Introduction to Water Supply, Irrigation and Drainage

1/11/2020

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Introduction to Water Supply, Irrigation and Drainage

Water is a very important natural resource.
It is necessary for both crops and livestock.

Uses of water in the farm;

Cleaning equipment.
Irrigation in dry areas.
Processing farm produce, for example, coffee.
Drinking by livestock and man.
Mixing agro-chemicals such as acaricide, fungicides and herbicides.
Providing power in water mills to grind grain crops.
Cooling engines.
Construction work.

Introduction to Water Supply, Irrigation and Drainage

Sources of Water in the Farm

Three major sources of water in the farm are:

Surface water:
Includes water from;

Rivers,
Streams
Dams.

Ground water:
Includes water from;

Springs,
Wells
Boreholes.

Rain water:
This is water tapped in various ways such as;

Rooftops
Rock surface, when it is raining and stored in various ways.

Collection and Storage of Water

Dams:
These are structures constructed across rivers and channels.
They collect and store water for use during the dry season.

Weirs:
These are structures constructed across rivers to raise the water level for easy pumping.
Unlike in the dams, water flows over the barrier created across the river.

Water Tanks:
These are structures made of concrete, stone, metal sheets and plastics.
They store water from rain or that which has been pumped from other sources.
Tanks should be covered to prevent contamination from dust.

Pumps and Pumping of Water

Pumping is the lifting of water from one point to another by use of mechanical force.
Water is pumped from the various sources and then conveyed to where it is required for use or storage.

Types of Water Pumps
Used to lift water from its source.

Centrifugal pumps
Piston or reciprocating pumps
Semi-rotary pumps and Hydram

Conveyance of Water
This is the process of moving water from one point, usually the source or point of storage to where it will be used or stored.

Piping;
This is where water is moved through pipes such as;

Metal pipes
Plastic pipes
Hose pipes

Use of Containers:
In this case water is drawn and put in containers, drums, Jerry cans, pots, gourds, tanks and buckets .
Which are carried by animals, bicycles, human beings and vehicles.

Use of Canals:
In this case water is conveyed from a high point to a lower one along a gradual slope to avoid soil erosion.
Water conveyed through this way is mostly used for irrigation and livestock.

Water Treatment

Raw water contains impurities which may be dissolved, floating or suspended in water.
These impurities are grouped into three categories, namely:

Physical impurities: these are dissolved impurities detected by colour, taste and smell.
Chemical impurities: these are dissolved impurities detected by use of chemical analysis.
Biological impurities: these are microorganisms in water such as bacteria, viruses and algae.

Importance of Treating Water

To kill disease causing microorganisms such as cholera and typhoid bacteria that thrive in dirty water.
To remove chemical impurities such as excess fluoride which may be harmful to human beings.
To remove smells and bad taste.
To remove sediments of solid particles such as soil, sand and sticks.

Methods of Treating Water

Aeration: this is the removal of smell and odour from water by fine spraying or bubbling of air.
Sedimentation: this is where water is put in large containers so that solid particles such as sand, metal and others can settle at the bottom.
Filtration: this is passing water through fine granular materials to remove solid particles and biological substances.
Coagulation: addition of chemicals which precipitate impurities and help in softening of hard water.
Chlorination: Sterilization to destroy disease causing organisms.