1a. Objectives (from AD-416):
Principal focus of the CEAP Watershed Studies is to evaluate the effects and benefits of conservation practices at the watershed scale, in support of policy decisions and program implementation.
1b. Approach (from AD-416):
The effects of conservation activities on water and soil quality will be assessed at the watershed scale using models such as ARS' Soil and Water Assessment Tool, in combination with ARS long-term watershed data sets, expertise, and resources.
3. Progress Report:
This multi-location project will be affiliated with the following location-specific projects: 3602-12130-001-00D; 6206-13610-007-00D; 6408-13000-023-00D, 6408-13000-023-00D, 6408-13660-007-00D; 3622-12130-005-00D; 3625-11610-001-00D, 3625-13000-010-00D; 6602-13000-026-00D; 5368-13000-008-00D; 1265-13610-028-00D; 6218-13000-011-00D; 3604-13000-011-00D. ARS researchers at West Lafayette, Indiana: Significant progress toward calibration/validation of APEX and application of the model to assess the impacts of conservation practices at the field scale has been made. Plots were established at the Throckmorton Purdue Agricultural Center to study the impacts of strategies to minimize soluble phosphorus losses from no-till farming. The St. Joseph River Watershed Conservation Effects Assessment Project (CEAP) Watershed Assessment Study (WAS) has been selected as one of two benchmark watersheds to be used for a multi-Agency effort to assess the impacts of conservation practices on environmental quality at the watershed scale. The Agency Priority Goals (APG) project is a collaboration between National Resources Conservation Service (NRCS), Farm Service Agency (FSA), United States Forest Service (USFS) and ARS to provide a cost/benefit analysis to conservation practices at the 12-digit Hydrologic Unit Code (HUC) level. Based on the scale, resolution, and quality of the data collected in the St. Joseph River Watershed CEAP WAS, the ARS researchers at West Lafayette, Indiana was contacted by NRCS headquarters as the first watershed requested to participate in the APG project. This will be an intensive 1 year effort, compiling monitored water quality and quantity data, ecological assessment data, cropping system attribute data, as well as field and watershed scale modeling efforts to provide the other agencies with information on the effectiveness of current conservation practices, and how those agencies may better target conservation practices in the future. In the young glacial till landscape of the upper Midwestern US, closed depressions occur widely – known locally as potholes. Surface drainage water from potholes will collect at the lowest spot in the pothole, and will keep the area too wet for farming, even with standard subsurface tile draining the field. Therefore, most potholes that are farmed are drained with subsurface tile, but also have supplemental drainage from a tile riser. A tile riser is a pipe with 1/2” – 3/4” holes drilled in the sides. Scientists at West Lafayette, Indiana. identified the extent of potholes within a watershed as being directly related to the concentrations or loads of nutrients lost from the watershed. An alternate practice, called a blind inlet, was researched to provide greater filtration of surface water from potholes. Loads of P can be decreased by about 78% when drained with a blind inlet compared to a tile riser, and nitrogen (N) loads can be decreased by greater than 50% when drained with the blind inlet. In 2012, ARS scientists have worked with NRCS to develop a conservation practice standard, and NRCS in Indiana is now offering blind inlets as a cost sharable practice through the Environmental Quality Incentives Program (EQIP). State NRCS offices in Ohio, Wisconsin and Iowa have shown interest in the practice. ARS researchers at Temple, Texas: This long-term project was designed to evaluate nutrient management practices for both organic and inorganic sources at the USDA-ARS Riesel Watersheds. This year marks the eleventh year of comparing poultry litter and inorganic fertilizer, and the economical and environmentally-friendly nutrient management strategies developed from this work have reduced the potential for water quality degradation from agriculture. Related research is evaluating the reduction of bacteria runoff and odor by in-house windrow composting of litter prior to land application. In addition, methods for determination of optimal fertilizer application rates have been determined and were evaluated. These enhanced nutrient management strategies represent important agronomic advancements with the potential for major agro-economic and environmental benefits.
