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ARS Home » Pacific West Area » Tucson, Arizona » SWRC » Research » Research Project #422899

Research Project: Ecohydrological Processes, Scale, Climate Variability, and Watershed Management

Location: Southwest Watershed Research Center

2017 Annual Report

1a. Objectives (from AD-416):
1. Improve watershed management by developing the capacity to more accurately predict soil and plant water dynamics utilizing a combination of remote sensing, modeling and in-situ measurements. 2. Quantify how seasonal, annual, and decadal-scale variations in climate (including climate forecasts) and plant community composition impact the cycling of energy, water and carbon in semiarid rangelands. 3. Develop improved watershed model components and decision support systems that more fully utilize and assimilate economic and remotely sensed data for parameterization, calibration and model state adjustment. 4. As part of the LTAR network, and in concert with similar long-term, land-based research infrastructure in Southwestern U.S., use the WGEW LTAR to improve the observational capabilities and data accessibility of the LTAR network, to support research to sustain or enhance agricultural production and environmental quality in agroecosystems characteristic of the Southwestern U.S., as per the LTAR site responsibilities and other information outlined in the 2011 USDA Long- LTAR Network Request for Information (RFI) to which the location successfully responded, and 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.

1b. Approach (from AD-416):
Methods of investigation include field and laboratory experimentation, as well as the development and use of state-of-the-science watershed models and the use of remote sensing for watershed characterization. Multiple methods and techniques will be employed to improve the prediction of plant-water soil dynamics under objective one. They include data assimilation techniques to incorporate both in-situ and remotely sensed measurements into simulation models. In addition, algorithms for enhanced retrieval of watershed characteristics and state variables will be developed. Results from this research are critical for extension of results to large-areas using remote sensing and critical for improved inputs and parameter estimates for the models addressed under objective three. Research undertaken to address objective two more closely focuses on ecohydrology and determining changes in the cycling of energy, water and carbon as well as changes in the composition of plant communities across a wide range of time scales. This includes global change impacts on ecohydrologic processes (including water, nutrient and energy cycles) that underpin ecosystem structure and function. Thus, objective two also focuses on the relationship between global change, ecohydrology and watershed response, which will allow the evaluation of the combined impacts of climate change, intensive land use and species invasions on ecohydrological processes that are critical to maintaining ecosystems. It includes three Multi-Location Projects (MLPs) led or co-led by scientists in this research unit, which will examine observations across decadal and continental scales using observations from USDA’s national network of experimental watersheds, ranges and forests. To address objective three we will develop tools and methods to enhance watershed and rangeland management through wider accessibility of databases from our long-term experimental watersheds, and by development and testing of watershed and decision support models which can assimilate remotely sensed data and incorporate economic and ecosystem service information.

