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)

nfohrer@hydrology.uni-kiel.de

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

Department of Hydrology and Water Resources Management - Fohrer et al. -23-

Scenarios: reduction of herbicides on drained areas