HYDROGEOLOGY

1. WHAT IS THE DEFINITION OF THE AQUIFER? WHAT ARE THE PRINCIPAL AQUIFER ROCK TYPES? PLEASE GIVE
EXAMPLES FOR THE VALUES OF HYDRAULIC CONDUCTIVITY IN CASE OF DIFFERENT ROCK TYPES. WHAT IS THE
DEFINITION OF THE STORAGE COEFFICIENT?

a. AQUIFER
It is a rock or sediment in a formation, group of formation or part of formation that is saturated and sufficient
permeable to transmit economic quantities of water to well and springs. It is the geologic unit that can store and
transmit water at rate fast enough to supply reasonable amounts to well.

b. PRINCIPAL AQUIFER ROCK TYPES:

Gravel, sand and sandstone, alluvium, cavernous limestone, fissured marble, fracture granite, weathered gneiss and
schist, heavily shattered quartzite, vesicular basalt, slate.

c. VALUES OF HYDRAULIC CONDUCTIVITY:

d. STORAGE COEFFICIENT:

The unconsolidated porous media aquifers have physical properties based on their grain size (solid matrix) distribution
that drives the hydraulic aspects of groundwater flow through the void space between them. Porosity, permeability,
and compressibility are the essential properties when aquifer behaviour evaluation is consider (LaMoreaux et al.,
2009).

a. Porosity ( )
It is defined as the void volume per total volume of soil sample. It has varieties.
The total porosity which is the volume of all void space in the sample
The effective porosity which is the interconnected void space of the sample (LaMoreaux et al., 2009).
=
= porosity (expressed as a percentage)
Vv = volume of voids
Vt = total volume of soil sample

Primary porosity is heritage of geological origin of the porous media, it depends on grain size distribution, shape of
the grain, mineral composition, packing arrangement, and cementation processes.
Secondary porosity is generated by geological process as dissolution, tectonism, or diagenesis; given as results
fractures, joins, cavities or recrystallization of the rock; disturbing the primary property.

Aquifer matrix Dry Bulk Total Porosity Effective

Clay 1.00 –Density
2.00 0.34 – 0.60 0.01 Porosity
– 0.2
Peat -- -- 0.3 – 0.5
Silt
Glac -- 0.34 – 0.61 0.01 – 0.3
Medium sand 1.37 – 1.81 -- 0.15 – 0.3
Coarse sand 1.37 – 1.81 0.31 – 0.46 0.2 – 0.35
Gravelly sand 1.37 – 1.81 -- 0.2 – 0.35
M
 Medium gravel 1.36 –2.19 -- 0.15 – 0.35
Coarse gravel 1.36 –2.19 0.24 – 0.36 0.1 – 0.25
Sandstone 1.60 –2.68 0.05 – 0.30 0.1 – 0.4

b. Hydraulic conductivity
Note that hydraulic conductivity, which is a function of water viscosity and density, is in a strict sense a function of
water temperature; however, given the small range of temperature variation encountered in most groundwater
systems, the temperature dependence of hydraulic conductivity is often neglected.

Hydraulic conductivity is the rate of flow under a unit hydraulic gradient through a unit cross-sectional area of aquifer.

In more strict hydrogeological description, where the fluid is within a specific rock body, Darcy introduce a simplified
equation to describe the key parameter of hydraulic conductivity (k)

=
k = hydraulic conductivity (L/T)
Q = flow rate through porous medium (L3/T)
A = cross-sectional area through which flow occurs (L2)
L = length of porous medium through which flow occurs (L)
H = fluid head loss along L (L)

The soil characteristics that control the hydraulic conductivity are particle size, porosity and bulk density. This
parameter can be defined by
- Laboratory methods as: Constant head and falling head
- Field methods as: test basis.

The test basin method consist on isolate a column of soil, ensure the saturation of the colum and apply a constant
head water at rate P.

If the hydroulic conductivity is on unsaturated soil, the field method is call ring infiltrometer and in laboratory is
used the instantaneous profile method.

c. Transmissivity (T)
It is a relevant parameter that describe the rate as a fluid is transmitted through a unit of width of and aquifer at a
unit hydraulic gradient calculated as the product of the aquifer thickness and its hydraulic conductivity.
Transmissivity is the rate of flow under a unit hydraulic gradient through a unit width of aquifer of thickness m (opening
B).

=
T = Transmissivity (L2/T)
k = hydraulic conductivity (L/T)
b = thickness of the layer (L)
 d. Compressibility (α)
The compressibility of the porous media is defined as the coefficient between differential volume of the of the body
and the initial volume multiplied by the differential of the pressure. This parameter is a function of the thickness of
the aquifer, and make reference not only to the formation, but the fluid too.
α=
α = compressibility of aquifer (P)
δv = differential volume V (L3)
δp = differential pressure P (P)
V = Initial volume (L3)

The importance of compressibility is the existing relation between volumetric deformation, the effective stress load
at any point in the aquifer, and the prevention of consolidation of the layer.

e. Storage coefficient (S)

It is the volume of water released (liberado) from
storage per unit decline in hydraulic head in the
aquifer, per unit area of the aquifer. It is
dimensionless quantity which fluctuate between 0
and the effective porosity of the aquifer.

S= = +
ℎ

Vw = volume of water released from storage (L3)

Ss = specific storage
Sy = the specific yield
b = the thickness of aquifer (L)

f. Specific yield (Sy) / unconfined

It is the amount of water that can be extracted under
gravitation force, and specific retention cannot be separated from the grain surfaces because it is attached by adhesion
forces. The same yield from unconfined aquifers can be obtained with less head changes over less-extensive areas
when compared to confined aquifers.

n=Sy+Sr
n is total porosity [dimensionless],
Sy is specific yield [dimensionless]
Sr is specific retention [dimensionless], the amount of water retained by capillary forces during gravity drainage of an
unconfined aquifer.

g. Specific storage (Ss)

It is the volume of water that a unit volume of aquifer takes into storage or releases from storage under a unit decline
in hydraulic head. It shows the ability of an aquifer to store water.

Ss=ρg(α+nβ)
ρ is mass density of water (= 1000 kg/m³) [M/L³],
g is gravitational acceleration (= 9.8 m/sec²) [L/T²],
α is aquifer (or aquitard) compressibility [T²L/M],
n is total porosity [dimensionless]
β is compressibility of water (= 4.4×10-10 m sec²/kg or Pa-1) [T²L/M].

