Artificial tracers in hydrology The use of artificial tracers in hydrogeology is a very ancient technique. It is an effective tool for managing and preserving water resources and protecting the environment.   The increasing demand for hydrological assessments requiring the use of artificial tracers is motivated by two main factors: the challenge of managing water resources and the growth in pollutant shipments.   This new technique means that the fluorescent and saline properties of tracers can be employed to detect the point of origin of water, the location of run-off and hydraulic connections, and to reveal the risks of pollutants spreading.   The results obtained can provide definitive answers to all these problems, helping empower economic and social actors regarding their environmental impact.

Overview of the different tracers

Below, a reminder of the different possible applications and their objectives:

 

Applications	Goals
Abstraction of groundwater/spring water	Delimitation of a supply catch basin
	Check that a determined point is found in the catch basin
	Study of the respective inputs of different waters
Protection areas of under-ground waters	Check of an hydraulic connection between the injection and catch point
	Study of transit times and flow velocity
	Sizing of protection zones
Supply areas of run-offs	Delimitation of feeding areas
	Check that a given location is found in the feeding area of capture
	Knowledge of underground inflows
Risks assessment / Incidents simulation	Check of a hydraulic connection and an installation/ a capture site
	Assessment of the operational timing
	Monitoring of implantation of the supervision point
	Estimate of the size of the impacts during risk assessments
	Simulation of the incidental effect causing infiltration of dangerous liquids in underground waters
Contaminated Sites / Dubious areas	Study of seepage runoff
	Verification of the right place of sampling points downstream from a site
Landfills	Verification of outflows under existing landfills
	Monitoring of seepage paths : meteoric waters flow towards foreseen drainages
	Monitoring of waterproofing of cover layers
	Assessment of sites for new landfills : e.g. verification that a site is away from a supply catch basin
	Verification of the right spot of the surveillance point
Interaction surface waters / ground waters	Detection and localization of seepage or water flows exfiltration sections
	Detection of outflows under water streams
	Identification of drain places of closed lakes
Detection of parasite waters	Identification et quantification of the arrival to a seepage catch coming from a water stream
	Verification of the arrival to a capture of close rainwater infiltrations
Drilling/Piezometer	Control of the representativeness of underground water samples through tagging the drilling fluid
	Control of leak-proof caps dividing various levels of catchment
Expert assessment in case of damages	Verification of the point of entry of waters seeping into a building
Determination of aquifer parameters / Modelling of ground-water flows	Determination hydraulic parameters such as  the  outflow velocity and dispersion coefficient
	Calculation of the storing volume from empty volumes allowing outflow
	Adapt and validate outflow models and mass transport in solution form
	Verifications of outflows directions predicted with respect to observed directions