Research Project: Conservation Practice Impacts on Water Quality at Field and Watershed Scales

Location: National Soil Erosion Research Laboratory

2020 Annual Report

Objectives
Objective 1. Advance the knowledge and improve mathematical representation of processes affecting sediment, nutrient, and pesticide losses in surface and subsurface waters. Subobjective 1.1. Quantify surface and subsurface hydrologic processes affecting transport and transient storage of sediments and chemicals. Subobjective 1.2. Evaluate and improve scientific understanding of nutrient dynamics from the rhizosphere, upland areas, riparian zones, and drainage waterways. Objective 2. Develop methods to reduce pollutant losses from agricultural fields and watersheds, thus protecting off-site water quality. Subobjective 2.1. Develop removal strategies for dissolved phosphorus in drainage water. Subobjective 2.2. Test the impact of established and new conservation practices at the field and watershed scale. Subobjective 2.3. Determine optimal BMPs for control of runoff, sediment, and chemical losses from agricultural fields and watersheds, under existing and future climates. Objective 3. Improve erosion and water quality modeling systems for better assessment and management of agricultural and forested lands. Subobjective 3.1. Develop WEPP model code, including testing and scientific improvement. Subobjective 3.2. Improve ARS soil erosion and water quality model software architectures, interfaces, and databases for end-user model delivery. Objective 4. As part of the LTAR network, and in concert with similar long-term, land-based research infrastructure in the Midwest region, use the Eastern Corn Belt 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 Midwest 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. Subobjective 4.1. Quantify the relationship between soil quality and water quality under different cropping and management scenarios at the CEAP and Eastern Corn Belt LTAR sites. Subobjective 4.2. Develop techniques that enhance field-to-watershed scale parameterization for improved hydrologic model predictions at the CEAP and Eastern Corn Belt LTAR sites. Subobjective 4.3. Provide data management and services for CEAP and LTAR research sites.

Approach
Lab experiments will be used to study topographic driven surface hydraulic processes and soil hydraulic gradient driven subsurface flow effects on sediment and chemical loading and transient storage. Landscape attributes will be used to confirm the lab findings on conditions for sediment and chemical transport processes and processes such as deposition and hyporheic exchange. Field rainfall simulation experiments will be conducted using pan lysimeters to collect leachate to assess the effect of fertilizer placement on phosphorus leaching to subsurface tile drains. Stable water isotopes will be measured at the outlet of a headwater watershed during storm events to identify potential flow pathways and infer potential nutrient sources. We will use lab prototypes to assess the efficiency of steel slag in three potential field-scale phosphorus removal structure configurations, i.e., blind inlet, cartridge, and in-ditch slag dam for testing, and information obtained will be used to design field-scale installations for testing in the St. Joseph River Watershed (SJRW). We will subject steel slag materials to anaerobic conditions, and determine the effects on P solubility, and also explore the feasibility of regenerating materials for P removal structures. Field- and watershed-scale studies will be conducted to assess the impact of conservation practices on water quality, and field-scale studies will be used to assess the impact of drainage design and drainage water management on water quality. The Water Erosion Prediction Project (WEPP), Agricultural Policy Extender (APEX), and Soil and Water Assessment Tool (SWAT) models will be applied to monitored fields and small catchments in the SJRW in northeastern Indiana. Data from General Circulation Models (GCM) will be downscaled to develop modified climate inputs which will allow examination of the impacts of projected future climate on flow and pollutant losses. WEPP development efforts will occur in: Atmospheric CO2 impacts on plant growth; Model response to subsurface tile drainage; Water quality components to simulate nutrient and pesticide pollutant losses. Model development and testing efforts will include maintenance of the WEPP model scientific code, development of user interfaces, model databases, and user support. The WEPP module in the NRCS Cloud Services Innovation Platform (CSIP) software architecture will be made available as an option in the NRCS Integrated Erosion Tool (IET). Additionally, a separate WEPP web-based interface is being developed that allows WEPP to be run using standard NRCS databases. Data will be collected from the new Eastern Corn Belt LTAR sites once they are identified. Real-time weather information, field-measured profile soil moisture data and remotely sensed surface soil moisture content from agricultural fields will be used to improve prediction of surface runoff and tile flow and better understand runoff generation mechanisms. Topographic attributes, soil profile characteristics, and land management will be used to quantify potential for runoff and tile flow (i.e., profile drainage).