2. WHAT IS HYDROGEOLOGY? PLEASE DESCRIBE THE DARCY-EQUATION AND ITS COMPONENTS. WHAT ARE THE
ELEMENTS OF HYDROLOGIC CYCLE? PLEASE DESCRIBE THE GLOBAL HYDROLOGICAL (WATER BUDGET)
EQUATION.
 a. HYDROGEOLOGY
It is the study of the law governing the movement of subsurface water. Addresses the occurrence, distribution,
movement and chemistry of the interrelationships of geologic materials and processes with subsurface water. Part of
hydrology that deals with the occurrence, movement and quality of water beneath the Earth’s surface.

b. DARCY’S LAW

a. Hydraulic gradient: It represent the difference in the water level of the column of fluid (∆ℎ) of two point
separated a determined distance. The negative sing means the flow will happen from high to low elevation.
∆ℎ
=−
∆

b. Darcy’s Law
Darcy found that the rate of water flow through a bed of a “given nature” is proportional to the difference in the
height of the water between the two end of the filter beds and inversely proportional to the length of the flow path.
He also determined that quantity of floe is dependent upon the nature of the porous medium

∆ℎ
=−
∆

q_specific discharge or velocity (L/T)

Q_discharge through the cross-sectional area (L3/T)
A_cross-sectional area (L2)
k_hydraulic conductivity (L/T)
Δh_change in height of the water or hydraulic head (L)
ΔL_flow length, distance between hydraulic heads (L)
∆
_hydraulic gradient [i] (-)
∆

Then, Darcy’ law (Equation 3) is considering the base of the equation of motion to obtain flow between the void space,
called as Darcy’s velocity (V ). (Specific discharge)
ℎ
V = =−

c. Hydraulic head of the reservoir:

h= +
where
h = head lose or piezometric head
z = elevation above some datum level (L)
p = pressure of the fluid (P)
= density (M/L3)
= gravity acceleration (L/T2)

d. Total head, is the expression of the total mechanical energy per unit weight of
fluid at a point within a porous medium domain calculated by:

h = + +
2
where
= averaging coefficient
V = intrinsic velocity (L/T)

c. WATER CYCLE

a. Evaporation: When water passes from the liquid to the vapor state, the result is evaporation.

The absolute humidity of a given air mass is the mass of water (g) per cubic meter of air.
The saturation humidity, maximum amount of moisture than air can hold, it is directly proportional to the
temperature of the air.

The relative humidity for an air mass is the percent ratio of the absolute humidity to the saturation humidity for
the temperature of the air mass. As the relative humidity approaches 100 % evaporation ceases.

The dew point for an air mass is the temperature at which condensation will begin.

Free-water evaporation is measured quite simply by using shallow land pans. Records are kept of the daily depth of
water, the volume of water added to replace evaporated water, and the daily precipitation into the pan.
Pan coefficient: a value less than 1. A land pan will be warmed much more readily than the surface waters. The reason
is the difference between the water depth in the pan and the depth of the surface layer of reservoir water.

b. Transpiration: Plants are continuously pumping water from the ground into the atmosphere through a
process called transpiration. Only a small percent (<1%) of the water is used by the plant, the remained part is
transpired to the atmosphere.

Phytometer is a container partially filled with soil. Transpiration causes an increase in the humidity, which can be
measured in the air around the plant.

c. Evapotranspiration: The sum of transpiration, evaporation from free-water, and soil moisture evaporation.
Under field conditions it is not possible to separate them totally, and it has little importance.

The term potential evapotranspiration is introduced by Thornthwaite as equal to „the water loss, which will occur if
at no time there is a deficiency of water in the soil for the use of vegetation. He recognized an upper limit to the
amount of water an ecosystem will lose by evapotranspiration. There is often not sufficient water available from soil
water, the term actual evapotranspiration is used to describe the amount of evapotranspiration that occurs under
field conditions.

Evapotranspiration can be measured directly using a lysimeter – a large container holding soil and plants. It should
design so that they accurately reproduce the soil type and profile, moisture content and type and size of vegetation
of the surrounding area. They should be buried so that the soil surface is at the same level inside and outside the
container.

d. Precipitation: For precipitation to occur several conditions must be meet:

- A humid air mass must be cooled to the dew-point temperature,
- Condensation or freezing nuclei must be present,
- Droplets must coalesce to form raindrops,
- The raindrops must be of sufficient size when they leave the clouds to ensure that they will not totally
evaporate before they reach the ground.

For measurements:
- Rain gauges: open containers, with different diameters
- The height of water is read and the water is emptied once a day
- Automatically recording gauges.
- The height of water column in mm is measured.
 e. Infiltration process: Is the process of water percolating through the soil and into permeable rocks. Rainfall
reaching the land surface can infiltrate into a pervious soil, which has a finite and variable capacity to absorb
water.

The infiltration capacity varies not only from soil to soil, but also is different for dry versus moist conditions in
the same soil. If the soil is initially dry, the infiltration capacity is high. Infiltration capacity will reach a more or
less constant value, an equilibrium value.

f. Surface runoff: is the horizontal water flows over the land into a stream.
g. Recharge: Is the amount of water which infiltrate into ground and it is incorporated to GW flow
 h. Seasonal and other impacts for shallow groundwater:
- Rainfall variability: Annual residual: The average rainfall is subtracted from the actual rainfall for a particular year
added to the sum of all previous residuals. Summing the residuals will give an indication of periods of time when
rainfall is above or below average. These are climatic cycles.
- Land use impact on recharge: It will limit the recharge rate by infiltration on the soil in dependence of the the
land. The recharge rate will be different in an annual pasture, crop, perennial pasture or native forest.
- Unsaturated zone storage: The soil moisture changes according with the soil type. Some soils can storage more
or less adhesion water based in its specific surface characteristic.

d. WATER BUDGET
Inflow = outflow - changes in storage

The equation is time dependent, and any differences between rates of inflow and outflow in a hydrologic system will
result in the change in the volume water stored in the system.

3. WHAT IS THE DEFINITION OF GROUNDWATER BASIN? PLEASE DESCRIBE THE HUBERT’S MODEL AND THE
TOTH’S FLOW MODEL. PLEASE DESCRIBE THE LOCAL, MEDIUM AND REGIONAL FLOWS IN A BASIN. PLEASE DESCRIBE
THE GHYBEN-HETRZBERG EQUATION IN CASE OF SEA WATER INTRUSION. HOW CAN THIS PHENOMENON
JEOPARDIZE DRINKING WATER SUPPLY IN COASTAL REGIONS?

a. GROUNDWATER BASIN
A groundwater basin is defined as an area underlain by permeable materials capable of furnishing a significant supply
of groundwater to wells or storing a significant amount of water.
A groundwater basin is three-dimensional and includes both the surface extent and all of the subsurface fresh water
yielding material.
It is an underground reserve of water which may take the form of a single aquifer or a group of linked aquifers.
It is an aquifer system that is bounded laterally and at depth by one or more of the following features:
- Rock of sediments of lower permeability
- Geologic structure (fault)
- Hydrologic feature such as a stream, lake or ocean

b. HUBERT’S MODEL “CONCEPTUAL MODEL OF REGIONAL FLOW”

This model predicts the characteristics of the flow net in both recharge and discharge areas and it is consistent with
the water table as a subdued replica of topographic surface.
It is essentially a 2D solution of Laplace’s equation where all boundaries except the upper surface are specified as no
flow. The upper surface can be specified as any function representing the form of the water table.

∅( , ) = + cosh . cos( )

Where:
ɸ_hydraulic potential
L_lenght of the flow cell

One specific solution when the water table (upper

surface boundary condition) is a simple cosine
function:

∅( , ) = − . cos

cosh
∅( , ) = − . cos
cosh

The theory states that groundwater discharges at the deepest topographic points, at the bottoms of valleys.

c. TOTH’S MODEL “MULTI-CELL MODEL OF REGIONAL FLOW”

Dashed lines sign the equipotential lines, along the head is constant. Continuous lines sign the flow lines. The total
head is constant along the equipotential lines: that will cause the level rises above the land surface, or drops below it.
If we drill at a recharge area, the water level decrease with depth, while at a discharge area the water level increase
with depth
First the significantly extend the conceptual work of Hubbert. Toth investigate a more complex flow system with a
sinusoidal water table superimposed on a regional slope. Toth identified local, intermediate and reginal flow systems
based on this simple topographic model boundary condition:
2
∅( , ) = − . sin( )
λ
Where
B’_regional slope
b_local sinusoidal relief (amplitude of the topography)
_number of flow cells

With the measurement of piezometric head from spatial distributed boreholes and observation wells is possible
construct a contour map of the piezometric surface. This surface express the elevation of piezometric head in a specific
point (Bear and Cheng, 2010). Based on fact that the groundwater tends to flow in direction of the greatest pressure
gradient, it will mean the flow lines in a groundwater system will be perpendicular to the piezometric lines. In
combination of the potential lines of the piezometric surface and the flow lines, the flow-net is calculated and
graphically presented given to de viewer a fast idea about the flow phenomena in the aquifer.

