Inverse Es ma on of Soil Hydraulic and Root Distribu on Parameters from Lysimeter Data

We inves gated the feasibility of simultaneous iden fi ca on of soil hydraulic and rootdistribu on parameters by inverse simula on of soil water fl ow in monolithic lysimeters under atmospheric boundary condi ons using the Richards equa on and a macroscopic root water uptake model. Weighable lysimeters are powerful test systems for this purpose because the boundary fl uxes (precipita on, actual evapotranspira on, and seepage across the bo om) can be determined very precisely. We analyzed the amount of informa on needed for the unique iden fi ca on of parameters and inves gated the magnitude of their uncertain es. First, we examined synthe c data sets for diff erent scenarios and instrumenta on campaigns that diff ered in their informa on content and complexity of soil proper es. Atmospheric boundary condi ons as measured at the lysimeter sta on in Wagna, Austria, were used as forcing data. The results show that for homogeneous profi les, cumula ve ou low and profi le-averaged water content data contain enough system informa on to allow the simultaneous es ma on of soil hydraulic proper es and root-distribu on parameters. In contrast, for soil profi les consis ng of two layers, unique soil hydraulic parameters and the correct roo ng depth could only be es mated if matric poten al measurements from both layers were included in the objec ve func on. Finally, soil hydraulic properes of the grass-reference lysimeter in Wagna were es mated using real measurements. Water dynamics in the lysimeter could be described well by an eff ec ve parameteriza on assuming a homogeneous soil profi le. Furthermore, the system behavior under diff erent boundary condi ons could be predicted adequately with the es mated parameters. This demonstrates the usefulness of the iden fi ed system proper es for predic ve modeling.

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