Progress Report
Sample collection at watershed scale for stable water isotopes proceeded as planned and will help provide a better understanding of water sources and flow pathways in tile-drained landscapes. At the field scale, we needed to add another year of data collection to quantify the effects of new tile drainage on discharge and water quality, as the farmer included an additional crop to his rotation. Data collection will continue for this project through the upcoming summer and fall, after which a drainage water management treatment will be implemented on one of the fields to evaluate the effectiveness of the practice. Our project evaluating the vadose zone hydrology in tile-drained fields was completed. For this project, we collected rainfall, soil water, groundwater, and tile drain discharge over a two-year period to determine sources of water and flow pathways to tile drains. All the data has been collected, sample analyses have been completed, and a publication is in progress. Pilot and laboratory-scale experiments were conducted regarding the impact of redox conditions on Fe/Al-rich Phosphorus (P) sorption materials (PSMs). The pilot-scale experiment was conducted in our large flow-through structure in the hydraulics lab, containing ~250 lbs of a sand-metal turning mixture (12%). After operating at continuous flow and P removal for two months, water flow was turned off with the box valves closed to prevent drainage. Glucose and nutrients were added, along with a “seed” of wetland soil to promote development of anaerobic conditions. Anaerobic conditions developed within three weeks, as evidenced by the formation of black pockets. Upon drainage, dissolved P concentrations were elevated, and with water flow resumed, dissolved P filtration was negative for about 24 h. However, after 24 h, P removal resumed and equilibrated to previous levels. P removal continued for three more months. Overall, the P release was insignificant compared to the total removal. More detailed incubations conducted under controlled atmosphere and temperature were also conducted. From this, we learned that use of agricultural runoff without added glucose to samples makes achievement of anaerobic conditions difficult to impossible. The phosphorus transport removal app (P-TRAP) has been completed and is now in a testing phase. This software will eventually be freely available as it has not yet been released to the public. It allows users to design a site-specific P removal structure for achieving desired P removal goals and structure lifetime. Many versions were created and shared with water quality colleagues for their feedback. From this, P-TRAP was constantly improved with their input. Three training modules for design and construction of P removal structures were completed for Natural Resources Conservation Service (NRCS)-American Society of Agronomy-American Society of Agricultural and Biological Engineers. Several more modules will follow over the next two years. Enhancement of the Water Erosion Prediction Project (WEPP) subsurface drainage component was completed in 2019, including model code changes, and calibration/validation studies. A journal paper was recently submitted to Agricultural Water Management detailing the improvements and validation study results. Additional testing for tile drainage under frozen soil conditions, and possible further code modifications may be necessary. Code modifications to WEPP to account for the effects of atmospheric carbon dioxide levels have been completed and will be incorporated into the next public release of the model. A journal paper describing the changes, and reporting results of model testing is in preparation. ARS scientists at West Lafayette, Indiana, participated in an ARS/NRCS Soil Erosion Research and Technology Meeting on September 10-12, 2019 in Beltsville, Maryland. This meeting included most of the ARS scientists involved in soil erosion research, as well as user representatives from Natural Resources Conservation Service (NRCS), the Forest Service, and universities. One of the important outcomes from this meeting was creation of a writing team to develop a strategic plan for ARS to address soil erosion research and modeling needs over the next 5-20 years. This document was developed by a team of ARS and affiliated university cooperator writers, including several National Soil Erosion Research Laboratory (NSERL) members from October-December 2019. It was completed in March 2020 and provided to the Office of National Programs (ONP). (Weltz, M., and Huang, C. (eds.). 2020. A Strategic Plan for ARS Erosion Research and Model Development. United States Department of Agriculture, Agricultural Research Service. 35 pp.) ARS scientists at West Lafayette, Indiana, met with National Sedimentation Laboratory (NSL) scientists and ONP members on December 9-10, 2019 in Oxford, Mississippi, to plan an additional WEPP and Revised Universal Soil Loss Equation, Version 2 (RUSLE2) model comparison study. The study utilized a very good weather record from Vermilion County, Illinois, and WEPP and RUSLE2 soil loss predictions were much more comparable than those from the 2019 study in Iowa. A complete report was prepared and submitted to National Program Leaders in early May 2020. A WEPP and Wind Erosion Prediction System (WEPS) coordination meeting was held with NRCS in May 2020 to define software updates for the WEPP and WEPS models, user interfaces, and web services. The meeting was coordinated by the NRCS National Erosion Specialist. The resulting action items from the meeting define much of the WEPP related work both over the short term and the next two years, with short term goals of addressing NRCS implementation of WEPP and longer-term goals of increased commonality between the WEPP and WEPS models. Work has continued organizing and importing the Conservation Effects Assessment Project (CEAP) data that the lab collects from field sites into the Aquarius water data management system. This has included putting boundary checks on the data and being able to visualize areas where data may not be correct. Ongoing field instrumentation updates have been supported through database configuration changes on the server and data access protocol changes on the data loggers and cell modems. Remote 2-way telemetry has been installed at three additional sites, giving NSERL fourteen fully remotely programmable monitoring sites in the CEAP watersheds. The Long-Term Agroecosystem Research (LTAR) site has been equipped with two flux towers that measure the exchanges of carbon dioxide, water vapor, and energy between terrestrial ecosystems and the atmosphere, which required a Wi-Fi network linking four nodes to the internet via a cell modem. Progress has been made linking legacy dataloggers into the cellular system already installed. Work continues with the NRCS implementation of WEPP. Website, database and model updates are periodically released to support NRCS during testing. Software developed for the WEPP NRCS user interface and converting RUSLE2 crop and operation databases to WEPP compatible data were shared with the SnapPlus group at the University of Wisconsin. Previously developed WEPP chemical transport routines are being reviewed, validated, and refined in collaboration with Purdue University. As part of this work, several validation datasets are being acquired to accomplish as much of the following as possible (given current data restraints): a hierarchical hillslope validation (i.e., validation of hydrology, sediment transport and chemical transport in that order), multiple overland flow element (OFE) scenarios (e.g., cropped and vegetative buffer strips), and multiple hillslope watershed validations.

