Form Six Geography Notes Ground Water
Water Cycle
– -Rain falls on the earth surface in filtrates (soaks into) the soil
– -Some water flows over the surface as overland flow (run off)
– -Some water lie on the surface as ponds and lakes and some return to the atmosphere as water vapour through evaporation and transpiration.
Factors enhancing water cycle
1. Nature of the soil and parent rocks
2. Steepness of the slopes
3.. Nature of climate ;- Is a continuous succession of movement, condensation, evaporation, run off, percolation and precipitation
-Water vapour is carried by wind to the land where it is deposit as rain or snow
-Movement of water and water vapour form a system called water cycle.
GROUND WATER (phreatic/subterranean H2O)
– -Is the concentration of water within the ground surface. /Water that sinks into the ground.
-The water existed within the interior of the earth crust. The water within the ground surface covered at the position of the pore space of the soil. A body of water derived from percolation contained in the soil, sub soil and underlying rocks above impermeable.
SOURCES OF GROUND WATER
-There are three main sources;
1.Rain formation
– Is the source of ground water which existed during the formation of rainfall. It’s providing about 90% of the total water.
2. Rock formation.
– During formation of rocks formed with the element of water. The common rocks are sedimentary and igneous rocks.
3. Water bodies.
– The water bodies like Ocean, Sea and river influence the development of ground water. The water penetrates from the water bodies.
TYPES OF GROUND WATER
-The ground water categorized according to their sources;
1. Meteoric water
2. Juvenile water
3. Connate water
4.. Oceanic water
1. METEORIC WATER:
– Is the underground water formed due to the influence of rain formation. The rainfall is the only source of meteoric water. (Precipitation)
-The type of H2O is re – circulated leading to hydrologic cycle.
2. JUVENILE WATER
– Is the ground water influence by igneous rocks during the formation of igneous rocks formed with the element of water.
Most of the juvenile water contain a lot of minerals like fluoride mineral and also are super heated water (hot spring)
3. CONNATE WATER
– Is the ground water formed after the formation of sedimentary rock during the formation of sedimentary rocks formed with the element of water (cold spring)
– H2O is usually salty originate from ancient seas
4. OCEANIC WATER
– Is the ground water formed from the water bodies. Their sources are river, lake and ocean water penetrates from the water bodies.
METHODS OF OBTAINING GROUND WATER.
Percolation
– Is the rapid penetration of water within the ground surface. This existed when there are availability of joint /cracks /fault on the land surface
Infiltration /filtration
-Is the penetration of water within the ground surface in very slow motion. The water penetrates through natural space (pore space)
FACTORS AFFECTING GROUND WATER
-Are that factor influence the variation of ground water. The common factor are;
1. CLIMATIC CONDITION.
– In desert area there is poor concentration of ground water due to increase in evaporation caused by high temperature.
– In equatorial and tropical region there is high concentration of ground water and this is due to heavy rainfall.
2. RELIEF / ANGLE OF SLOPE
-Is the actually appearance of the landscape
-Steep sided area, there is low concentration of ground water since the water is moving down the slope.
-Gentle slope (plain) there is large concentration of ground water (free penetration of water) since the speed of water has decreased.
. NUMBER OF WATER BODIES
-E.g. lakes, ocean, rivers
– Availability of water bodies bring about the availability of ground water.
4. AMOUNT OF VEGETATION COVER
-Presences of vegetable bring about the availability of ground water since vegetation help in the formation of rainfall.
-Absence of vegetation brings about the unavailability of ground water.
5. NATURE/PERMEABILITY OF ROCKS
-Permeable rocks are rocks which allow free penetration of water downward.
-Impermeable rocks are rock which do not allow free movement/penetration of water
-Primary permeability (porosity) result from open texture, pores
-Secondary permeability (previous) result from joint and cracks.
SATURATION ZONE
-Are those layers within the ground surface which contain the element of water. These zones either are permanent or seasonal.
TYPES OF SATURATION ZONE
1. Non – saturated zone
2. Seasonal saturated zone
3. Permanent saturated zone
4.Impermeable rocks
1. NON – SATURATED ZONE
– Is the part within the ground surface which is not containing the element of water. / It is layers immediately below the surface. It allows H2O to pass through.
2. SEASONAL SATURATED ZONE
-Is the part within the ground surface which containing water periodically.