1. Lake water quality improves with watershed best management practices (BMP) installation. Beasley Lake Watershed is a 915 hectare intensively-farmed Mississippi Delta watershed. The oxbow lake, Beasley Lake, was sediment impaired resulting in poor sport fishing and degraded water quality. Over the course of 14 years, ARS scientists in Oxford, Mississippi, monitored lake water quality following installation of watershed-wide management practices within-field, at the edge-of-field, as well as enrollment in the Conservation Reserve Program. Reduction of nutrients and solids resulting in improved water quality and sport fisheries have been noted over the evaluation period. Results will provide action agencies and landowners with information to improve and sustain lake and flood plain water quality using conservation practices.
2. Gully formation and erosion contribution in Conservation Effects Assessment Project (CEAP) agricultural fields identified and characterized. Knowing where gullies form and their contribution to total sediment load within watersheds is critical in assessing the impact of agricultural conservation practices to reduce gully erosion. ARS scientists at Oxford, Mississippi obtained results from CEAP and international experimental sites to locate and evaluate the impact of gully erosion on total watershed load. Enhanced technology was developed and applied within the USDA-ARS Annualized Agricultural Non-Point Source pollution model (AnnAGNPS) to: predict the location of gully channel initiation points; characterize gully properties; and assess gully conservation practices to reduce sediment load at these sites. Utilizing improved gully identification and assessment technology has provided action agencies, such as adoption by USDA-NRCS state offices in Ohio and Kansas, with enhanced information and management tools to evaluate gully erosion control practices critical in the development of effective management plans that reduces sediment loads within watershed systems.
3. Contaminant transport in two central Missouri karst recharge areas. Karst hydrology is the most vulnerable groundwater setting for contamination by surface land use activities. A three-year study was conducted by ARS researchers at Columbia, Missouri. in two karst recharge areas to characterize the flow and contaminant transport of these cave systems prior to significant urbanization. Despite similarities in land use, geology, and weather, the quality of the water in the two cave streams was very different, with the Devils Icebox recharge area having significantly greater concentrations and total loads of nutrients, sediment, and herbicides than the Hunters Cave recharge area. Within the Devils Icebox recharge area, 94% of the row crop areas occurred on high runoff potential soils compared to only 57% for the Hunters Cave recharge area. Previous research has demonstrated that these high runoff potential claypan soils are especially problematic with respect to surface transport of contaminants. Because of these findings, a stakeholder-led watershed plan for the Bonne Femme watershed, which includes the two cave watersheds, was developed with the primary goal of improving water quality by implementing management practices for protection of karst recharge areas.
4. Delineating critical management areas within fields. Identifying the critical management areas within claypan soil fields is essential to maximize grain production and minimize environmental impacts. In this field-scale study conducted by ARS researchers at Columbia, Missouri two indices that use readily available soil and landscape data were proposed for identifying field areas most vulnerable to losses of atrazine and sediment. A computer simulation model was used to provide estimates of crop yields and for prediction of sediment and atrazine losses within the field. The index values correlated well with the model simulated sediment and atrazine losses, and also with the lower corn yield areas of the field. Management scenarios were simulated that differentiated the management of the critical areas from the rest of the field. The developed indices were capable of identifying areas of higher environmental risk and lower productivity that could provide objective criteria for effective targeting of best management practices.
5. Streambank erosion in claypan soil watersheds. Stream water contamination by sediment remains a major environmental concern in the United States because soil deposited in streams results in impaired aquatic habitat and sedimentation of lakes and reservoirs. This study, conducted in collaboration with researchers at the University of Missouri, Iowa State University, and ARS at Columbia, Missouri, was undertaken to compare the streambank erosion rates of streams in the Crooked and Otter Creek watersheds, two claypan watersheds located in northeastern Missouri. Results showed that streambanks accounted for an average of 88% of the annual in-stream sediment and 23% of the total nitrogen exported from these watersheds. Thus, streambanks were the dominant source of sediment in these streams and a significant contributor to nitrogen transport. Improved management of riparian areas to decrease streambank erosion would result in significant water quality improvement in streams of the Central Claypan Areas.