Accomplishments
1. A strategic plan for ARS' erosion research and model development. ARS has been conducting erosion research and developing prediction technologies that are used worldwide for erosion assessment and conservation planning. In the past 30 years, separate science and technologies for wind and water erosion on croplands and rangelands have evolved. These different developments have resulted in different database requirements and different intermediate results from sub-processes (e.g. different plant growth and residue cover production). There is an urgent need to develop a unified approach that uses common databases and identical subprocesses for an integrated and scalable wind and water erosion prediction system. ARS scientists at West Lafayette, Indiana, coordinated an agency-wide effort and developed a strategic plan for ARS' erosion research and model development, which calls for new research thrusts, critical staffing, and program resources. This plan is being used by ARS leadership to formulate erosion and modeling efforts for the next 5 to 20 years.

2. Phosphorus removal by steel slag: insight from an innovative experiment. Steel slag has been used in previous laboratory and field experiments, as well as in some field demonstration projects to remove dissolved phosphorus (P) from drainage waters (i.e. P removal structures). Although it is well understood that slag removes dissolved P through precipitation reactions with slag calcium (Ca) to form Ca phosphate, the spatial nature of this particular mechanism within a P removal structure is less understood. Further understanding of how this particular mechanism manifests itself within a P removal structure will allow us to better design field scale P removal structures. ARS scientists at West Lafayette, Indiana, and a Purdue University visiting scholar designed a four-segment flow-through system that provided spatial and temporal data inside a P removal structure. The results highlighted the interaction between each segment, with P removal (via Ca phosphate precipitation) occurring as a front that moved through the segments as initially ample Ca and elevated pH supplied by the slag were depleted in that same front. The findings of this research improved the understanding of the P removal mechanism within a slag bed and the design of a more efficient P removal structure.

3. Performance of phosphorus removal structures. Dissolved phosphorus (P) losses to surface waters are considered the main cause of surface water eutrophication, such as in Lake Erie. Phosphorus removal structures are large landscape-scale filters for trapping dissolved P in non-point drainage before reaching surface waters. ARS scientists at West Lafayette, Indiana, and Columbus, Ohio, and cooperators from the Ohio State University built several P removal structures in Ohio and Indiana. Results showed that untreated steel slags, which remove P, would clog up with time due to calcium carbonate precipitation from bicarbonate-rich tile drainage water, while aluminum-coated slag was more effective in removing dissolved P. Since different P removal materials have different P removal mechanisms, we showed that these materials need to be characterized and proper sizes selected as a part of the engineering design. The USDA - Natural Resources Conservation Service is currently developing conservation standards for P removal structures for field adoption.

