1. Ankur Bansal
09010408

2. Groundwater Exploration
• Involves Mapping of potential aquifer
horizons.
• Location of water table through field
investigation helps to define the saturated
zone of the aquifer.
• Several surface and subsurface investigations
are carried out.

3. Movement of Groundwater
• Groundwater velocity. Most groundwater moves slowly relative to
stream flow. Water velocity varies greatly for a variety of reasons.
Water flow underground flows in response to differences in water
pressure and elevation.
• Elevation. Water within the upper part of the saturated zone
(phreatic zone) moves down hill from high head to low head. The
greater the change in elevation, the faster it will flow.
• Water table slope. The slope of the water table strongly influences
ground water velocity where the steeper the slope the faster the
water flows. Slope is controlled by topography .Groundwater will
not move if the water table is flat.
• Permeability. Groundwater flows faster in aquifers with high
permeability.
• Pressure. Water under pressure will move faster than water not
under pressure.

4. Effective Porosity of Ground
• Some of the pore spaces may be too small or
too poorly connected to permit the water they
contain to flow out easily
• The effective porosity can be thought of as the
volume of pore space that will drain in a
reasonable period of time under the influence
of gravity

5. Diagram showing effective porosity

6. Velocity of Groundwater Flow
• Velocity of Flow is calculated using Darcy’s
Law.

8. • Groundwater flow is very slow compared to surface
water movement.
• This is thousands of times slower than river flow
(typically measured in feet per second), and means
that a 'parcel' of groundwater takes over a decade to
move a mile, and about a century to cross a township.
• This natural time scale underscores the importance of
long-term planning and management, and helps
explain why resource depletion or contamination
cannot be quickly or easily rectified

9. Rock Interaction
• Things are not as simple as that of a stream
flow, flow beneath the earth surface occurs
through the rocks and soil.
• So, velocity and pattern of flow depends
highly on the nature of the rock present at any
particular location.
• More the permeability, more will be the
velocity.

10. Factors affecting the flow underneath
Type of Rock:
• Igneous and Metamorphic rocks both have
primarily low porosity i.e. 8-10 %, but in Basalt
porosity is higher due to vesicles.
• Sedimentary Rocks includes sandstone, siltstone,
shale, clay stone and limestone
1. Sandstone possesses variable porosity
depending on its concentration. Coarse Grained
sandstone and partly consolidated sandstones
perform better as aquifers.

11. 2. Limestone are better aquifers as solution
cavities are present within them.
3. Claystones, clay and shale have low
permeability values and are poor aquifers.
Effect of Faults in rocks
• Joints and Cracks contribute to secondary
porosity.
• Joints decrease in their frequency with depth
• Occurrence of impervious dykes and sills
contribute to the groundwater localization.