Spatial mapping of actual evapotranspiration and soil moisture in the Murrumbidgee catchment: Examples from National Airborne Field Experimentation

Mohsin Hafeez, Shahbaz Khan, Kaishan Sng, Umair Rabbani

Research output: Book chapter/Published conference paperConference paperpeer-review

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Spatial knowledge of land surface evapotranspiration and root zone soil moisture is of prime interest for environmental applications, such as optimizing irrigation water use, irrigation system performance, crop water deficit, drought mitigation strategies and accurate initialisation of climate prediction models especially in arid and semi arid catchments where water shortage is a critical problem. The recent drought in Australia and concerns about climate change has highlighted the need to manage water resources more sustainably especially in the Murrumbidgee catchment which utilizes bulk water for food production. This study focused on estimation of daily actual evapotranspiration and soil moisture in Yanco area including Coleambally Irrigation Area (CIA) area and Kyeamba creek, using the SEBAL model applied to a remote sensing TERRA/MODIS,NOAA AVHRR 18 and Landsat 5 TM sensor during different satellite over pass days in National Airborne Field Experimentation (NAFE) campaign, lasted over 3 weeks (October 30 to November 21,2006). All ground truth data for calibration of model was collected during the field campaign. Instruments like a thermal imager and a tri-spectral scanner was flown onboard a small environmental research aircraft at different altitudes together with coincident ground data collection on soil moisture, surface roughness, skin and soil temperature, and vegetation water content. Results showed that actual ET estimated from NOAA AVHRR 18 was always overestimating (range from 11.5% to 59.3%) as comparison to Eddy system (on average 37%) during the image acquisition dates. However, for the same image acquisition dates, TERRA/MODIS ET ranges from 9.8% lower to 14.3% higher than the Eddy system. Landsat 5 TM modeled ET results were comparable to the Eddy Covariance system having a minor error of -1.21%. Similarly, root zone soil moisture modeled results showed that soil moisture ranges from 0.3-0.7 degree of saturation for Yanco area and 0.3-0.5 degree of saturation for Kyeamba creek on November 14. The effect of rainfall on Nov. 12 was captured in soil moisture results because most of the pixels showing high degree of saturation. It was proven possible to simultaneously use SEBAL for different sensors with the combination of high spatial and temporal resolution to estimate ET spatial distribution characteristics; though the accuracy of NOAA-AVHRR derived result is not ideal. The Landsat ET results in this study match very well with the Eddy system. Considering the lack of high spatial resolution thermal satellite and need of time-series ET dynamics, the MODIS data could be used to provide seasonal actual ET for regional studies. The combination of MODIS and Landsat can be a better choice for future ET study at regional or catchment scale, but further study need to be conducted to integrate to provide both high spatial and temporal ET. Estimation of actual ET and soil moisture from TERRA MODIS in combination with Landsat imagery indicated relatively good accuracy and potential for use in the water balance and water productivity analysis at the catchment level. In future, the ET will be modeled from high resolution airborne data acquired during NAFE campaign over Yanco area and Kyeamba creek and the results will be compared with the optical satellite imagery results to find out uncertainty in up-down scaling modeling for ET estimation.
Original languageEnglish
Title of host publicationLand, Water and Environmental Management
Subtitle of host publicationIntegrated Systems for Sustainability
EditorsLes Oxley, Don Kulasiri
Place of PublicationChristchurch, New Zealand
PublisherModelling and Simulation Society of Australia and New Zealand
Number of pages7
ISBN (Electronic)9780975840047
Publication statusPublished - 2007
EventInternational Congress on Modelling and Simulation (MODSIM) - Christchurch, New Zealand
Duration: 10 Dec 200713 Dec 2007


ConferenceInternational Congress on Modelling and Simulation (MODSIM)
Country/TerritoryNew Zealand


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