1. WATER AS A
RESOURCE
UGRC 140

2. Global water budgets

3. Global water budgets
• Globally, the oceans account for the highest
percentage of all water on the planet (accounting for
about 97.5% of all water)
• Land accounts for 2.4%
• Atmosphere holds less than 0.001%
• Ice sheets account for 1.8% of all water on Earth
• Groundwater accounts for 0.63% of Earth’s water
budgets
• 25.7% of this volume of groundwater is fresh
• Saline surface lakes, rivers, and streams account for
0.007%

4. Global water budgets
• Fresh surface water bodies account for 0.009% of all water on
the planet
• Groundwater is the highest reservoir of useable freshwater on
Earth, accounting for about 98% of all freshwater
• Groundwater is therefore a very important water supply
source all over the world
• However, the geologic setting in which groundwater is often
found determines how much is locally available as well as its
accessibility

5. The Hydrologic Cycle
 The hydrologic cycle begins with
precipitation in the form of snow or
rain, representing the initial input into
the hydrologic system.

6. Precipitation
 Any form of liquid or solid water particles that fall from the
atmosphere and reach the surface of the Earth
 Caused when a mass of warm, moist air hits a mass of cold
air
 Condensation causes the moisture to form droplets that
become rain or crystals that become snow or ice
 When droplets or crystals become too heavy to be
suspended in the atmosphere, they fall to Earth as
precipitation

7. The hydrologic cycle

8. Aftermath of Precipitation
 Evapotranspiration
 Surface run-off
 Infiltration

9. Evapotranspiration
A fraction of the precipitation is returned to the atmosphere
by two processes;
Evaporation, driven by solar energy, is the physical conversion
of some of the precipitation to water vapour that is returned
to the local atmosphere.
Transpiration - the process by which plants release water into
the atmosphere

10. Surface Runoff
The runoff tends to move toward sinks or temporary storage
locations such as;
streams/rivers
lakes
wetlands
the ocean

11. Infiltration

12. Subsurface water
•
resources some of
After every precipitation event,
the water gets the soil soaked up, and if it
is sufficiently permeable, some of the
water infiltrates vertically down the soil
zone
• Surface flow occurs only after the soil’s
infiltration capacity has been exhausted
• The vertical downward movement of water
down the soil profile will continue until the
water reaches an impermeable boundary

13. Subsurface water
• Water will continue to accumulate over such an impermeable layer
until the whole layer of material above the impermeable material
gets fully filled with water
• The zone in the subsurface, whereby all the pores are filled up with
water is referred to as the zone of saturation
• Above the zone of saturation, the pores are partially filled with
water and partially filled with air
• This is the zone of aeration or vadose zone

14. Infiltration – groundwater storage
Vadose Zone
Saturated Zone
Impermeable
layer

16. Subsurface water
Subsurface water is all water stored in all pore
spaces of geologic materials below ground
surface
Groundwater, in the strictness sense refers to
subsurface water in the saturated zone only
It is only this water in the subsurface zones
that can be tapped
The top of the saturated zone (or phreatic
zone) is defined by the water table where the
saturated zone has no overlying confining beds

18. Subsurface water
In some cases, the water table coincides
with the ground surface
This results in the development of lakes,
streams, or wetlands
The water table is not necessarily flat like
the top of a table
It may undulate to correspond with the
variations in the topography, permeability
of overlying material, variations in the
depth of the lower confining beds

19. Subsurface water
Groundwater can be found hundreds of meters or kilometers down
the surface
However, due to confining pressures down depth, the pores spaces
get closed
In this case, the water holding capacities of the rocks will depend on
the development of fractures in the rocks
The process whereby groundwater is replenished through vertical
infiltration and percolation is referred to as recharge

20. Subsurface water
The porosity (or effective porosity) of
the rock or soil determines how much
water can be stored
In most situations, there isn’t enough
groundwater to be extracted due to
limited recharge and/or limited storage
A rock or soil that holds and transmits
groundwater that can be tapped in large
quantities is referred to as an aquifer

21. Subsurface water : - Basic
terms
Aquifer, aquitard, and aquiclude
 Aquifer
• A saturated permeable geological unit that is
permeable enough to yield economic quantities
of water to wells
Examples
 Unconsolidated sand and gravel (most
common examples)
 Permeable sedimentary rocks (sandstond
and limestone)
 Heavily fractured or weathered volcanic and
crystalline rocks

22. Subsurface water : - Basic
terms
Aquifer, aquitard, and aquiclude
 Aquitard
• A geological unit that is permeable enough to
transmit water in significant quantity, but its
permeability is not sufficient to justify production
well being placed in it
Examples
 Clays
 loams
 shales

23. Subsurface water : - Basic
terms
Aquifer, aquitard, and aquiclude
 Aquiclude
• An impermeable geological unit that does not
transmit water at all
Examples
 Dense unfractured igneous or metamorphic
rocks

24. Subsurface water : - Basic
terms
Types of aquifer
There are three main types of aquifer
• Confined aquifer
• Unconfined aquifer
• Leaky or semi – confined aquifer

