Cellular Automata based Modeling for the Assessment of Ecohydrological Dynamics at the Hillslope Scale: Preliminary Results

Abstract

An improved version of a Cellular Automata (CA)-based ecohydrological model developed using a Macroscopic CA approach was applied in a numerical experiment over a large hillslope. The original model was made up of a Vegetation Dynamic Model (VDM) coupled to a Soil–Vegetation–Atmosphere Transfer (SVAT) scheme and to a three-dimensional unsaturated flow and heat diffusion model. It was built in a problem solving environment that uses macroscopic CA both as a tool to model and simulate dynamic complex phenomena and as a computational model for parallel processing. The new version of the ecohydrological model adds flow generation and flow routing modules, allowing to govern liquid water interactions between surface and subsurface domains, to account for depression storage, obstruction storage exclusion and changing surface roughness owing to vegetation dynamics.This paper shows the preliminary results of the analysis of vegetation-hydrology dynamics performed on a ‘reference’ hillslope, with the same morphological characteristics of the Biosphere 2 hillslope experiment, hypothesized fully vegetated with alfalfa grass. Soil moisture and turbulent fluxes spatial and temporal variability was assessed for a period characterized by a single wetting event followed by a dry-down period. The computational performance of the CA-based model allowed a sensitivity analysis over the hillslope, varying both precipitation intensity and soil moisture initial conditions. Surface runoff, soil moisture, evapotranspiration and Leaf Area Index space-time distributions were evaluated for each scenario, highlighting the main differences depending on the changing features of the experiments.