3. Progress Report:
This is the final report for this project that expired in January of 2017. Please see the report for the new project, 2022-13610-012-00D, “Understanding Water-Driven Ecohydrologic and Erosion Processes in the Semiarid Southwest to Improve Watershed Management”, for more information. This project is under National Program (NP) 211 - Water Availability & Watershed Management. The first objective of this project is associated with National Action Plan Components 1 and 4; the second objective with Component 4, the third objective with Components 3 and 4; and the fourth objective with Components 2, 3, and 4. A number of the objectives involved multi-location projects, several led by scientists in this research unit, to capitalize on the historical knowledge and databases of ARS experimental watersheds and ranges across the country. Several personnel changes impacted the project. A scientist was moved to another location via an Area-directed reassignment in FY13 due to sequestration and projected budget shortfalls. This resulted in a number of associated milestones not being met under objectives 1 and 2. In addition, the total productively for this project was affected by two retirements. Retirement of one scientist early in FY14 resulted in a vacancy that took nearly three years to fill. In early FY16, an ARS Hall of Fame scientist retired. Recruitment was initiated to fill that position but subsequently frozen. On the positive side, the research unit and its associated experimental watershed and range facilities were selected as one of ten foundation Long-Term Agro-ecosystem Research (LTAR) sites. These ten sites were provided with large program increases in FY14. Objective 4 was added to this project at that time to reflect new LTAR research priorities. Another positive reflection on the research unit and this project was its selection for new buildings both in Tucson and our field station in Tombstone as a result of the ARS Capital Investment Strategy study considering both the importance of research programs and state of existing facilities. The new facilities are currently in early design phases and we expect construction to be initiated in FY18. Major accomplishments made under Objective 1 leveraged research, remote sensing and in-situ measures (from the Walnut Gulch LTAR and a number of international sites) on a number of fronts. As part of AgriSAR, the Agricultural bio/geophysical retrieval from frequent repeat pass Synthetic Aperture Radar (SAR) and optical imaging, effort, SAR imagery was used to improve estimates of soil moisture and plant phenology in the U.S., Canada, Spain and the Netherlands. Using “big data” and machine learning, MODerate resolution Imaging Spectroradiometer (MODIS) and Landsat (30 meter) was combined was a number of climatic, geographic and ecological data to quantify green and senescent vegetation cover to assess public land ranch management on allotments in southeastern Arizona and New Mexico. A new and improved rainfall intensity retrieval algorithm resulted from analysis of ten years of observations from the dense Walnut Gulch LTAR rain gauge network with Tropical Rainfall Measurement Mission (TRMM) satellite radar retrievals. The value of the knowledge and observational database of the Walnut Gulch LTAR site was further demonstrated, along with a number of other LTAR sites, in the validation of the Soil Moisture Active Passive (SMAP) satellite mission. Validation results indicate that the SMAP soil moisture data product meets its expected performance. An ARS scientist in Tucson, Arizona, developed an innovative prototyping approach for worldwide appliction of SMAP data products as Chair of the SMAP Applications Working Group. Several major project accomplishments were also completed under Objective 2. The early 21st-century drought in the western U.S. resulted in higher grassland mortality due to higher ambient temperatures than in past equally dry droughts and found fundamental differences in how Desert and Plains grasslands responded to the early 21st century drought. Another important result found that grasslands absorb more carbon dioxide than shrublands in the current climate of the Southwest but shrubs were able to conduct photosynthesis across a broader temperature range. This has important implications for the conversion of grasslands to shrublands that is being observed worldwide. A broader scale analysis across the Southwest region was also conducted to understand how water availability affects productivity. The conclusions were that net and gross productivity in grasslands, woodlands and forests showed very similar temporal responses to interannual changes in water availability, and these temporal responses at a site were the same as spatial relationships across the climatic gradient of sites. This increases our confidence that temporal responses from several years of data can be extrapolated to predict productivity under anticipated climate change. Significant progress was made under Objective 3 to further improve the Automated Geospatial Watershed Assessment (AGWA) tool and the KINematic runoff and EROSion model (KINEROS2) rainfall-runoff-erosion model. Improvements included: 1) Incorporation of the dynamic version of the Rangeland Hydrology and Erosion Model (RHEM) hillslope runoff and erosion engine; 2) Incorporate methods to represent impacts of military training activities and detention/erosion control ponds; 3) Developed and validated an urban model element with green infrastructure features to estimate the amount of “new” manageable water that arid and semi-arid communities have due to urbanization for beneficial uses such as aquifer recharge; 4) Coupled AGWA and the Facilitator decision support tool to enable AGWA and other decision factors to be compared in a structured manner; 5) Ingest radar-rainfall data from National Weather Service (NWS) radars as well as near-real time rain gauge intensity measurements to improve flash flood forecasting including testing at several NWS Weather Forecast Offices; 6) Post-fire model parameterization for identification of at risk watershed areas for Burned Area Emergency Response (BAER) teams to target wildfire mitigation efforts. For Objective 4, leadership on a number of fronts for the ARS LTAR network was provided. ARS staff from Tucson, Arizona, serve on the Field Leadership Team, Co-Chair the Meteorology Working Group, spearheaded efforts to identify, tested and implemented management and BaseCamp collaboration software for LTAR, lead development of the internal and external looking LTAR website, and developed and LTAR dash-board for network level viewing and analysis of diverse sets of big data. A “business-as-usual” versus “aspirational agriculture” common experiment to assess ecosystem services from brush management was designed and initiated and pre-experimental characterization was completed. Additionally, several high-impact, national level accomplishments were achieved beyond the objectives of this project. At the request of Natural Resources Conservation Service (NRCS), we utilized our modeling (RHEM, KINEROS2, AGWA) and remote sensing expertise to develop and complete a Congressionally mandated rangeland Western Conservation Effects Assessment Project (CEAP) on the Cienega Creek Watershed. Findings from this pilot project, with additional collaboration from the Forest Service, were also incorporated into a report fulfilling an FY13 USDA Agency Priority Goal (APG) for the USDA Water Team led by the Deputy Under Secretary of Natural Resources and Environment. These results directly led to Strategy in Action #3 item in the USDA FY 2014-2018 Strategic Plan calling for “a combined water quality and watershed condition monitoring and modeling approach to document water outcomes. The application of these approaches will enable USDA to prioritize locations for water quality activities and increase the effectiveness of conservation and management actions. USDA is now adapting water quality activities to include the recommendations and lessons learned from this APG” (, page 17). The Environmental Protection Agency (EPA) invited us to document the importance of ephemeral streams for the physical, chemical, and biological integrity of the Nation's waters in a comprehensive national report (EPA-2015: Connectivity of Streams & Wetlands to Downstream Waters: A Review & Synthesis of the Scientific Evidence). The portion of the report covering ephemeral and intermittent streams in the Southwest was written by an ARS scientist in Tucson, Arizona, who was the only non-EPA co-author of the report. The ephemeral and intermittent findings drew substantially on research conducted by our research unit in the Walnut Gulch Experimental Watershed and the larger San Pedro Basin. A key conclusion was that the physical, chemical, and biological integrity of downstream waters depends on the tributary ephemeral and intermittent streams. To quote one of many independent assessments of the report by the American Society of Civil Engineers (ASCE), "...also supports the recommendations and findings of the Science Advisory Board (SAB), namely, that “the available science supports the conclusion that the types of water bodies identified as waters of the United States … exert strong influence on the physical, biological, and chemical integrity of downstream waters.”

