Abstract
AbstractMultiannual data (2016–2018) from 12 weighed lysimeters (four soil types with textures ranging from sandy loam to silt loam, three replicates) of the TERENO SOILCan network were used to evaluate if evaporation (E) rates could be predicted from weather data using the FAO Penman–Monteith (PM) method combined with soil water flow simulations using the Richards equation. Soil hydraulic properties (SHPs) were estimated either from soil texture using the ROSETTA pedotransfer functions, from in situ measured water retention curves, or from soil surface water contents using inverse modeling. In all years, E was water limited and the measured evaporation rates (Em) surprisingly did not vary significantly among the four different soil types. When SHPs derived from pedotransfer functions were used, simulated evaporation rates of the finer textured soils overestimated the measured ones considerably. Better agreement was obtained when simulations were based on in situ measured or inversely estimated SHPs. The SHPs estimated from pedotransfer functions represented unrealistically large characteristic lengths of evaporation (Lc), and Lc was found to be a useful characteristic to constrain estimates of SHPs. Also, when soil evaporation was water limited and Em rates were below Epot (PM evaporation scaled by an empirical coefficient), the diurnal dynamics of Em followed those of Epot. The Richards equation that considers only isothermal liquid water flow did not reproduce these dynamics caused by temperature dependent vapor transport in the soil.
Highlights
Bare soil evaporation (E) is a critical component of the water cycle at local and global scales
Subobjectives were to examine (a) how soil hydraulic property (SHP) that are derived from pedotransfer function (PTF) or from direct in-situ measurements perform in the prediction of E; (b) whether the characteristic length for evaporation (Lc) can be used an indicator of parameter sets that generate unrealistic estimates of E, and (c) the dynamics of evaporation during Phase II, which are influenced by temperature dependent vapor fluxes
Since the measured cumulative evaporation rates were reproduced the best by the simulations that used hydraulic parameters derived from in situ measured retention curves, ESHP, we evaluated the simulated daily evaporation rates only for ESHP
Summary
Agrosphere (IBG-3), Forschungszentrum Jülich, Jülich 52425, Germany 2 Working Group “Hydropedology,” Research Area 1 “Landscape Functioning, Leibniz Centre for Agricultural Landscape Research, Müncheberg 15374, Germany 3 Institute for Modelling Hydraulic and Environmental Systems, Univ. Funding information Deutsche Forschungsgemeinschaft, Grant/Award Number: VA 351/15-1
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