Improving APEX for Simulating Terrestrial Transport of Salt in the Upper Colorado River Basin
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The Agricultural Policy and Environmental eXtender (APEX) model will be enhanced in its modeling capacity to better simulate the fate and transport of salt and sediments in the Colorado River Basin (CRB) to identify critical sources and the pathways of highly saline terrestrial runoff, stream and groundwater salt flow and to evaluate related rangeland management scenarios. A series of the cutting-edge process models/algorithm will be integrated to APEX including KINEROS, MODFLOW, PHT3D, and AERO model for simulating lateral overland flow, reactive transport processes of salt ions in the root zone soils and shallow aquifers, and wind erosion. This will allow the recipient to make a recommendation on best management practices (BMPs) for controlling salt concentration for public lands contributing to sediment and salt yield to the Colorado River. In addition, the wind erosion module of APEX will be enhanced with the recently developed AERO model, which is being used by BLM AIM and AIR programs.The integrated APEX model with enhanced graphical user interface, autocalibration and parameter sensitivity analysis and related manuals will provide a cutting-edge simulation tool for BLM that can be utilized to understand processes controlling the transport of sediment and salt from upland areas to streams in the CRB, to identify critical source areas for management implementation, and to evaluate the effectiveness of management scenarios as a strategic decision and policy support tool.