Groundwater vulnerability maps for pesticides for Flanders

2016 - 2017
VMM (Griet Heuvelmans)

Pesticides are increasingly being detected in shallow groundwater and and are one of the main causes of the poor chemical status of phreatic groundwater bodies in Flanders. There is a need for groundwater vulnerability maps in order to design monitoring strategies and land-use strategies for sensitive areas such as drinking water capture zones. This project focuses on the development of generic vulnerability maps for pesticides for Flanders and a tool to calculate substance-specific vulnerability maps at the scale of Flanders and at the local scale. The generic vulnerability maps are constructed using an index based method in which maps of the main contributing factors in soil and saturated zone to high concentrations of pesticides in groundwater (organic matter content, texture, groundwater depth, thickness and conductivity of the phreatic layer) are classified and overlain. Secondly a tool is developed that calculates substance-specific vulnerability maps for Flanders or at the local scale combining a process-based leaching model GeoPEARL with vulnerability indices for the saturated zone or combining them with flowline calculations of pesticide transport in the saturated zone. The tool is validated in a case-study focusing at a drinking water production site in West Flanders.