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GROUNDWATER TRACING

TECHNIQUESBY,

V.SANATH KUMAR

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INTRODUCTION

The fundamental idea of the tracer technique is simple andclear ,that is, water is marked with the aid of a tracer and

its propagation is followed. They often require fewer assumptions about

hydrogeological conditions than do hypothetical ornumerical simulations.

They can be more reliable.

It was initially developed for the investigation of karstaquifers

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OBJECTIVE

To obtain empirical data related to ground water recharge,

flow direction, flow rates, flow destinations, and flow-

system boundaries.

To identify active conduits.

To analyze the significance of ground water to human life.

Example:- Florida boasts the highest concentration of

springs on the planet. People drank the water without

treatment. But Florida's spring water quality has beendeclining markedly for more than 10 years, with the most

notable problem being increasing nitrates.

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TRACING METHODS

In general, tracing can be divided into two categories: label tracing and

pulse tracing

LABEL TRACING:

Using tracers as labels, allows for identification of specificwaters or plumes.

PULSE TRACING:

Pulse tracing involves sending an identifiable signal through

part of a ground water flow system at concentrationssignificantly above background.

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TYPES OF TRACERS

Ground water tracers can be divided into two types:

natural tracers and

artificial tracers.

NATURAL TRACERS:Naturally occurring isotopes are the most common

natural tracers used in ground water investigations.

These include isotopes of common elements such as

carbon,

oxygen,

hydrogen, and

isotopes of radioactive elements, such as tritium

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1.NATURAL TRACERS

Stable isotopes of oxygen and hydrogen are ideal

tracers of water sources and movement because they

are the two constituents of the water molecule and the

ratios of each element tend to stay constant as long as

the water has not experienced freezing or

evaporation.

Oxygen isotopes include O16, O17, and O18

and hydrogen isotopes include protium (1H),

deuterium (2H), and tritium (3H).

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2.ARTIFICIAL TRACERS

Artificial tracers are those introduced into the groundwater flow system either purposely as part of a designedtracer test or inadvertently as a spill.

To serve as a suitable tracer, a substance must be

nontoxic to humans and the ecosystem.

either absent from the ground water system orpresent at very low, near-constant levels.

soluble in water with the resultant solution havingnearly the same density as water

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2.ARTIFICIAL TRACERS

The artificial tracers used are

Salts(chloride, bromide etc.)

Organic Dyes

CFC (CFC 11,CFC 12 and CFC 13)

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MISCELLANEOUS TRACING

METHODS

Fiber Optic Flourimeter

Analytical Methods

Darcys law

Thiess Equation

Semi-Analytical Methods

Seismic Refraction method

Nuclear method and

Electro-magnetic method.

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ADVANTAGES ANDDISADVANTAGES

Advantages Disadvantages

Application and monitoring can bedesigned in a controlled way. Tracer tests can have overheads interms of cost and time, particularly

when investigating longer or slower

groundwater flow paths.

Tracers can be used to assess the

significance of local geological

features on stream-aquifer

connectivity.

Requires careful planning and design

with some pre-test knowledge of

hydrogeology.

Seepage can be assessed either

qualitatively or quantitatively .

Unanticipated short travel times can

lead to high tracer concentrations being

released to watercourses and potentially

into public water supplies.

Tracers can provide direct evidencefor the movement of water from one

point to another.

Dyes can have complex chemicalinteractions which tend to be pH-

dependent or can be selectively

sorbed with geological material.

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CONCLUSION

Groundwater, in its natural state, containsenvironmental isotopes and conclusions may bedrawn from the distribution variations.

The distribution of the stable isotopes, deuterium and

oxygen-18, of groundwater correlated with averageisotopic data of precipitation define the origin andmovement of subsurface waters.

The use of isotope techniques which complementhydrochemical and hydrogeological studies should beencouraged in both surface water and groundwaterresource development.

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THANK YOU