Tool T01 · Travel Time
How old is your water?
Groundwater moves slowly. Pick an aquifer, adjust the distance from recharge, and see how long it took a single drop to reach your tap.
Clean quartz sand — high conductivity, moderate porosity.
20 mi
1 miMemphis → Fayette ~20 mi80 mi
0.0010
Typical Memphis Sand: ~0.001. Steeper = faster flow.
Your water fell as rain about
1,200 yr
ago · through 20 miles of memphis sand
velocity = 0.240 ft/day · 88 ft/yr
200
years ago
American Civil War
1,000
years ago
Norse in North America
2,500
years ago
Ancient Rome founded
The formula
v = K × i / n_eff t = L / v
v = average linear (seepage) velocity · K = hydraulic conductivity · i = hydraulic gradient · n_eff = effective porosity · L = flow path length
This is Darcy's Law for groundwater travel time. It assumes purely advective flow through a homogeneous aquifer — real aquifers have dispersion, heterogeneity, and preferential pathways that make travel times distributions rather than point estimates.
Data:USGS·CAESER (University of Memphis)