1. Robert N. Lerch Soil Scientist, USDA-ARS Cropping Systems & Water Quality Research Unit, Columbia, MO Soil Scientist, USDA-ARS Cropping Systems & Water Quality Research Unit, Columbia, MO ARS Scientists: E. E. Alberts, C. Baffaut, W. W. Donald, F. Ghidey, A. T. Hjelmfelt, N. R. Kitchen, E. J. Sadler, K. A. Sudduth Collaborators: P. E. Blanchard, Univ. of Missouri; M. L. Bernards, Univ. of Nebraska P. J. Shea, Univ. of Nebraska; M. Milner, Univ. of Nebraska

2. Data Sources: multi-scale approach to monitoring herbicide transport Data Sources: multi-scale approach to monitoring herbicide transport –Regional: Northern Missouri/southern Iowa region (1997-1999) –Basin: Salt River Basin (2005-2010) –Watershed: Goodwater Creek Experimental Watershed (GCEW) (1992-present) Identifying vulnerability in space and time Identifying vulnerability in space and time –Direct Observation  Areal herbicide loss rates on a mass per treated area basis –Temporal Index  Development of a cumulative vulnerability index (CVI) for annual atrazine loads –Process-Based Index Model  Predicting the risk of pesticide transport temporally and spatially Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO

3. Grab samples were collected at 21 USGS hydrologic monitoring stations between April 15 and July 15 from 1997 to 1999. Grab samples were collected at 21 USGS hydrologic monitoring stations between April 15 and July 15 from 1997 to 1999. Watershed areas ranged from 210 to 18,000 km 2 ; total area ~56,700 km 2 Watershed areas ranged from 210 to 18,000 km 2 ; total area ~56,700 km 2 Samples were analyzed for 6 commonly used corn and soybean herbicides: acetochlor, alachlor, atrazine, cyanazine, metolachlor, and metribuzin; and 4 triazine metabolites: cyanazine amide (CYAM), deethylatrazine (DEA), deisopropylatrazine (DIA), and hydroxyatrazine (HA). Samples were analyzed for 6 commonly used corn and soybean herbicides: acetochlor, alachlor, atrazine, cyanazine, metolachlor, and metribuzin; and 4 triazine metabolites: cyanazine amide (CYAM), deethylatrazine (DEA), deisopropylatrazine (DIA), and hydroxyatrazine (HA). Herbicide loads computed using linear interpolation of concentration data multiplied by daily discharge. Herbicide loads computed using linear interpolation of concentration data multiplied by daily discharge. Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO

4. Load Calculations Linear Interpolation Date (month/day) Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO

5. Land Use Row Crops Row crop intensity ranged from 22% to 77% of the watershed areas from 1997-99 Row crop intensity ranged from 22% to 77% of the watershed areas from 1997-99 Corn, soybeans, and sorghum account for essentially all row crop production in the region Corn, soybeans, and sorghum account for essentially all row crop production in the region Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO

6. Watershed Vulnerability = Areal Loss on a Treated Area Basis* *Average sum of 6 herbicides and 4 metabolites for 1997 to 1999 4 metabolites for 1997 to 1999 Hydrologic Soil Groups C and D Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO

7. Herbicide Contribution to the Missouri and Mississippi Rivers * Average of 1997-99 Watershed Drainage Area DischargeATRCYNACETALAMETOLMETR -------------------- % of Missouri River at Hermann, MO ------------------------ MO River Tributaries 3.114.2*383730122155 --------------------- % of Mississippi River at Grafton, IL ----------------------- MS River Tributaries 3.43.27.49.12.37.55.440 Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO

8. Claypan Soils Goodwater Creek Watershed Salt River Basin 33,000 km 2 in MO and IL Claypan Characteristics Smectitic mineralogy (high shrink-swell clays) Smectitic mineralogy (high shrink-swell clays) Near surface feature; top 1m of soil profile Near surface feature; top 1m of soil profile Very low saturated hydraulic conductivity (K sat ~1  m/s) Very low saturated hydraulic conductivity (K sat ~1  m/s)

9. Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO Salt River Basin Salt River Basin –~6,500 km 2 in area –Mark Twain Lake is major public water supply in the region  Serves ~42,000 people  EPA 303(d) list for Atrazine until 2003 13 Sites Monitored from 2005-2011 13 Sites Monitored from 2005-2011 –Automated samplers for runoff events –Supplemental grab samples following events and under baseflow –Discharge data from 10 USGS gauged sites –Rating curves to developed at 3 sites Measurements: Measurements: –Discharge –Rainfall –Herbicides (atrazine, acetochlor, metolachlor, metribuzin, selected atrazine metabolites) –Nutrients (total and dissolved N and P) –Sediment Missouri Salt R. Basin Salt River Basin

10. Monitoring encompasses ~4,600 km 2 (71%) of the Salt River basin. Individual watershed areas monitored represent 63 to 94% of the entire watershed areas. In general, the larger watersheds (North, Middle, Elk and South Forks) have more grassland and forested areas and less cropland than the smaller watersheds (44%) (33%) (18%)

