This paper uses detailed hydrometeorological data to evaluate the influence of channel bed processes on the river energy budget at an experimental site on the regulated River Blithe, Staffordshire, UK. Results from a pilot study are presented for eight days during July, September, October and November 1994.
Total energy gains were dominated by net short-wave radiation (97·60%) with significant contributions from sensible heat exchange and friction (1·17 and 1·06%, respectively) and minor additions from condensation and bed conduction (0·16 and 0·01%, respectively). Net long-wave radiation, evaporation, conduction into the river bed, sensible heat transfer and the energy advected during evaporation accounted for 53·98, 23·56, 16·27, 5·25 and 0·94% of the total heat losses. On average, over 82% of the total energy transfers occurred at the air-water interface. Approximately 15% of the total energy exchanges occurred at the channel bed, but maximum daily heat exchanges accounted for up to 24% of the daily total energy transfer. The amount of short-wave radiation attenuated in the water column, and values measured at the channel bed varied considerably from those calculated using a standard coefficient. Values of bed conduction varied in response to different vertical thermal profiles in the channel bed, reflecting the variable influence of sedimentology and groundwater flux. Fluctuations in levels of periphyton and macrophyte cover were also shown to have a significant effect on energy fluxes at the channel bed.