25. Subsurface water : - Basic
terms
Confined aquifer
• Bounded above and below by an aquiclude
• In confined aquifer, pressure of water is usually
higher than atmospheric pressure
• A well tapping such an aquifer, the water in it
stands above the aquifer
• Water that overflows to the ground surface is
referred to as artesian well

26. Subsurface water : - Basic
terms
Unconfined aquifer
• Bounded below by an aquiclude but is not
restricted by any confining layer above it
• Water in a well penetrating an unconfined aquifer
is at atmospheric pressure and does not rise
above the water - table

27. Subsurface water : - Basic
terms
Leaky aquifer
• An aquifer whose upper and lower boundaries are
aquitards, or one boundary is an aquitard and the
other is an aquiclude
• Water is free to move through the aquitards, either
upward or downward

28. Water level
Confined Aquifer
Aquiclude
Aquifer
Aquiclude

29. Water level
Unconfined Aquifer
Water table
Aquifer
Aquiclude

30. Water level Leaky Aquifer
Aquitard
Water table
Aquifer
Aquiclude

31. Water level Leaky Aquifer
Water table
Aquifer
Aquitard
Aquifer
Aquiclude

32. Subsurface water
A perched aquifer is a saturated zone within the zone of
aeration that overlies a confining layer.
A perched aquifer sits above the main water table.
A well may be drilled into a perched aquifer, but it usually only
yields enough water for a household.

34. Factors that affect
groundwater availability
The availability of groundwater is dependent on several
factors
Principal amongst these factors is the level of recharge from
various sources
Groundwater recharge can be achieved through vertical
infiltration and percolation
Recharge can also occur through sub-surface inter-basin
flows

35. Factors affecting groundwater
availability
Our ability to identify and protect groundwater recharge areas
is key to managing the resource for development
In Ghana, groundwater recharge areas for the major aquifers
have not yet been identified and delineated
We also need to identify the prolific aquifers and protect them
from contamination

36. Consequences of groundwater
withdrawal
When groundwater is pumped from wells the groundwater
table progressively drops
This drop in the groundwater level is known as
groundwater level drawdown
In groundwater resources management studies, our ability
to manage draw downs is critical to the sustainable
management of the resource

37. Effects of groundwater
withdrawals
As water is progressively pumped through wells tapping an
aquifer, a cone of depression develops
A cone of depression is a circular lowering of the water table
around the vicinity of the pumping well
When several wells drilled through the same aquifer are
pumped progressively, their cones of depression can overlap

39. Effects of groundwater
withdrawal
Unregulated groundwater pumping through wells can adversely
affect regional groundwater budgets
Groundwater mining occurs when groundwater withdrawal
exceeds the rate at which the aquifers are replenished through
recharge
In sustainable groundwater resources management, groundwater
withdrawal from wells is regulated in such a way that it does not
exceed recharge

40. Effects of groundwater withdrawals
from wells
Groundwater mining over long periods of time can lead to the
depletion of the resource
In some serious cases, the aquifers are destroyed by having their
permeable entities closed up due to confining pressure and
increased withdrawals
High levels of groundwater withdrawals can also lead to ground
subsidence as the pore spaces which were previously filled with
water close up due to over pumping

43. OTHER ENVIRONMENTAL
PROBLEMS ASSOCIATED WITH
GROUNDWATER

47. water Pollution
To understand water pollution, it is necessary to first
understand the major sources of water
 Groundwater
Any subsurface water that occurs beneath the
water table in soil and other geologic forms
 Surface water
Refers to water on the Earth's surface. It occurs
in streams, lakes, and wetlands, as well as bays
and oceans

48. water Pollution
Each source of water has a unique set of contaminants
Because of interconnectivity of groundwater and surface
water; the contaminants may be shared between the two
sources. Example, pollutions on the surface can leach and be
released to the groundwater.

49. What is water pollution?
 Water pollution is any chemical, physical or biological change
in the quality of water that has a harmful effect on any living
thing that drinks or uses or lives (in) it. Water pollution can
also make water unsuited for the desired use.
 Two types of water pollution exist; point source and nonpoint
source. Point sources discharge pollutants at specific
locations through pipelines or sewers into the surface water.
Nonpoint sources are sources that cannot be traced to a
single site of discharge.
Examples of nonpoint sources are: acid deposition from the
air.

50. Causes of water pollution
Water pollution can be caused by natural
processes and human activities. Natural
processes are as a result of conditions such as
geology, climate, the amount and type of
vegetation present, etc.
The major causes of water pollution by human
activities can be classified as domestic,
industrial and agricultural discharges.
Natural: groundwater contains some impurities,
even if it is unaffected by human activities. The
types and concentrations of natural impurities
depend on the nature of the geological material
through which the groundwater moves and the
quality of the recharge water.

