Multistep optimization of HyPix model for flexible vertical scaling of soil hydraulic parameters

Efficient simulation of water-flow processes in the vadose zone is crucial to increase agricultural productivity within environmental limits. This requires deriving detailed soil hydraulic parameters profile that highly challenging, particularly for heterogeneous soils. We therefore developed an alternative indirect methodology calibrate from water content time series measured at multiple depths by using new physically based hydrological model HyPix. propose a novel, efficient, multistep optimization algorithm layered soils derives optimal set desired number layers. For each selected layer, HyPix five physical, bimodal, Kosugi describe retention and conductivity novel reduces degree sensitivity freedom parameters. The upscales gradually incorporating heterogeneity. method overcomes problems associated with layer individually, which leads poor results because it does not represent cohesive dynamics across unsaturated zone. tested measurements different experimental sites New Zealand. show how accuracy simulated balance components increases detailed, into fewer provides estimate uncertainty reduced also pedological description can provide indication minimum layers vertical discretization required accurately compute components.