Sediment Budget for a High Energy Glacial Lake

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Abstract
A detailed sediment budget study was undertaken for a relatively shallow glacial lake in the Purcell Mountains of British Columbia. The lake, with it's relatively large water and sediment input levels and short water residency time, may be characterized as a high energy lacustrine environment. Using detailed measurements of the major aspects of the entire climatic-hydrologic-sedimentological system, involving some 100 channels of data in conjunction with a systematic coring program, a careful analysis was made of the components of the budget and resulting deposits in this environment. The results indicate that the major inputs consisted of: 1) low sediment concentration level inputs which result in either suspension settling of material to the lake floor, or the transport of material by relatively low overall density lake surface currents (termed overflows) through the system and out the outlet stream with essentially little material being deposited in the lake; 2) higher level sediment concentrations which result in the material being deposited on the lake floor by turbidity currents; 3) extreme discharge events which bring in large amounts of material as bedload to be deposited in the delta; and 4) snow avalanches which deliver large amounts of material to the lake ice surface with the possibility of subsequent rafting. These findings differ somewhat from the findings of other studies. Of particular note they point to: 1) the capacity of overflows to transport material through such lakes with little deposition (thereby significantly affecting the budget); 2) the significance of snow avalanche delivered material as a major component of the budget in such environments. The results of the study also indicate the need for careful monitoring of all input and output operations if a better understanding of glacial lake sediment deposition processes are to be achieved.

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