Thot discovered groundwater discharge not only in the deep valleys but in the sides of higher topographic elevations.

d. LOCAL, MEDIUM, AND REGIONAL FLOWS

CONDITIONS
- If b’=0 (not scale topography) only regional flow occurs
- If B’=0 (not reginal scale topography) only local flow systems develop
- If b’=B’=0 (not topography) water logged conditions will develop with the water table near the surface
discharging by evapo-transpiration
- If b’ and B’> 0, and L/∆>>0 then the regional, intermedia and local flow systems can be developed.

Local systems are where the recharge and discharge areas are adjacent to each other.
The greatest amount of groundwater flow in aquifer systems is commonly in local flow systems. Groundwater level
and flow in local flow systems is the most affected by seasonal variations in recharge, because the recharge areas of
these relative shallow; transient groundwater flow systems make up the greatest part of the surface of a drainage
basin.

Intermediate systems are when recharge and discharge areas are separated by one or more topographic highs and
lows.

Regional systems appear when recharge areas are along groundwater divides and discharge areas are at the bottom
of major drainage basins.

Groundwater divided are the imaginary impermeable boundaries.

Recharge area is that portion of the drainage basin in which the net saturated flow of groundwater is directed away
from the water table. In a recharge area the water table usually lies at some depth.

Discharge area is that portion of the drainage basin in which the net saturated flow of groundwater is directed toward
the water table. In a discharge area it is usually at very nearest surface.

e. GHYBEN-HERTZBERG EQUATION IN CASE OF SEA WATER INTRUSION

 Migration of saltwater into fresh water aquifer under
the influence of groundwater development. When
groundwater is pumped from aquifers that are in
hydraulic connection with the sea the gradients that
are set up may induce a flow of salt water from the
sea toward the well.
Ghyben and Hertzberg analysis assumed simple
hydrostatic conditions the weight of a unit column of
freshwater extending from the water table to the
interface is balanced by a unit column of saltwater
extending from sea level to the same depth as the
point on the interface. This is expressed as:
−
ℎ = ℎ
hf_elevation difference between the phreatic surface
and the sea level
hs_elevation difference between the sea level and
the sea water-fresh water interface at a given point
δs_density of the sea water
δf_density of fresh water

The equation also can be expressed by the elevation:

1
= ( − ∅)
−

∅=ℎ −

∅_elevation of the groundwater table

Hs_thickness of seawater from the impermeable aquiclude

f. EFFECT OF THE SALTWATER INTRUSION TO DRINKING WATER SUPPLY (JEOPARDIZE)

Decreased water quality by salinization of the resources, the fresh water budget will decrease because the sea water
will fill the aquifer. Salinity that can cause hearth diseases. The most characteristic water quality degradation.

- Source of saline water is connate water below inland freshwater

aquifers, as subsurface sea water below inland aquifers, on the seaward
edge of coastal aquifers
- The shape and position of the boundary between saline ground water
and fresh ground water is a function of the volume of fresh water
discharging from aquifer
- Any action that changes the volume of fresh-water discharge results
change in salt-water-fresh-water boundary
- Minor fluctuation in the boundary position occurs with tidal actions
and seasonal and annual changes in the amount of fresh-water
discharge. The boundary is in state of quasi-equilibrium

Saline water encroachment: Human action that results in saline ground

water entering a fresh-water aquifer. Two type: active and passive
 - Passive: when some fresh water has been diverted from the aquifer-yet the hydraulic gradient still sloping
toward the salt-water-fresh-water boundary. In this case the boundary
slowly shifts landward until reaches the new equilibrium position. We
find this problem in many coastal aquifers where ground water
resources are being developed.

- Active: the natural hydraulic gradient has been reversed and fresh
water is actually moving away from salt-water-fresh-water boundary.
This occurrence is due to concentrated withdrawal of ground water (in
a well) creating a deep cone of depression. The boundary zone moves
more rapidly than it does during passive saline-water encroachment.
Example: aquifers beneath Brooklyn were destroyed with active saline
water encroachment, when the water table was lowered 9 to 15 m
below sea level

Dry land salinity: Dryland salinity is a process of environmental

degradation that is a result of broad-scale change of land use. The
replacement of native forests and woodlands with shallow rooted
annual crops and grassland changed the amount of water entering the soil. The increased soil moisture in turn
increased the rate of recharge, as more water reached the groundwater the level of groundwater started to rise.
The groundwater contained salts at concentrations that inhibited the plants’ capacity to uptake water, causing loss of
production and ultimately replacement by species that could cope with higher salinities. Where the water table came
within several meters of the surface, groundwater could then be evaporated directly from the water table. This
concentrated the salt from the groundwater in the shallow soil profile.

4. PLEASE DESCRIBE THE MAIN STEPS OF THE THEIS PUMPING TEST EVALUATION. PLEASE GIVE THE MAIN
EQUATIONS WITH THE WELL FUNCTION. WHAT IS THE MEANING OF RECOVERY DATA IN WELL HYDRAULICS?
WHY CAN EXPERTS PREFER FIELD DATA TO LABORATORY DATA CONCERNING THE HYDRAULIC CONDUCTIVITY?

a. Main steps of Theis’s pumping test

a. Plot the function w(u) versus 1/u on log-log paper. (Such a plot of dimensionless the theoretical response is
known as a type curve.)
b. Plot the measured time-drawdown values, h0-h vs. t on log-log paper of the same size and scale as the type
curve
c. Superimpose the field curve on the type curve keeping the coordinate axes parallel. Adjust the curves until
most of the observed data points fall on the type curve.
d. Select an arbitrary match point A on the overlapping portion of the two sheets and read its coordinates W(u),
1/u, s, and t/r2. Note that it is not necessary for the match point to be located along the type curve. In fact,
calculations are greatly simplified if the point is selected where the coordinates of the type curve are W(u) =
1 and 1/u = 1O;
e. Substitute the values of W(u), s, and Q into equation and solve for T;
f. Calculate S by substituting the values of T, t/r2, and u into Equation

b. Main equations:

The Theis Recovery Solution assumes the following:

•The aquifer is confined and has an “apparent” infinite extent
•The aquifer is homogeneous, isotropic, and of uniform thickness over the area influenced by pumping
•The piezometric surface was horizontal prior to pumping
•The well is fully penetrating and pumped at a constant rate
•Water removed from storage is discharged instantaneously with decline in head
•The well diameter is small, so well storage is negligible

The data requirements for the Theis Recovery Solution are:

•Recovery vs. time data at a pumping or observation well
•Distance from the pumping well to the observation well
•Pumping rate and duration
 = ( ) = ( )
4 (ℎ − ℎ) 4 ( , )

4
= =
4
r _ distance from pumping well (m)
t _ time since pumping started (s)
s(r,t) _ (h0-h) drawdown (m)
Q _ pumping rate (m3/s)
S _ storage coefficient
T _ transmissivity
w(u) _ well function
u _ parameter of the well function

e. Recovery data meaning

A recovery test is a controlled field
experiment performed at the end of a
pumping test (constant-rate or step-
drawdown) after pumping in the pumped
(control) well has ended. Water-level
response (residual drawdown) is measured
after pumping has stopped in one or more
surrounding observation wells and
optionally in the control well itself.

