Evaluating Regional Solutions to Salinization and Waterlogging in an Irrigated River Valley

Potential solutions to high soil salinity levels and waterlogging problems are investigated on a regional scale using calibrated finitedifference flow and mass transport modeling for a portion of the Lower Arkansas River Valley in Colorado. A total of 38 alternatives incorporating varying degrees of recharge reduction, canal seepage reduction, subsurface drainage installation, and pumping volume increases are modeled over three irrigation seasons (1999-2001). Six performance indicators are used to evaluate the effectiveness of these alternatives in improving agroecological conditions, compared to existing conditions. Predicted average regional decrease in water table elevation (as great as 1.93 m over the irrigation season) is presented for selected alternatives, as well as the spatial mapping of results. Decrease in soil salinity concentration (with regional and seasonal average reduction as high as 950 mg/L) is also predicted and mapped. Estimated groundwater salinity changes, reduction in total salt loading to the river, increase in average regional crop yield, and changes in net water consumption indicate the potential for marked regional-scale enhancements to the irrigation-stream-aquifer system.