Modeling the Influence of Hyporheic Exchange in Dry Valley Streams
Project Duration: 1998 - 2001; My dissertation research
Wetted margin along Lake Joyce, Pearse Valley, Antarctica.
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Overview: The polar desert of the Dry Valleys is the largest ice-free portion of Antarctica, located at 78degS, 161degE, on the western edge of the Ross Sea. The climate is very cold, with annual air temperatures of –20 degC, and very dry, with less than 10 cm water equivalent of precipitation annually. The landscape is dominated by glaciers, barren expanses of rock and exposed soils, ice-covered closed basin lakes, and glacial meltwater streams. There are no large indigenous terrestrial plants or animals, although soils are inhabited by nematodes, rotifers, and tardigrades, and some streams and lakes have extensive benthic algal communities.
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Dry Valley streams flow for 6 to 10 weeks per year. Melt water is produced at the glaciers during the austral summer. Flow rates recorded at stream gauges may vary from periods of little or no flow to peak flows on the order of 500 L s-1. Early stream flow may only saturate the porous space of the streambed, which must be filled before consistent channel flow can be established. Streambeds are generally composed of very sandy porous alluvium (porosity of 0.3 is typical), except in areas where a stone pavement has developed. The stone pavement is developed by broad, flattened sides of large rocks being positioned right-side-up due to the legacy of geologic timescale freeze-thaw interactions. The stone pavement provides a stable substrate for benthic algal mats. Streams vary in length from hundreds of meters to several km, and vary in gradient, ranging from 0.02 to 0.55. The very porous streambed material allows for the development of an extensive zone of wetted sediment adjoining the stream. Because of the cold climate, there is no regional groundwater system that is in contact with the streams. Thus, all water in this wetted sediment comes from the streams. Permafrost is generally found at 0.5 to 0.7 m below the ground surface, acting as a lower boundary to the vertical extension of this wetted zone. Laterally, the wetted zone may extend several meters from the stream edge. This wetted zone makes up the hyporheic zone of a typical Dry Valley stream, as water that enters may later return to the stream.
My Ph.D. research was broken up into a few specific studies. Together, the results of these studies increased our understanding of hydrologic processes in Dry Valley streams of Antarctica, and yielded intriguing ideas about hydrologic-biogeochemical interactions that may be occurring in any stream system.
Weathering reactions and hyporheic exchange controlling solute concentration in Dry Valley streams
This study simply focused on the hydrologic control that the hyporheic zone plays on Dry Valley stream hydrology, and the chemical weathering reactions that are occurring in the hyporheic zone. The alluvium that makes up the hyporheic zone of these streams is unconsolidated and relatively fresh, geologically speaking. Such a situation is very vulnerable to rapid glacial meltwater exchange, and consequent rapid chemical weathering of the alluvial substrate.
Using stable isotopes of D and 18O to determine hyporheic zone flow paths in Antarctic streams.
In this study, 9 piezometers were placed in and near Green Creek to sample subsurface water. The results show that subsurface water is generally more enriched in D and 18O than flowing stream water, suggesting a long residence time in the subsurface, during which fractionation can occur (possibly due to evaporation, chemical weathering, or biological processes). Further discritization of the data suggested that the lateral extents of the hyporheic zone exchange on much slower timescales than the portion of the hyporheic zone that is directly under the stream.
Denitrification in Antarctic streams
This study was intended to address the various controls N transformation dependent on hydrologic exchange between 1) the stream and the benthic algal mats, and 2) the stream and the hyporheic zone. The benthic algal mats of Antarctic streams are sparsely distributed on the stream beds. Stream tracer/nutrient enrichment data suggested that nitrite was being produced very quickly from injected nitrate, the first step in denitrification. Previous modeling efforts suggested that hyporheic exchange was rapid in Green Creek. Further modeling suggested that nitrate conversion could not be accomplished in the hyporheic zone alone. The final modeling effort in this study discritized the benthic algal mat and the hyporheic zone as two seperate storage zones.
My Ph.D. research was broken up into a few specific studies. Together, the results of these studies increased our understanding of hydrologic processes in Dry Valley streams of Antarctica, and yielded intriguing ideas about hydrologic-biogeochemical interactions that may be occurring in any stream system.
Weathering reactions and hyporheic exchange controlling solute concentration in Dry Valley streams
This study simply focused on the hydrologic control that the hyporheic zone plays on Dry Valley stream hydrology, and the chemical weathering reactions that are occurring in the hyporheic zone. The alluvium that makes up the hyporheic zone of these streams is unconsolidated and relatively fresh, geologically speaking. Such a situation is very vulnerable to rapid glacial meltwater exchange, and consequent rapid chemical weathering of the alluvial substrate.
Using stable isotopes of D and 18O to determine hyporheic zone flow paths in Antarctic streams.
In this study, 9 piezometers were placed in and near Green Creek to sample subsurface water. The results show that subsurface water is generally more enriched in D and 18O than flowing stream water, suggesting a long residence time in the subsurface, during which fractionation can occur (possibly due to evaporation, chemical weathering, or biological processes). Further discritization of the data suggested that the lateral extents of the hyporheic zone exchange on much slower timescales than the portion of the hyporheic zone that is directly under the stream.