The goal of a recovery test (aquifer test) is to

estimate hydraulic properties of an aquifer
system such as Transmissivity, hydraulic
conductivity, and storativity (storage
coefficient).

The rate of recovery provides a second

method for calculating aquifer
characteristics. Monitoring recovery heads is an important part of the well-testing process.
Typically, aquifer properties are estimated from a recovery test by fitting mathematical models (types curves) to
residual drawdown data through a procedure known as curve fitting.

Three methods available for estimating aquifer properties from recovery test data include the following:
- residual drawdown analysis (s' versus log t/t')
- Agarwal method (recovery versus Agarwal equivalent time)
- combined analysis of drawdown and recovery data (s versus t)

f. FIELD DATA TO LABORATORY DATA

More accurate data from field than the laboratory data. The representative properties from a sample is limited by the
factors as how it was taking or how part of aquifer it represented.

5. PLEASE DESCRIBE THE EVOLUTION OF THE SAFE YIELD CONCEPT. WHAT ARE THE MOST IMPORTANT
GROUNDWATER MANAGEMENT TOOLS? WHAT KINDS OF ASPECTS HAVE THE TERM OF SUSTAINABILITY?

a. SAFE YIELD CONCEPT

It is the amount of water that can be withdraw from it annually without producing an undesired result. According Lee
(1915), is used to denote the sustainable maximum rate at which water can be withdraw without dangerous depletion
of storage.

According Conkling (1946) and modified by Banks (1953) is an annual extraction rate that does not:
- Exceed the average annual recharge
- Lower the water table so that pumping is uneconomic
- Lower gradient so as to admit intrusion of water of undesirable quality
- Fall to protect existing water right

The Conklig-Banks single-value concept of safe yield encompasses:

- Hydrologic considerations
- Economic considerations
- Quality considerations
- Legal considerations

Parody of safe yield: The term safe yield was apparently used in this regard as early 1915 (Lee). At that time, safe
yield was regarded as the amount of water that could be pumped regularly and permanently without dangerous
depletion of the storage reserve. Later, other necessary factors are added such as economics of groundwater
development, protection of the quality of the existing store of the groundwater and protection of existing legal rights
and potential environmental degradation. Other names for save yield are: Potential sustained yield, permissive
sustained yield, and maximum basin yield.

Final definition: safe yield is the amount of naturally occurring groundwater that can be withdraw from an aquifer on
a sustained basin, economically and legally without impairing the native groundwater quality or creating an
undesirable effect such as environmental dangers.

The abandonment of the term safe yield has been proposed on the ground that it does not take into account the
interrelationships of groundwater and surface water and may produce the dupe of the storage functions of an aquifer.
However, in spite of the reservation of many hydrogeologists with regards to the concept must be applied wherever
the use of an aquifer is planned and managed. In general, the safe yield must be adjusted in such a way neither the
quantity or the quality of groundwater is allowed to reach unacceptable limits.

In practical studies, the safe yield should be less than the annual average recharge in order to compensate minor
groundwater losses. If the safe yield is overlapped for some time then the aquifer is bound to be mined, which is an
undesirable situation in groundwater management strategies.

b. GROUNDWATER MANAGEMENT TOOLS:

INSTRUMENTS:
- Groundwater use rights
- Abstraction permits or concessions
- Groundwater tariffs
- Groundwater markets
- Water harvesting
- Conjunctive management
- Policies
- Well spacing according to aquifer properties
- Regulatory framework
- Integrated resource management

The manageability of groundwater will depend on:

- The size of country and aquifers
- Aquifers yield
- Storage capacity
- Population density
- Abstraction for agriculture.

METHODS OF TOOLS:
- Optimizing the location and abstraction rates of wells
- Defining zones for the protection of groundwater sources
- Using brackish groundwater by blending it with fresh surface water
- Using telemetry to monitoring aquifer conditions and inform users of a necessary adjustments to abstraction rates
- Implementing different methods to improve water use efficiency in irrigated agriculture
- Enhance aquifer recharge
- Institutional framework
- Stakeholder participation - education

c. SUSTAINABILITY
On a broad-scale, sustainable use of water implies resources conservation, environmental friendliness, technological
appropriateness, economic viability and social acceptability of development issues.

Sustainable water resources systems are those designed and managed to fully contribute to the objective of society,
now and in the future with maintaining their ecological, environmental and hydrologic integrity.
Defining sustainability with respect water resources must consider three important aspects of water resources,
particularly in arid and semiarid lands:

- Groundwater and surface water resources are part of integrated hydrologic systems in which nay changes in
water input or output necessarily effects other parts of the system.
- Water cycles within the hydrologic systems and it is important to consider all parts of the systems
- The response of hydrologic systems to perturbations, whether they are caused by humans or natural, can be
slow because of transient and delayed responses.

Sustainability requires management of water resources with a long-term perspective. Sustainable water resources
systems are thus designed and operated in ways that make them more adaptative, robust and resilient to future
uncertainties.

The sustainability paradigm has largely evolved to the concept that we should live within the renewable supply of
groundwater and that stored groundwater should be breathed as a revolving account in which none of it or not much
more of it is permanently depleted.

The groundwater sustainability is the development and use of groundwater resources in a manner that can be
maintained for an indefinite time without causing unacceptable environmental, economic or social consequence.

Aspects of sustainability:
 - Environmental: This aspect acknowledges the need to enhance and maintain the bio-physical systems that
sustain all life on the earth. If includes the structure and function off natural ecosystems and the interaction
between them and people.
- Social: This aspect acknowledges the need for equity within and between generations and social groups. It is
inclusive of people’s mental and physical well- being and the cohesion of their communities based on a far
distribution of resources.
- Cultural: This aspect acknowledges the need to nourish and share attitudes and values that represent diverse
worldviews, and the political need for all people to express their views freely and to participate in decision
making.
- Economic: This aspect acknowledges the interactions of humans with the natural environment in using
resources to creates good and services which add value to their lives. It acknowledges the resources use and
waste disposal must occur within the capacity of our planet.

6. HOW DOES ARTIFICIAL RECHARGE WORK IN REALITY? WHICH REGIONS CAN BE SUITABLE FOR THIS
METHOD? WHAT ARE THE MAIN TECHNICAL SOLUTIONS FOR IMPLEMENTING THE ARTIFICIAL RECHARGE? WHAT IS
THE ADVANTAGE OF CONJUNCTIVE WATER USE?

a. ARTIFICIAL RECHARGE:
Involves augmenting the natural infiltration of precipitation or surface water into the ground by some kind of
environmental method. Involves building infrastructure and/or modifying the landscape to intentionally enhance and
treat water in aquifers.

Aims:
- Replenish depleted storage
- Prevent or retard saline infiltration
- Store water where surface storage is limited or unavailable as arid climates, tidal rivers and urban areas.
- Maintain wetlands
- Improve water quality by pre-treatment and post-treatment

b. REGIONS

Arid climates, urban areas and tidal rivers.