11. Drainage area - 77 km 2 Drainage area - 77 km 2 72 km 2 monitored 72 km 2 monitored 1 st – 3 rd order streams 1 st – 3 rd order streams Flat to gently rolling topography (1-3% slopes) Flat to gently rolling topography (1-3% slopes) Claypan soils Claypan soils Restrictive layer generally within top 25 cm of soil surface Restrictive layer generally within top 25 cm of soil surface High runoff potential (HSG C and D) High runoff potential (HSG C and D) Surface water hydrology Surface water hydrology 39-yr record 39-yr record Discharge and Sediment Discharge and Sediment Weather station and rainfall network Weather station and rainfall network Surface water quality Surface water quality 19-yr record 19-yr record Nutrients Nutrients Herbicides Herbicides Goodwater Cr. Watershed Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO

12. Persistent, high atrazine concentrations resulted in exceedance of EPA ecological criteria in 10 of 15 years (1992-2006) Persistent, high atrazine concentrations resulted in exceedance of EPA ecological criteria in 10 of 15 years (1992-2006) Pattern of high atrazine concentrations following spring runoff events suggested that interflow (flow over the saturated claypan) may be the cause Pattern of high atrazine concentrations following spring runoff events suggested that interflow (flow over the saturated claypan) may be the cause

13. Surface Soil Claypan Interflow Alluvial Aquifer Alluvial Aquifer Recharge Stream Channel Surface Soil Claypan Interflow Seep Surface Seep Recharge SummitSide slopeToe slope Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO

14. AtrazineMetolachlor Metolachlor Trend

15. Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO Critical Loss Period Atrazine mass transported (kg) Large runoff events during the critical loss period

16. Small runoff events at the end of the critical loss period Critical Loss Period Atrazine mass transported (kg) 2000 Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO

17. Development of a Cumulative Vulnerability Index DW i = the daily weight; Ev i = runoff event indicator, 0 if the daily discharge 10 mm/d; k = 0.0625/d; first-order rate constant for atrazine soil dissipation kinetics, Ghidey et al.(2005); t = time, in days; and LA = the length of time over which the daily weights were computed, chosen to be 100 days. Daily Weight Cumulative Vulnerability Index CVI = cumulative vulnerability index; LS = the length of the planting season for a given year. DPj = the daily planting progress fraction; daily planting progress was used as a surrogate for herbicide application timing, and this data was obtained from weekly planting progress data for the northeastern crop reporting district (USDA-NASS, 1992-2006).

18. CVI The CVI accounts for: Atrazine application timing Occurrence and timing of runoff events Dissipation of atrazine in soils Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO

20. Where: A cs = area planted to corn and sorghum; A ws = area of the watershed; R = atrazine application rate, assumed to be 1.63 kg/ha for this 4-year period; k = 0.06117 (Ghidey et al., 2010), first- order atrazine soil dissipation rate

21. Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO

22. Youngs Creek – June 2006 Runoff Event Process-Based Index Model for Assessing Risk of Contaminant Transport

23. Flow-Chart of Process-Based Index Model SSURGO – Soil and Landscape Properties by Soil Series (SS) Soil and Hydrologic Weighting Functions Herbicide and Soil Properties Dissipation Functions Sorption – Partition between Solution and Sorbed Phases Degradation – Applied to Solution and Sorbed Compound Landscape Risk Risk SS = Remaining Herbicide(t)/Landscape Risk Three hydrologic transport pathways considered: leaching; solution runoff (SRO); and particle adsorbed runoff (ARO)

24. Watershed Scale Risk of Atrazine Transport in Runoff Youngs Creek Watershed Process-based index model that accounts for claypan hydrology Soil properties used to assess risk (SSURGO) Includes spatial and temporal risk Topsoil depth over claypan and slope are key risk factors Day 30 Low High Transport Risk Day 1 Day 0.1 Day 7 6.02 4.292.92 6.84

25. Identified claypan and restrictive layer soils as being most vulnerable to herbicide transport Identified claypan and restrictive layer soils as being most vulnerable to herbicide transport At the regional-scale, mass input of agricultural chemicals was not the key factor controlling contamination of streams. At the regional-scale, mass input of agricultural chemicals was not the key factor controlling contamination of streams. Within a watershed, the CVI showed that annual variation in atrazine loads was a function of: Within a watershed, the CVI showed that annual variation in atrazine loads was a function of: Atrazine application progress (planting progress as surrogate) Occurrence/timing of runoff events Dissipation of atrazine in soils Process-based index model showed that slope and topsoil depth over the claypan were key landscape factors associated with atrazine transport Process-based index model showed that slope and topsoil depth over the claypan were key landscape factors associated with atrazine transport Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO

26. Provides needed information about the scope and seasonality of contaminant transport, leading to the development of hypotheses and practical solutions Provides needed information about the scope and seasonality of contaminant transport, leading to the development of hypotheses and practical solutions –CVI explains annual variation in atrazine transport  Directly applicable to 3.3 Mha in the Central Claypan Areas and applicable to portions of another 15 Mha within the Corn Belt –Process-based indices can predict risk of pesticide transport across the Corn Belt Monitoring informs policy Monitoring informs policy –Identification of vulnerable areas for targeting conservation practices (NRCS, SWCDs) –Effectiveness of conservation practices (NRCS, SWCDs) –Re-registration of atrazine by EPA  Possible label restrictions for restrictive layer soils Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO