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

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

‘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

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

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

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

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

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

Sandy aquifer, Kirkwood-Cohansey formation

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

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

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

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

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

Locust Grove, Delmarva

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

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

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

Complex systems La Bolle, 2006

La Bolle, 2006