- Areas where groundwater levels are declining on regular basis
- Areas where substantial amount of aquifer has already been dehydrated
- Areas where availability of groundwater is inadequate in lean months
- Areas where salinity ingress is taking place

c. TECHNICAL SOLUTIONS
- Availability of source water in space and time
- Sites which have suitable hydrogeological environment for creating the sub-surface reservoir
- Other: Hydrogeological assessment
Hydrogeologic investigations
Assessment of environmental risk
Evaluation of financial and economic cost and benefits
Assessment of engineering methods
Engaging stakeholders and assessing social acceptance
Assessing regulatory and institutional mechanism

Recharge methods:
- Aquifer storage and recovery (ASR) – injection of water into a borehole for storage and recovery from the same
borehole.
- Aquifer storage transfer and recovery (ASTR) – injection of water into a borehole for storage and recovery from
a different borehole, generally to provide additional water treatment.
- Bank filtration – extraction of groundwater from a borehole, well or caisson near or under a river or lake to
induce infiltration from the surface water body thereby improving and making more consistent the quality of
water recovered.
- Dune filtration – infiltration of water from ponds constructed in dunes and extraction from boreholes, wells or
ponds at lower elevation for water quality improvement and to balance supply and demand.
- Infiltration ponds - ponds constructed usually off-stream where surface water is diverted and allowed to infiltrate
(generally through an unsaturated zone) to the underlying unconfined aquifer.
- Percolation tanks – a term used in India to describe harvesting of water in storages built in ephemeral streams
where water is detained and infiltrates through the base to enhance storage in unconfined aquifers and is
extracted down-valley for town water supply or irrigation.
- Rainwater harvesting – roof runoff is diverted into a borehole, well or a caisson filled with sand or gravel and
allowed to percolate to the water-table where it is collected by pumping from a borehole or well.
- Soil aquifer treatment (SAT) – treated sewage effluent, known as reclaimed water, is intermittently infiltrated
through infiltration ponds to facilitate nutrient and pathogen removal in passage through the unsaturated zone
for recovery by boreholes after residence in the aquifer.
- Sand dams – built in ephemeral streams in arid areas on low permeability lithology, these trap sediment when
flow occurs, and following successive floods, the sand dam is raised to create an “aquifer” which can be tapped
by boreholes in dry seasons.
- Underground dams – in ephemeral streams where basement highs constrict flows, a trench is constructed across
the streambed keyed to the basement and backfilled with low permeability material to help retain flood flows in
saturated alluvium for stock and domestic use.
- Recharge releases – dams on ephemeral streams are used to detain flood water and uses may include slow
release of water into the streambed downstream to match the capacity for infiltration into underlying aquifers,
thereby significantly enhancing recharge.

d. CONJUNCTIVE WATER USE

This is related with the combined use of groundwater and surface water.
- Due to the augmented water source higher water receivability can be achieved
- Acts as a buffer for periods of water scarcity
- The ides of this management approach are to use surface water when the water table is high and change to
groundwater when the water table is low
- Surface water is used in wet years and groundwater is used in dry years

Basic design principles:

1. Recharge: when the water table is high, the use of surface water is to be maximized. Recharge of groundwater
can be enhanced artificially.
2. Recovery: During dry season, water is drawn from groundwater resources.

Advantages:
- Improved security of water sources
- Protection of the groundwater level
- Reduced environmental impact
- Increase of agricultural productivity

Disadvantages:
 - Complex implementation
- Benefits may only be visible on long term

7.WHAT IS THE IMPORTANCE OF TRANSBOUNDARY AQUIFERS? WHICH IS THE MORE PREFERABLE POSITION IN
CASE OF WATER MANAGEMENT? DOWNSTREAM SIDE OR UPSTREAM SIDE? WHAT IS THE SITUATION IN
HUNGARY CONCERNING THE INTERNATIONALLY SHARED AQUIFERS? HOW CAN GROUNDWATER FLOW
SIMULATIONS HELP THE DECISION MAKERS?

a. IMPORTANCE OF TRANSBOUNDARY AQUIFERS

Groundwater is a crucial natural resource and it is a vital element of the natural environment. About 50% of the
world’s population drinks groundwater every day. Groundwater is also vitally important for agriculture as it
contributes to more than 50% of the world’s production of irrigated crops. Groundwater sustains ecosystems,
maintains baseflow of rivers and stabilizes land in areas with soils that are easily compressed.

A large proportion of the world’s groundwater is contained in aquifers which are shared by several countries. These
aquifers are known as transboundary aquifers.

The transboundary nature of these aquifers requires a specific approach in terms of assessment, management and
governance.

b. PREFERABLE POSITION IN CASE OF WATER MANAGEMENT

Upstream is better because downstream is more probable the occurrence of problems as contamination, poorless
water quality or depletion of resource.
The upstream part is better for production, because this is the area of recharge. However, if the upstream side is
overproduced, it can cause problems on the downstream side, so for good water management a good
cooperation between the countries is required.

c. SITUATION OF HUNGARY
- Out of 185 groundwater bodies classified in Hungary. Forty are transboundary.
- Exchange of information
- Joint problem diagnosis
- Joint decisions on transboundary measures
- Working together in coordination of common interested measures
- The largest specific number concerning internationally shared aquifers in Europe.

It shares the boundary with 7 countries: Austria, Croatia, Rumania, Serbia, Slovakia, Slovenia and Ukraine.
Hungary – Ukraine start to develop a common hydrogeological data-base with additional field measurements. They
have a common interpretation of the geological and hydrogeological setting to create the conceptual model of the
transboundary aquifer, regional groundwater modelling, the model simulation of different scenarios for water
management purposes and review of the main result obtained from the transboundary approach with identification
if mineral and thermal water resources exist in the region.

d. GROUNDWATER FLOW SIMULATIONS AND DECISION MAKERS

Groundwater flow simulations may be used to predict the effects of hydrogeological changes for abstraction or
irrigation, or to establish protection and rehabilitation strategies.
- Improve the estimation of recharge and safe yield for new application decisions
- Forecast expected response and benefits to alternate future conditions
- Assist in groundwater impairment investigations
- Assist in evaluating larger, more complex change applications

8. DRINKING, MINERAL, MEDICINAL AND THERMAL WATER RESOURCES AND THEIR UTILIZATION FROM AQUIFERS. PLEASE
GIVE THE BASIC DEFINITIONS. HOW CAN GEOTHERMAL GRADIENT AND HEAT FLOW BE DEFINED? WHAT IS THE RELATIONSHIP
BETWEEN HYDROGEOLOGY AND GEOTHERMAL ENERGY UTILIZATION?

a. WATER TYPES
SCALING
Hard water mineral deposits which precipitate to form limescale (insoluble mineral deposits)

GEOTHERMAL WATER
Water with temperatures above 20˚C and elevated dissolved mineral content. As result of the temperature rise
associated with depth increase on average globally in an increase of 30˚C/1000m while the confines of the Hungarian
basin is 50˚C/1000m.

NATURAL MINERAL WATER

A kind of water which is in its natural form intended for human consumption and officially recognized as a result of a
specified procedure. It must have favorable effects thanks to its mineral and trace element content as well as its other
components.
It must originate from a secure aquifer layer has to be originally pure, without any contamination and its composition
and temperature should be nearly constant. According to the bath act every line of mineral water must contain at
least 1000mg/l of solid ingredients.

SPRING WATER
Originates in deep layers, it is bottled locally. Its parameters at its place of origin must parallel the specifications of
drinking water regulations and it has to be handled the same as mineral waters. The use of CO2 as an additive is
allowed. While the iron and Sulphur have to be extracted from it. It must be a constant and it has to match the
microbiological specifications too. It does not have to be recognized or does it have to originate from a protected
aquifer layer.

