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DAVID KASMER, NATHANIEL BOOTH, and DIANE MCKNIGHT, Institute for Arctic and Alpine Research, University of Colorado, Boulder, Colorado 80302
Two major river systems receive inflow from numerous tributaries in the McMurdo Dry Valleys: the Alph River system and the Onyx River system located in Wright Valley. The Onyx River has been studied extensively since first being gauged in 1969; the Alph River was studied during the 1985-1986 season. We report here results obtained in January of 1996 and 1997 on the Alph River, including the flow and water chemistry. Also, a comparison of the distribution/location of algal mats in the Alph River to other streams in the McMurdo Dry Valleys is presented.
The Alph River runs roughly 15 kilometers along the side of the Koettlitz Glacier. Trough Lake and its inflow tributaries are the source. We studied the Alph River below Howchin Lake, an ice-covered lake receiving flow from tributaries originating at the Walcott Glacier and Howchin Glacier. From Howchin Lake, the Alph flows through a channel away from the Koettlitz Glacier to the sampling site at 78°12'57.7"S 163°33'95.8"E. The river at the sampling site has riffles and runs. Orange algal mats occur in the riffles and sides of runs as in the Commonwealth Stream (in Taylor Valley) but at a larger scale (Alger et al. 1997). Within the stream bed, ripples in the sand occur in the runs.
The Alph River and the Onyx River are similar in that both flow from a headwater lake (Trough Lake and Brownsworth Lake, respectively), but Brownsworth Lake abuts a piedmont glacier whereas Trough Lake is more inland. Because of its proximity to the Ross Sea, the Onyx River system is affected by a maritime climate. Further, the Alph River runs at the base of a glacier through other lakes whereas the Onyx River runs down valley through dry land. The Alph River below Howchin Lake was visited on 18 January 1997. During this visit, pH, specific conductivity, and temperature were recorded with field meters following methods described by Alger et al. (1997). A discharge measurement was performed to U.S. Geological Survey standards using a pygmy meter and wading rod over a measured cross section. Table 1 contains the results, along with data collected in a similar manner during the 1996 field season. A stream sample was collected and filtered for major cations and anions, dissolved organic carbon, and alkalinity. The concentrations of major cations and anions found during the analysis of the sample can be found in table 2.
Howard-Williams and Vincent (1986) showed that the flow remained constant over several days of measurements. We gauged the river at the same site. The constant flow was attributed to the dampening effects of the lakes (Trough, Walcott, and Howchin) on the typical diurnal cycle seen in other dry valley streams (Howard-Williams and Vincent 1986). Measurements made on 18 January 1997 show a discharge of 0.86 cubic meters per second (m3/sec); Howard-Williams and Vincent report a discharge of 1.17 m3/sec on 18 January 1986. Discharge measurements made in January 1997 at the Onyx at the Vanda weir ranged from 0.67 m3/sec on 7 January 1997 to 0.12 m3/sec on 20 January 1997. The water temperature of the Alph on 18 January 1997 was 1.5°C whereas on 18 January 1986 Howard-Williams and Vincent (1986) report water temperature ranging from 0.5°C to 0.8°C. Water temperatures of the Onyx at the Vanda weir were 3.2°C on 7 January 1997 and 2.4°C on 20 January 1997.
Table 1 reports the field meter data for pH and conductivity obtained by two separate trips to the Alph River. It can be seen that the levels of major cations and anions found in water samples taken at the same site both years remained somewhat constant. This finding holds with the fact that the pH and specific conductivity are fairly constant. Table 3 contains field-meter data obtained at the Onyx during the 1997 season. By comparing the field-meter data contained in table 1 of the Alph River and the field-meter data contained in table 3 of the Onyx River, it can be seen that the pH and specific conductivity of the Onyx River are lower than the sample site on the Alph River below Howchin Lake.
Although the Alph River and Onyx River share the similarity of being the largest flowing freshwaters in Antarctica, the pattern of flow and chemical makeup of each differs due to geographical location and type of terrain. The Onyx experiences a maritime climatic influence due to its proximity to the Ross Sea.
This research was supported by National Science Foundation grant number OPP 92-11773.
Alger, A.S., D.M. McKnight, S.A. Spaulding, C.M. Tate, G.H. Shupe, K.A. Welch, R. Edwards, E.D. Andrews, and H.R. House. 1997. Ecological processes in a cold desert ecosystem: The abundance and species distribution of algal mats in glacial meltwater streams in Taylor Valley, Antarctica (occasional paper no. 51). Boulder: Institute of Arctic and Alpine Research.
Howard-Williams, C., and W.F. Vincent. 1986. The Alph River ecosystem: A major freshwater environment in southern Victoria Land. New Zealand Antarctic Record , 7, 21-33.