1. ABSTRACTED GROUND
WATER USE AND THE
EFFECTS OF
OVERDRAFTING.
SEMINAR PRESENTATION
BY
ALADETAN FELIX ILERIOLUWA
DEPARTMENT OF GEOLOGY
FACULTY OF PHYSICAL SCINCES
UNIVERSITY OF BENIN
BENIN, EDO STATE
DATE: 12JULY, 2011.

2. CONTENTS
• ABSTRACTS
• INTRODUCTION
• GENERAL HYDROGEOLOGY OF NIGERIA
• REASONS WHY GROUNDWATER IS PREFERRED
TO SURFACE WATER
• GROUNDWATER AND USES
• EFFECTS OF OVERDRAFTING
• CONCLUSION AND RECOMMENDATIONS
• REFERENCES.

3. UNIVERSITY OF BENIN
FACULTY OF PHISICAL SCIENCE
DEPARTMENT OF GEOLOGY
SEMINA PRESENTATION
BY
ALADETAN FELIX ILERIOLUWA
•
• ABSTRACT
• Water is important to life, without it, life can not go on. Human life as with
animals and plant life on the planet is dependent on water. When surface
water becomes increasingly polluted, people turn to ground water for
alternative supplies. Therefore, the development and efficient management of
groundwater resources is of keen concern in the Middle East, Africa and Latin
America particularly the Sudano –Sahelian belt (WHO,2000).In these areas,
not only is there scarcity of water resources and quality degredation
(Problems), but also they face high evaporation rates and high level of
anticipated future demands due to their unprecedental population increase.

4. INTRODUCTION
• In a populated country like Nigeria and the USA, with great interest in groundwater as
an alternative source of water for agriculture, domestic and industrial uses, it is almost
impossible not to experience the temptation to over use it. leading to the problem of
groundwater depletion also known as overdrafting. And because of the intimate
relationship between water and life, water is said to be woven into all culture and
religious societies.
• NIGERIA: LOCATION AND CLIMATE
• Geographical Co-ordinates: longitude 2˚ 15ˈ E and 14˚ 45ˈ E, latitude 4˚ 10ˈ N and 13˚
50ˈ N.
• Land Area: 924,000km²
• Population: 120 million
• Climate: Two Ecological Zones, Humid South & Dry North
• Mean Annual Rainfall:>3000mm in SE at coast ,< 250mm at the extreme NE part of the
country
• Average Annual Temperature: 23˚C- 32˚C.
•

5. GENERAL HYDROGEOLOGY
OF NIGERIA
• Ground water which can be extracted by bore holes occur in permeable
geological formations known as aquifers which have properties that allow
storage and movement of water through them. The geological structure of
Nigeria gave rise to two types of groundwater pore type water in
sedimentary cover (water in the primary pore spaces) and fissure type water
found in crystalline rocks (with limited resources).The occurrence of
groundwater varies with the geology of the area.
• In basement complex terrain, groundwater occurs in weathered regolith and
in the fractures in the fresh crystalline rocks, it is here that wells and
boreholes tap the groundwater for water supply.
• The use of geophysical techniques coupled with down the hole hammer has
revolutionized groundwater development in the basement complex areas.
Many communities now obtain water from boreholes either with hand
pumps or motorized pumps.

6. Figure2: Groundwater Provinces Of
Nigeria

7. Fig .1 Hydro- Metrological
Map of Nigeria.

8. REASONS WHY GROUNDWATER
IS PREFERRED TO SURFACE
WATER
1.Its relative low costs compared to surface water.
2.Availability in most areas: Groundwater makes up about 20% of the world’s fresh
water supply, which is about 0.61% of the entire world’s water, including ocean &
permanent ice. Nearly one half the population of the USA use groundwater as
primary source for drinking water. Fortunately, the total amount of groundwater
available in the USA is great, accounting for approximately 20% of water use.
3.Portable without treatment
4.Employs low cost technologies
5.The frequent drougth problems enforce the use of groundwater source as many small
intermittent rivers dry out during the dry season.