MEDICAL WATER
Con be either cold or warm and they are both for bathing and drinking. This is mineral water that has a proven medical
effect. The main types of medical water with common salt content, iodine earthy calcareous water, Sulphur water,
carbonate with radon content. 25-30000 mg/l

DRINKING WATER:
Drinking water is water that is safe to drink or to use for food preparation. Drinking water is safe enough to be
consumed by humans or used with low risk of immediate or long-term harm.
Typically, in developed countries, tap water meets drinking water quality standards. Tap water is either spring water,
water coming from below the earth or is collected on the surface breaded.
According to the World Health Organization, "access to safe drinking-water is essential to health, a basic human right
and a component of effective policy for health protection."
Soda water is drinking water saturated with carbonic acid, enhanced with CO2 and unobjectionable from
bacteriological and chemical aspects.

b. GEOTHERMAL GRADIENT
It is the amount of the Earth’s temperature increases with depth, indicating heat flowing from the Earth’s warm
interior to its surface. On average the temperature increases by about 25˚C/1000m pf depth.

HEAT FLOW MOVEMENT of heat (energy) from the interior of Earth to the surface. It is calculating using the rock
thermal conductivity multiplied by the temperature gradient. Energy transport because of a temperature difference.

Potential difference  temperature difference

Thermal conduction:
- The mechanism: energy is transported between parts of continuum by the transfer of kinetic energy between
particles or groups of particles at the atomic level.
- Purely thermal conduction: in solid opaque bodies (opaque: not permeable for radiation) the thermal
conduction is the significant heat transfer mechanism because the material doesn’t flow and there is no
radiation.
- In flowing fluids, thermal conduction dominates in the region very close to the boundary layer, where
o the flow is laminar
o the flow parallel to the surface
o there is no eddy motion
Thermal convection:
Energy transfer is involved by fluid movement and molecular conduction. Heat transfer means energy transfer
• from liquids and gases to the surface of a body or a wall
• from the surface of a body to the liquid.

Thermal radiation
The radiation energy transfer is through energy-carrying electromagnetic waves that are emitted by atoms and
molecules due to change in their energy content.
It means: does not depend on an intermediate material. The rate of thermal energy emitted by a surface depends on
its quantity and its absolute temperature. A black surface absorbs all incident radiation.

GEOTHERMAL ENERGY is the thermal energy contained in the rock and fluid in the Earth’s crust. It indicates heat
flowing from the Earth’s warm interior to its surface. This difference in temperatures drives the flow of geothermal
energy and allows humans to use this energy for heating and electricity generation.
The Earth's underground heat is from radioactive elements. Specifically, geothermal heating is caused by
the decay of elements such as potassium, uranium and thorium.

c. RELATIONSHIP BETWEEN HYDROGEOLOGY AND GEOTHERMAL ENERGY

Thermal waters hotter than 30 °C play an important role in bringing heat or energy to the surface and its utilization.
The situation is complicated by the fact that thermal waters in many places in the Carpathian Basin are connected
hydraulically to strata used for drinking water production. A special water management strategy must be established
in order to fulfil groundwater needs of drinking water, medicinal and energy purposes sustainably.
The hydrogeological conditions play an immense role in a gives area in what kind of geothermal utilization can be
expected. The knowledge of subsurface flow systems is extremely important from the point of view of determining
the extent of supply conditions, water extraction opportunities as well as convective heat transport.

9.PLEASE DESCRIBE THE MAIN PROPERTIES, FEATURES AND ASPECTS OF KARST AQUIFERS? WHAT KINDS OF
METHODS ARE EXISTING IN KARST INVESTIGATIONS? PLEASE GIVE INFORMATION ABOUT HYDROGRAPH
ANALYSIS. WHAT ARE THE MAIN PROCESSES OF KARSTIFICATION? WHAT KIND OF DISTRIBUTIVE METHODS CAN
BE USED IN KARST MODELING?
A. PROPERTIES, FEATURES AND ASPECTS OF KARTS AQUIFERS
They are terrains with distinctive hydrogeology and landforms arising from high rock solubility. Most common karst
rock are carbonates (limestone and dolomites). Evaporates are also karstifiable (gypsum, anhydrite). Carbonates are
manly formed in shallow tropical seas and const of the skeletons of coral and algae.
+ + = +2
Show characteristic landforms such as: karst, dolinas and sinkholes, poljes, stream and river sinking by via shallow
hole. Karst aquifers are characterized by a network of conduits and caves formed by chemical dissolution, allowing
for rapid and often turbulent water flow.
Particularities:
- Dissolution
- High heterogeneity
- Duality in infiltration and floorward discharge.
 Epikarst: It is a weathered zone of entrance porosity on or near
the surface or at soil/bedrock contact of many karst landscapes.
- Upper boundary of a karst system
- Reaction Chamber where many organics accumulates and
react with the percolating water
- Stores and directs percolating recharge water to the
underlying karsts
- Permeability decrease with depth below the surface.
Acts as perched aquifer with a saturated zone that transmits
water laterally for some distance until it drains slowly through
fractures or rapidly at shaft drains or domes.

B. METHODS TO INVESTIGATE KARST AQUIFERS:

1. Geologic methods: The lithology, stratigraphy, fracturing, fault patterns and fold structures are awarded in
understand groundwater flow.
2. Speleology: Conduits and underground channels. Caves make it possible to enter the aquifer and observe and
study part of the channel networks.
3. Hydraulic methods (Pumping test): Potentiometric maps and hydraulic test in boreholes and wells.
4. Hydraulic methods: Continuous monitoring of water quality and quantity is necessary due to the high
variability of flow rates of sinking streams, caves streams and karst spring.
5. Isotopic technics (Hydrochemistry): Stable and radioactive isotopes can help to identify the origin of the
water, determine transit times and characterize many processes.
6. Tracer tests: Used to identify point connection, characterize flow and transport in the conduit networks.
7. Geophysical methods: Help to identify locations for well drilling investigate subsurface cavities.
8. Modelling: Mathematical models can help to better understand speleo-genesis, flow and transport in karst
aquifers.

d. HYDROGRAPH ANALYSIS
Graphical plot of discharge (Q) of a river at a given location overtime.

1. Rising limb: Influenced by storm and basin characteristics. Rises

slowly in the early stage of flooding but more rapidly towards the end
portion.

2. Peak: Contained peak flow. Maximum area contributes.

3. Recession limb: Represent withdraw of water from the storage built

up in the basin.
= =
=

4. Base flow: Runoff receiving water from groundwater storage.

Main feature of hydrograph pick: Depending upon the rainfall-basin characteristics, the peak may be sharp flat
or may have several well-defined peaks
Maillet formula: Used in calculation of the recession curve
=
− ℎ
− ℎ
− (1/ )
 Recession coefficient: Represent the ratio of the discharge after a unit time step of some specific initial discharge.

e. THE MAIN PROCESSES OF KARSTIFICATION

- Dissolvable rock, compact, thick, and have many fissures
- Enough rainfall (>250 mm/year)
- Exposed rock on elevated that possible develop water circulation or vertical drainage

The carbonic acid that causes karstic features is formed as rain passes through Earth's atmosphere picking up carbon
dioxide (CO2), which dissolves in the water. Once the rain reaches the ground, it may pass through soil that can provide
much more CO2 to form a weak carbonic acid solution, which dissolves calcium carbonate. The primary reaction
sequence in limestone dissolution is the following:
H2O + CO2 → H2CO3
2 HCO−
CaCO3 + H2CO3 → Ca2+ +
3

