BurVal Title valleythe cap of a buried how to quantify vulnerability Reinhard Kirsch & the BurVal working group Author NN1. Author NN2
Vulnerability: sensitivity of groundwater quality to contaminant load contaminant degradation can occur when the infiltration time is high enough
Groundwater age project areas Tyrsting Rødekro Ellerbek Cuxhaven young groundwater high aquifer vulnerability old groundwater infiltration time > 40 y low vulnerability Klaus Hinsby
Groundwater age project areas Tyrsting Rødekro Ellerbek Cuxhaven infiltration time depends on hydraulic conductivity young groundwater old groundwater Klaus Hinsby
sand grains hydraulic conductivity of clayey sediments clay pore filling (water and air) after Scheffer & Schachtschabel 1984
clayey sediments: high infiltration time
clayey sediments: low electric resistivity electric resistivities sand (saturated) till, clay 80 200 Ωm 10 60 Ωm
Distribution of clayey sediments can be mapped resistivity methods electric resistivities sand (saturated) till, clay 80 200 Ωm 10 60 Ωm
large scale resistivity mapping: pulled array technique HydroGeophysics Group, Aarhus
pulled array survey: resistivity 10 15 m bsl Bording valley Mads Kjaerstrup & Peter Erfurt
pulled array survey: resistivity 10 15 m bsl sandy layers clayey layers
no clay cover vulnerability Bording valley Mads Kjaerstrup & Peter Erfurt clay cover
How to quantify vulnerability? characterisation of layers covering the aquifer
How to quantify vulnerability? thickness and hydraulic conductivity of the covering layers
Aquifer vulnerability index AVI (van Stempvoort et al. 1992) hydraulic resistance = thickness / hydraulic conductivity
Aquifer vulnerability index AVI (van Stempvoort et al. 1992) high hydraulic resistance = low vulnerability
Aquifer vulnerability index AVI (van Stempvoort et al. 1992) drillings required!
geophysical approach: integrated electric conductivity IC integrated electric conductivity = thickness electricic conductivity
mapping the electric conductivity SkyTEM HEM-BGR electric conductivity distribution under the flight line
vulnerability Ellerbeker Rinne, HEM-BGR data integrated conductivity IC low IC high vulnerability high IC low vulnerability
vulnerability Ellerbeker Rinne, HEM-BGR data integrated conductivity IC our valley
combination of seismic and SkyTEM protective clay layer Lauenburger Ton
Tyrsting Valley, SkyTEM data clay thickness high medium low vulnerability Klaus Petersen & Sanne Østergaard Nielsen
near surface vulnerability for shallow wells
Near surface test field Hassloh, Ellerbeker Rinne transition from till to sand in the uppermost layers
GPR EM 31, mean value of electric conductivity VES, layered electric resistivity drilling results
GPR EM 31, mean value of electric conductivity VES, layered electric resistivity drilling results
GPR profiles Ingelise Møller
GPR profiles high absorption of Radar signal due to high electric conductivity of till propagation speed of Radar signal water content of the soil hydraulic conductivity
Conclusions Aquifer vulnerability can be quantified by drilling results and resistivity mapping For the calculation of infiltration times we have to link electric conductivity to hydraulic conductivity New project??