2. Artificial Tracers
they can be used to evaluate the extent to which aquifers interact with surface water features, providing information on groundwater flow paths, travel times, velocities, dispersion, flow rates and the degree of hydraulic connection.
they should have low toxicological impact.
This differs from natural tracers methods which rely on the measurement and interpretation of background concentrations of the chemical constituents of water, such as major ions, stable or radioactive isotopes.
Carbonate, organic carbon and hydrocarbon
Bromine, lithium and boron
There are two basic types of dye tracer tests:-
1.Qualitative Tracer Tests.
2. Quantitative Tracer Tests.
Possible applications of the tracer technique in different aquifer types
•Regional surveys of groundwater flow
•Establishment of conceptual models of karst systems
•Detection of karstic networks
•Regional investigations of groundwater flow
•Delimitation of catchments (containment areas)
•Delimitation of contaminant leakage zones
Hillslope groundwater and fractured aquifers
•Detection of flow paths in hard rocks
•Investigation of water bearing structures (e.g. joints, fractures and layering)
Main focuses of tracer investigations in hydrogeology
•Catch works (wells, springs)
•Groundwater protection zones
•Risk assessments, simulation of hazards
•Ancient waste deposits, contaminated sites
•Interaction between ground and surface water
•Evidence of “foreign water”
•Determination of aquifer parameters/ groundwater modelling
•Expertise in case of damage
•Boreholes, groundwater observation network
Advantages and Disadvantages
•Groundwater, in its natural state, contains environmental isotopes and conclusions may be drawn from the distribution variations.
•The distribution of the stable isotopes, deuterium and oxygen-18, of groundwater correlated with average isotopic data of precipitation define the origin and movement of subsurface waters.
•Radioisotopes, such as tritium, provide valuable information on recent recharge whereas carbon-14 data show slow-moving groundwater.
•The use of isotope techniques which complement hydrochemical and hydrogeological studies should be encouraged in both surface water and groundwater resource development.