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                    U.S. DEPARTMENT OF AGRICULTURE
 Southwest Watershed Research Center: Tucson, AZ
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ARS Home Pacific West Area Tucson, Arizona SWRC Research





- Scott, Russell - Russ
- Goodrich, David - Dave
- Heilman, Philip - Phil
- Nichols, Mary
- Williams, Christopher - Jason
- Biederman, Joel
- 2022
- 2021
- 2020
- 2019
- 2018
- 2017
- Publications
- Water Availability and Watershed Management (211)
- Soil and Air (212)
- Grass, Forage, and Rangeland Agroecosystems (215)

Research Project: **Location:
                            Southwest Watershed Research Center** Project Number: 2022-13610-012-000-D
                        
                        Project Type: In-House Appropriated Start Date: Jan 30, 2017
                        
                        End Date: Jan 29, 2022 **Objective:**
                        
                        1:As part of the LTAR network, and in concert with similar long-term, land-based research infrastructure in the region, use the Walnut Gulch LTAR site to improve the observational capabilities and data accessibility of the LTAR network and support research to sustain or enhance agricultural production and environmental quality in agroecosystems characteristic of the semiarid Southwest region. Research and data collection are planned and implemented based on the LTAR site application and in accordance with the responsibilities outlined in the LTAR Shared Research Strategy, a living document that serves as a roadmap for LTAR implementation. Participation in the LTAR network includes research and data management in support of the ARS GRACEnet and/or Livestock GRACEnet projects. 
1.1:Improve & continue long-term measurements & analysis of water budgets on WGEW & Santa Rita Experimental Range (SRER) watersheds. 
1.2:Expand variables measured on WGEW & SRER watersheds based on recommendations of the LTAR Meteorology, Hydrology, CO2, Non-CO2 Gas, Soil, Biology, & Wind Erosion Committees. 
1.3:Develop a long-term monitoring program. 
1.4:Implement an experiment on the SRER watersheds to quantify the effects of brush management on a set of ecosystem services. 
1.5:Compute trends in sub-daily & daily precipitation intensity across LTAR sites. 
1.6:Evaluate National Weather Service dual pole radar precipitation data & its ability to improve flash flood forecasting. 

2:Quantify how seasonal, annual, and decadal-scale variations in climate, plant community composition, and management impact processes controlling the cycling of water, energy, and carbon in semiarid rangelands 
2.1:Determine how changes in vegetation structure & climate affect ecosystem-atmosphere water vapor & CO2 exchange using long-term flux tower observations.
2.2:Use isotopes in pond deposition sediments to understand & quantify erosion & sediment yields in semiarid landscapes as a function of ecological sites. 
2.3:Quantify the impact of erosion control structures on runoff & sediment transfers in semiarid landscapes. 
2.4:Estimate annual production & minimum total foliar cover using Landsat & MODIS satellite.
2.5:Develop methods to assess climate impacts on rangeland vegetation composition & production across the West. 

3:Develop a new conceptual framework and corresponding experimental methods to understand and model the dynamics of semiarid upland and channel erosion processes.
3.1:Conduct experiments to quantify the effects of surface condition. 
3.2:Conduct experiments to develop a remote sensing method to estimate hydraulic roughness. 

4:Improve hillslope (RHEM) and AGWA/KINEROS2 watershed models and develop methods to incorporate new remotely sensed, meteorologic, & land surface information.
4.1:Complete development & post-disturbance testing of the RHEM for application in Western rangelands.
4.2:Develop a mechanism to extend the findings from the Walnut Gulch LTAR site across Arizona & New Mexico & support collaborative vegetation management of public lands to improve watershed function. 
4.3:Incorporate a variety of KINEROS2 (K2) / AGWA model enhancements. **Approach:**
                        
                        Objective 1: 
1. Use co-located rain gauges to quantify uncertainties in long-term precipitation datasets. 
2. Use radar stage measurements to test remote methods to measure runoff stage
3. Deploy mobile x-band Doppler radar and compare with Dual Pole radar rainfall rain-gauge observations, and runoff observations on the WGEW. 
4. Meet LTAR objectives by: a) using observational datasets to quantify the individual components of the watershed water balance in Walnut Gulch Experimental Watershed WGEW), b) using satellite and ground measurements of vegetation to document changes in watershed vegetation, c) determining trends and magnitude of precipitation intensities and precipitation extremes across the continental US, and d) implementing the LTAR common experiment to assess the effects of brush management on a set of ecosystem services.

Objective 2:
1. Use long-term flux tower observations to determine how changes in vegetation structure and climate affect ecosystem-atmosphere water vapor and carbon dioxide exchange.
2. Use 210Pb pond stratigraphy to determine erosion rates and their historical dynamics on small watersheds over the past 50-100 years.
3. Quantify runoff and sediment yields on watersheds to quantify the impact of erosion control structures on runoff and sediment transfers.
4. Use satellite, climate, site productivity and management data to estimate annual production and minimum total foliar cover.
5. Use LiDAR, point cloud, and new satellite datasets to construct canopy height models to assess climate impacts on rangeland vegetation composition and production.

Objective 3:
1. Use rainfall simulator experiments to quantify the effects of surface condition on infiltration, runoff, concentrated flow dynamics, sediment transport processes, and surface evolution.
2. Use radar backscatter roughness and hydraulic roughness at a laboratory, rainfall simulator, and small watershed scales using airborne and satellite active radar imagery to develop a remote sensing methods to estimate hydraulic roughness. 

Objective 4:
1. Complete development and post-disturbance testing of the Rangeland Hydrology and Erosion Model (RHEM) for application in Western rangelands.
2. Create a web interface to identify problem areas in watersheds, compare across watersheds, and assess trends in time prior to KINEROS2 modeling.
3. Incorporate RHEM, improved process model representations, and higher-resolution, model inputs, sub-surface and variable width routing, and interstorm processes into KINEROS2.


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