Development and sensitivity analysis of the GLEAMS-IR model

In response to the need for improved agricultural best management practices in irrigated lands, the GLEAMS (Groundwater Loading Effects of Agricultural Management Systems) model was modified to include a component that models furrow, basin, and border irrigation practices. The irrigation component of the new model, GLEAMS-IR, was validated with results from SRFR, a full hydrodynamic irrigation model. Sensitivity of nutrient and irrigation output parameters to model input parameters was assessed with a single-variable method and a stochastic method, Monte Carlo. Means and distributions of soil parameters for a surface-irrigated cotton field in Marana, Arizona, were used for sensitivity analysis. For both single-variable and Monte Carlo sensitivity analyses, output parameters were most sensitive to infiltrated depth after 120 min, permanent wilting point, and field capacity. A study of sludge application on the same field (1x and 3x sludge application, nitrogen fertilizer application, and control with no nitrogen) was used to evaluate the GLEAMS-IR model results for different management scenarios and to compare GLEAMS-IR results with nutrient concentrations at different locations along the furrow. The variability of measured nitrate concentrations along the furrow indicated the need to account for variable infiltration along the furrow in GLEAMS-IR.