Geography Notes Form 4
Geography Notes Form 4
Form 4 Geography
Land Reclamation
Land reclamation is the process of converting wasteland into farm land for growing of crops and keeping of animals while land rehabilitation is the process of restoring land to its former productive state.
Importance
1. Intensify food production to feed the ever increasing population
2. To overcome land shortage and pressure.
Methods of Land Reclamation Irrigation
– Artificial method of supplying water to a region which doest receive adequate rainfall or to ensure continuous crop production.
– Done in dry areas with low rainfall and regions experiencing dry periods to sustain growth of crops.
– Dams are used to store water.
Advantages
(a) Can be used for HEP generation
(b) For fish farming
(c) Supply water for domestic use
(d) Control floods.
Negative effects
a) Can be a cause of deaths by drowning
b) Breeding ground for mosquitoes which transmit Malaria.
c) breakage can cause destruction of life and property
Factors Determining the Amount of Water Required for Irrigation
a) Climate: Areas receiving low rainfall require more water.
b) Soils: Sandy soils require more water than clays due to low water retention ability.
c) Crop: Paddy rice requires water logged soils while vegetables require wet and well drained soils.
d) Size of fields: Small plots require small amounts of water while large plots require large amount of water.
Methods of Irrigation
(a) Water lifting method
– Lifting water from a source by using a bucket or watering can and pouring it on the crops.
– Used widely in market gardens and on farms adjacent to the water.
(b) Flood/basin irrigation
– Diverting river water into a canal then to plots where it’s flooded.
– Commonly used in irrigation schemes.
(c) Sprinkler or overhead irrigation
– Taking water to the fields by pipes and applying it on crops by rotating sprinklers mounted on vertical pipes.
– Used on golf courses and market gardening.
(d) Trickle irrigation
– Plastic pipes with holes laid in the fields through which water trickles to the base of plant.
– Popular where fruits and flowers are grown.
(e) Canal irrigation
– Directing water through canal to farms.
– Commonly used in areas experiencing low rainfall e.g. Yatta in Machakos
(f) Drip irrigation
– Inverting bottles filled with water into the roots of a plant.
– Used in low rainfall areas to grow trees, fruits and flowers.
Drainage of Swamps
– Process of draining excess water from the land.
– Problems of land with excess water are:
a) Is breeding ground for disease causing vectors.
b) Is water logged and unsuitable for agriculture.
c) Is prone to flooding which destroys life and property.
Processes Involved
(a) Digging ditches for water to ooze into and flow away by gravity
(b) Planting eucalyptus which takes up a lot of water e.g. at Kakuzi in Makuyu.
(c) Laying perforated pipes in ditches which water will seep into and flow away by gravity.
– Areas in Kenya with have been reclaimed by draining are:
(a) Yala on lower courses of R.Yala
(b) Bunyala on lower courses of R.Nzoia.
– The project was conceived in 1970.
Objectives of the Project of Draining Them
(a) Free the area of pests.
(b) Prepare land for settlement and agriculture.
(c) Ease population on Kano plains.
(d) Reduce flooding and associated hazards.
(e) Develop the otherwise remote area.
Achievements
(a) Flooding has been controlled.
(b) About 800 hectares are available for agriculture and settlement.
(c) Water borne diseases have been brought under control.
Control of Pests
Mosquitoes
(a) Fumigation
(b) Draining of stagnant water
(c) Spraying
(d) Clearing of bushes near settlements.
Rodents, birds, squirrels and porcupines
(a) trapping
(b) poisoning
(c) hunting
(d) Scaring away
Tsetse flies
– They thrive in damp areas with high temperatures and prefer bushy vegetation as breeding grounds.
– Examples of tsetse fly infested areas are Lambwe valley in Kenya and Miombo woodland in Tanzania.
– The control of tsetse fly at Miombo woodland was aimed at:
– The control was done by The International Centre for Insect Physiology and Ecology (ICIPE).
a) Eliminating the pest to obtain land for agriculture.
b) To treat the sick people and animals to check the spread of resultant diseases.
Measures Taken
Bush Clearing
– Selective clearing of bushes was applied to prevent soil degradation.
– Caused tsetse fly to lack a place to breed and killed adult flies and pupae due to low humidity.
Bush Spraying
– Spraying from the ground or from a low flying aircraft.
– Doesn’t affect other organisms.
Disadvantages
a) Some insecticides such as DDT have serious environmental effects.
b) The fly develops resistance and a high dose of chemicals has to be used.
c) Kills other useful organisms.
