Return to the Table of Contents for this chapter.

McMurdo Dry Valleys LTER: Stream discharge as a function of ambient temperature and incoming shortwave radiation in Taylor Valley, Antarctica

Daryl L. Moorhead, Ecology Program, Department of Biological Sciences, Texas Tech University, Lubbock, Texas 79409-3131

Diane M. McKnight, U.S. Geological Survey, Boulder, Colorado 80303

Of the several streams in the McMurdo Dry Valleys, southern Victoria Land, Antarctica, many are relatively short (less than 4 kilometers), receiving water primarily from melting glaciers and flowing only during the brief, austral summer. Benthic microbial mats are widespread in many streams (Alger et al. 1996), exhibit substantial net primary production (Howard-Williams and Vincent 1989), and transform a considerable fraction of the inorganic and urea nitrogen entering the streams into other organic forms (Howard-Williams et al. 1989). In a recent modeling study, Moorhead, McKnight, and Tate (in press) noted the influence of stream discharge rate on nitrogen uptake by benthic mats. Thus, factors controlling discharge rates are likely to have a considerable impact on the nitrogen dynamics of dry valley streams. The objectives of this study were to examine the correlations between discharge patterns for streams in the McMurdo Dry Valleys and to evaluate the relationships between daily discharge, mean daily temperature, and total incident shortwave radiation.

As part of the U.S.-sponsored, McMurdo Dry Valley Long-Term Ecological Research (LTER) program, discharge of streams and local meteorological conditions in Taylor Valley (77°S 163°E) are being recorded (Von Guerard et al. 1994; Doran et al. 1995). Measurements of streamflow for use in this study were obtained from the U.S. Geological Survey (H. House, via U.S. Geological Survey Antarctic Hydrology homepage, http://srvdwimdn.er.usgs.gov/hrhdocs/index.html). Meterological observations were obtained for three meteorological stations located near Commonwealth Glacier, Lake Hoare, and Lake Fryxell, Taylor Valley, from the McMurdo LTER (K. McGwire, via the LTER homepage, http://mcm.maxey.dri.edu/lter/).

We examined the temporal patterns of discharge for eight streams draining into Lake Fryxell, Taylor Valley (Canada Stream, Huey Creek, Lost Seal Stream, Aiken Creek, Von Guerard Stream, Crescent Stream, Delta Stream, and Green Creek), during the period of maximum flow (15 December through 25 January) in the austral summers of 1993-1994 and 1994-1995. Hydrological observations were concurrent with meteorological records available through the McMurdo LTER. The pattern of daily discharge during these summers showed peak values in early January 1994, sometimes exceeding 3 cubic meters per day, although considerable differences existed between streams and between years ( figure 1). When discharges were expressed as the fraction of the maximum value recorded for each stream in each year, a similar pattern emerged; streams showed peak discharges in late December and early January. Such patterns suggest a likely correlation to ambient temperature and radiant energy levels, which also peak during this time. Thus, we hypothesized that

Pearson product-moment correlations of daily stream discharge were calculated for each pair of streams. Relationships between stream discharge and these climatic factors then were analyzed with multiple linear regressions using relative daily discharge as the dependent variable and climatic factors as independent variables.

Strong correlation existed between daily discharge for all streams, ranging between 0.743 (Huey Creek and Aiken Creek) and 0.979 (Green Creek and Crescent Stream); most correlations exceeded 0.9. Multiple linear regressions, however, revealed that stream discharge was weakly related to radiation and temperature, with overall R2 values rarely exceeding 0.4 (table). Moreover, an overall regression (all streams in both years) yielded a low coefficient of regression (R2=0.163, N=440) between stream discharge and climatic factors.

Temporal patterns of stream discharge were nonlinear and peaked only during a brief period in both summers, implying a seasonal control on streamflow that was partly independent of general radiation and temperature regimes. Contrasting patterns of discharge for Canada Stream, Aiken Creek, and Von Guerard Stream also suggest that controls differ among streams ( figure 2):

A number of geographic and climatic factors apparently control streamflow (cf. McKnight, House, and Von Guerard 1994; House, McKnight, and Von Guerard 1995; Conovitz et al. in press). For example, Canada Stream is short (less than 2 kilometers) and receives meltwater from northern faces of Canada Glacier (west of Lake Fryxell). Thus, discharge should reach relatively high values early in the summer and remain high, as seen in figure 2. In contrast, Von Guerard Stream is longer than Canada Stream (approximately 5 kilometers) and is fed by the northwest face of a glacier located in the Kukri Hills (southeast of Lake Fryxell). Thus, peak flows should occur somewhat later than for Canada Stream and be more temporally constrained by the orientation of the source glacier. Aiken Creek receives meltwater from two sources: the northwest face of Wales Glacier, in the Kukri Hills, and the south and east faces of Commonwealth Glacier, to the northeast of Lake Fryxell. Moreover, flows from the Wales and Commonwealth Glaciers combine to form Many Glaciers Pond, in which Aiken Creek has its source. Thus, peak flow of Aiken Creek may be delayed by the time required for the source pond to fill.

In conclusion, it is clear that simple multiple linear regressions of daily temperature and radiation regimes are insufficient to provide an accurate prediction of discharge patterns for streams of Taylor Valley. Discharge patterns appear to be strongly influenced by attributes of stream geometry and orientation of source glaciers, as noted by Conovitz et al. (in press). A more mechanistic, physically based approach where these attributes are quantified, may be useful in developing predictive relationships between climate and streamflow in the McMurdo Dry Valleys.

This work was supported by a National Science Foundation grant OPP 92-11773.

References

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. 1996. Ecological processes in a cold desert ecosystem: The abundance and species distribution of algal mats in glacial meltwater streams in Taylor Valley, Antarctica. Boulder: U.S. Geological Survey.

Conovitz, P.A., D.M. McKnight, L.M. MacDonald, and A. Fountain. In press. Hydrologic processes influencing streamflow variation in Fryxell basin, Antarctica. Washington, D.C.: American Geophysical Union.

Doran, P.T., G.L. Dana, J.T. Hastings, and R.A., Wharton, Jr. 1995. The McMurdo LTER automatic weather network (LAWN). Antarctic Journal of the U.S., 30(5), 276-279.

House, H.R., D.M. McKnight, and P. Von Guerard. 1995. The influence of stream channel characteristics on streamflow and annual water budgets for lakes in Taylor Valley. Antarctic Journal of the U.S., 30(5), 284-286.

Howard-Williams, C., R. Pridmore, M.T. Downes, and W.F. Vincent. 1989. Microbial biomass, photosynthesis and chlorophyll a related pigments in the ponds of the McMurdo Ice Shelf, Antarctica. Antarctic Science, 1(2), 125-131.

Howard-Williams, C., and W.F. Vincent. 1989. Microbial communities in southern Victoria Land streams (Antarctica) I. Photosynthesis. Hydrobiologia, 172, 27-38.

McKnight, D., H. House, and P. Von Guerard. 1994. McMurdo LTER: Streamflow measurements in Taylor Valley. Antarctic Journal of the U.S., 29(5), 230-232.

Moorhead, D.L., D.M. McKnight, and C.M. Tate. In press. Modeling nitrogen transformations in antarctic streams. Washington, D.C.: American Geophysical Union.

Von Guerard, P., D.M. McKnight, R.A. Harnish, J.W. Gartner, and E.D. Andrews. 1994. Streamflow, water-temperature, and specific-conductance data for selected streams draining into Lake Fryxell, Lower Taylor Valley, Victoria Land, Antarctica (Open-file Report 94-545). Boulder, Colorado: U.S. Geological Survey.