4. Accomplishments
1. Projected future increases in atmospheric dryness leads to greater plant water stress. Plants experience drought stress via two different mechanisms that are difficult to disentangle. There is a supply limitation at their roots due to drying soils and an increasing demand for moisture at their leaves due to drier air. Using data collected throughout the U.S. over a broad variety of different ecosystems, an ARS scientist in Tucson, Arizona, collaborated with others to show that, in many ecosystems, atmospheric dryness often independently limits both plant photosynthesis and water use more than soil moisture, especially in forests that are the largest sink for atmospheric carbon dioxide. Furthermore, we analyzed future projections from climate models to show that climate change will likely result in nearly universal increases in atmospheric aridity but with more widely varying and inconsistent changes in soil moisture. These results suggest that plant responses to future drought stress could diverge from our present conceptual understanding, and management approaches like increasing irrigation amounts during drought may become increasingly ineffective at mitigating plant stress.

2. Development of a modified scientific method for assessing big data. Data-intensive research will increase understanding of environmental problems at large spatial extents. Systems like the USDA Long-term Agro-ecosystem Research (LTAR) network provide data that is ecologically and hydrologically diverse to aid in exploring regional environmental dynamics. However, there is a need for an overall structure and specific approach for processing these large, multi-location time series data sets. ARS scientists in Tucson, Arizona, developed a modified scientific method, where new ideas originate from individual scientists and the hypothesis, analysis, and conclusions are developed with the broader scientific community. The research results using the modified scientific method have been recognized for solid scientific contributions as measured by publication in high-impact journals, high citation records, and recent awards.