4. Blind inlets can additionally serve as dissolved phosphorus (P) removal structures. Blind inlets, which are limestone-gravel filters for removing sediment from agricultural drainage water in field depressions, have been shown to be effective at decreasing losses of particulate P (i.e. P bound to sediment) by virtue of sediment filtration. However, typical blind inlets are ineffective at removing dissolved P, which is a greater water quality hazard than particulate P. ARS scientists at West Lafayette, Indiana, improved a blind inlet by construction with steel slag, a material that has a high affinity for dissolved P. A field-scale blind inlet was constructed and monitored for impact on water quality. Use of steel slag over the traditional limestone-gravel resulted in appreciable filtration of dissolved P, particulate P, nitrogen, glyphosate, and dicamba, over a three-year period.

5. Using electrical conductivity in tracer injection experiments. Tracer injection is a common technique used in studying chemical or pollutant transport in streams and channels. However, tracer studies require sample collection and analyses and the sampling interval is usually limited, which may not capture the rapid changes in tracer concentration in order to fully understand the transport process. Electrical conductivity (EC), which reflects the amount of soluble compounds in water, can be easily measured at high frequency at a very low cost. ARS researchers at West Lafayette, Indiana, and Purdue University cooperators conducted tracer injection experiments in two laboratory flumes that allow for measurement of flow and solute transport. Water samples were collected intensively at multiple locations, and EC was continuously recorded. The results showed that EC measurement should not be used as a replacement for actual sample collection, but it could reduce the number of collected samples. On the other hand, if the study stream reach has additional solute sources, it will complicate the interpretation of chemical transport processes. This research is useful for scientists interested in studying chemical transport processes in channels and streams when designing optimal sampling strategies.

6. Implications of climate change at the Western Lake Erie Basin. ARS scientists at West Lafayette, Indiana, and Columbus, Ohio, believed that the climate change might have contributed to the HAB problem. By analyzing rainfall records from 1975 to 2017, they found that heavy and very heavy rainfall have increased across the basin with the largest increases during the spring season when the potential for erosion and nutrient losses are high. Changing rainfall patterns have resulted in increased tributary discharge despite increases in watershed storage capacity, resulting in more frequent water quality impairment incidents. These findings are important in understanding climate change effects and in developing mitigation strategies to minimize the occurrence of HAB.

7. Web-based interface for application of the APEX model. The Agricultural Policy Environmental eXtender (APEX) model is used by ARS and NRCS in national and regional assessments of the impacts of conservation practice implementation on water quality, and to provide inputs to larger basin-scale models, such as the Soil and Water Assessment Tool (SWAT). However, APEX can be difficult for county-level NRCS and Soil and Water Conservation District (SWCD) employees to apply at an individual field or farm scale. ARS scientist at West Lafayette, Indiana, and Purdue University cooperators developed a web-based interface that allows for easy and rapid application to any location in the contiguous United States, using largely existing topographic, soils, and climate databases. Users have the option to delineate a small field watershed by selecting a channel outlet point or drawing a trapezoidal field boundary which the software can use to determine all catchments that intersect with that field, to be set up and run in APEX simulations. This interface provides an alternative way for field conservation staff to evaluate the effects of land management and conservation practices.