9. ABSTRACTED
GROUNDWATER USE
• GROUNDWATER: Groundwater is the water stored in an aquifer in pore
spaces or fractures in rocks or sediments. Groundwater is usually refers to
the water below the water table where saturated condition exist.
• Groundwater is generally a readily available source of water through out
populated Africa but the construction cost for sustainable supplies are high.
• An aquifer on the other hand is an underground zone or body of earth
material from which groundwater can be obtain i.e (from a well) at a useful
rate.
• 1.Agricultural purposes such as in irrigation
• 2.Municipal or domestic purposes; cooking, drinking, washing and bathing
• 3.Industrial purposes; coolant, economic (bottled and sachet water) and as
a major ingredient in most canned and bottled drinks.

10. THE EFFECTS OF OVERDRAFTING
ON GROUNDWATER
• Groundwater in aquifers usually moves slowly at rates of centimeters or meters per day. When
water is pumped from an aquifer, the water table is depressed around the well forming a cone of
depression.
• Overdraft often result when the rate of abstraction of groundwater is far more than the rate of its
recharge. To date, only about 5% of the total groundwater resources have been depleted but
water level have declined by as much as 30-60m (100-200ft) in part of USA.
• In many areas, the pumping of groundwater has forever changed the character of the land as can
be seen as stated below;
• 1.Well yield decrease;(Increase in energy cost for pumping water)
• 2.Ecological impacts e.g. damage to river ecosystem and loss of riparian vegetation in Tuscan,
Arizona USA.
• 3.Flood hazard e.g. in Tuscan USA
• 4.Pollution: Saline water intrusion into groundwater in some part of the coastal states of
Nigeria.(topography can also be a great factor) Boreholes and wells in Bama town area of Borno
State (2006) were more polluted in areas nearer farms and sanitation units than the areas further
away from them.
• 5.Land Subsidence. Surface subsidence (sinking or settling of the land) in Mexico city, Phoenix,
Houston and the San Joaquin Valley in California, and Puerto rico. Especially in a limestone
supported aquifer.

11. FIG.4 The Winter Park, Florida, sinkhole that formed on May 8,1981.
Note damage to the municipal swimming pool, roads, and vehicles
trapped in the depression.

12. FIG .3 GROUNDWATER LEVEL FLUCTUATION IN
SABIYE WELL , KEBBI STATE, OCT 1998- JULY
2000 (15 days measurement interval)

13. CONCLUSIONS AND
RECOMMENDATIONS
In conclusion, the role of groundwater to any nation cannot be overemphasized. It is
necessary to stress the fact that everything should be done to understand groundwater
in terms of exploration, exploitation and management. The following are
recommended;
1.Hydro-geological mapping of a country is regard as a fundamental maps which has to be
prepared and produced with utmost accuracy given the available data as a base for
further groundwater development.
2.Our maintenance culture and attitude should be encourage to change for the better in
the groundwater resources development by planning for and allocating sufficient funds
and transparency using such funds for regular maintenance.
3.Although it takes a very long time to deplete groundwater ,never theless, it is essential
that the regulations by the government to control the pollution of surface water should
be taken extremely serious and if the funds and technology are available, desalination
of sea water can also be adopted.
4.It is obvious then that the problems of overdraft are not what we can stop from
happening, but we can simulate nature by initiating an artificial recharge mechanisms
and by also discouraging the continuous abstraction of water from wells already
showing early sings of overdraft.

14. REFFERENCES
• Eduvie O.M(2003);Exploration, Evaluation of
groundwater in Southern Kaduna State Nigeria.pp242.
• FMWR(2000) Natural water supply policy.
• Habila,O.N (2003):Rural water supply and sanitation
development in Nigeria.
• Water supply and management,pp 396-397.
• Onugba. A. and Sara, S.G.(2003); Rural water supply
and Handpump Development in Nigeria.
• Pre-Pint of the 29th WEDC Conferences Abuja Nigeria
2003.

15. THANK YOU VERY MUCH FOR
YOUR ATTENTION
• THE END!