Vulnerability: sensitivity of groundwater quality to contaminant load

Transkript

1 BurVal Title valleythe cap of a buried how to quantify vulnerability Reinhard Kirsch & the BurVal working group Author NN1. Author NN2

2 Vulnerability: sensitivity of groundwater quality to contaminant load contaminant degradation can occur when the infiltration time is high enough

3 Groundwater age project areas Tyrsting Rødekro Ellerbek Cuxhaven young groundwater high aquifer vulnerability old groundwater infiltration time > 40 y low vulnerability Klaus Hinsby

4 Groundwater age project areas Tyrsting Rødekro Ellerbek Cuxhaven infiltration time depends on hydraulic conductivity young groundwater old groundwater Klaus Hinsby

5 sand grains hydraulic conductivity of clayey sediments clay pore filling (water and air) after Scheffer & Schachtschabel 1984

6 clayey sediments: high infiltration time

7 clayey sediments: low electric resistivity electric resistivities sand (saturated) till, clay Ωm Ωm

8 Distribution of clayey sediments can be mapped resistivity methods electric resistivities sand (saturated) till, clay Ωm Ωm

9 large scale resistivity mapping: pulled array technique HydroGeophysics Group, Aarhus

10 pulled array survey: resistivity m bsl Bording valley Mads Kjaerstrup & Peter Erfurt

11 pulled array survey: resistivity m bsl sandy layers clayey layers

12 no clay cover vulnerability Bording valley Mads Kjaerstrup & Peter Erfurt clay cover

13 How to quantify vulnerability? characterisation of layers covering the aquifer

14 How to quantify vulnerability? thickness and hydraulic conductivity of the covering layers

15 Aquifer vulnerability index AVI (van Stempvoort et al. 1992) hydraulic resistance = thickness / hydraulic conductivity

16 Aquifer vulnerability index AVI (van Stempvoort et al. 1992) high hydraulic resistance = low vulnerability

17 Aquifer vulnerability index AVI (van Stempvoort et al. 1992) drillings required!

18 geophysical approach: integrated electric conductivity IC integrated electric conductivity = thickness electricic conductivity

19 mapping the electric conductivity SkyTEM HEM-BGR electric conductivity distribution under the flight line

20 vulnerability Ellerbeker Rinne, HEM-BGR data integrated conductivity IC low IC high vulnerability high IC low vulnerability

21 vulnerability Ellerbeker Rinne, HEM-BGR data integrated conductivity IC our valley

22 combination of seismic and SkyTEM protective clay layer Lauenburger Ton

23 Tyrsting Valley, SkyTEM data clay thickness high medium low vulnerability Klaus Petersen & Sanne Østergaard Nielsen

24 near surface vulnerability for shallow wells

25 Near surface test field Hassloh, Ellerbeker Rinne transition from till to sand in the uppermost layers

26 GPR EM 31, mean value of electric conductivity VES, layered electric resistivity drilling results

27 GPR EM 31, mean value of electric conductivity VES, layered electric resistivity drilling results

28 GPR profiles Ingelise Møller

29 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

30 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??