6. Enhancing degradation of atrazine in root zone soils. Atrazine has been widely used for weed control in U.S. corn production for decades, but public health and ecological concerns have been raised because of contamination of surface and ground water by atrazine and its breakdown products, which may be toxic to humans and aquatic life. In an effort to achieve more complete atrazine degradation in soil and prevent off-site transport, ARS researchers at Columbia, Missouri and University of Missouri researchers investigated the potential of adding a bacterium, Pseudomonas sp. strain ADP, to soils to enhance atrazine degradation. In this research, we tested the ability of a switchgrass rhizosphere (root zone soil) to sustain one of the degrading genes (atzA) in soil compared to bulk soil with no plants. The results showed that switchgrass rhizospheres sustained a higher number of degrading genes compared to the control for about three weeks; the numbers were similar thereafter. In the presence of the degrading bacteria, more than 50% of the atrazine was completely broken down within seven days. The sustained gene numbers and high degradation rates observed indicated that the bacteria would be an effective addition to grass buffers for enhancing the degradation of atrazine and reducing stream and ground water contamination.
7. Developing a practice to minimize water quality impacts following manure spills. After a manure spill has reached surface waters (drainage ditches and streams), the most common method of remediation is to contain the contaminated area using earthen dams, remove the water from the stream using pumping equipment, and to redistribute the recovered waste into an alternative storage system or to land apply the waste in compliance with state regulations. Recent studies have examined the fate of phosphorus (P) during a manure spill and the effectiveness of the current manure spill clean-up method. These studies found that the current remediation of manure spills that reach surface water focus primarily on the contaminated water, while nutrient rich sediments remain in the stream. These sediments have been found to further contaminate the water column for up to 2 months after the spill. ARS researchers at West Lafayette, Indiana have developed a supplemental clean-up method using aluminum sulfate (alum) as a sediment treatment to prevent the release of P from contaminated sediments to the water following a manure spill. We determined that treating sediments with the highest rates of alum (roughly 270 pounds alum/1000 square foot) resulted in a 98-100% reduction in P released to the water following a 24 hour manure spill simulation. Sediments that contained the greatest clay content and extractable Fe and Al content required greater alum treatment rates to reduce P release. The impact of this study is the demonstration of technology following manure spills that reduce P availability to aquatic plants such as algae and downstream transport of soluble P to lakes and reservoirs to prevent contributions to eutrophic conditions.
8. Demonstrated the effectiveness of an NRCS special Environmental Quality Incentives Program (EQIP) addressing atrazine in a drinking water supply reservoir. Atrazine is a popular and economical corn herbicide that has a history of exceeding drinking water standards in many supply reservoirs of the upper Midwest. The NRCS EQIP program was utilized to incentivize operators to adopt one of four practices aimed at reducing atrazine in the drinking water supply reservoir. The combined effect of adopting these practices was a significant reduction of atrazine in the reservoir. The findings also confirmed the economic viability of the program. For every dollar spent in EQIP practice incentives a $2.04 savings was realized for the City of Columbus downstream water treatment facility.
9. Identified conservation plans for channelized agricultural headwater streams need to address both physical and chemical habitat degradation. Ecological evaluations of grass filter strips (CP21) and atrazine reduction practices (NRCS practice #595) within channelized agricultural headwater streams (i.e., agricultural drainage ditches) in the Upper Big Walnut Creek watershed documented that implementation of these conservation practices does not influence physical habitat, water chemistry, or the fishes within these degraded streams. These results are concordant with concurrent assessments of fish-habitat relationships that indicate physical habitat has a greater effect on fishes than water chemistry within these small streams (watershed sizes < 8.1 km2). Overall, our results suggest that conservation plans for channelized agricultural headwater streams in the Midwestern United States need to implement conservation practices capable of addressing both physical habitat degradation and poor water quality. This information can be used by state, federal, and private agencies responsible for managing agricultural watersheds and restoring streams.
