2013 Annual Report
1a.Objectives (from AD-416):
The long-term objective of this project is to develop soil and water conservation decision support information for policy makers, land managers, and producers to help identify the scope of additional conservation measures to mitigate the detrimental impacts of anticipated climate change. The Fort Cobb Reservoir watershed in west central Oklahoma is representative of the physiography of the region and was selected as the project watershed.
Obj 1: Quantify the effects of past climate variations on runoff, soil erosion, sediment transport and fate, and nutrient movement for the Fort Cobb Reservoir (FCR) watershed, using available data records, reconstructed chronology of reservoir sedimentation, and computer modeling of watershed processes.
1A: Identify past climate variations; determine corresponding impacts on watershed runoff, sediment yield, and reservoir sedimentation; derive climate-flow-sediment relationships.
1B: Reconstruct chronology of watershed sediment yield from reservoir sedimentation profiles; identify sediment sources; estimate sediment yield of major erosive storm-runoff events for calibration/validation of simulation models.
1C: Identify reference land use, conservation, and climate conditions to serve as baseline for assessment of climate change scenario impacts; calibrate/validate hydrologic and erosion simulation models using data developed under subobj 1A/1B.
Obj 2: Determine the potential impacts of three selected climate change scenarios on the hydrologic system and on the soil and water resources of the FCR watershed.
2A: Determine trends in annual precipitation and air temperature for 3 greenhouse gas (GHG) emission scenarios; identify changes in seasonal/monthly precipitation and temperature distribution within a year, estimate monthly precipitation and temperature statistics expected to prevail around the half century mark.
2B: Develop/evaluate spatio-temporal downscaling methods that integrate changed climate statistics into a synthetic weather generator; generate ensembles of daily weather outcomes for each GHG emission scenario that reflect the statistical characteristics of projected climate change for use in climate impact assessment in Obj 3.
Obj 3: Identify soil and water conservation strategies and options that are adapted to and mitigate the detrimental impacts of climate change, and test their effectiveness at enhancing the resilience of agricultural landscapes under anticipated climatic changes.
3A: Estimate extent of soil erosion/sedimentation under 3 selected GHG emission scenarios assuming constant baseline land use and conservation conditions; identify soil conservation options/practices/coverage that mitigate soil erosion and sedimentation directly attributable to climate change; determine risk of exceeding soil erosion and sedimentation rates under climate change.
3B: Develop communication tools that synthesize information across combinations of conservation practices, conservation coverage, climate change scenario, and conservation effectiveness and help land managers select conservation options that best meet soil/water conservation goals.
1b.Approach (from AD-416):
The effects of past climate variations on runoff, soil erosion, sediment transport and fate, and nutrient movement for the Fort Cobb Reservoir (FCR) watershed are quantified based on available climate, hydrology, and environmental data records, reconstructed chronology of reservoir sedimentation, and computer modeling of watershed processes. Published climate data from Global Climate Models (GCM) are used to determine trends in annual precipitation and air temperature for three greenhouse gas (GHG) emission scenarios, identify changes in seasonal and monthly precipitation and temperature distribution within a year, and estimate monthly precipitation and temperature statistics that are expected to prevail around the half century mark. Synthetic weather generation models are used to generate daily weather outcomes that reflect the statistical characteristics of the projected climate change. Soil and water conservation strategies and options that are adapted to and mitigate the detrimental impacts of climate change are identified based on simulated soil erosion and sedimentation. Selected soil conservation options, practices, and coverage are tested with regard to their effectiveness at enhancing the resilience of agricultural landscapes under anticipated climatic changes. Risk of exceeding predefined soil erosion and sedimentation rates under climate change are determined. Information across combinations of conservation practices, conservation coverage, climate change scenario, and conservation effectiveness is synthesized and communicated in a format relevant to land managers, conservationists, and producers, as well as other practitioners.
A farm cluster analysis was conducted by Tarleton State University for the Upper Washita River Basin. Planning was initiated for a Fort Cobb Reservoir Watershed workshop with producers and conservationists to demonstrate the Nutrient Tracking Tool, to gain information on preferences and perspectives on agricultural conservation, and to develop improved understanding of producer management goals, strategies, and practices. Completed calibration and validation of SWAT for hydrology. Landsat land use, STATSGO soils, a 10-m DEM, and climate data were used to build the SWAT project. The surface runoff, ET, and groundwater parameters were included in the calibration for hydrology. The Nash-Sutcliffe efficiency factor and percent bias statistical measures were used for calibration and validation. In addition, water budgets, and crop yields were assessed to ensure that the model simulated correct stream flow for the right reasons. Completed acquiring available total P data and performing quality control. These data include the bi-weekly ARS sample and the USGS low-high flow sampling data. The ARS sampling is still continuing, while the USGS low-high flow sampling spanned 2005 to 2011. The recently developed data model and analysis tool, SPELLmap, was used to perform thorough QA/QC. 27 soil cores were taken from cultivated land in the Bull Creek watershed. 50 sediment samples from 6 storm events were also collected from 14 sites. Nitric acid extraction was completed for about 150 soil and sediment samples, and the extracts were analyzed for 27 selected geochemical elements. More than 200 soil cores and about 30 sediment samples were measured for Cesium-137 activity. Particle size distributions of all soil and sediment samples were completed. Selected tracers are being used to proportion sediment sources. Preliminary analysis of Cesium-137 data was conducted to estimate spatial soil erosion redistributions along several hillside transects. Sediment cores of 12 flood control reservoirs were collected and processed for analysis of texture, chemical composition, and age dating by depth. Mitigation and adaptation practice for forage-grazing systems were developed collaboratively with research and extension partners in an AFRI-CAP project. Based on meetings with collaborating agencies, our adaptation and mitigation strategies for annual cropping will focus on no-till, crop rotation, cover crops, and buffers to address the NRCS soil health initiative. The capabilities of computer-generated synthetic weather by software SYNTOR have been expanded to include generation of weather for seasonal forecasts and climate change scenarios, and to generate daily weather records that are representative of changed climatic conditions. Software SYNTOR has been tested with weather records and projected climate changed conditions in central Oklahoma. We assessed future climate change projections for seven ARS watershed sites representing diverse physiographic regions across the continental United States. Multi-decadal climate trends were identified based on climate change projections produced by Global Circulation Models (GCM).
Conservation tillage mitigates soil loss under climate change. In Oklahoma, annual precipitation is anticipated to decrease and extreme rainfall events to increase as the climate changes with global warming. Soil erosion under such a climate is expected to increase because of increased occurrence and intensity of heavy storms. ARS researchers at El Reno, Oklahoma, evaluated the effectiveness of various tillage and cropping systems to control soil erosion under climate change using computer models. Results showed that under the same tillage and cropping systems, soil loss will increase in the future despite projected decrease in annual precipitation, primarily due to the increase in heavy storms. However, conservation tillage, especially no-till, is able to keep soil loss within acceptable levels. Wheat is more effective in reducing soil loss than cotton, soybean, or sorghum. This work provides a scientific base for widespread adoption of conservation tillage to combat soil erosion in the region under climate change.
Zhang, X.J. 2012. Cropping and tillage systems effects on soil erosion under climate change in Oklahoma. Soil Science Society of America Journal. 76(5):1789-1797.
Zhang, X.J., Chen, J., Garbrecht, J.D., Brissette, F.P. 2012. Evaluation of a weather generator-based method for statistically downscaling non-stationary climate scenarios for impact assessment at a point scale. Transactions of the ASABE. 55(5):1745-1756.