Denitrification in Antarctic streams
This study was intended to address the various controls N transformation dependent on hydrologic exchange between 1) the stream and the benthic algal mats, and 2) the stream and the hyporheic zone. The benthic algal mats of Antarctic streams are sparsely distributed on the stream beds. Stream tracer/nutrient enrichment data suggested that nitrite was being produced very quickly from injected nitrate, the first step in denitrification. Previous modeling efforts suggested that hyporheic exchange was rapid in Green Creek. Further modeling suggested that nitrate conversion could not be accomplished in the hyporheic zone alone. The final modeling effort in this study discritized the benthic algal mat and the hyporheic zone as two seperate storage zones.
Published Results from this Project (* indicates student lead author)
- Gooseff, MN, DM McKnight, WB Lyons, and AE Blum. 2002. Weathering reactions and hyporheic exchange controls on stream water chemistry in a glacial meltwater stream in the McMurdo Dry Valleys. Water Resources Research, 38(12): 1279, DOI 10.1029/2001WR000834.
- Maurice, PA, DM McKnight, L Leff, JE Fulghum, and M Gooseff. 2002. Direct observations of aluminosilicate weathering in the hyporheic zone of an Antarctic Dry Valley stream. Geochimica et Cosmochimica Acta, 66(8): 1335-1347.
- Gooseff, MN, JE Barrett, P Doran, AG Fountain, WB Lyons, AN Parsons, DL Porazinska, RA Virginia, and DH Wall. 2003. Snow patch influence on soil biogeochemical processes and invertebrate distribution in the McMurdo Dry Valleys, Antarctica. Arctic, Antarctic, and Alpine Research, 35(1): 92-100.
- Gooseff, MN, DM McKnight, RL Runkel and BH Vaughn. 2003. Determining long time-scale hydrologic flow paths in Antarctic streams. Hydrological Processes, 17(9):1691-1710.
- Gooseff, MN, DM McKnight, RL Runkel, and JH Duff. 2004. Denitrification and hydrologic transient storage in a glacial meltwater stream, McMurdo Dry Valleys, Antarctica. Limnology and Oceanography, 49(5): 1884-1895.
- Gooseff, MN, DM McKnight, and RL Runkel. 2004. Reach-scale cation exchange controls on major ion chemistry of an Antarctic glacial meltwater stream. Aquatic Geochemistry, 10(3): 221-238.
- Gooseff, MN, WB Lyons, DM McKnight, BH Vaughn, AG Fountain, and C Dowling. 2006. A stable isotopic investigation of a polar desert hydrologic system, McMurdo Dry Valleys, Antarctica. Arctic, Antarctic, and Alpine Research, 38(1): 60-71.
- McKnight, DM, RL Runkel, CM Tate, JH Duff, and DL Moorhead. 2004. Inorganic N and P dynamics of Antarctic glacial meltwater streams as controlled by hyporheic exchange and benthic autotrophic communities. Journal of the North American Benthological Society, 23(2):171–188.
- Runkel, RL, DM McKnight, ED Andrews. 1998. Analysis of transient storage subject to unsteady flow: diel flow variation in an Antarctic stream. Journal of the North American Benthological Society, 17(2):143-154.
Conference Presentations from this Project
- Gooseff, MN, and DM McKnight. 1999. Ion exchange reactions controlling Li transport in the hyporheic zone of a polar desert stream (poster). American Geophysical Union Fall Meeting, San Francisco, CA.
- Gooseff, MN, and DM McKnight. 2000. Phosphorous uptake by benthic algal communities in Antarctic streams (oral). North American Benthological Society Annual Meeting, Keystone,CO.
- Gooseff, MN, DM McKnight, and PA Conovitz. 2000. Subsurface water temperatures in polar desert streams (oral). American Society of Limnology and Oceanography, Copenhagen, Denmark.
- Gooseff, MN, DM McKnight, E Chatfield, C Jaros. 2000. The McMurdo Dry Valleys stream hydrology (poster). All Scientists Meeting, Snowbird, UT.
- Gooseff, MN, JE Berret, and PT Doran. 2000. Snow pack coverage and influence on soils of a polar desert (poster). Ecological Society of America Annual Meeting, Snowbird, UT.
- Gooseff, MN, WB Lyons, AE Blum, and DM McKnight. 2000. Modeling weathering reactions in the hyporheic zone (poster). American Geophysical Union Fall Meeting, San Francisco, CA
- Gooseff, MN and DM McKnight. 2001. Flow path dependent weathering rate calculation methods for streams and watersheds (oral). American Geophysical Union Hydrology Days, Ft. Collins, CO
- Gooseff, MN, DM McKnight, and B Vaughn. 2001. Using stable isotopes to discern hyporheic flow paths in Antarctic streams (oral). North American Benthological Society Meeting, La Crosse, WI
- McKnight, DM, WB Lyons, and M Gooseff. 2001. Glacial meltwater streams in the McMurdo Dry Valleys: Hyporheic zone controls and climate responses . Geological Society of America Annual Meeting, Boston, MA
- Gooseff, MN and DM McKnight. 2001. Determining long hyporheic flow paths in Antarctic streams using D and 18O isotopes as tracers (poster). American Geophysical Union Fall Meeting, San Francisco, CA.
- Gooseff, MN, DM McKnight, RL Runkel, JH Duff. 2003. Denitrification in a glacial meltwater stream, McMurdo Dry Valleys Antarctica. American Society of Limnology and Oceanography Aquatic Sciences Meeting, Salt Lake City, UT.