Review Publications
Shellito, P., Small, E., Colliander, A., Bindlish, R., Cosh, M.H., Berg, A., Bosch, D.D., Caldwell, T., Goodrich, D.C., Lopez-Baeza, E., McNairn, H., Prueger, J.H., Starks, P.J. 2016. SMAP soil moisture drying more rapid than observed in situ following rainfall events. Geophysical Research Letters. 43(15):8068-8075.
Chan, S., Bindlish, R., O'Neill, P., Njoku, E., Jackson, T.J., Colliander, A., Chen, F., Burgin, M., Dunbar, R., Peipmeier, J., Yueh, S., Entekhabi, D., Cosh, M.H., Caldwell, T., Walker, J., Wu, X., Berg, A., Rowlandson, T., Pacheco, A., McNairn, H., Thibeault, M., Martinez-Fernandez, J., Gonzalez-Zamora, A., Seyfried, M.S., Bosch, D.D., Starks, P.J., Goodrich, D.C., Prueger, J.H., Palecki, M., Small, E., Zreda, M., Calvet, J., Crow, W.T., Kerr, Y. 2016. Assessment of the SMAP level 2 passive soil moisture product. IEEE Transactions on Geoscience and Remote Sensing. 54(8):1-14. doi:10.1109/TGRS.2016.2561938.
Lopez-Ballesteros, A., Serrano-Ortiz, P., Kowalski, A., Sanchez-Cañete, E., Scott, R.L., Domingo, F. 2017. Subterranean ventilation of allochthonous CO2 governs net CO2 exchange in a semiarid Mediterranean grassland. Agricultural and Forest Meteorology. 234-235:115-126. doi: 10.1016/j.agrformet.2016.12.021.
Novick, K., Ficklin, D., Stoy, P., Williams, C., Bohrer, G., Oishi, A., Papuga, S., Blanken, P., Noormets, A., Sulman, B., Scott, R.L., Wang, L., Phillips, R. 2016. The increasing importance of atmospheric demand in regulating ecosystem functioning. Nature Climate Change. 6:1023-1027.
Sanchez-Cañete, E., Scott, R.L., Van Haren, J., Barron-Gafford, G. 2017. Improving the accuracy of the gradient method for determining soil carbon dioxide efflux. Journal of Geophysical Research-Biogeosciences. 122:50-64.
Chen, F., Crow, W.T., Colliander, A., Cosh, M.H., Jackson, T.J., Bindlish, R., Reichle, R., Chan, S., Starks, P.J., Goodrich, D.C., Seyfried, M.S. 2016. Application of triple collocation in ground-based validation of soil moisture active/passive (SMAP) level 2 data products. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing. 99:1-14.
Moran, M.S., Heilman, P., Peters, D.C., Holifield Collins, C.D. 2016. Agroecosystem research with big data and a modified scientific method using machine learning concepts. Ecosphere. 7(10):e01493.
Ma, X., Huete, A., Moran, M.S., Ponce Campos, G.E., Eamus, D. 2015. Abrupt shifts in phenology and vegetation productivity under climate extremes. Journal of Geophysical Research-Biogeosciences. 120:2036–2052.
Ma, X., Huete, A., Cleverly, J., Eamus, D., Chevallier, F., Joiner, J., Poulter, B., Zhang, Y., Guanter, L., Meyer, W., Xie, Z., Ponce Campos, G.E. 2016. Drought rapidly diminishes the large net CO2 uptake in 2011 over semi-arid Australia. Scientific Reports. 6:37747.
Weltz, M.A., Nouwakpo, S.K., Hernandez, M., Nearing, M.A., Stone, J.J., Armendariz, G.A., Pierson, F.B., Al-Hamdan, O., Williams, C.J., Spaeth, K.F., Wei, H., Heilman, P., Goodrich, D.C. 2015. USDA internet tool to estimate runoff and soil loss on rangelands: rangelands hydrology and erosion model. The Progressive Rancher. 8:24-25.
Goodrich, D.C. 2017. Arid zone hydrology. In: Vijay P. Singh, editor. Handbook of Applied Hydrology. Second edition. New York, NY:McGraw-Hill Education. p. 88-1 to 88-7.