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Evaporation and energy balance of a wet grassland at Tadham Moor on the Somerset Levels

Harding, R. J.; Lloyd, C. R.. 2008 Evaporation and energy balance of a wet grassland at Tadham Moor on the Somerset Levels. Hydrological Processes, 22 (13). 2346-2357. 10.1002/hyp.6829

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Abstract/Summary

Wet grasslands are important both for their conservation value and for their important hydrological function. Evaporation is an important component of the water balance of a wetland. Where water is limited rainfall and/or surface (or sub-surface) inflows are required to balance the summer evaporation and thus become a significant factor in the maintenance and environmental health of a wetland. This study presents an almost complete year of measurements of the water and energy balance of a wet grassland in the Somerset Levels in southwest England. The majority of the radiant energy at this site goes into evaporation. There is a strong seasonality of the controls on evaporation; the roughness length varies by a factor of 10 between winter and summer. The surface resistance to evaporation is low, close to zero, during the winter when the water table is at, or just below the surface. In the summer the water table drops to 80 cm below the surface; there is no sign of soil water stress on the evaporation but a clear effect of the senescence of grass during seed head production and of the subsequent harvest. There is clear evidence that water for evaporation is provided by the drainage ditches through sub-surface flow. Standard evaporation formulae - such as the Penman-Monteith equation with constant and standard parameters - provide a reasonable simulation of the total evaporation at this site, although they miss some of the seasonal detail.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1002/hyp.6829
Programmes: CEH Programmes pre-2009 publications > Biogeochemistry
CEH Sections: Harding (to 31.07.11)
ISSN: 0885-6087
Additional Keywords: wetland, evaporation, Somerset Levels, peat, water table, energy fluxes, resistances
NORA Subject Terms: Meteorology and Climatology
Ecology and Environment
Earth Sciences
Date made live: 24 Jul 2008 13:31
URI: http://nora.nerc.ac.uk/id/eprint/3561

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