-This layer lies immediately below the non – saturated zone. Also known as intermittent saturation
-This layer can dry out after a period of drought.
3. PERMANENT SATURATED ZONE.
– Is the part within the ground surface which cover with water through out. This layer extends as far down as the impermeable layer, forming the limit to down ward percolation.
AQUIFER/TABLE –Is the beds which allow water to pass through it and is under lain by an impermeable stratum (rock) forming / becoming water – holding.
AQUICULTURE-Rock mass /layer that prevent the movement of ground water.
4. IMPERMEABLE ROCKS
-Is a rock which its zone does not allow free penetration of water.
A: ARTESIAN BASIN
– Is the position on the ground surface /landscape which contain the element of water. This slows the element of existence of ground water.
– An artesian basin is basins which consist of a layer of permeable rock lying between two layers of impermeable rocks.
Condition for presence of artesian well
i. Climate condition – Rainfall availability
ii. Angle of the slope –Depression /gentle sided
iii. Amount of vegetation cover should be availability
iv. Presence of water bodies
v. Presence of a layer of permeable rock lying between 2 impermeable rock
B. WELL
– Is a hole / hollow sunk in the ground up to bellow the water table. This is either natural or man made.
C. ARTESIAN WELL
-Is a position on the land surface which showing the element of existence of well.
-These are well in order to tap water from the artesian basins.
-When the well is sunk into the basin the hydrostatic pressure in the ground force it to come out. If the water doesn`t reach the surface it is known as semi –artesian well. (Construction of well).
Condition for development of permanent well
-Climate condition – Summer season in order to know the dry season water table
-Angle of the slope – Gentle slope
-Amount of vegetation cover should be available
-Water bodies available.
D. SPRINGS
– Is the out flowing of water from the group surface.
– Springs develop where the water tables meet the surface.
Condition of development of spring.
i. The presence of enough ground water
ii. The presence of depression on the landscape
iii. The water table should lie near the earth surface.
iv. The presence of soft rock and cracks on the landscape. They allowing free penetration of water.
v. Permeable rocks should be lies on the impermeable rocks.
vi. The presence of internal pressure. This force the out flowing of water. Internal pressure influenced by the earth compaction.
Ways in which spring can be formed (types)
Spring can occur where the rock are well jointed water enter the rock via joint frequently occur where water table meet the surface.
The impounding of water by a dyke whereby it cuts across the layer of permeable rock then the water on the up – slope sided of the dyke is impounded. Water table rises and gives rise to spring where it meets the surface.
-Gently sloping layers of alternate permeable and impermeable rocks rain falling on exposed ends of permeable rocks are socked in the sloping bedding planes and finally comes out as spring are sometimes in line
HOT SPRING
-Is the out flowing of super heated water from the ground surface this involves the heated water.
-The hot spring develop from the juvenile water (ground water force during the formation of igneous rocks)
CONDITIONS
-Refer to the condition of spring.
-The pressure of heat and pressure within the interior of the earth crust
Importance/Effect of ground water
Water from wells may be used for irrigation in the dry area in Sahara; agriculture is practiced around the oases.
Spring form a major source of water for both domestic and industrial use.
Site of settlement in many regions of the world.
Formation of hot spring and geyser on areas with volcanic influence, likely to be a tourist
Water for cattle ranches Kansas in North America
Influence land slides
Destruction of mineral
Reappearance at a new sight.
Karst processes factor and resulting process.
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KARST SCENERY
Karst
Is the landscape formed from the dissolution of soluble rocks including limestone, dolomite and gypsum.
Rain water become acidic as it comes in contact with carbon dioxide in the atmosphere and the soil. As it drains into fractures in the rock, the water begins to dissolve away the rock creating a network of passage overtime, water flowing through the network continues to the passage.(CaCo3) + (Co3 ) -> Ca (HCo3 )2
Karst Topography
– A form of land form denudation base almost exclusively on carbonation (chemical weathering).
Factors for the formation of karst region.
i. The outcrop should be hard, previous and well jointed
ii. The climate of the area should be humid. The climate found in e.g. temperate region.
iii. The water table should be deep enough to allow percolation of water.
Major characteristics of karst scenery
Absence of surface drainage.
