Characterising the dynamics of surface water-groundwater interactions in intermittent and ephemeral streams using streambed thermal signatures. (September 2017)

• Record Type: Journal Article
• Authors: Rau, Gabriel C.; Halloran, Landon J.S.; Cuthbert, Mark O.; Andersen, Martin S.; Acworth, R. Ian; Tellam, John H.
• Is Part Of: Advances in water resources. Volume 107(2017)
• Page Start: 354
• Page End: 369
• Publication Date: 2017-09
• Subjects: Surface water-groundwater interactions -- Ephemeral and intermittent streams -- Heat as a tracer -- Hydrological characterisation -- Streambed thermal regimes; Hydrology -- Periodicals; Hydrodynamics -- Periodicals; Hydraulic engineering -- Periodicals; 551.48
• DOI: 10.1016/j.advwatres.2017.07.005
• Languages: English
• ISSNs: 0309-1708

Abstract

Highlights: Amplitude ratios of the daily temperature component at two different depths in the streambed can be used to distinguish dry from saturated sediment. Multi-level streambed temperature records reveal distinct thermal signatures that characterize water flow. Ephemeral or intermittent surface water-groundwater interactions can be categorized into a sequence of hydrological regimes. Abstract: Ephemeral and intermittent flow in dryland stream channels infiltrates into sediments, replenishes groundwater resources and underpins riparian ecosystems. However, the spatiotemporal complexity of the transitory flow processes that occur beneath such stream channels are poorly observed and understood. We develop a new approach to characterise the dynamics of surface water-groundwater interactions in dryland streams using pairs of temperature records measured at different depths within the streambed. The approach exploits the fact that the downward propagation of the diel temperature fluctuation from the surface depends on the sediment thermal diffusivity. This is controlled by time-varying fractions of air and water contained in streambed sediments causing a contrast in thermal properties. We demonstrate the usefulness of this method with multi-level temperature and pressure records of a flow event acquired using 12 streambed arrays deployed along a ∼ 12 km dryland channel section. Thermal signatures clearly indicate the presence of water and characterise the vertical flow component as well as the occurrence of horizontal hyporheic flow. We jointly interpret thermal signatures as well as surface and groundwater levels to distinguish four different hydrological regimes: [A] dry channel, [B] surface run-off, [C] pool-riffle sequence, and [D] isolated pools. The occurrence and duration of the regimes depends on the rate at which the infiltrated water redistributes in the subsurface which, in turn, is controlled by the hydraulic properties of the variably saturated sediment. Our results have significant implications for understanding how transitory flows recharge alluvial sediments, influence water quality and underpin dryland ecosystems.