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ARS Home » Plains Area » Fort Collins, Colorado » Center for Agricultural Resources Research » Water Management and Systems Research » Research » Research Project #422726

Research Project: Spatial Modeling of Agricultural Watersheds: Water and Nutrient Management and Targeted Conservation Effects at Field to Watershed Scales

Location: Water Management and Systems Research

2012 Annual Report

1a. Objectives (from AD-416):
Objective 1. Develop and apply new watershed modeling tools to evaluate the long-term effects of innovative cropping, limited water, and nitrogen management on water quantity, water quality, and crop production in selected agricultural sub-basins in Colorado. [Contributes to Problem Area #1, Effective Water Management in Agriculture, Problem Statements 1.1.3 and 1.4.2 of the new National Program (NP) 211 Action Plan (FY 2011 – 2015)] Objective 2. Using data from Colorado and the Midwest, improve model components to quantify and assess spatially targeted agricultural conservation effects on water quantity and quality. [Contributes to Problem Area #4, Improving Watershed Management and Ecosystem Services in Agricultural Landscapes, Problem Statement 4.1 of the new National Program (NP) 211 Action Plan (FY 2011 – 2015)] Objective 3. Simulate the combined effects of projected climate change on crop production, water use, and nitrate transport, and assess potential cropping system adaptations at field to sub-basin scales in Colorado. [Contributes to Problem Area #4, Improving Watershed Management and Ecosystem Services in Agricultural Landscapes, Problem Statement 4.3 of the new National Program (NP) 211 Action Plan (FY 2011 – 2015)]

1b. Approach (from AD-416):
As population increases and climate changes, we face global crises of conserving and managing water quantity and quality for agricultural and urban demands. Distributed agro-hydrologic modeling tools are needed to address complex system interactions in space and time for different soils and climates. Impacts of water and nutrient management and of targeted conservation practices within and adjacent to fields must be assessed in terms of water quantity and quality at designated watershed outlets. This project focuses on developing simulation tools for evaluating and proposing solutions to critical emerging problems in diverse agricultural systems over scales ranging from approximately 50 to 50,000 ha under current and future conditions. The component-based AgroEcoSystem-Watershed (AgES-W) model, developed in the Object Modeling System (OMS) framework, explicitly simulates the hydrologic and agronomic responses from spatially distributed land use, management, and weather conditions across inter-connected ecosystem response units (ERUs). AgES-W will be enhanced for: 1) routing water and nutrients across a watershed, 2) diverse cropping system responses to water deficits, 3) model uncertainty analyses and scaling, and 4) plant responses to atmospheric CO2. New OMS tools will include ERU delineation, sensitivity analysis, spatial visualization, statistical analyses of outputs, and web-based cloud computing. Selected conservation practices will be evaluated under existing and projected climates in the semi-arid West (Colorado), and spatially targeted conservation will focus on the sub-humid Midwest (Iowa), resulting in new agricultural adaptation strategies. These case studies address agricultural water and nutrient management issues in the American West and Midwest, while providing component-based modeling tools globally.

3. Progress Report:
Documentation of both the Object Modeling System (OMS, version 3) and the AgroEcoSystem-Watershed (AgES-W) computer model have progressed with emphasis on user examples of applying OMS3 and AgES-W. Model parameters and their relationships with simulated processes in AgES-W and its source models have been clarified. A full user manual (electronic) for AgES-W and technical documentation/ user manual (web-based) for OMS3 are in progress. Completion of these documents will be essential for broad application by new users. The AgroEcoSystem-Watershed (AgES-W) computer model was modified to input and output soil water contents by horizon (vertical layer in the model). This improved the user experience and made it possible to calibrate the model to match measured soil water contents in different horizons. Subsequently a model parameter estimation tool, called LUCA, was revised and applied to automatic calibration of model parameters by soil horizon. LUCA was also used for autocalibration of AgES-W nitrogen and sediment input parameters with subsequent evaluation of the tool using observed water quality data from the Upper Cedar Creek Watershed in northwest Indiana. These advancements will facilitate model calibration and application at watershed scales. The AgroEcoSystem-Watershed model graphical user interface (AgESGUI) underwent detailed debugging and evaluation and was further enhanced with additional options for scenario comparisons and model spatial and temporal output visualization. Completion of AgESGUI will expedite setup and simulation of the underlying AgES-W simulation model and facilitate model application by new and existing users. Agricultural watersheds within the Cache la Poudre Watershed in Colorado were delineated for simulation across a range of scales (field, farm and subwatershed), where smaller watersheds are “nested” within larger watersheds to aggregate the responses across scales. Initial model runs are based on these watershed delineations, and the software tools have undergone enhancements to redefine model simulation units and watershed areas as needed in the future. In consultation with our collaborator in Iowa, key conservation practices for the South Fork Watershed in Iowa were selected to simulate using the AgroEcoSystem-Watershed (AgES-W) model. The high priority practices include grassed waterways, tile intake replacement/plugging, filter strips and riparian buffers. AgES-W will be applied with and without these practices to estimate the potential benefits in terms of nitrate transport. Some modifications to the model are needed to simulate the overland and subsurface processes of water flow and nitrate transport.

4. Accomplishments