data obtained during a year-long interdisciplinary study of the Kamloops Lake/Thompson River system in central British Columbia (Fig. 1) The morphometry of Kamloops Lake is given in Table 1. Briefly, the lake is typical of fjord-type intermontane lakes; it is long (25 km), narrow (2.1 km), deep (maximum depth, 145 m), and situated in a relict glacial valley. The flow of the Thompson River, the dominant river entering Kamloops Lake, shows high seasonal variability (range, 100-3000 m3s-l; annual mean, 700 rn3s-l; see also Fig. 2). As a consequence, lake level varies annually by up t o 7 m, while the bulk residence time for lake water (defined as T= V / R , where V is lake volume and R is streamflow) varies from approximately 1 year in late winter t o less than 20 days during spring freshet. This large and variable KAMLOOPS LAKE BATHYMETRV IN METRES THOMPSON RIVER KILOMETRES 0 2 4 6 Fig. 1. Kamloops Lake, British Columbia. (a) Location and drainage basin; (b) bathymetry.
The seasonality of physical structure in a deep, temperate lake (Kootenay Lake) is described in relation to its major river inputs (Kootenay and Duncan Rivers). The lake's volume is 37 km3 and its annual outflow is 25 km3 yr-I, yielding a residence time of about 1.5 years. Water mass distributions are controlled by the interactions of three processes: riverine circulation, mixed-layer dynamics, and internal wave behavior. The riverine circulation is determined by the inflow rate and by the relative density of incoming water and ambient lake water. Mixed-layer structure varies in relation to the combined action of the wind and surface heat flux on both seasonal and synoptic time scales. Internal waves may periodically raise a given stratum of water, such as the riverine layer, to a depth where wind mixing is more intense. Knowledge of these processes, their relative importance, and their time-space variability can aid in understanding the ecology of the lake.An important parameter of any natural or man-made lake is its residence time, defined as basin volume divided by outflow rate T, = V/R. In long residence-time systems, wind and local heat exchange are the principal means of setting water in motion (Mortimer 1974;Hollan and Simons 1978). As residence time shortens, the interaction between a lake and its through-flowing river becomes increasingly important, eventually resulting in the so-called run-of-the-river system in which river inputs completely dominate the distribution of properties. In the middle of this spectrum are many lakes whose dynamics are influenced by river through-flow but modified by other physical mechanisms within the lake. As a category, such lakes are still poorly understood. For example, a review of ecosystem modeling of northern lakes by Fox et al. (1979) contains no reference to the processes of lakeriver interaction" We discuss here the annual cycle of mixing and circulation in Kootenay Lake, British Columbia, and show how the seasonal patterns of circulation and water mass distribution are controlled by the interplay of advective and surface-driven processes.
The Strait of Georgia is a long, narrow, semi-enclosed basin with a restricted circulation and a single sediment source, the Fraser River, providing practically all the sediment now being deposited in the Strait. This river is building a delta into the Strait from the east side near the south end. Ridges of Pleistocene deposits within the Strait and Pleistocene material around the margins, like bedrock exposures, provide local sources of sediment of only minor importance.Sandy sediments are concentrated in the vicinity of the delta, and in the southern and southeastern parts of the Strait. Mean grain size decreases from the delta toward the northwest along the axis of the Strait, and basinwards from the margins. Silts and clays are deposited in deep water west and north of the delta front. Bedrock or poorly sorted sediments containing gravel occur near tidal passes, on the Vancouver Island shelf area, on ridge tops within the Strait, and with sandy sediments at the southeastern end of the study area. The Pleistocene ridges are areas of nondeposition, having at most a thin veneer of modern mud on their crests and upper flanks.
A description is given of the heat and water balances of Kootenay Lake, British Columbia. Although the lake has a moderately high throughflow (781 m 3 s-•), the heat budget is more in character with a lake that is little influenced by rivers. The discussion focuses upon the role of rivers in the thermal history of lakes; a contrast is drawn between Kootenay Lake and Kamloops Lake, British Columbia, a strongly riverinc lake with a much greater heat budget. It is suggested that the riverinc nature of lakes can be characterized using a renewal time that applies to that region of the lake lying above the base of the river plume. Furthermore, the relative roles of advective and surface effects can be qualitatively described using a ratio of surface buoyancy or wind energy to river production of turbulent energy. These parameterizations may prove to be useful descriptors in a lake classification system based upon riverinc quality.
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