The oxidation of sulfides leading to the formation of sulfuric acid can also be one of the corrosion factors in karst
formation. As oxygen(O2)-rich surface waters seep into deep anoxic karst systems, they bring oxygen, which reacts
with sulfide present in the system (pyrite or hydrogen sulfide) to form sulfuric acid (H2SO4). Sulfuric acid then reacts
with calcium carbonate, causing increased erosion within the limestone formation. This chain of reactions is:
H2S + 2 O2 → H2SO4 (sulfide oxidation)
SO2−
H2SO4 + 2 H2O → + 2 H3O+ (sulfuric acid dissociation)
4

CaCO3 + 2 H3O+ → Ca2+ + H2CO3 + 2 H2O (calcium carbonate dissolution)

Ca2+ + SO42- → CaSO4 (formation of calcium sulfate)
CaSO4 + 2 H2O → CaSO4 · 2 H2O (formation of gypsum)
This reaction chain forms gypsum

f. DISTRIBUTIVE METHODS CAN BE USED IN KARST MODELING

 Distributed parameter groundwater flow models include two principal concepts. The discrete concept considers
the flow within individual fractures or conduits. In contrast, the continuum concept treats heterogeneities in
terms of effective model parameters and their spatial distribution. These concepts can be combined into five
alternative modelling approaches, according to the geometric nature of the conductive features represented in
the model (Teutsch & Sauter 1991, 1998) (Fig. 10.7).
• Discrete Fracture Network Approach (DFN)
• Discrete Channel Network Approach (DCN)
• Equivalent Porous Medium Approach (EPM)
• Double Continuum Approach (DC)
• Combined Discrete-Continuum (Hybrid) Approach (CDC)
The physical parameters of the flow medium can be directly or indirectly derived from real field observations
(deterministic models) or can be determined as random variables (stochastic models). Each method has its
respective advantages and limitations, and the selection of the appropriate modelling approach may be crucial
with respect to the outcome of the simulation.

10. WHAT ARE THE MAIN STEPS OF THE COMPREHENSIVE WATER MANAGEMENT FOCUSING ON WATER STATUS? PLEASE
DESCRIBE THE CONCEPTS OF THE WATER FRAMEWORK DIRECTIVE. WHY IS THE DANUBE WATERSHED SO SPECIAL?

a. The main steps of the comprehensive water management:

1. Set an overarching policy and goals, to develop a comprehensive strategic plan, set specific water use reduction
targets.
2. Asses current water uses and cost. Collect water and cost data and determining a baseline for overall water
reduction applications.
3. Develop a water balance. Compares the total water supply baseline to water that is used equipment and
applications.
4. Asses water efficiency opportunities and economics. Increase water efficiency and reduce water use.
5. Develop and implementation plan
6. Measure progress
7. Plan for contingencies, water and drought contingency plans.

b. Water Framework Directive:

- Prevent water deterioration and improve the status of aquatic ecosystems.
- Promote the sustainable use of water by means of saving water and water reuse
- ensure the progressive reduction of pollution and avoid new environmental threats
- Reduce the effect of flood and droughts
- Assessment of the ecological status the health of bodies of water in order to determine this status, identify the
pressures impacts and risk affecting these bodies of water assessment.
- Agreement on how to improve the quality of bodies of water and drawing up river basin management plans
- Evaluation in economic terms of managements
- Common frameworks of action in terms of water management in all member states
- Concepts of sustainability, encompasses the maintenance of water resources and fall transparency and citizen
participation influence management plans of programs.

Concepts: - Hydrogeological_ management

- Ecological_ Water ecosystem
- Economic_ Recovery test
 - Social_ Participation

c. Danubio watershed:
- Passes through 10 countries (Germany, Austria, Slovakia, Hungary, Serbia, Croatia, Bulgaria, Moldova, Ukraine,
Rumania)
- Principal resource for: industry, agriculture, transport, power generation, fishing
- The basin covers 19 countries: Albania, Austria, Bosnia and Herzegovina, Bulgaria, Croatia, Czech Republic,
Germany, Hungary, Italy, Macedonia, Moldova, Poland, Rumania, Serbia, Montenegro, Slovakia, Slovenia,
Switzerland, Ukraine.
-
It has 300 tributaries, size 817000 km2
- Home to 7 endangered fish species

11. PLEASE DESCRIBE THE ISOTOPE HYDROLOGY TECHNIQUES IN GROUNDWATER INVESTIGATION. PLEASE GIVE
THE MOST IMPORTANT RADIOACTIVE AND STABLE ISOTOPES IN HYDROGEOLOGY. WHAT ARE THE METHODS FOR
GROUNDWATER AGE DATING?

a. Isotope hydrology techniques:

This is when tracers are injected into sinking streams and monitored in springs with the aims of:
- Identify underground connections
- Define spring catchments
- Localize groundwater divides
- Define the geometry, morphology and hydraulics of the conduit
- Derivation of hydraulic parameters for groundwater flow and transport models.

The tracer’s types are:

- Stable in the environment
- Does not interact with aquifer
- Absent from out readily soluble in water
- Easy to detect
- Non toxic
- Invisible
- Inexpensive
- Easy to handle

In principle there are two possibilities:

(a) One can inject tracer substances into the

groundwater intentionally and thereby in
controlled doses, time intervals and locations; the
tracer method can be adapted in the best way to
the hydrological problem and situation, but there
are limitations regarding the size of the
investigation area and the time period of the
experiment.

To this method is necessary:

- to develop specific groundwater tracers with
controlled physico-chemical characteristics and
therewith known interactions in different aquifers
(e.g. special fluorescent dyes);
- to improve the methodology of drifting particles
with regard to new tracers, as well as to develop
efficient detection methods;
- to establish the absence of health risk involved in
the responsible use of groundwater tracers through toxicological investigations and therewith to find a generally
accepted basis to permit tracer experiments in the field.
(b) one can make use of natural and also unintentional anthropogenic labelling existing within the water cycle;
such labelling can be caused by temporal and spatial differences of "natural" tracer concentrations. The
investigation can be extended over wide areas and long time periods, but the tracer concentrations and their
spatial and temporal differences are predetermined, often without sufficient knowledge as to how and why these
concentration differences have originated.

For the use of natural tracers there is a need:

- to further develop measuring techniques for noble gas tracers, with the aim of lowering the costs of analyses
- to improve the determination of input functions for natural groundwater labelling, e.g. by sampling in the frame
of groundwater quality surveys and by investigations of initial concentrations in newly recharged groundwater.

"Ideal tracer": Are those that show the same transport characteristics as the groundwater to be investigated;
however, one has to bear in mind that the tracer characteristics depend on the local aquifer parameters and
therefore ideal tracers always have to be defined in relation to the respective aquifer and the hydrological problem
to be solved.
- Isotope species of the water molecule (3H, 3H16H16O[tritiated])
- Dissolved noble gases (He, Ar, Kr, etc)
- Anions of salts (NaCl, LiCl, KC1, H14CO-3, 36Cl-)
- Organic compounds and fluorescent dyes (U, eosin, pyranine, 14C)
- Drifting particles (bacteria, spores, etc)

Isotope: Same atomic number but different atomic weight. The main role of environmental isotopes is to verify
conceptual and mathematical models.

