Estimation of crop water stress in a nectarine orchard using high-resolution imagery from unmanned aerial vehicle (UAV)

S. Park, A. Nolan, D. Ryu, S. Fuentes, E. Hernandez, H. Chung, M. O'Connell

Research output: Chapter in Book/Report/Conference proceedingConference PaperResearchpeer-review

13 Citations (Scopus)


Adequate and timely irrigation based on real-time monitoring of crop water status is critical for efficient and sustainable water use. However, detection of water status in large crop fields is not a trivial task as manual inspection can be time consuming and costly. Moreover, the symptoms of water stress are visually detectable only after the crops are already in a significantly water deficient stage. Consequently, capability of monitoring water status in crops on a regular basis could maximize productivity and water use efficiency. As an indicator, the crop water stress index (CWSI) has been widely used to estimate water status in the crop fields. CWSI can be derived from ground-based leaf temperature measurements, however, airborne or UAV-borne high-resolution thermal sensing provides a superior platform to cover large regions within a short time window. In this paper, UAV-borne thermal sensing was conducted to map plant water stress and spatial variability in water control and deficit plots over 1 ha of a nectarine orchard at an altitude of 100 m from ground level. Targets of ground control points (GCPs) were designed to suit the image spatial resolution as well as the visibility in the thermal infrared spectral range. The target was made of aluminium body marked with a black cross, which can be detected as a cool object in the thermal infrared image due to its low emissivity. Thermal infrared images were post-processed to generate single temperature-based orthomosaic image for the entire study field. CWSI map was computed using canopy temperatures at the centre of canopies from the mosaic image. Histogram analysis was used to estimate the lower boundary temperature (Twet), representing the temperature of fully transpiring leaves. The upper boundary temperature (Tdry) was determined by air temperature + 6 0C. Ground measurements of midday stem water potential (SWP) and stomatal conductance (gc) were collected concurrently with UAV operation and used to correlate the thermal measurement to crop biophysical parameters. Results showed that CWSI was in good agreement with both SWP and gc with determination coefficients (R2) of 0.92 and 0.97, respectively. Thus, remotely estimated CWSI from a UAV platform can play an important role in effective mapping of spatial variability of nectarine water stress and subsequently in optimal management of irrigation.

Original languageEnglish
Title of host publicationProceedings - 21st International Congress on Modelling and Simulation, MODSIM 2015
EditorsTony Weber, Malcolm McPhee, Robert Anderssen
Place of PublicationCanberra ACT Australia
PublisherModelling and Simulation Society of Australia and New Zealand (MSSANZ)
Number of pages7
ISBN (Print)9780987214355
Publication statusPublished - 2015
EventInternational Congress on Modelling and Simulation 2015: Partnering with industry and the community for innovation and impact through modelling - Gold Coast Convention and Exhibition Centre, Broadbeach, Australia
Duration: 29 Nov 20154 Dec 2015
Conference number: 21st


ConferenceInternational Congress on Modelling and Simulation 2015
Abbreviated titleMODSIM2015
OtherThe 21st International Congress on Modelling and Simulation (MODSIM2015) was held at the Gold Coast Convention and Exhibition Centre, Broadbeach, Queensland, Australia from Sunday 29 November to Friday 4 December 2015.

It was held jointly with the 23rd National Conference of the Australian Society for Operations Research and the DSTO led Defence Operations Research Symposium (DORS 2015).

The theme for this event was Partnering with industry and the community for innovation and impact through modelling.

Papers from these proceedings should be cited using this format:

Walmsley, B.J., Oddy, V.H., Gudex, B.W., Mayer, D.G. and McPhee, M.J. (2015). Transformation of the BeefSpecs fat calculator: Addressing eating quality and production efficiency with on-farm decision making. In Weber, T., McPhee, M.J. and Anderssen, R.S. (eds) MODSIM2015, 21st International Congress on Modelling and Simulation. Modelling and Simulation Society of Australia and New Zealand, December 2015, pp. 490–496. ISBN: 978-0-9872143-5-5.
Internet address


  • Canopy temperature
  • Crop Water Stress Index (CWSI)
  • Stem Water Potential (SWP)
  • Thermal infrared imagery
  • Unmanned Aerial Vehicle (UAV)

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