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Mcmurdo LTER: Streamfiow Measurements in Taylor Valley DIANE MCKNIGHT, U.S

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Mcmurdo LTER: Streamfiow Measurements in Taylor Valley DIANE MCKNIGHT, U.S McMurdo LTER: Streamfiow measurements in Taylor Valley DIANE MCKNIGHT, U.S. Geological Survey, Boulder, Colorado 80303 HAROLD HOUSE, U. S. Geological Survey, Madison, Wisconsin 53 719-1133 PAUL VON GIJERARD, U.S. Geological Survey, Grand Junction, Colorado 81501 ne of the most basic measurements for understanding lishing a gaging site on exposed bedrock is not possible. Owatershed processes and aquatic ecosystem dynamics is Although this is a challenge, it minimizes the long-term alter- streamfiow variation. In the McMurdo Dry Valleys, stream- ation caused by activities in a stream channel at a local gaging flow measurement is particularly important because of indi- station. Obtaining stream-stage data and defining the relation cations that lake levels have been rising rapidly. Lake-level of stream stage and streamflow (rating curve) are very difficult rise has been attributed to increasing temperatures resulting in these conditions. The rating curve is developed from flow in greater meltwater generation from the glaciers (Chinn measurements at a range of low and high flow conditions. 1993, pp. 1-51). Because of the high variability in streamfiow Three installations (methods) were used to obtain accu- on hourly time scales, intermittent measurements using flow rate data. One method used was to select a site in the stream meters (such as a Pygmy meter or an AA meter) provide an that had an adequate channel or section control for the devel- inadequate description of flow regimes and continuous mea- opment of a rating curve. Another method used was to install surements are required (Green et al. 1989, pp. 129-148). As a weir (V-notched or broad-crested) and continuously meas- part of the basic data collection for the McMurdo Dry Valley ure water level (Chinn 1979). For low streamfiows, the theo- Long-Term Ecological Research (LTER), we have established a stream gaging network for the Streamfiow and water -quality monitoring sites three major lake basins in Taylor L Valley. These data are critical for Stream name and determining nutrient budgets for 1 location L the lake ecosystems and for understanding physical factors Lake Fryxell Streams controlling microbial mats in the Canada Stream 7703650 16300314 Continuous 9-inch Parshall flume and weir streams. Huey Creek 7703622 16300727 Continuous 9-inch Parshall flume and weir Obtaining accurate continu- Lost Seal Stream 7703542 16301440 Continuous Channel and section Aiken Creek 770 ous streamfiow measurements for 3620 16301530 Continuous 9-inch Parshall flume and weir von Guerard Stream 7703628 16301440 Continuous Channel and section dry valley streams is a challenge. In addition to taking the highly Crescent Stream 7703710 16301100 Continuous Channel and section Delta Stream 7703726 16300628 Continuous Channel variable flow into account, Green Creek 7703721 16300350 Continuous Channel and section researchers find that the very low McKnight Creek 7703630 163 01500 Periodic Channel flow rates, which occur during Harnish Creek 7703630 16301415 Periodic Channel cold spells in the austral summer, Bowles Creek 7703720 16300300 Periodic Channel are difficult to measure accurate- Maria Creek 7703725 16300250 Periodic Channel ly. An important consideration in Andrews Creek 7703715 16300240 Periodic Channel designing a gaging station is mini- Lake Hoare/Chad Streams mizing contact of the streamwater Anderson Creek 7703730 162°5428 Continuous 9-inch Parshall flume and weir with materials that might leach Vestal Stream 7703837 16204440 Continuous 6-inch Parshall flume and weir solutes and affect the chemistry of Wharton Creek 7703845 16204450 Periodic Channel McKay Creek 7703841 16204450 Periodic Channel the streamwater. The streams in the dry valleys have very low con- Lake Bonney Streams Priscu Stream centrations of solutes because 77°42OO 16203205 Continuous 6-inch Parshall flume and weir Hendy Stream 7704323 16201600 Continuous 9-inch Parshall flume and weir they are fed by glacial meltwater Parker Creek 77°4340 16201630 Periodic Channel and because geochemical weath- Lawson Creek 77°4322 162°1605 Periodic Channel ering processes are constrained to Red River 77°4322 16201605 Periodic Channel the streambed and adjacent areas. Sharp Creek 77°4320 16201450 Periodic Channel Finally, the unstable nature of the Lizotte Creek 7704215 16202900 Periodic Channel stream channels make measure- Bartlette Creek 7704315 16202500 Periodic Channel ments difficult. The streams now Vincent Creek 77°4313 16202530 Periodic Channel through unconsolidated alluvium New Harbor Stream barren of vegetation, and estab- Commonwealth Stream 7703348 163 02251 Continuous Rock weir ANTARCTIC JOURNAL - REVIEW 1994 230 retical rating of the weir is used; otherwise, when the theoreti- crate that is secured at a location above the channel using cal rating is exceeded, the rating must be defined using ropes