51. Groundwater moving through sedimentary rocks
and soils may pick up a wide range of compounds
such as magnesium, calcium, and chlorides. Some
aquifers have high natural concentration of
dissolved constituents such as arsenic, boron, and
selenium.
Climate influences water quality because
temperature, precipitation, and wind affect the
physical, chemical, and biological characteristics of
water.
In areas where vegetation is abundant, it falls into
the water, mixes with it, breaks apart, decomposes,
and becomes part of the water. In some cases,
excessive decaying vegetation can color the water.

52. Causes of water pollution-cont’t
Domestic discharges mainly septic systems and
sewerage treatment plants can be a source of
many categories of contaminants, including
bacteria, viruses, nitrates from human waste, and
organic compounds. Septic systems can cause
water pollution when they are placed in areas with
poor soil conditions, high water tables, or in areas
without sufficient area for them to function properly.

53. • For example, septic systems do not work well when
placed in tightly packed, fine-grained soils such as
clay, because effluent from the septic tank cannot
pass through the soil easily. Instead, it collects at or
near the surface of the ground and may run off into
nearby waters.
• In addition, improper storage or disposal of
household chemicals such as paints, synthetic
detergents can lead to groundwater contamination.
• Wastes dumped or buried in the ground can
contaminate the soil, streams/rivers and also leach
into the groundwater.

54. Causes of water pollution-con’t
Industrial-Manufacturing and service industries
have high demand for water (for cooling,
processing and cleaning purposes). Groundwater
pollution occurs when used water is returned to
the hydrological cycle.
Other sources of contamination include disposing
of waste in septic systems or dry wells, storing
hazardous materials in uncovered areas or in
areas that do not have pads with drains or
catchment basins.

55. • Storage tanks holding petroleum products, acids,
solvents and chemicals can develop leaks from
corrosion, improper installation, or mechanical failure
of the pipes and fittings and thereby polluting water
sources.
• Agricultural: Pollution from this category are varied
and numerous: runoff during storm of fertilizers into
surface water, spillage of fertilizers and pesticides
during handling, runoff from the loading and washing
of pesticide sprayers or other application equipment,
etc.

56. Effects of water pollution
Virtually all types of water pollution are harmful
to the health of humans and animals.
Water pollution may not damage our health
immediately but can be harmful after long term
exposure.
Different forms of pollutants affect the health of
animals in different ways:
Heavy metals from industrial processes can
accumulate in nearby lakes and rivers.

57. • These are toxic to marine life such as fish and
shellfish, and subsequently to the humans who eat
them.
• Heavy metals can slow development; result in birth
defects and some are carcinogenic.
• Industrial waste often contains many toxic
compounds that can also damage the health of aquatic
animals.
• Some of the toxins in industrial waste may only have
a mild effect whereas others can be fatal.
• They can cause immune suppression, reproductive
failure or acute poisoning.

58. Effects of water pollution-con’t
Microbial pollutants from sewage often result in
infectious diseases that infect aquatic life and
terrestrial life through drinking water.
Microbial water pollution is a major problem in
the developing world, with diseases such as
cholera and typhoid fever being the primary
cause of infant mortality.
Organic matter and nutrients causes an increase
in aerobic algae and depletes oxygen from the
water column. This causes the suffocation of fish
and other aquatic organisms.

59. • Suspended particles in freshwater reduces the
quality of drinking water for humans and the aquatic
environment for marine life.
• Suspended particles can often reduce the amount of
sunlight penetrating the water, disrupting the growth
of photosynthetic plants and micro-organisms.

60. Controlling water pollution
Ideally, pollution should be prevented from
occurring because it is more expensive in
treating polluted water.
Some of the best opportunities available for
preventing water pollution involve 3Rs- reduce,
reuse, and recycle.
When we reduce our generation of garbage and
other refuse, less solid waste ends up in
landfills.
Less solid waste in landfills provides less
opportunity for creating leachate,

61. • reusing treated and disinfected wastewater for
irrigation or reusing processed waters for wash down
or cleanup
• recycling paper helps prevent water pollution by
lowering the demand for raw timber, allowing more
trees to remain in the forest for stabilizing the soil,
cooling tributary waters, and otherwise benefiting
water quality.

62. Controlling water pollution-con’t
The main goal of treating domestic wastewater is
simply to reduce its content of suspended solids,
oxygen-demanding materials, dissolved inorganic
compounds, and harmful bacteria.
The characteristics of industrial waste waters can differ
considerably both within and among industries. Three
options are available in controlling industrial
wastewater.
Control can take place at the point of generation in the
plant; wastewater can be pretreated for discharge to
municipal treatment sources; or wastewater can be
treated completely at the plant and either reused or
discharged directly into receiving waters.

63. GROUNDWATER RESOURCES OF
GHANA
Aquifers underlie almost everywhere
in Ghana and can be tapped at
relatively shallow depths to provide
groundwater

64. Groundwater quality problems in
Ghana
Although groundwater is generally clean in Ghana, there
have been cases of contamination
In the Upper East Region (Bongo area), groundwater of
extremely high fluoride levels have been noted
High fluoride in groundwater (>1.5 mg/L) can cause dental
and skeletal fluorosis

65. Dental Fluorosis

66. Skeletal Fluorosis