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Department of Hydrology and Water Resources Management - Fohrer et al. -1-
SWAT conference Toulouse 2013 16.11.2012
Assessement of the environmental fate of the herbicides Metazachlor & Flufenacet with the SWAT model
A. Dietrich, U. Ulrich and N. Fohrer
Christian-Albrechts-Universität zu Kiel Institut für Natur- und Ressourcenschutz
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Project background
Development of management options to reduce herbicide loads
in a rural watershed
funded by the State Agency for Agriculture,
Environment and Rural Areas
(LLUR) from 2010 - 2012
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Output
Calibration phase
Water balance
Herbizide fate
M o d e l a p p l i c a t i o n
Management Impact of pcp
pattern
mm/d Basis dry moist
Ø 3.5 0.1 8.9
Range (0-33) (0-2) (0-71)
Re d u c t i o n o f h e r b i c i d e e n t r y i n w a t e r b o d i e s
scenarios
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Study Area – Rural lowland catchment Kielstau
Low hydraulic gradients, near-surface groundwater
• 2 % Slope on average
High potential for water retention
• Riparian wetlands and interaction between
groundwater & surface water
• Depression areas
• 1 Lake
Anthropogenic influences
• Fertilizer and pesticides application
• 5 sewage treatment plants
• River regulations
• Drainages
27-79 m ASL
56 % arable land 30 % grassland / fallow 9 % forest
50 % Stagnic Luvisols 38 % drained area (FOHRER ET AL. 2007)
Area: 50 km²
Mean T: 8.2 °C
PCP: 870 mm/a
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Setup of SWAT 2009
stream
gauge
Subbasins: 17 HRU: 938 Thresholds: (0% land use, 20 % soil, 20 % slope)
Topography (DEM 5x5 m)
Land use (mapping in 2008)
Soils (1:200.000)
Climate (1993 – 2009)
Precipitation, Wind, Humidity, Temperature
Calculating ALPHA_BF (Baseflow Program; ARNOLD ET AL. 1995)
Initial Setup
LVERMA (2005)
GOLON (2009)
BGR (1999)
DWD (2010)
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Input Input Drain
Input Depression
Drain input: - Artificial drained areas calculated after FOHRER ET AL. (2007) - Via soil properties (Ksat, AWC)
Initial Setup
KIESEL ET AL. (2010)
Depression input: - After the approach by KIESEL ET AL. (2010) - Input as Wetlands
Digitalised drained area
Simulated drained area (FOHRER ET AL. 2007)
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Other Rape
Winter cereals
Input Initial Setup
RAPE WWHT WBAR
Maize
RAPE WWHT WWHT
POTA WWHT WBAR
BARL Maize
Land use (mapping in 2008, GOLON 2009)
Input typical Crop Rotations Input Drain
Input Depression
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Input Initial Setup
Input typical Crop Rotations
Input Pesticides Input Drain
Input Depression
• Measurements at the outlet by ULRICH 2010, LLUR 2010
MET: 2008 (09/01-11/30/2008)
FLU: 2009 (09/24-12/05/2009)
• Farmer interviews:
- application date, products
- application amount
- MET: 52 % of rape fields
- FLU: 43 % of winter cereal fields
1998 2003 2009 Discharge Metazachlor
Flufenacet
Warm-up Calibration period Validation period
2006
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S e l e c t e d h e r b i c i d e p r o p e r t i e s
Metazachlor Flufenacet
Water solubility [mg/l] 450 56
Sorptivity [Koc ml/g] 220 354
Persistence [DT50soil d] 9 30
Persistence [DT50Waterd] 216 54
crops Oil seed rape
(RAPE)
Winter grain
(WHHT, WBAR)
Simulation year
(Sept until Nov/Dec) 2008 (24 d) 2009 (36 d)
Application amount 0.7 kg/ha 0.36 kg/ha
Mobile, low sorptivity in soil Moderately mobile and
medium sorptivity
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Discharge simulation
Validation period
calibration period
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Sensitivity of pesticide properties
Soil absorption coefficient
Wash off fraction
Half live foliage
Half live soil
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Sensitivity of pesticide properties
Application efficiency Percolation efficiency
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Metazachlor loads
NSE: 0.68, r²=0.62
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Flufenacet loads
NSE: 0.13, r²=0.51
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Analysis of potential entry pathways
Flufenacet entry pathways
Metazachlor entry pathways
Surface runoff
Tile drainage flow
lateral flow
groundwater flow
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Erosion assessment
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Output
Calibration phase
Water balance
Herbizide fate
B M P A n a l y s i s
Management Impact of pcp
pattern
mm/d Basis dry moist
Ø 3.5 0.1 8.9
Range (0-33) (0-2) (0-71)
Re d u c t i o n o f h e r b i c i d e e n t r y i n w a t e r b o d i e s
scenarios
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Management restrictions
• 1. min. distance to stream at application:
– 5 m, 10 m, 20 m if slope > 1.75 %
• 2. drained areas
– a. only half of the appl. amount on drained areas
– b. no application on drained areas
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Basis run Distance to stream Appl. On Tile Drainage
5 m 10 m 20 m 1/2 Drain No Drain
True pcp 15.69 12.86 10.04
(0-83.76) (0-83.76) (0-83.76) (0-83.76) (0-69.67) (0-67.82)
moist 31.68 19.73 17.01 13.66 26.29 20.93
(0-417.67) (0-212.66) (0-165.83) (0-108.39) (0-349.36) (0-280.93)
dry 0.42 0.42 0.42 0.42 0.42 0.42
(0-36.19) (0-36.19) (0-36.19) (0-36.19) (0-36.19) (0-36.19)
MET-concentration (ng/l) | pcp regime and legal restrictions
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Conclusion: pesticide project
Satisfying representation of herbicide fate and BMPs
Weather conditions during/after application are essential for effectiveness of BMP
under moist conditions application on drained areas should be restricted and max. distance to stream kept
under dry conditions no visible effect of BMP for MET
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Conclusion: SWAT model
Distribution of application time is crucial
AP_EF and PERCOP are very sensitive
Herbicide properties have low sensitivities
No degradation in groundwater so far
No consideration of transformation product
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T h a n k y o u f o r y o u r a t t e n t i o n .
Kielstau (Springer, 2007)
Assessment of the Environmental Fate of the Herbicides Flufenacet
and Metazachlor with the SWAT Model
Nicola Fohrer, Antje Dietrich, Olga Kolychalow and Uta Ulrich
Journal of Environmental Quality 2013
0: 0: - doi:10.2134/jeq2011.0382
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Scenarios: reduction of herbicides on drained areas