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ARS Home » Plains Area » Fort Collins, Colorado » Center for Agricultural Resources Research » Water Management and Systems Research » Research » Publications at this Location » Publication #300924
Title: The AgroEcoSystem (AgES) response-function model simulates layered soil water dynamics in semi-arid Colorado: sensitivity and calibration

Author
item Green, Timothy
item Erskine, Robert - Rob
item COLEMAN, MICHAEL - Colorado State University
item DAVID, OLAF - Colorad0 State University
item Ascough Ii, James
item KIPKA, HOLM - Colorad0 State University

Submitted to: Vadose Zone Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/3/2015
Publication Date: 8/21/2015
Citation: Green, T.R., Erskine, R.H., Coleman, M.L., David, O., Ascough Ii, J.C., Kipka, H. 2015. The AgroEcoSystem (AgES) response-function model simulates layered soil water dynamics in semi-arid Colorado: sensitivity and calibration. Vadose Zone Journal. doi:10.2136/vzj2014.09.0119.

Interpretive Summary: Simulation of vertical soil hydrology is a critical component of simulating complex soil water dynamics in space and time. The AgroEcoSystem (AgES) model is applied to vertical simulation of soil-water content (SWC). Details of the infiltration and soil-water processes are explained to facilitate model sensitivity analysis, calibration and evaluation. The Object Modeling System links AgES to a calibration tool called Luca. We analyzed sensitivities, then applied different strategies of implementing Luca to layered SWC data. The profile dynamics of SWC compared well with field data, but optimal parameter sets were not unique, and model results did not fully capture the measured dynamics. AgES simulations compared favorably with previous simulations of SWC at this site using a Richards’ equation model, making the layered soil hydrology suitable for three-dimensional watershed modeling.

Technical Abstract: Simulation of vertical soil hydrology is a critical component of simulating even more complex soil water dynamics in space and time, including land-atmosphere and subsurface interactions. The AgroEcoSystem (AgES) model is defined here as a single land unit implementation of the full AgES-W (Watershed) model. AgES simulated vertical soil water dynamics using global and layered soil response functions with conceptual storages as state variables. We modified AgES to compute and output volumetric soil-water content (SWC) as a state variable for model parameter calibration, and to specify initial SWC by depth interval. A detailed description of the response functions that control infiltration, evaporation and soil-water processes facilitates sensitivity analysis and calibration. The Object Modeling System links AgES to a shuffled complex evolution tool called Luca. We used Luca, along with fractional factorial experimental designs, to analyze parameter sensitivities and then applied different strategies of implementing Luca to layered SWC data. The profile dynamics of SWC compared well with field data (maximum Nash-Suttcliffe Efficiency = 0.81 to 0.93 for calibration and -0.35 to 0.69 for cross-validation in years 2003 and 2005, respectively), but optimal parameter sets were not unique, and model results did not fully capture the measured dynamics. AgES simulations compared favorably with previous simulations of SWC at this site using a Richards’ equation model, making the layered soil hydrology suitable for three-dimensional watershed modeling.