GROUNDWATER VULNERABILITY MAPS FOR PESTICIDES FOR FLANDERS

GROUNDWATER VULNERABILITY MAPS FOR PESTICIDES FOR FLANDERS

Jef Dams, Ingeborg Joris*, Jan Bronders, Aäron TrippaerDirk Vanden Boer, Griet Heuvelmans

Contact: *Ingeborg.Joris@vito.be

INTRODUCTION

» VMM (Flanders Environment Agency) is responsible forwater quality monitoring and status reporting in Flanders (N-Belgium)

» Frequent detects of PPPs and metabolites in (shallow) groundwater

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2014

Pesticides in Flemish groundwater

INTRODUCTION

» Develop a tool to calculate groundwater vulnerability maps for PPPs» Substance-specific» As much as possible process-based (incl. saturated zone)» Making optimal use of available datasets and models» At different scales (Flanders and local)

» Use of this tool: 1. support monitoring strategies2. management of sensitive zones such as drinking water capture zones

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Aim of the study

INTRODUCTION

Definitions groundwater vulnerability

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Factors taken into account in assessing vulnerability

Europe US-EPA

Subsoil characteristics Intrinsic vulnerability Aquifer sensitivity or intrinsic susceptibility

Subsoil characteristics + substanceproperties

Specific vulnerability

Subsoil characteristics + substanceproperties + application

Risk Aquifer vulnerability

Groundwater vulnerability NRC (1993): “the tendency of or likelihood for contaminants to reach a specific positon in the groundwater system after introduction at some location above the uppermost aquifer”

Vulnerability saturated zone:- Fast spreading lower concentrations- Low spreading higher concentrations

OVERVIEW METHODOLOGY

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Tool for vulnerability maps

Flanders-scale Local-scale

Hybrid method Process based method

Leaching calculations Leaching calculations

Indices for saturated zoneFlowpath calculations

Simulation scales

METHODOLOGYLEACHING

» Hydrological model SWAP» Pesticide fate model PEARL

Leaching to groundwater - GeoPEARL

Groundwater depth(4 classes)

Soil map(536 units)

Land-use

METHODOLOGYFLANDERS-SCALE

Hybrid approach

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Leaching concentrations

Indices for saturated zone

Thickness of phreatic layer

Conductivity of phreatic layer

P90-concentrations over 20-yr period

+

» Leaching» process-based calculations

(GeoPEARL)» Saturated zone

» Indices

METHODOLOGYLOCAL SCALE

» Leaching concentrations with time from GeoPEARL

» Input to 1D-transport calculations along flowlines with F-LEACH (analytical solution of CDE taking into account sorption and degradation)

» Concentration at the receptor (screen) is calculated as a function of time

» For each of the grid cells in the capture zone 3 assessments are made:

1. Max. conc. at the receptor relative to applied dose2. Time of breakthrough at the receptor3. Ratio of mass reaching the receptor to mass

applied

» Vulnerability map for the capture zone indicating the critical zones contributing most to the PPP load in the well

Process based approach

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1D-transport alongflowline with

sorption/degradation(analytic)

GeoPEARL

MODPATH

(Brouyère et al., 2011)

METHODOLGYIMPLEMENTATION

Python tool

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RESULTS

» Example:» Vulnerability of phreatic groundwater in Flanders for pesticide x» Settings: properties of pesticide x (molmas, Koc, DT50,..) and typical application dose and

time, applied on entire Flanders as if maize

Flanders-scale

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Conc

.[µ

g/l]

P90Leaching concentration

groundwater-vulnerability class

Vuln

erab

ility

Cl

ass

[-]

RESULTS

» Example:» vulnerability of pesticide x for a drinking water well in Western part of Flanders» Settings: pesticide properties and typical application data, applied on the whole entire

withdrawal area as if maize

Locale-scale

11 Pumping wells

Max. conc. relative to applied dose

Breakthrough time Ratio of mass reaching the receptor to mass applied

CONCLUSIONS

» Specific vulnerability for PPPs in Flanders/local scale to assist monitoring strategies

» Due to data constrains hybrid approach at Flanders-scale

» Local scale process based approach

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More informationIngeborg Joris ingeborg.joris@vito.beJef Dams jef.dams@vito.be

VITO, Environmental Modelling UnitTeam Water management & TechnologyVITO NV | Boeretang 200 | B-2400 Mol | Belgium