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| Titel |
Influence of soil structure on unsaturated water flow including root uptake |
| VerfasserIn |
Anna Kuhlmann, Insa Neuweiler, Sjoerd van der Zee, Rainer Helmig |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250044379
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| Zusammenfassung |
| The development of effective irrigation strategies is of great importance as the scarcity of
water during extended dry periods in aride areas leads to limited water uptake by roots and
thus to restricted growth and eventually to wilting of plants. To approach this goal a broad
understanding of the factors which influence the distribution of the water potential and the
interactions with root uptake is crucial. Soil structure is supposed to have a large
impact on water flow especially under dry conditions when the variability of soil
parameters is increased. For field applications, predictions of the water flow are
needed for large scales where the scarcity of measurements leads to a high level
of uncertainty about the detailed distribution of soil parameters. Thus stochastic
methods in which heterogeneity of soil is described by a random parameter field are
used.
In this presentation, the interrelation of root uptake and heterogeneity is analyzed using
numerical simulations. Random parameter fields with Gaussian and non-Gaussian
dependence were parameterized according to the Las Cruces Trench Site dataset and used as
input for the numerical model. Transpiration is considered in a macroscopic way as a sink
term with a prescribed potential extraction rate at each node, determined by the density
distribution of the plants and with restricted uptake due to unfavorable conditions as lack of
water and oxygen (modeled according to the Feddes - Function).
With this basic model, water flow in two dimensional random fields has been investigated
under dry conditions. It was observed that dry spots - regions in which roots dry up to the
wilting point form when the structure shows isolated high extreme values in conductivity. In
these dry regions, roots take up a decreased amount of water such that the total potential
demand is not met anymore. This seems rather unrealistic as sufficient water is available at
other locations of the domain. Thus two other approaches are analyzed in comparison to
the basic model where additionally optimizing mechanisms as preferential uptake
in wet domains or redistribution of stressed conditions to unstressed regions are
included. With this setup the influence on the hydraulic variables and total root uptake
term is investigated in order to gain a deeper understanding of the joint effect of
soil structure and root uptake using the example of the Las Cruces Trench Site
dataset. |
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