HR: 14:55h
AN: H13K-05    [Abstracts]
TI: Quantification of Groundwater-surface Water Fluxes Using Temperature Time Series
AU: Keery, J
EM: j.keery@lancaster.ac.uk
AF: Lancaster University, Dept. Environmental Science Lancaster University, Lancaster, LA1 4YQ United Kingdom
AU: * Binley, A
EM: a.binley@lancaster.ac.uk
AF: Lancaster University, Dept. Environmental Science Lancaster University, Lancaster, LA1 4YQ United Kingdom
AU: Smith, J
EM: jonathan.smith@environment-agency.gov.uk
AF: Environment Agency, Olton Court, 10 Warwick Road, Olton, Solihull, B92 7HX United Kingdom
AB: Reliable estimates of water fluxes at the aquifer-river interface have enormous value for management of water resources, particularly in areas where groundwater may threaten or sustain the quality of surface waters. Values for these fluxes may be inferred using hydraulic gradients measured in river bed piezometers combined with estimates of hydraulic conductivity, or using seepage meters installed in the river bed (although in practice, values derived from aquifer-river model calibration are often adopted). Measurements obtained from either field-based approach suffer from a high degree of uncertainty and unreliability. In addition, seepage meters do not permit monitoring of the temporal variability of fluxes, without significant labour costs. The temperature gradient across the groundwater-surface water interface has been widely acknowledged as a useful source of information about the state of water flux at this boundary. Here, we explore the value of utilizing the temporal variability of water temperature to estimate vertical water fluxes within the hyporheic zone. The diurnal signal associated with the river water body propagates through the underlying sediment as a function of downwards conduction and upwards (or downwards) advection. Measurement of temperature time series throughout the river bed profile, appropriate time series analysis of diurnal behaviour and the estimation of heat transfer parameters thus permit the computation of vertical fluxes throughout the profile. Since the parameters required to `disconnect' conductive and advective heat fluxes (and hence determine mass advective flux) exhibit a narrow range in sediments (in contrast to the hydraulic conductivity, required for application of Darcy's Law), the uncertainty in mass flux estimates is relatively low. We present the framework for estimating water fluxes in this manner and illustrate results from the implementation in a UK lowland river. At this field site, temperature arrays were installed at six locations along a 1km gaining reach. Fluxes derived from the proposed methodology showed significant variation along the reach, which was supported by measurements using seepage meters and piezometer arrays. The approach shows immense potential as a reliable and robust field-based method for estimation of water fluxes at the groundwater-surface water interface.
DE: 1829 Groundwater hydrology
DE: 1830 Groundwater/surface water interaction
DE: 1895 Instruments and techniques: monitoring
SC: Hydrology [H]
MN: Fall Meeting 2005