UAV imagery offers multiple irrigation applications

During the last two decades, technological advances have made a significant impact on many aspects of our lives. The agricultural sector has incorporated such technologies through precision agriculture applications. Remote sensing, using satellites, has been widely adopted for farming to monitor large-scale operations. Although spatial and temporal resolution tradeoffs can be a concern, these issues can be solved using unmanned aerial vehicles. Generally known as drones, UAVs show potential for applications related to daily farming operations such as scouting, irrigation, spraying, weed detection and crop monitoring.

Arkansas producers are making incredible strides in increasing irrigation efficiency to sustain water resources for future generations.

Drones can be equipped with various sensors (cameras) that are readily available in the market. Sensor selection is typically based on the output of interest, available sensor and cost. An RGB sensor is more suitable for visual inspection, while a multispectral sensor can be utilized for crop vegetation growth monitoring. Some drones can use a combination of multispectral and thermal sensors for evapotranspiration estimation for irrigation scheduling purposes. Drones with the addition of a real-time kinematic base station can be used for elevation data.

Arkansas is known as the rice capital of the United States, accounting for half of the country’s total rice acres. Arkansas rice producers have used many irrigation management practices over the years, such as flood, pivot and furrow irrigation. When the groundwater in the aquifers started to decline, producers began implementing several irrigation water management strategies such as multiple inlet rice irrigation, alternate wetting and drying, and land leveling. Arkansas producers are making incredible strides in increasing irrigation efficiency to sustain water resources for future generations.

Drones are useful for multiple irrigation applications such as rice levee tracing, irrigation design, irrigation design validation, irrigation scheduling, and topography mapping for surface, sprinkler and drip irrigation design. The following are some examples of drone usage for irrigation.

Contour levee tracing

Contour levees are considered one of the most laborious methods of managing rice irrigation, due to the substantial mechanical operation requirements to design and maintain levee spills, plant rice on levees, control water depth with unpredictable precipitation, and manage levees to avoid potential levee failure. In this method, levees are constructed to maintain a particular slope in each paddy, as shown in figure 1A. Straight levees is another method of growing rice (see fig. 1B). Scott Matthews is a rice grower in Arkansas, and he utilized drone imagery to trace each contour and straight rice paddy for irrigation design and management purposes, as shown in figure 1C.

Rice growers can utilize drones to measure the surface area for each rice paddy to enhance the irrigation design. Such an application has many advantages, including adjusting the irrigation gates in the polypipe, managing precipitation without causing levee failure and enhancing crop growth and yield.

Irrigation design validation

Matthew Morris, an early drone adopter in Arkansas, utilized his RGB-equipped drone to evaluate the the performance of the irrigation design tools and applications used. After implementing the irrigation design, Morris flew the drone to assess the uniformity of his irrigation system. After inspecting the drone imagery, he realized the irrigation design needed to be adjusted to ensure equal distribution of the irrigation water across the field. Morris readjusted the blue irrigation gates installed on the polypipe, and the images in figure 2 show the irrigation design performance before and after the adjustments. This drone imagery solution for his field helped Morris win first place in an Arkansas irrigation contest.

Drainage canals & ditches

With unpredictable precipitation events, ditches and drainage canals need to be maintained to clear debris or other problems caused by such events. Figure 3 shows where a drone was utilized to fly over the ditches and drainage canal, and a map was created to guide the excavator driver to the debris location. This method has advantages for ditch cleaning over driving along the drainage canal, including potential time savings, cost savings and efficient flood control.

Topographical mapping

Irrigation educators and consultants are playing a significant role in topographical mapping for irrigation design purposes. Many growers are concerned about the handling and processing of these technologies, especially during the busy growing season. Surveying drones show great potential benefits for growers, especially for irrigation purposes. High accuracy elevation data can be obtained using a real-time kinematic drone flown on the head of the field to assess the elevation change across the top of the field where the irrigation tubing is laying. The elevation data obtained from drones is fed to the irrigation design application for accurate irrigation design calculations. This method is extremely important to get accurate elevation data for irrigation designs (see fig. 4).

Drones have shown various solutions for many daily farming operations. With the continuous advance of technologies, more applications would benefit irrigators and the agriculture sector overall. None of these applications were available five years ago. Today we are using drones for irrigation designs, elevation surveys and identifying problem areas, among many others. If you think those applications are beneficial, just wait and see what the next five years bring.  Academic institutions will continue to play a significant role in evaluating the accuracy of such technologies and training young generations to utilize them.

Ahmed Hashem, PhD, is an assistant professor of agricultural systems technology at Arkansas State University in Jonesboro, Arkansas, and the University of Arkansas Division of Agriculture. He is an agricultural engineer and certified UAS pilot.

Mike Hamilton, MSc, is an irrigation instructor with the University of Arkansas Division of Agriculture Cooperative Extension Service and an irrigation specialist with the U.S. Department of Agriculture-Natural Resources Conservation Service in Arkansas.