B. ISOTOPES TYPES:
Radioactive Stable
Tritium (3H) Deuterium (δ2H)
Radio carbon (14C) Oxygen-18 (δ 18O)
Chorine-36 (36Cl) Carbon-13 (13C)
Argon-39 (39Ar) Helium (3He, 4He, 3He/4He)
Kryptom-85 (85Kr) Nitrogen-15 (δ 15N)
Decay series (U,Th,Actinion) Sulphur-34 (δ 34S)
Chorine-37 (δ 37Cl)

c. GROUNDWATER AGE:
1. Tritium method
Groundwater tritium concentration reflect atmospheric tritium levels when the water was last in contact with
atmosphere

Tritium is a radioactive isotope of hydrogen, which has a half life of 12.3 years, emitting low-energy beta radiation. T
is produced in the atmosphere in small concentration by the influence of cosmic radiation, being oxidized to water and
after that entering in the water cycle (with a concentration of about 6 TU).

The natural level of tritium in precipitation is as much as 25 TU at high latitudes, decreasing to about 4 TU in the
equatorial zone (TU= tritium unit, which is defined as 1 tritium atom per 1018 atoms of hydrogen, which corresponds
to 0.118 Bq/l water).

According to the classical model by Kaufman and Libby, the age of the sample can be calculated from the decrease in
tritium activity with time using equation
A=A0e-λt

where A refers to the tritium activity of the sample, A0 is the initial tritium activity of the water and l is the decay
constant.
The hydrological application of tritium is based mostly on tracing by artificially produced tritium from the
thermonuclear test series since 1952. In 1963 the yearly average of the tritium content in precipitation had reached
the thousand-fold of the natural content and is still high (ť100 TU) at the present time.

Tritium labelling has made possible the study of short-term transport, mixing processes and exchange in the
groundwater (in particular the 3H labelling allows for determination of mean residence times of unconfined
groundwater in fractured and sedimentary aquifers). The qualitative detection of tritium is a certain prove of the
presence in a sample of fresh groundwater (recharged after 1964).

Tritium has a special place among the radioactive tracers since water labelled with tritium
(3HHO) is chemically identical with the groundwater investigated and can be expected to represent the flow processes
of groundwater very accurately.

Its determination differs from that of most other radioactive tracers, because it requires the measurement of low
energy β-radiation. However, tritium as a hydrological tracer can be applied with limitation and with great precaution
only in order not to disturb the insights into the hydrological water cycle by measurement of the natural tritium
content (including fallout tritium from atomic bomb tests).

The tritium content decreases according to the law of the radioactive decay within the water cycle. Thus, if we know
the tritium concentration of the infiltrating precipitation water, we can draw conclusion regarding the residence time
of groundwaters. Dating is possible up to about 50 years. Problems are occurring only when mixed waters with
different ages are investigated.

Detection of tritium in groundwater provides a definite indication for ongoing groundwater recharge and using
different models mean residence times (MRT) can be calculated for groundwater from aquifers receiving diffuse
recharge. In the same time, recharge rates or proportion of recent water components can be estimated and the
delineation of recharge areas is possible as well.

2. 3H-3He ingrowth method:

Tritium decays to the knowing this decay rate allows for a more accurate shallow groundwater recharge age. 3H /3He
ratios are useful for groundwater ager raking from several months to about 30 years but no farther than 50 from
several months to about 30 years no farther than 50

Decay: N(t) = N0 e-kt

Tritium activity is determined via the stable helium-3 produced by the decay of the tritium. The samples are distilled,
degassed and then stored at least half a year in a tightly sealed aluminosilicate container under vacuum. The 3He
produced during the storage time is measured by a static noble gas mass spectrometer (VG-5400). The tritium
concentration (C3H) is calculated from the concentration (C3He) of 3He as follows:

where
C3H tritium concentration in TU
C3He measured tritiogenic 3He in ccSTP
C conversion factor from ccSTP to TU (2.4889*10-15 [(ccSTP/g)/TU])
λ reciprocal of mean lifetime of tritium (17.93a, [122])
ts, te, tm dates of sampling, extraction and measurement, respectively
W0 , weights of the sample before and after the extraction, respectively
W
S salinity in
 α correction for the 3H/H fractionation due to loss of (distilled) water during gas extraction. a=1.15 (ratio of
tritium concentration in the liquid phase to tritium concentration in the water vapor [122].
The tritium detection limit and the measurement precision is a function of the degassed water volume, the applied
ingrowth time and depends on the process blanks to which the sample is exposed. The detection limit achieved in our
lab fin case of 2 months ingrowth time and 3 l of sample is 2.6 ą 1.1 mTU

12. HOW CAN YOU ESTIMATE THE GROUNDWATER RECHARGE WITH ENVIRONMENTAL ISOTOPES IN THE
UNSATURATED AND THE SATURATED ZONE? WHAT KIND OF INTERACTION CAN EXIST BETWEEN GROUNDWATER
AND SURFACE WATER?

a. ESTIMATE THE GROUNDWATER RECHARGE WITH ENVIRONMENTAL ISOTOPES:

Environmental isotope techniques are pre-eminently suitable for studding the unsaturated and saturated zone, the
latter particularly concerning the stable and radioactive natural isotopes.

- Stable isotopes data preferentially yield information on the origin of groundwater

- Radioactive isotopes allow groundwater to be “dated” in support of geo-hydraulic investigations

Most frequently used environmental isotopes include the heavy isotopes of the elements of the water molecules,
hydrogen and oxygen and carbon occurring in water as constituents of dissolved inorganic and organic compounds.

Application of stable isotopes ratios of hydrogen and oxygen in groundwater are based primarily upon isotopic
variations in atmospheric precipitation, that is in the input to the hydrogeological system understudy.

Radioactive isotopes occurring in groundwater originated from cosmogenic nuclear reactions in arid and semi-arid
climatic conditions, isotopes techniques constitute virtually the only approach for identification and quantification
of groundwater recharge.

Radioactive decay of environmental isotopes makes these isotopes a unique tool for the determination of
groundwater residence time to better understanding of aquifer dynamics.

Groundwater tracing may be defined as the attempt to solve groundwater-related hydrological problems by means
of measurements and interpretation of tracer concentrations in groundwater. The main parameters that can be
determined are:
- The origin of groundwater (recharge area)
- groundwater flow paths
- groundwater flow velocity and direction
- groundwater residence time
- hydrodynamic dispersion
- groundwater recharge
- groundwater flow rate (discharge).

b. INTERACTION OF GROUNDWATER AND SURFACE WATER

Groundwater recharge:
GW dependent ecosystem:
Water as habitat and as landscape element is increasingly appreciated, and this volume is considering as the water
demand of the environment. This is the ecological water demand, which can be formulated in different branches
according to needs, must has a guaranteed flow.

Surface water- GW interaction: Surface water and GW interact on different physical scales and over long periods of
time. The interaction of significant interest includes:
- GW discharge as baseflow to streams
- GW discharge as a source of spring
- Streamflow supply of recharge to the GW system
- GW flow into and out of reservoirs, lakes, ponds and lagoons.
GW abstraction from unconfined and confined aquifers
- Unconfined aquifer GW abstraction: Surface of the groundwater (the water table) is at the same
pressure as the atmosphere

- Confined aquifer GW abstraction: The “surface” of the groundwater is constrained by an aquitard. It is

under pressure. If the aquifer is tapped, the water level will rise up in response to the pressure. The
distribution of pressure is called the potentiometric surface.
Lower the potentiometric surface in a confined aquifer with the resulted water level still above the
aquifer materials. The aquifer remains saturated. When the head in a saturated aquifer changes, water
will be either stored or expelled.