Review Publications
Srivastava, A., Brooks, E.S., Dobre, M., Elliot, W.J., Wu, J.Q., Flanagan, D.C., Gravelle, J.A., Link, T.E. 2019. Modeling forestry management effects on water and sediment yield from nested, paired watersheds in the interior Pacific Northwest, USA using WEPP. Science of the Total Environment. 701:134877. https://doi.org/10.1016/j.scitotenv.2019.134877.
De Lima Moraes, A.G., De Carvalho, D.F., Homem Antunes, M.A., Bacis Ceddia, M., Flanagan, D.C. 2019. Steady infiltration rate spatial modeling from remote sensing data and terrain attributes. Geoderma Regional. 20:e00242. https://doi.org/10.1016/j.geodrs.2019.e00242.
Liu, J., Li, P., Liu, G., Flanagan, D.C. 2020. Quantifying the effects of plant litter in the topsoil on the soil detachment process by overland flow in typical grasslands of the Loess Plateau, China. Hydrological Processes. 34(9):2076-2087. https://doi.org/10.1002/hyp.13713.
Schull, V.Z., Daher, B.T., Gitau, M.W., Mehan, S., Flanagan, D.C. 2019. Analyzing FEW Nexus modeling tools for water resources decision-making and management applications. Food and Bioproducts Processing. 119:108-124. https://doi.org/10.1016/j.fbp.2019.10.011.
Liu, J., Liu, G., Flanagan, D.C., Wang, G., Wang, Z., Xiao, J. 2019. Effects of soil-incorporated plant litter morphological characteristics on the soil detachment process in grassland on the Loess Plateau of China. Science of the Total Environment. 705:134651. https://doi.org/10.1016/j.scitotenv.2019.134651.
Williams, M.R., King, K.W. 2020. Changing rainfall patterns over the Western Lake Erie Basin (1975-2017): Effects on tributary discharge and phosphorus load. Water Resources Research. 56(3). Article E2019WR025985. https://doi.org/10.1029/2019WR025985.
Feng, Q., Flanagan, D.C., Engel, B., Yang, L., Chen, L. 2019. GeoAPEXOL, a web GIS interface for the Agricultural Policy Environmental eXtender (APEX) model enabling both field and small watershed simulation. Environmental Modelling & Software. 123:104569. https://doi.org/10.1016/j.envsoft.2019.104569.
Botero-Acosta, A., Chu, M.L., Huang, C. 2019. Impacts of environmental stressors on nonpoint source pollution in intensively managed hydrologic systems. Journal of Hydrology. 579:124056. https://doi.org/10.1016/j.jhydrol.2019.124056.
Cochrane, T.A., Yoder, D.C., Flanagan, D.C., Dabney, S.M. 2019. Quantifying and modeling sediment yields from interrill erosion under armouring. Soil & Tillage Research. 195:104375. https://doi.org/10.1016/j.still.2019.104375.
Gonzalez, J.M., Murphy, L.R., Penn, C.J., Boddu, V.M., Sanders, L.L. 2020. Atrazine removal from water by activated charcoal cloths. International Soil and Water Conservation Research. 8(2):205-212. https://doi.org/10.1016/j.iswcr.2020.03.002.
Gonzalez, J.M., Penn, C.J., Livingston, S.J. 2020. Utilization of steel slag in blind inlets for dissolved phosphorus removal. Water. 12(6):1593. https://doi.org/10.3390/w12061593.
Hanrahan, B.R., King, K.W., Macrae, M.L., Williams, M.R., Stinner, J.H. 2020. Among-site variability in environmental and management characteristics: Effect on nutrient loss in agricultural tile drainage. Journal of Great Lakes Research. 46(3):486-499. https://doi.org/10.1016/j.jglr.2020.02.004.
Macrae, M., Ali, G., King, K.W., Plach, J., Pluer, W., Williams, M.R., Morrison, M., Tang, W. 2019. Evaluating hydrologic response in tile drained landscapes: Implications for phosphorus transport. Journal of Environmental Quality. 48(5):1347-1355. https://doi.org/10.2134/jeq2019.02.0060.
Mehan, S., Aggarwal, R., Gitau, M.W., Flanagan, D.C., Wallace, C.W., Frankenberger, J.R. 2019. Assessment of hydrology and nutrient losses in a changing climate in a subsurface-drained watershed. Science of the Total Environment. 688:1236-1251. https://doi.org/10.1016/j.scitotenv.2019.06.314.
Revuelta-Acosta, J.D., Flanagan, D.C., Engel, B.A. 2019. Development of a stochastic storm generator using high-resolution precipitation records. Applied Engineering in Agriculture. 35(4):461-473. https://doi.org/10.13031/aea.13259.
Wang, S., Flanagan, D.C., Engel, B. 2019. Estimating sediment transport capacity for overland flow. Journal of Hydrology. 578:123985. https://doi.org/10.1016/j.jhydrol.2019.123985.
Williams, M.R., McAfee, S.J., Kent, B.E. 2019. Dye tracers reveal potential edge-flow effects in undisturbed lysimeters sealed with petrolatum. Vadose Zone Journal. 8:190040. https://doi.org/10.2136/vzj2019.04.0040.
Zheng, F., Zhang, X.J., Wang, J., Flanagan, D.C. 2019. Assessing applicability of the WEPP hillslope model to steep landscapes in the northern Loess Plateau of China. Soil & Tillage Research. 197:104492. https://doi.org/10.1016/j.still.2019.104492.