EXPLAINER

How Remote Sensing Technology Improves Efficiency of Irrigation Systems

New technology can help improve farming efficiency and production. Photo credit: ADB.
New technology can help improve farming efficiency and production. Photo credit: ADB.

Published: 23 July 2020

Earth observation data can help farmers increase crop yields and save water at the same time.

Introduction

The vast majority of renewable water resources in Asia goes to the irrigation sector. With worsening water scarcity and the expansion of irrigation systems, the gap between supply and demand is widening. There is currently a dire need to measure the flow of water in irrigation canals, the volume of groundwater pumped, the amount of water in the soil, and the amount of water consumed. With approximately 300 million hectares of irrigated land in Asia, it is not feasible to install flow meters and soil moisture probes everywhere. Instead, a system based on earth observation data is suggested.

With the increase of free satellite data combined with scientific algorithms and cloud computing capacity, developing affordable operational monitoring systems for irrigation management is now feasible. The use of virtual field sensors can help farmers improve irrigation management for increased water savings and better crop production. Drone measurements are used to verify the satellite images.

The Asian Development Bank (ADB) is currently using a mobile application (app) called IrriWatch for irrigation scheduling on select corn, sugar beet, and potato fields in Kazakhstan. This is a pilot and demonstration activity under the Knowledge and Innovation Support for ADB's Water Financing Program.

How does the app work?

IrriWatch provides information every night to guide farmers and irrigators on what to do during the next 24 hours. It shows the amount of moisture in the soil and how much water should be used the next day. It also provides daily data of applied and consumed water for fields subscribed to the app and the crop production the past day, which enable farmers to know the impact of their irrigation. The system allows farmers and communities to gauge every field’s needs for better efficiency and water productivity.

In addition, it provides an irrigation management platform for managers and public entities, such as irrigation departments. It displays the daily situation for every individual field and shows on-farm water productivity, irrigation efficiencies, and field scale uniformities. The portal displays irrigation water provided to and consumed by each individual field, which is useful for operational decisions on water withdrawals and canal operations for achieving equity in water supplies. Careless use of scarce water will be detected immediately. The same information is given to water resources planners, irrigation managers, irrigation advisory service providers, and farmers to promote transparency.

The app can be downloaded for free from the PlayStore and AppStore.

How does the app get its information?

The app receives information through satellites. Earth observation satellites measure spectral radiation from irrigated crops. The images from satellites—Landsat, EcoStress, Sentinel, Visible Infrared Imaging Radiometer Suite (VIIRS), Meteosat Second Generation (MSG), and Global Precipitation Mission (GPM)—are available for free and may be used to create a time series. Raw satellite data, however, does not mean anything unless it is analyzed.

Remote sensing algorithms are built to convert raw data into several key biophysical parameters to quantify the irrigation process. Crop temperature is most useful for determining the soil moisture status of irrigated crops. Well-irrigated crops have a low surface temperature (see examples below). With moisture depleting from the root zone, crop temperature rises. Hence, the crop temperature in combination with auxiliary satellite data can be used to infer soil moisture and actual evapotranspiration without any instrument in the field.

Other satellites measure the fraction of vegetation cover that represents the crops’ phenological phase, the amount of solar radiation absorbed for photosynthesis, and rainfall. Phenology is the study of crop development cycles and how these are influenced by climate change and habitat factors.

Sample of crop temperature that can vary between 298 K (25οC) to 308 K (35οC), depending on the soil moisture conditions of the root zone. Moist land displays low temperature.

How can farmers benefit from using the app?

While agriculture agencies have programs on improving irrigation water management, farmers are the ones in the field who make essential daily decisions. Meteorological, soil and crop dynamics vary daily. Farmers and their irrigators need guidance and support to (i) irrigate not more than what is needed (otherwise the water leaks away), and (ii) irrigate sufficiently to avoid crop production losses (crop yield declines if there is no sufficient moisture available for the roots of the crop). The challenge is to find the point where crops remain healthy but with lower water supply. This point, however, cannot be reached through intuition. Technological help is needed to measure a field every 10 meters by 10 meters. By using local dynamics, one can achieve a sustainable and profitable product that is more climate-resilient and environmentally friendly.

IrriWatch sends the following information at 10 p.m. to their mobile phones:

  • Do you need to irrigate tomorrow? (Y/N)
  • If Y, what is the range of water to be applied (minimum to maximum amount in millimeters per day)
  • If N, what is the time until next irrigation (X days)

The minimum amount of applied water is based on restoring soil moisture back to a level that is above the critical soil moisture from where crop production is not adversely affected—taking into account daily evapotranspiration rates and expected rainfall based on weather forecasts. The maximum range is based on not exceeding soil water-holding capacities and the type of irrigation system in place. The farmer will utilize his skills to decide on the final amount of irrigation water to be applied and should search within the range provided in the app.

