4 Tracer Tests

Question 1

Tracer tests

Answer 1

Tracer tests serve a multitude of purposes, e.g. to determine:

-flow velocity of groundwater (maximum, average etc., dispersion)

• void volume (porosity) of aquifers
• reactive properties of aquifer matrix (reactive tracers)

-interconnection of surface waters (e.g. rivers, springs) and groundwater, especially in Karst regions

→ delineation of capture and protection zones

Question 2

Tracer tests: chemical requirements

Answer 2

• Non toxic (env friendly)
• Easily detectable (analysis not complicated)
• Detectable at low concentration
• Low reactivity (e.g. adsorption to rock material)
• Cheap and availabe
• Well soluble in water (or transportable by water)

Question 3

Tracer tests: typical chemicals

Answer 3

fluorescent dyes

salts

stable isotopes

short-lived radio-nuclidies

particles

Question 4

Dispersion: background

Answer 4

Pore size

Path length

Friction in pore