River energy budgets with special reference to river bed processes

Abstract

Abstract:This paper uses detailed hydrometeorological data to evaluate the in¯uence of channel bed processes on the river energy budget at an experimental site on the regulated River Blithe, Staordshire, 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 signi®cant 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 coecient. Values of bed conduction varied in response to dierent vertical thermal pro®les in the channel bed, re¯ecting the variable in¯uence of sedimentology and groundwater¯ux. Fluctuations in levels of periphyton and macrophyte cover were also shown to have a signi®cant eect on energy¯uxes at the channel bed. #

What causes cooling water temperature gradients in a forested stream reach?

“…The bed heat flux plate was located directly below each AWS and buried at 0.05 m depth to avoid radiative and convective errors (after Hannah et al, 2008). The heat flux plate provided aggregated measurements of convective, conductive, advective and radiative heat exchanges between the atmosphere and the riverbed and between the riverbed and the water column (after Evans et al, 1998;Hannah et al, 2008). All sensors were cross-calibrated prior to installation and correction factors applied if required.…”

“…Bed heat flux plates connected to each AWS provided aggregated measurements of heat exchange due to convective, conductive, advective and radiative heat exchanges between the atmosphere and the riverbed and between the riverbed and the water column (after Evans et al, 1998;. Hyporheic exchange should be expected in coarse, highly permeable gravel-bed rivers such as the Girnock Burn (e.g.…”

Influence of watershed‐climate interactions on stream temperature, sediment yield, and metabolism along a land use intensity gradient in Indonesian Borneo

“…Research in small temperate headwater catchments suggests that most energy exchange occurs at the airwater interface [Evans et al, 1998] and that riparian vegetation cover plays a critical role in stream water temperature regulation [Lorion and Kennedy, 2009]. In the Brazilian Amazon, studies have found significant warming in soybean and pasture compared to forested catchments; higher temperatures were driven, in part, by reductions in riparian vegetation [Macedo et al, 2013;Neill et al, 2013].…”

The influence of riparian vegetation shading on water temperature during low flow conditions in a medium sized river

“…Upstream water temperature and discharge, hyporheic exchange, ground water inflow, bed heat conduction, tributary inflow and its water temperature, turbulent exchange (sensible and latent heat), solar radiation (incident, reflected), and long wave radiation are components of these processes (Moore et al, 2005;Caissie, 2006). Taking into consideration atmospheric conditions, air temperature and incoming short-wave radiation are mentioned as major influencing factors on water temperatures by Evans et al (1998). They recorded total energy gains dominated by a net short-wave radiation of 97.6%.…”