How has the pilot and demonstration activity in Kazakhstan fared?

The ADB pilot and demonstration activity have shown that current irrigation applications could be reduced by 33%. Instead of irrigating every day, the pivots at the KyzylSha farm are now irrigated 2 out of 3 days. Pivot is a crop irrigation method in which the equipment rotates around a pivot and crops are watered with sprinklers.

The app advised lower irrigation amounts than what is traditionally practiced for corn in this semi-arid region, and the farm manager instructed his irrigators to cut back water supply. Water for this area is pumped from the nearby Chu River; now more water remains at the source and can be utilized by downstream users. This also saves 33% in energy costs, reducing demand for fossil energy and fuel expenses of the farmer.

Actual evapotranspiration from center pivot systems in Chu. This can be interpreted as the minimum amount that should be irrigated to replenish the soil moisture in the root zone. These values are lower than estimated by conventional methods.

Why do we need to control water volume in irrigation?

While most water services—such as those for domestic use—are allocated, regulated, and measured, this is not the case for the irrigation sector, and this needs to change. We need to know where every drop of water goes and whether it is used efficiently.

While discharge measurement structures and flow meters are often encouraged as part of standard measurement programs in irrigation systems, these are hardly used in farm operations because of operational costs and maintenance challenges. Groundwater abstractions are also largely unmetered.

Irrigation water originates from surface water and groundwater sources. But more control is needed to ensure efficient water delivery at the farm gates. Volumetric allocations should be prepared before the onset of the growing season. Groundwater abstractions should also be considered because it is an important source of water, especially during periods of drought.

It is important to note that irrigation water supply should meet only the crop water and soil leaching requirements and not be wasted. The basic concept of irrigation is to provide water taken up by crop and transported as sap flow for transpiration into the atmosphere. No more, no less, except for leaching out excessive salts.

Next steps

Agricultural and non-agricultural users want to use every drop of water efficiently. The construction of infrastructure and investments in micro-irrigation technologies make for better irrigation management. However, these are by no means a guarantee for achieving water savings, higher water productivity, and irrigation efficiency. Many examples exist of suboptimal operations.

A system based on field-by-field and day-by-day measurements, such as the app, has the potential to create changes. It helps to implement policy developments in the field and shape the big picture strategies that address broader economic and societal issues.

Remote sensing, such as the one used by the app and portal, should be considered an operational necessity for improved irrigation management—similar to purchasing a weather station or a four-wheel-drive vehicle. Investments in irrigation modernization are not enough.

The last bit is to manage water better, and according to local and daily crop, soil, and weather conditions. This is a game-changer, requiring a mental shift from building infrastructure to managing water, and it is a pre-requisite for utilizing these new technologies.

Resources

Asian Development Bank. Knowledge and Innovation Support for ADB's Water Financing Program.

C. Perry. 2007. Efficient Irrigation; Inefficient Communication; Flawed Recommendations. Irrigation and Drainage. 56 (4). pp. 367–378.

IrriWatch. “Showreel Irriwatch.” 13 February 2020. YouTube video, 2:07.

M. Tatalovic. 2009. Irrigation Reform Needed in Asia. Nature. 17 August.

R. van der Lee. “Introduction to Irriwatch.” 2 July 2020. YouTube video, 38:33.

Ask the Expert

  • Wim Bastiaanssen
    Irrigation and remote sensing expert

    Wim Bastiaanssen has developed remote sensing models, including Surface Energy Balance Algorithm for Land (SEBAL) and Scalable Water Balance for Earth Observations (SWEO) for rapid water accounting. He consults and advises for the Asian Development Bank, World Bank, and Food and Agriculture Organization of the United Nations on remote sensing applications for agricultural water management. He established IrriWatch in 2019 to meet the growing need for practical on-farm technologies that improve irrigation water management.

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The views expressed on this website are those of the authors and do not necessarily reflect the views and policies of the Asian Development Bank (ADB) or its Board of Governors or the governments they represent. ADB does not guarantee the accuracy of the data included in this publication and accepts no responsibility for any consequence of their use. By making any designation of or reference to a particular territory or geographic area, or by using the term “country” in this document, ADB does not intend to make any judgments as to the legal or other status of any territory or area.




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