Chapter 2: Install farm irrigation and drainage systems

Farm irrigation and drainage systems are fundamental for maintaining optimal soil moisture and preventing waterlogging in horticultural enterprises across Kenya. Effective installation of these systems enhances crop productivity, supports sustainable water use, and mitigates risks associated with erratic rainfall patterns common in many Kenyan regions. This chapter focuses on the practical aspects of installing, types of, and testing irrigation and drainage systems tailored for horticultural farms, preparing professionals to execute these tasks with precision and efficiency.

2.1 Installation of farm irrigation and drainage system

Installing a farm irrigation and drainage system means placing the planned components in the field, connecting them in the correct order and making them ready for testing. Water normally passes from the source through a pump or tank, a filter, a water meter and flow meter, the mainline and submains, and then to the drip lines or other application devices, while drains carry surplus water away. Every one of these stages relies on the right tools and equipment, chosen for the size of the farm and the crop. This topic explains why the tools and equipment matter and describes the main items: the drip kit, pipes, fittings, water meter, flow meters and pumps.

2.1.1 Importance of farm irrigation and drainage system tools and equipment

The tools and equipment decide how well the system will work, how long it will last and how much water it will save. Their importance is as follows.

• Water delivery: correctly sized pipes, pumps and fittings deliver the planned amount of water at the right pressure to every plant, so that crops receive water evenly.
• Efficient water use: meters, flow meters and well-chosen application devices reduce losses and show how much water is used.
• Reliability and durability: good quality, correctly selected items resist sun, pressure and soil chemicals, so there are fewer leaks, bursts and breakdowns.
• Speed and accuracy of installation: the right fittings and tools let a crew cut, join and lay pipes quickly and neatly, and mistakes in the layout are avoided.
• Safety: proper tools and equipment reduce injuries from lifting, cutting and digging, and good connections prevent bursts under pressure.
• Control and monitoring: valves, meters and flow meters allow the farm to control and record water use, which supports good records and decisions.
• Lower running costs: items that suit the system waste less water and energy and need less repair.

Choosing the wrong item has the opposite effect. Undersized pipes give low pressure at the end of the line, weak pumps leave blocks short of water, and poor fittings leak.

2.1.2 Types of farm irrigation and drainage system tools and equipment

The main items are summarised below, and each is described afterwards.

2.1.2.1 Drip kit

A drip kit is a ready-made set of parts for a small drip irrigation system, usually sold for an area such as a kitchen garden, a small vegetable plot or a greenhouse. It normally contains a filter, a mainline pipe, drip lines or tapes with emitters at set spacing, start connectors, joiners and end caps. Emitters commonly discharge between about 1 and 4 litres of water per hour. Many small kits are low-pressure and are fed from a raised tank, so that gravity gives the pressure, while larger kits are fed by a pump. The kit chosen must match the area, the crop spacing and the pressure available.

Example: a farmer with a plot of vegetable rows chooses a kit whose drip line spacing matches the row spacing, and checks that the supplied emitter flow will not exceed what the tank or pump can deliver.

2.1.2.2 Pipes

Pipes carry water from the source to the field and, in drainage, away from it. Irrigation pipes are made of polyvinyl chloride (PVC), which is rigid and used for buried mainlines, or of polyethylene, which is flexible and supplied in rolls for drip lines and laterals. A pipe is described by its diameter in millimetres and by its pressure rating, which is the greatest working pressure it can hold. Pipes laid above ground should be UV-resistant, and black polyethylene contains carbon black for this purpose. Drainage pipes are corrugated, perforated and often wrapped in a filter sock to keep soil out.

2.1.2.3 Fittings

Fittings join pipes and control the water. They include couplers to join two pipes, elbows to turn corners, tees for branches, reducers to join different sizes, end caps and plugs to close lines, adaptors to change from one type of connection to another, and valves to switch parts of the system on and off. Fittings must match the pipe in material, diameter and pressure rating. PVC fittings are joined with solvent cement, threaded joints are sealed with thread seal tape, and polyethylene pipe is joined with compression or barbed fittings. Poorly matched or badly made joints are a frequent cause of leaks.

2.1.2.4 Water meter

A water meter measures the total volume of water that has passed through it, in cubic metres, and is read like the distance meter of a vehicle. It is installed in the supply pipe with the flow arrow on its body pointing in the direction of flow, with a strainer and an isolating valve, and in a protected, accessible chamber or box. Records from the meter show how much water has been used for each crop or block.

Example: if the reading at the start of the week is 1,250.0 m³ and at the end it is 1,262.5 m³, the water used is 1,262.5 − 1,250.0 = 12.5 m³, which is 12,500 litres.

2.1.2.5 Flow meters

A flow meter shows the rate at which water is moving, for example in litres per second or cubic metres per hour. Types include paddle-wheel or turbine meters, variable-area meters with a floating ball in a tapered tube, and electromagnetic and ultrasonic meters. Many are placed after the pump or at the head of a block, with a straight length of pipe on each side as the maker specifies, so that the reading is steady.

Example: a block has 400 emitters of 2 litres per hour each, so the expected flow is 400 × 2 = 800 litres per hour, or 0.8 m³ per hour. A flow meter reading much lower suggests blocked emitters or a filter, and a reading much higher suggests a broken pipe.

A water meter shows how much water has been used in total, and a flow meter shows how fast it is flowing now, so the two answer different questions.

2.1.2.6 Pumps

A pump lifts water from a source such as a river, well, borehole or tank and gives it the pressure to travel through the pipes. Types include:

• Surface pumps, usually centrifugal: placed beside the water source and driven by an electric motor or an engine. They need priming, a short and airtight suction pipe, and a strainer or foot valve.
• Submersible pumps: placed below the water in a well or borehole, and they are common for deep sources.
• Solar pumps: run from solar panels and suit sites without a power line.
• Manual pumps: foot-operated or hand-operated pumps suit small plots.

A pump is chosen for the flow rate it must deliver and the total head against which it must work. The total head includes the height the water is lifted, the height of the delivery point and the pressure lost through friction in the pipes. A surface pump cannot draw water from great depth, because suction depends on atmospheric pressure, so the pump is kept as close to the water level as possible.

Chapter Summary

This chapter covered the installation of farm irrigation and drainage systems, highlighting their critical role in enhancing crop productivity and managing water resources effectively. Various types of irrigation and drainage components were examined, including drip kits, pipes, fittings, water meters, flow meters, and pumps, each essential for efficient system operation. The process of testing these systems was emphasized to ensure proper functionality and water distribution. Maintenance practices for irrigation and drainage tools and equipment were discussed to prolong their service life and optimize performance. Detailed procedures for installing the tools and equipment were outlined to guarantee correct setup and operation. Testing of the installed tools and equipment was also explored to verify their readiness for use. Finally, the chapter addressed ongoing maintenance activities necessary to sustain system efficiency and prevent breakdowns, ensuring reliable farm water management.