Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 64768
Title Evaporation of grass under non-restricted soil moisture conditions
Author(s) Bruin, H.A.R. de; Stricker, J.N.M.
Source Hydrological Sciences Journal 45 (2000)3. - ISSN 0262-6667 - p. 391 - 406.
Department(s) Hydrology and Quantitative Water Management
Meteorology and Air Quality
Publication type Refereed Article in a scientific journal
Publication year 2000
Keyword(s) evapotranspiratie - graslanden - bodemwater - stroomgebieden - modellen - evapotranspiration - grasslands - soil water - watersheds - models
Categories Hydrology
Abstract The behaviour of various formulas for evapotranspiration of grass in non-restricted soil water conditions is considered. These are the expressions based on the Penman formula, i.e. "old" Penman, Penman-Monteith, Thom-Oliver and the version recommended more recently by the FAO. Moreover, the Priestley-Taylor and the Makkink formulas are considered, which are radiation-based. Comparisons are made between daily mean values estimated with these formulas and direct measurements. The latter were collected over grass in the period 1979–1982 in the catchment area of the Hupselse Beek (The Netherlands). It was found that if all required input data were measured, the Priestley-Taylor and the "old" Penman formula yielded the best results. The assumption that soil heat flux can be neglected introduces a systematic and a random error of roughly 5ÐThe empirical estimates for net radiation from sunshine duration, temperature and humidity appear to perform rather poorly. These estimates improved significantly if solar radiation was measured directly. The empirical expression proposed by Slob (unpublished) that requires incoming solar radiation only as input, provided better results than the other more complicated expressions. Moreover, this study reveals that evaporation of unstressed grass is primarily determined by the available energy, i.e. good evaporation estimates can be obtained by using simply l E = 0.86(Rn – G). The Makkink method appears to be attractive for practical applications. These findings support the use of Makkink’s formula for routine calculations of crop-reference evapotranspiration as has been done by the Royal Netherlands Meteorological Institute since 1987.
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