Document Type

Thesis

Degree Name

Master of Arts (MA)

Department

Geography & Environmental Studies

Faculty/School

Faculty of Arts

First Advisor

Gordon J. Young

Advisor Role

Thesis Committee Member

Second Advisor

Houston Saunderson

Advisor Role

Thesis Committee Member

Third Advisor

Michael English

Advisor Role

Thesis Committee Member

Abstract

The purpose of this thesis is to investigate relationships between meltwater flow and production and flushing of suspended-sediment beneath two alpine glaciers. During the ablation seasons of 1987 and 1988, discrete, hourly measurements were taken of discharge, stage, suspended-sediment concentration and electrical conductivity in two rivers draining catchments of the Bualtar and Batura Glaciers in the Karakoram, N. Pakistan. The discharge time series of the Bualtar River reveals that flow varies over a daily period of three to four weeks, at a diurnal level and over one to four hours. Over all three time scales, electrical conductivity is inversely proportional to discharge suggesting that at high flows, outwash water is derived from surface melt while at low discharges, water originates from subglacial and englacial stores. Variations in suspended-sediment concentration are proportional to discharge at a daily time scale but become less well defined at diurnal and shorter periods. In the Batura River, stage measurements show that diurnal flow variations are superimposed on a longer-term rising limb and have fluctuations over periods of one to four similar to those observed in the Bualtar River in 1987. Conductivity in the Batura River is inversely proportional to discharge. The suspended-sediment concentration record at both sites demonstrates that timing of maximum and minimum sediment flushing over diurnal and shorter periods is not constant with respect to associated flow variations. Investigation of empirical linear regression relationships between flow and sediment transport in both rivers shows that changing hysteresis relationships between variables does not permit adequate prediction of suspended-sediment from discharge. Hence, further development of a deterministic model of subglacial erosion, design by Keeley (1986), is undertaken in order to account for processes of sediment supply and removal at the glacier bed which regression analysis cannot model. Model prediction of variations in suspended-sediment transport in the Bualtar River at the daily level are good suggesting that rates of removal of subglacially eroded bedrock and sediment are directly proportional to discharge variations in arterial conduits. However, short, hourly fluctuations are not simulated well by the model. At this level, sediment accessibility to changing conduit networks within the glacier is more important than subglacial erosion. At a diurnal scale, model performance is variable demonstrating that varying sediment loads in outwash channels are the result of more complex processes of sediment supply and removal than the model accounts for.

Convocation Year

1990

Convocation Season

Fall

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