Outcrop of bare, rugged rock and steep sided dry valley
Numerous solution depression and residual hills of various sizes
A subterranean network of caverns and water courses
Joint are at right angle to each other
LIMESTONE
Is a rock consisting of at least 80% calcium carbonate./is a well-joint rock and its joint and bedding plane soon become opened up by rain water that fall on its surface./is an organic sedimentary rock formed by remains of tiny shells and micro – skeletons deposited on the sea bed.
Carboniferous limestone.
-Formed from the remains of organic matters usually sea shells and plant, coral.
Characteristic of carboniferous limestone
It is hard, sedimentary rock with a large number of joint (vertical cracks ) and bedding planes (horizontal planes )
Main process which affect it are carbonation and solution
Landforms in Karst region
-The land form in Karst region are divided into two
1. Surface feature
2. Subterranean/under ground feature
1.SURFACE FEATURES
·Limestone pavement.
-Is a bare rock surface crisis – crossed by numerous gullies where solution has worked along the joint – these are areas of exposed limestone.
Land form in karst regions.
Example of limestone pavement
Grikes.
Are deep irregular grooves(gullies) formed when water erode the crack when running on the surface before disappearing underground.
Clints.
are ridge/blocks on the limestone rock separating the grikes.
Swallow holes (sink holes) – This is a vertical hole leading to an underground cave system which is produced when the joint are in large by water percolating into the rock. The running water may sink down through the swallow hole.
Doline -Is a shallow depression /hollow with gently sloping side and generally circular or oval in plan.
– They originate from water percolating underground at the intersection of major joints.
– When swallow holes join together form a large depression called doline.
Uvala
-Is a large closed depression with diameter general greater than 500m.It is formed by coalescence/joining of several do lines. The floor is often hummocky consist of several interconnected hollows.
Example of Uvala
Polje:
– This is a very large/shallow steep-sided depression with a generally flat floor.
– It may be many kilometer in size. The flat floor is often emphasized by the deposition of Terra rossa a red clay material which form an impermeable layer and leads to flooding after heavy rains.
-Is a very large depression which is formed when several uvalas collapse, the collapse can be due to faulting some poljes even have small lakes.
Dry valley
-Is a valley with no permanent stream and often with steeps almost vertical sides.
– Most are caused by gradual lowering of the water table which itself is often due to the entrenchment of major stream into the limestone. As the water table falls, small stream become intermittent first and finally vanish.
Limestone gorge
– This is the deep steps sided valley formed by a large river with its head waters beyond the limestone area steadily entrenching itself into the land surface. The steeps cross profile is partly a result of the nature of rock jointing, formed when roof of a cave collapses inwards. E.g. cheddar
Example of limestone gorge
Resurgence
–Here the surface drainage reappears.
SUBTERRANEAN FEATURES
-These are feature formed below the surface
. 
Limestone caves and caverns
-These are underground chamber formed due to solution of the limestone rock underground.
– First tunnel is form, followed by the enlargement of the chamber or cave. Subsequently due to further solution a layer cave forms a cavern e.g. Ambon caves in Tanga.
Example of limestone caves and cavern.
Stalactites:
– These are finger like masses of calcite hanging vertically from the roof of the cavern. They a formed through deposition of drops of water containing calcium bicarbonate which have the crevices /joints.
– Calcite is deposited through evaporation and when carbon dioxide is released from water.
Below is an example of Stalactites
Stalagmites:
– Are stumpy rock masses which grow from the floor of the cavern upward. They are much thicker than stalactites to the floor where they crystalline and grow slowly but steady towards the roof.
Natural pillar
– This is the natural column or pillar formed either when the stalactites and stalagmites join or when the stalagmites grow to the point of reaching the roof.
Example of Karst region in the world
Karsts region in Yugoslavia
Causes region in south west France
Kentucky plateau in U .S .A
Ambon – Tanga
5. D R C
6. Morocco –atlas region
7. Madagascar.
Economic importance of karst regions:
Used for / as a tourist attraction hence brings foreign currency to the country e.g. Ambon caves in Tanga.
Karstified limestone act as an aquifer where water can be store underground and later extract by human e.g. in Texas
Create complex underground water flow network and large causes enough for human access.
Limestone is an important rock that is used in building and for making cement e.g. sokoto, ewekoro in Nigeria
Sufficient pasture to support goals sheep and cattle but not good for activation since the soil is poor an