Sprinkler irrigation is a method of water application that closely mimics natural rainfall, distributing water over a field in a controlled spray pattern. This technique delivers water under pressure through a network of pipes and specialized nozzles, moving away from the traditional practice of flooding a field. It provides uniform application of water to crops across various landscapes. The system is versatile, adapting to different crop types and soil conditions, helping farmers stabilize yields.
How Sprinkler Systems Work
The fundamental function of a sprinkler system relies on creating and maintaining water pressure to propel water into the air. A typical system begins with a pumping unit that draws water from a source, such as a well or reservoir, and then pressurizes it. This high-pressure water is transported across the field through a primary network of large-diameter pipes known as the main line.
The main line feeds into smaller, branching conduits called lateral lines, which run adjacent to the crop rows. Specialized devices called sprinkler heads or nozzles are installed at regular intervals along these lines. When the pressurized water reaches the nozzles, it is forced out through small orifices, breaking into a spray of droplets that fall onto the crops and soil. Careful selection of nozzle size and operating pressure allows for a uniform application rate, preventing surface runoff.
Defining the Major Types of Sprinkler Systems
Sprinkler technology is categorized into various types based on their mobility, scale, and method of deployment. One of the simplest configurations is the Permanent or Solid Set system, where all pipes and sprinkler heads remain fixed throughout the irrigation season. These systems are often used for high-value crops or areas requiring precise water delivery. While this fixed setup ensures high uniformity, it requires a substantial initial investment for the extensive piping network.
A major category of large-scale, mechanized irrigation is the Center Pivot system, widely used in commercial agriculture. This system consists of a long lateral pipe mounted on wheeled towers and anchored to a central pivot point. The structure rotates slowly around this point, irrigating a circular area of the field. A variation, the Lateral Move system, moves linearly across a rectangular field, maintaining a straight path using guidance systems.
A third type is the Traveling Gun, also known as a big gun sprinkler, which is a high-capacity, mobile system. This system uses a single, large-capacity nozzle mounted on a trailer that slowly winds itself across the field using a hose reel mechanism. Traveling guns discharge water at a high flow rate and cover a large radius. Although portable and requiring less field infrastructure, they generally operate at higher pressures and are often among the least efficient sprinkler types.
Water Conservation and Resource Management
Sprinkler irrigation offers a significant improvement in water application efficiency compared to traditional surface methods like flood irrigation (40% to 60% efficiency). Standard sprinkler systems generally achieve a field application efficiency between 70% and 85%, reducing water lost to runoff or deep percolation. However, this is less efficient than precise methods, such as drip irrigation, which often exceed 90% efficiency by delivering water directly to the plant’s root zone.
A primary factor affecting sprinkler system efficiency is the loss of water before it reaches the ground, mainly through wind drift and evaporation. Evaporative losses occur as droplets travel through the air, intensified by high air temperature, low humidity, and small droplet size. Combined spray losses from evaporation and drift can range from 1.5% to over 29.0% of the total water discharged, depending on environmental conditions.
Wind speed is a predominant factor, increasing both evaporation and the physical drift of the spray pattern outside the target area. To mitigate these losses, many center pivot systems use Low Elevation Spray Application (LESA) or Low Energy Precision Application (LEPA) sprinklers. These sprinklers are mounted very close to the ground, sometimes below the crop canopy. This placement significantly reduces the time the water is exposed to the air and lowers wind speeds, improving application efficiency.