1. Tracer Modeling Two goals:
more reasonable interpretation of tracer data in terms of travel time
Calibration target for groundwater flow and transport models

2. Various modeling approaches
‘lumped parameter’ models
1- dimensional vertical or horizontal advection/ dispersion models
MODFLOW/MODPATH, no dispersion
3D advection/dispersion models
calibration target:
concentration fields
residence time, e.g. 3H/3He ages

3. ‘Lumped parameter’ models
e.g. exponential model
Qin = Qout
Residence time:  = V/Qin
Weighting function:
t-1 exp(-t/t)
Maloszewski and Zuber, 1982, 1983

4. ‘Lumped parameter’ models
Example: Exponential model
Maloszewski and Zuber, 1982, 1983

5. 1-dimensional vertical or horizontal advection/dispersion models
v=1 m/y
Schlosser et al., 1989; Solomon and Sudicky, 1991,
Solomon et al., 1993; Ekwurzel et al., 1994, Stute et al., 1997

6. Example: Sturgeon falls
Determination of:
gw recharge rate
molecular diffusion and mechanical mixing coefficient
Solomon et al., WRR, 29 (1993) 2951

7. Two tracers in comparison
Delmarva peninsula
1 dimensional model
Ekwurzel et al., 1994

8. Calibration of groundwater models
Targets:
hydraulic head
streamflow gain/losses
groundwater flow velocities
tracer concentration fields
residence times

9. Sandy aquifer,
Kirkwood-Cohansey formation

11. 3H/3He Tracer data
Szabo et al., WRR, 32 (1996) 1023

12. 3H/3He and CFC ages
Szabo et al., WRR, 32 (1996) 1023

13. conceptual: numerical:
Szabo et al., WRR, 32 (1996) 1023

14. Szabo et al., WRR, 32 (1996) 1023

15. Excellent agreement between model and tracer data
Szabo et al., WRR, 32 (1996) 1023

16. Locust Grove, Delmarva

19. Reilly et al., WRR,
30 (1994) 421

20. No dispersion necessary!
Locust Grove, Delmarva
No dispersion necessary!
Reilly et al., WRR,
30 (1994) 421

21. 3H/3He ages as calibration targets Example: buried-valley aquifer, Ohio
Sheets et al. WWR, 34 (1998) 1077

22. Complex systems
La Bolle, 2006

23. La Bolle, 2006