Sterilisation males
– Making the insect unable to reproduce by obstructing its reproductive organs.
- Luring the male flies to some chemical substance which sterilises them.
- When they mate with the females fertilisation doesn’t occur which reduces insect population.Traps
(a) Square of black cloth coated with glue on which the insects stick.
(b) Traps impregnated with insecticides which kills the insects.
Creation of Buffer Zones
-Belt of 5 km wide with dense cultivated vegetation to create barrier which the fly couldn’t cross.
Killing of the Hosts
Wild animals which the fly fed were selectively hunted and killed.
Methods of Land Rehabilitation
Afforestation and Reafforestation
– Improve the productivity of land in the following ways:
a) Controls soil erosion by:
– Acting as wind breakers
– Leaves reduce impact of raindrops on the soil
– Roots hold/bind the soil particles together.
b) Vegetation reduces runoff and increases the rate of infiltration of rain water ensuring there is a complete water cycle.
c) Decayed vegetation provides humus which restores soil fertility.
d) Roots help moisture to percolate deeply into the ground.
e) Modifies the climate of an area by moisture being released to the atmosphere causing higher rainfall and lowering the temperature.
Bush Fallowing
– Cultivating a field for a period of 2-3 years then abandoning it for another so that it may regain fertility naturally by wild vegetation adding humus into the soil.
Grass Strips and Cover Crops
– Grass and cover crops e.g. sweet potato vines, beans and peas reduce the speed of running water thus helping to check soil erosion.
Mulching
– Covering the soil using crop residues or artificial materials such as polythene sheets.
– Helps to conserve the soil in the following ways:
a) Reduces evaporation helping to conserve moisture in the soil.
b) Help to check the speed of running water.
c) Reduces the splashing effect of rain drops.
d) Reduces runoff and increases infiltration ensuring more moisture is going to be available for plants growth.
e) Mulch from crop residues decomposes releasing nutrients into the soil.
f) Controls weeds.
Application of Manure and Fertilizer
– Replenishing nutrients depleted from the soil by constant application of manure or chemical fertilizers.
Controlled Grazing
To solve the problem of overgrazing:
a) The government is advising the farmers through extension officers on the importance of matching the number of livestock with the carrying capacity of land.
b) Emphasizing on quality than quantity by introducing exotic breeds and cross breeds.
c) Establishing ranches in livestock farming regions e.g. Kaptuei group ranch.
d) The land should be subdivided into paddocks so that different sections have time to regain pasture at different intervals.
Filling Quarries
– Filling the pits with rocks and topping with fertile soils e.g. Bamburi Nature Trail where trees have been planted and animals introduced.
Drainage Trenches Flooded areas can be rehabilitated by:
– Digging trenches to drain off excess water to rehabilitate flooded areas.
– Another method is to construct dams across rivers.
Planting Drought Resistant Crops
– Planting in Arid and Semi Arid Lands drought resistant and quick maturing crops which take advantage of the short wet season e.g. Pigeon peas, cassava, millet, sorghum, Katumani maize etc.
Irrigation Schemes in Kenya
Mwea Irrigation Scheme
– Located in Kirinyaga district in central province in Mwea plains on the foot of Mt. Kenya.
– Started by the colonial government in 1954.
Objectives
a) To reclaim the unproductive land from semi-arid conditions.
b) To occupy detainee labour since Mwea was a detention camp for political detainees during 1952s state of emergency.
c) To settle former detainees and the landless.
d) To create employment for former detainees.
e) To increase agricultural production.
Factors Which Influenced the Location of the Scheme
Physical Factors
a) Availability of extensive land which made created room for future expansion.
b) Black cotton soils with high water retention capacities suitable for rice growing.
c) Freely draining clay loamy soils suitable for growing of other cash and food crops.
d) Gently sloping land which allows use of tractors and allows water to flow by gravity reducing the cost of pumping it to the fields.
e) Availability of plenty of water from permanent rivers Thiba and Nyamindi draining the area.
f) Experiences warm weather during the second part of the year suitable for rice growing.
Human Factors
a) The land was not inhabited due to its arid conditions therefore there was no displacement of people from the area.
b) Availability of labour for rice growing to presence of former detainees.
c) Desire by the colonial government to start a project that could occupy detainees.
d) Location near major urban centres such as Nairobi, Embu, Nyeri and Kerugoya which provide immediate market for rice.
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