Heat Transmission in the Hyporheic Zone Jennifer Goshorn Outline Defining the hyporheic zone Importance of the hyporheic zone Heat transport mechanisms Temporal fluctuations Hydrology Biogeochemistry Ecology Concluding remarks Defining the Hyporheic Zone Conceptual models reflecting the aims of different disciplines Ecologist - active ecotone between surface and groundwater in which fauna characteristic of the hyporheos are distributed and live. (Boulton et al., 1998) Hydrologist - part of the sub-surface in which both surface and groundwater are present, but surface water exceeds 10%of the total volume. (Triksa et al., 1989) Hydrogeologist - water beneath the surface of the ground in the saturation zone in direct contact with the subsoil. (Smith, 2005) Buss et al., 2009 Importance of the Hyporheic Zone controls the flux and location of water exchange between stream and subsurface provides a habitat for benthic and interstitial organisms provides a spawning ground and refuge for certain species of fish provides a rooting zone for aquatic plants provides an important zone for the cycling of carbon, energy and nutrients provides a natural attenuation zone for pollutants by biodegradation, sorption and mixing moderates river water temperature provides a sink/source of sediment within a river channel. Heat Transport in the Hyporheic Zone Conceptual diagram showing the different processes that influence hyporheic water temperatures Advection transports heat via fluid flow Conduction transports heat between sediment and hyporheic water Dispersion and conduction occur as groundwater/surface water and hyporheic water interact Burkholder et al., 2008 Solar radiation indirectly warms water via conduction and transfer of latent and sensible heat Temporal Heat Fluctuations in the Hyporheic Zone Temperature as a tracer for infiltration of stream water by interpreting time shifts in temperature signals as retarded travel times Temperature vs. Depth curve Time-series profiles document changes in water flux into and out of a stream Maximum and minimum temps during a complete cycle form a ‘temperature envelope’ within which all measured temperatures reside. Bounds of envelope (Jan & July, dawn & afternoon) When groundwater is flowing into a gaining stream, the annual/daily envelope collapses toward the streambed surface. Upwelling groundwater is buffered from temperature fluctuations – constant temp When the stream is losing water to underlying sediments, the envelope expands downward. Water is heated at the surface and carried down. (Constantz et al., 2003) Thermal Effects on Hydrology in the Hyporheic Zone Permeability depends of the hydraulic conductivity of the sediment layers Viscosity and density of water are temperature dependent Stream and streambed temperatures and hydraulic gradients from a stream piezometer in Indiana Dramatic increases in stream temperature fluctuations reflect fluctuations in hydraulic gradients Delayed response of subsurface temperatures earlier in the season Constantz, 2008 Thermal Effects on Biogeochemistry in the Hyporheic Zone The hyporheic zone is characterized by steep physiochemical gradients, which are controlled by heat and water flux between the GW/SW interface. Microbial activity and chemical transformations in the Hyporheic Zone Temperature controls the rate of the chemical reactions As temperature increases less oxygen is dissolved in water Emission of nitrogen gases increases with temperature (Winter et. al, 1998) Thermal Effects on Hydroecology in the Hyporheic Zone During cold weather, up-welling groundwater prevents freezing of rivers and provides temperature moderation during the hot summer. Predictive models have been developed to relate temperature to embryo development and timing of hatching and emergence under saturated dissolved oxygen conditions (Crisp, 1988 and 1990) Smith, 2005 Conclusions Temperature plays a vital role in the hyporheic zone and surrounding environments Heat as a tracer to model the direction and velocity of flow Controls chemical reactions Biological dependency New research due to advancements in modeling technology Cooperative work between different fields The full potential of thermal data within the hyporheic zone is still unrecognized Questions? References Anderson, M. P., 2005, Heat as a Ground Water Tracer: Ground Water, v. 43, n. 6, p. 951-968 DOI 10.1111/j.1745-6584.2005.00052.x Baskaran, S., Brodie, R. S., Ransley, T., Baker, P., 2009, Time-series measurements of stream and sediment temperature for understanding river-groundwater interactions: Border Rivers and Lower Richmond catchments, Australia: Australian Journal of Earth Sciences, v. 56, p, 21-30 Boulton, A. J., Datry, T., Kasahara, T., Mutz, M., Stanford, J. A., 2010, Ecology and management of the hyporheic zone: stream-groundwater interactions of running waters and their floodplains: North American Benthological Society, v. 29, i. 1, p. 26-40 DOI: 10.1899/08- 017.1 Buss, S., Cai, Z, ...,Wood, P., 2009, The Hyporheic Handbook: Environmental Agency, p. 280, ISBN: 978-84911-131-7 Burkholder, B. K., Grant, G. E., Haggerty, R., Khangaonkar, T., Wampler, P. 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