Agriculture Form 1 – Water Supply, Irrigation and Drainage

Introduction

• Water is a very important natural resource essential for life.
• It is necessary for both crops and livestock to grow and thrive.

Uses of Water in the Farm

• Cleaning farm equipment to maintain hygiene and prevent disease spread.
• Irrigation in dry areas to supplement rainfall and ensure crop growth.
• Processing farm produce, for example, washing and processing coffee beans.
• Drinking water for livestock and humans to maintain health.
• Mixing agro-chemicals such as acaricides, fungicides, and herbicides for pest and disease control.
• Providing power in water mills to grind grain crops into flour.
• Cooling engines used in farm machinery to prevent overheating.
• Construction work on the farm requiring water for mixing and other purposes.

Sources of Water in the Farm

There are three major sources of water on the farm:

• Surface water:

This includes water collected from:

• Rivers,
• Streams,
• Dams.

• Groundwater:

This includes water obtained from:

• Springs,
• Wells,
• Boreholes.

• Rainwater:

This is water collected in various ways such as:

• From rooftops,
• From rock surfaces during rainfall, stored for later use.

Collection and Storage of Water

• Dams:

• Structures constructed across rivers and channels to collect and store water.
• They provide water for use during dry seasons when rainfall is insufficient.

• Weirs:

• Structures built across rivers to raise the water level for easier pumping.
• Unlike dams, water flows over the barrier created by the weir.

• Water Tanks:

• Constructed from concrete, stone, metal sheets, or plastic materials.
• Used to store rainwater or water pumped from other sources.
• Tanks should be covered to prevent contamination from dust and debris.

Pumps and Pumping of Water

• Pumping involves lifting water from one point to another using mechanical force.
• Water is pumped from sources and conveyed to where it is needed for use or storage.

Types of Water Pumps

These pumps are used to lift water from its source:

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

Conveyance of Water

• This is the process of moving water from the source or storage point to where it will be used or stored.

• Piping:

• Water is moved through pipes to the desired location.

Common types of pipes include:

• Metal pipes
• Plastic pipes
• Hose pipes

• Use of Containers:

• Water is drawn and carried in containers such as drums, jerry cans, pots, gourds, tanks, and buckets.
• These containers can be transported by animals, bicycles, humans, or vehicles.

• Use of Canals:

• Water is conveyed from a higher point to a lower point along a gradual slope to avoid soil erosion.
• This method is mostly used for irrigation and providing water to livestock.

Water Treatment

• Raw water contains impurities that may be dissolved, floating, or suspended.

These impurities are grouped into three categories:

• Physical impurities: dissolved impurities detected by colour, taste, and smell.
• Chemical impurities: dissolved impurities identified through chemical analysis.
• Biological impurities: microorganisms such as bacteria, viruses, and algae present in water.

Importance of Treating Water

• To kill disease-causing microorganisms such as cholera and typhoid bacteria that thrive in dirty water.
• To remove harmful chemical impurities such as excess fluoride.
• To eliminate unpleasant smells and bad taste.
• To remove sediments like soil, sand, and sticks.

Methods of Treating Water

• Aeration: removal of smell and odour by fine spraying or bubbling air through water.
• Sedimentation: allowing water to stand in large containers so solid particles settle at the bottom.
• Filtration: passing water through fine granular materials to remove solid particles and biological substances.
• Coagulation: adding chemicals that precipitate impurities and soften hard water.
• Chlorination: sterilizing water to destroy disease-causing organisms.

Irrigation

• Irrigation is the artificial application of water to crops in dry areas or where natural water is insufficient.
• It is a method of land reclamation in arid and semi-arid regions to improve crop production.

Factors to Consider in Identifying and Assessing Land for Irrigation Development

• Topography of the land to ensure water flow and distribution.
• Soil type to determine water retention and suitability for crops.
• Type of crop to be grown and its water requirements.
• Availability of water sources for irrigation.
• Human factors such as skills, capital availability, and economic activities.

Types of Irrigation

• Surface irrigation:

• Includes flood irrigation and basin irrigation methods.
• Commonly used in flat areas.
• Challenges include water loss through seepage and increased soil salinity.

• Sub-surface Irrigation:

• Uses porous or perforated pipes to deliver water below the soil surface.
• Suitable for sloping areas and where water is limited.

• Overhead or Sprinkler Irrigation:
• Used in areas that are not steep, simulating rainfall by spraying water over crops.

• Drip or Trickle Irrigation:

• Delivers water directly to the roots of plants, conserving water.
• Ideal for areas with limited water and relatively flat or gently sloping land.

Drainage

• Drainage is the method of removing excess water or lowering the water table from marshy or waterlogged land.
• It is also a method of land reclamation to improve soil conditions for farming.

Importance of Drainage as a Method of Land Reclamation

• Increases soil aeration, allowing roots to access oxygen.
• Raises soil temperature, promoting better crop growth.
• Enhances microbial activity in the soil, improving fertility.
• Reduces toxic substances that accumulate in waterlogged soils.
• Increases soil volume available for root exploitation.

Methods of Drainage

• Use of open ditches to channel excess water away.
• Installation of underground drain pipes to remove water below the surface.
• French drains, which are gravel-filled trenches with perforated pipes.
• Cambered beds to facilitate surface runoff of excess water.
• Pumping out water from the soil in severely waterlogged areas.
• Planting tree species such as eucalyptus that absorb large amounts of water.

Water Pollution

• Water pollution is the process by which harmful substances enter water bodies.
• The harmful substances are called pollutants.

Agricultural practices that contribute to water pollution include:

• Use of inorganic fertilizers that can runoff into water sources.
• Use of pesticides that contaminate water bodies.
• Poor cultivation practices such as over-cultivation and farming along riverbanks.
• Overgrazing, which leads to soil erosion and siltation in water sources.

Methods of Preventing Water Pollution

• Implementing soil conservation measures to minimize soil erosion.
• Fencing off water sources to prevent contamination by animals and humans.
• Adopting organic farming practices, such as controlling pests and weeds without chemicals.
• Planting grass along riverbanks to reduce siltation and soil runoff.
• Proper disposal of empty chemical containers to prevent pollution.