and buried weights. streamfiow measurements. This method creates an impound- The figure presents streamfiow data for the 1993-1994 ment even at low flows. Finally, a flume, such as a Parshall austral summer for three streams in Taylor Valley, located in flume, was installed for measurements of low flow with a weir each of the three lake basins. The data show that the large diel installed in the cutoff wall for measurements at high flow. At variation is a common feature of the flow regimes of dry valley high flow, when water flows through the weir, a rating curve is streams. The major factors controlling the diel variation are used for calculation of discharge. When the flow is contained probably Sun angle and the aspect of the glaciers. The other in the flume, discharge can be calculated based on the flume feature illustrated in the figure is that the timing of initiation geometry. With this method, no impoundment occurs at low of flow between streams varies greatly, ranging from early flow, and accurate measurements can be obtained because of November to late December. Again, this timing is a character- the geometry of the flume. istic of the source glacier more than the lake basin itself. For In the dry valleys, all three methods described above example, Canada Stream and Green Creek, which are fed by have been used. The simplest method is the use of a channel the Canada Glacier and flow into Lake Fryxell, also began or section control, but this method results in much less accu- flowing in mid-November. rate data, especially at low flows. Also, the stream channels The results indicate that several years of streamfiow are unstable, and rating curves must be regularly updated record will be necessary for development of reliable correla- each year. The use of weirs has been generally successful, but tions between streams and for predicting streamfiow as a problems with washout at high flow and formation of an ice- function of climate. By establishing the stream-gaging net- cover in the impoundment at low flow have been encoun- work at the onset of the McMurdo Dry Valley LTER, it will be tered. The weirs have the disadvantage of altering the inter- possible to achieve some critical watershed modeling goals action with the lake, because the sediment carried in the stream is retained behind the 10 weir at all flow regimes. This effect is not 8 sustained, because once the weir is removed the retained sediment would be E.I 8 transported to the lake in a few years. We have primarily used combined flume and weir installations and channel or in t.0 2 section control stations (table). At streams that flow for a shorter period and have low 0 streamfiow, periodic streamflow measure- VON GUERARD STREAM, LAKE FRYXELL ments were made. We will use correlations between the different streams to infer con- tinuous measurements for streams where 1.5 periodic measurements are made. The . flumes are made of black fiberglass, which is . relatively inert. Because of continuous sun- light, the black color minimizes problems j with ice formation in the flume. The advan- 0.5 tages of the use of Parshall flumes are that high-quality data can be obtained at low 0 flow and retention of waterborne sediment during low and moderate flow is minimal. VESTAL STREAM, LAKE CHAD For the flume/weir stations, we chose sites to minimize the length of the cutoff walls, and we built the cutoff walls using polyester cloth sandbags filled with alluvium from near the stream channel. Because the sand- bags are filled with channel material, there 2 is little possibility of directly altering stream chemistry. Stream-stage records were col- lected using techniques described by Rantz and others (1982a, b). Stream stage was col- 0 lected at 15-minute intervals using a pres- sure sensor system connected to a data log- PRISCIJ STREAM, LAKE BONNEY ger. The equipment is housed in a plywood Discharge hydroc raphs for selected streams. ANTARCTIC JOURNAL - REVIEW 1994 231 during the initial 6 years of the project. This work is supported Green, W.J., T.J. Gardner, T.G. Ferdelman, M.P. Angle, L.C. Varner, by National Science Foundation grant OPP 92-11773. and P. Nixon. 1989. Geochemical processes in the Lake Fryxell Basin (Victorialand, Antarctica). In W.I. Vincent and J.C. Ellis- References Evans (Eds.), Hydrobiologia 172. Belgium: Kluwer. Rantz, S.E., and others. 1982a. Measurement and computation of Chinn, T.H. 1979. Hydrologic Research Report, Dry Valleys, Antarctica, stream/low: Volume 1, Measurement of stage and discharge (U.S. 1972-73. Wellington: New Zealand Ministry of Works and Devel- Geological Survey Water-Supply Paper 2175). Washington, D.C.: opment. U.S. Government Printing Office. Chinn, T.H. 1993. Physical hydrology of the dry valley lakes. In W.J. Rantz, S.E., and others. 1982b. Measurement and computation of Green and E.I. Friedmann (Eds.), Physical and biogeochemical stream/low: Volume 2, Computation of discharge (U.S. Geological processes in antarctic lakes (Antarctic Research Series, Vol. 59). Survey Water-Supply Paper 2175). Washington, D.C.: U.S.
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