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Robert N. Lerch

Combining Long-Term Monitoring with Identification of Vulnerable Areas in Restrictive Layer Watersheds. Robert N. Lerch Soil Scientist, USDA -ARS Cropping Systems & Water Quality Research Unit, Columbia, MO. ARS Scientists : E. E. Alberts , C. Baffaut , W. W. Donald, F. Ghidey,

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Robert N. Lerch

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  1. Combining Long-Term Monitoring with Identification of Vulnerable Areas in Restrictive Layer Watersheds Robert N. Lerch 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. Presentation Overview • 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 • Direct Observation • Areal herbicide loss rates on a mass per treated areabasis • 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. Regional-Scale Monitoring • 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 km2; total area ~56,700 km2 • Samples were analyzed for 6 commonly used corn and soybean herbicides: acetochlor, alachlor, atrazine, cyanazine, metolachlor, and metribuzin; and 4 triazinemetabolites: cyanazine amide (CYAM), deethylatrazine (DEA), deisopropylatrazine (DIA), and hydroxyatrazine (HA). • 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 CalculationsLinear 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 UseRow Crops • 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 • 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 Watershed Vulnerability = Areal Loss on a Treated Area Basis* Hydrologic Soil Groups C and D *Average sum of 6 herbicides and 4 metabolites for 1997 to 1999 • 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 • Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO

  8. Extent of Claypan Soils Major Land Resource Area 113 Central Claypan Areas 33,000 km2 in MO and IL Salt River Basin Claypan Soils Goodwater Creek Watershed • Claypan Characteristics • Smectitic mineralogy (high shrink-swell clays) • Near surface feature; top 1m of soil profile • Very low saturated hydraulic conductivity (Ksat ~1 mm/s) • Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO

  9. Salt River Basin ~6,500 km2 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 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: Discharge Rainfall Herbicides (atrazine, acetochlor, metolachlor, metribuzin, selected atrazine metabolites) Nutrients (total and dissolved N and P) Sediment Salt R. Basin Missouri Basin-Scale Monitoring Salt River Basin • Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO

  10. Land-Use Monitored Area In general, the larger watersheds (North, Middle, Elk and South Forks) have more grassland and forested areas and less cropland than the smaller watersheds • Monitoring encompasses ~4,600 km2(71%) of the Salt River basin. • Individual watershed areas monitored represent 63 to 94% of the entire watershed areas. (18%) (44%) (33%)

  11. Watershed-Scale MonitoringGoodwater Creek Experimental Watershed (GCEW) • Drainage area - 77 km2 • 72 km2 monitored • 1st – 3rd order streams • Flat to gently rolling topography (1-3% slopes) • Claypan soils • Restrictive layer generally within top 25 cm of soil surface • High runoff potential (HSG C and D) • Surface water hydrology • 39-yr record • Discharge and Sediment • Weather station and rainfall network • Surface water quality • 19-yr record • Nutrients • 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. Atrazine Concentrations In Goodwater Creek • 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 • Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO

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

  14. Goodwater Creek - Trends in Herbicide Loads Atrazine Metolachlor • Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO Metolachlor Trend

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

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

  17. Daily Weight DWi = the daily weight; Evi = runoff event indicator, 0 if the daily discharge <10 mm/d and 1 if daily discharge was >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. 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). What Factors Control the Annual Variation in Atrazine Load? Development of a Cumulative Vulnerability Index • Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO

  18. Cumulative Vulnerability Index • The CVIaccounts 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

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

  20. Generalized Cumulative Vulnerability Index Where: Acs = area planted to corn and sorghum; Aws = 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 • Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO

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

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

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

  24. 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 Transport Risk High Low Day 0.1 Day 1 Day 7 Day 30 Watershed ScaleRisk of Atrazine Transport in RunoffYoungs Creek Watershed 6.84 6.02 4.29 2.92

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

  26. Value of Monitoring Data • 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 • 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

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