10. Identified the frequency and extent of floodplain interaction on a tributary of Upper Big Walnut Creek (UBWC). Floodplain interaction has been shown to be important for both nutrient retention and cycling as well as ecological diversity. A tributary of UBWC was surveyed and monitored for one year to determine the frequency and extent of floodplain interaction. The findings were used to populate a computer model to project the number of out of bank flows. The findings establish the need for further exploration on the water quality benefits of floodplain interaction and support the movement for development of two-stage ditch design.
11. Established a paired edge-of-field (EOF) data collection network in two high priority watersheds: Quantifying effects of conservation practices continues to be an emphasis by multiple state and federal agencies to understand the processes governing pollutant transport from agriculture. Eight paired EOF sites (16 fields) were instrumented to facilitate event based discharge and water quality measurement. The sites are representative of both surface and subsurface (tile) transport. Data collected from the sites will provide critical insight to the mechanisms and pathways leading to nutrient transport and provide a platform for measuring the effects of different management practices intended to reduce or eliminate those pollutant discharges.
12. Documented need for greater adoption of watershed scale atrazine reduction practices within watersheds of channelized agricultural headwater streams. The watershed scale impacts of conservation practices that lead to the reduction of pesticide usage has not been quantified. Understanding the effects of reducing pesticide usage at the watershed scale will assist with developing watershed management guidelines for headwater streams within the Midwestern United States. Watershed management practices intended to reduce atrazine usage did not influence atrazine concentrations, pesticide mixtures, or fish communities within channelized agricultural headwater streams in central Ohio during the spring and summer. Our results suggest the implementation of watershed management practices within 30% or less of the watersheds of channelized agricultural headwater streams may not influence pesticides or fishes in these small streams. This information can be used by state, federal, and private agencies responsible for managing agricultural watersheds and restoring streams.
13. Watershed scale simulations based upon limited data: Watershed scale simulation models can be useful for examining the impacts of climatic variation and changes in land-use. The ARS researchers at Tifton, Georgia examined the accuracy that could be obtained in hydrologic simulation within watersheds where no hydrologic data were available utilizing data from similar watersheds where hydrologic data were available. Simulation results indicate the method can be used to produce reliable hydrologic results (plus/minus 25%) within the Coastal Plain region. Results also indicate that assessments of water quality responses to conservation practices based upon these simulations will accurately predict the direction of the change in water quality (up or down), but not the absolute magnitude of the predicted change. These results can be directly applied to establish levels of confidence in computer simulations often used to make watershed assessments.
14. Hydrologic impacts of projected land-use changes to accommodate bio-energy production: USDA goals for meeting renewable fuels standards by 2022 indicate that 50% of the advanced biofuels to be produced in the U.S. are expected to come from the Southeastern U.S. Meeting these goals will require conversion of row-crops to high-yielding biomass crops. Changes in water resources, both quantity and quality, are anticipated with these changes. ARS researchers at Tifton, Georgia used computer simulations to show that conversion of existing production land into grass biomass crops may result in: 1) decreased evapotranspiration; 2) increased streamflow; 3) decreased sediment loading; and 4) seasonal shifts in streamflow. Results also indicate an increase in forested area for biomass production will result in: 1) increased evapotranspiration; 2) decreased streamflow; 3) decreased sediment loading; and 4) seasonal shifts in streamflow. These results give an indication of the hydrologic changes which would accompany large scale changes in land-use associated with biomass production.
15. Assessment of the impact of agriculture on the Jobos Bay National Estuary: The Jobos Bay National Estuarine Research Reserve (JBNERR) is a semi-enclosed ecosystem along the southeast coast of Puerto Rico. Agriculture, including vegetable, row crop, tree fruit, pasture, and poultry, is an important land use within the watershed. To better understand the potential impact of agriculture on JBNERR, the watershed was designated as the first USDA tropical Conservation Effects Assessment Project (CEAP). ARS researchers at Tifton, Georgia identified an agricultural field near the land/estuary interface for detailed study. Groundwater and water quality studies in the area indicate that the primary mode of transport to the estuary is through surface runoff generated during intense rainfall events. Groundwater transport is expected to be low due to low rates of movement in the surface aquifer. These findings should be valuable to management agencies selecting conservation practices that will reduce surface runoff and agricultural chemical loading to the bay during these intense rainfall events.
16. Simulation of riparian buffers in the Jobos Bay Watershed, Puerto Rico: ARS scientists at Tifton, Georgia working in conjunction with USDA-NRCS, used the Agricultural Policy/Environmental eXtender (APEX) and Riparian Ecosystem Management Model (REMM) models to show that riparian buffers had the potential to keep nutrients and pesticides in runoff from an agricultural field from reaching a mangrove wetland. APEX simulations confirmed that most of the transport on nutrients and pesticides occurred in large events (tropical storms). REMM simulated buffers were less effective in tropical storms but showed that if surface runoff was directed into buffers of at least 35 meter width that about 35% of nutrients and 70% of atrazine could be removed from runoff.
17. Simulation of riparian buffers impact on water quantity and quality in the coastal plain: Riparian buffers are an extremely important component of Coastal Plain Watersheds, dramatically impacting the quality of surface and subsurface flow reaching Coastal Plain streams. Until recently, large scale watershed simulation models have not adequately addressed these riparian buffers in their simulation methods. ARS researchers at Tifton, Georgia in cooperation with ARS researchers in Temple, Texas and researchers at Tarleton State University in Waco, Texas incorporated these functions into the Soil Water Assessment Tool and Agricultural Policy/Environmental eXtender models. Preliminary tests were conducted to examine the accuracy of the new simulation methods. These new simulation tools appear to offer significant improvements in the way riparian buffers are simulated in these models.
18. Assessment of conservation practice approaches in the Little River Watershed. ARS researchers at Tifton, Georgia used the Soil Water Assessment Tool model to simulate the water quality effect of upland conservation practices (CPs) commonly adopted in the Little River Experimental Watershed (LREW) for either erosion or nutrient control and compared those results to the simulated impact of the riparian forest buffers currently in the LREW. Erosion CPs resulted in the greatest reductions in sediment and phosphorus while nutrient reduction practices were most effective in reducing total stream nitrogen. We also evaluated three different prioritization scenarios for implementing CPs. Prioritizing based upon nonpoint source pollutant load yielded more efficient water quality improvements while the other implementation schemes were less efficient. Riparian forest buffers offered the most comprehensive reduction of all three pollutants. Simulation results indicate that the current level of riparian forest cover in the LREW may be the single greatest contributor to nonpoint source pollutant reduction.
19. Satellite derived mapping algorithm. Conservation tillage is a commonly adopted best management practice for improving soil quality and reducing erosion. However, there are currently no methods in place to monitor conservation tillage adoption at the watershed scale. A mapping algorithm, using commonly available satellite imagery, has been developed to depict conservation tillage adoption within the Little River Experimental Watershed. The resulting map identified farm sites using conservation tillage (defined as having >30% crop residue cover) with 71-78% confidence. Models used to map conservation tillage adoption were created using a subset of 44 sample points and validated using 94 sample points. Results are encouraging and suggest that currently available satellite imagery can be used to map conservation tillage adoption with a minimum amount of ground control points.
20. Assessment of conservation practice placement. ARS scientists worked in conjunction with USDA-NRCS to develop a 26 year history of NRCS-assisted conservation practices in the Little River Experimental Watershed (LREW). The database was used to evaluate placement of conservation practices in the landscape. Nearly 50% of all cropped fields were identified as having participated in NRCS conservation programs. Sixty-two percent of these fields (77% of land area) received assistance for soil erosion and water erosion quality control practices in high resource concern areas (slope > 2.7 % and low infiltration). Sixty percent of the fields receiving assistance for soil and water erosion control were located within 50 meters of a water body. We estimated that 30-40% of the time erosion control practices were implemented in areas not rated as a high concern. A subset of the LREW was used to evaluate adoption and placement of erosion control practices both with and without NRCS assistance. Forty-seven percent of all fields in the sample implemented visible erosion control-specific conservation practices. The implementation was linearly related to slope class. The relationship observed between erosion control practice placement and slope in the sub-watershed database is encouraging and suggests a commitment to good stewardship regardless of participation in federally funded conservation programs.