Journal cover Journal topic
Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
doi:10.5194/hess-2016-467
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
08 Sep 2016
Review status
This discussion paper has been under review for the journal Hydrology and Earth System Sciences (HESS). The manuscript was not accepted for further review after discussion.
Reliability of meteorological drought indices for predicting soil moisture droughts
Devanmini Halwatura, Neil McIntyre, Alex M. Lechner, and Sven Arnold Centre for Water in the Minerals Industry, Sustainable Mineral Institute, The University of Queensland, Australia
Abstract. Meteorological drought indices based on precipitation and/or evaporation are commonly used to detect the presence, severity and duration of soil moisture droughts. However, it is debatable whether droughts can be adequately characterised using only precipitation and/evaporation, or whether more physical based methods using soil water deficits and pressures is necessary. To address this question, the performances of two commonly used meteorological drought indices, the Standard Precipitation Index (SPI) and the Reconnaissance Drought Index (RDI), are evaluated against soil moisture droughts identified using a physically based soil water model. Our analysis is based on three sites in Eastern Australia, each representing specific soil-climate conditions. Drought duration and severity were estimated using SPI and RDI and soil water pressure data were simulated with Hydrus-1D. The performance of the two drought indices was measured in terms of their correlation with simulated monthly minimum soil water pressures, and their ability to estimate the frequency with which the simulated pressure drops below threshold values. There was a significant correlation between the two drought indices (SPI and RDI) and the monthly minimum soil water pressure. Failure rate (FR) and false alarm rate (FAR) of drought indices detect soil moisture drought reasonably well (FR and FAR is <50 %) for both drought indices (SPI and RDI) and soil depths (5 cm and 30 cm) (except Melbourne). Overall SPI performs better (except shallow soils in Bourke) than RDI. However an uncertainty of the FR and FAR in the soil water retention curve is always higher than the uncertainties of drought indices. The complexity and the uncertainty in the model encourage to use the simple drought indices, however the model provide physically relevant soil water pressure values which are species specific for plants.

Citation: Halwatura, D., McIntyre, N., Lechner, A. M., and Arnold, S.: Reliability of meteorological drought indices for predicting soil moisture droughts, Hydrol. Earth Syst. Sci. Discuss., doi:10.5194/hess-2016-467, 2016.
Devanmini Halwatura et al.
Interactive discussionStatus: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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RC1: 'Comments to the paper HESS-2016-467', Anonymous Referee #1, 07 Oct 2016 Printer-friendly Version 
AC1: 'Author Responses on behalf of all Co-Authors for the comments of Anonymous Referee #1', Devanmini Halwatura, 21 Oct 2016 Printer-friendly Version Supplement 
AC2: 'Author Responses on behalf of all Co-Authors for the comments of Anonymous Referee #1', Devanmini Halwatura, 13 Nov 2016 Printer-friendly Version Supplement 
 
RC2: 'revision on hess-2016-467', Anonymous Referee #2, 26 Oct 2016 Printer-friendly Version 
AC3: 'Author Responses on behalf of all Co-Authors for the comments of Anonymous Referee #2', Devanmini Halwatura, 13 Nov 2016 Printer-friendly Version Supplement 
 
SC1: 'Review', Danny Heuvelink, 30 Oct 2016 Printer-friendly Version 
AC4: 'Author Responses on behalf of all Co-Authors for the comments of short communication #1', Devanmini Halwatura, 13 Nov 2016 Printer-friendly Version 
 
SC2: 'Short Comment', Judith Poelman, 31 Oct 2016 Printer-friendly Version 
AC5: 'Author Responses on behalf of all Co-Authors for the comments of short communication #2', Devanmini Halwatura, 13 Nov 2016 Printer-friendly Version 
 
SC3: 'Review', Heleen Westerveld, 31 Oct 2016 Printer-friendly Version 
AC6: 'Author Responses on behalf of all Co-Authors for the comments of short communication #3', Devanmini Halwatura, 13 Nov 2016 Printer-friendly Version 
 
RC3: 'Review', Ryan Teuling, 03 Nov 2016 Printer-friendly Version 
AC7: 'Author Responses on behalf of all Co-Authors for the comments of Dr Ryan Teuling and his students Danny Heuvelink, Judith Poelman and Heleen Westerveld', Devanmini Halwatura, 13 Nov 2016 Printer-friendly Version Supplement 
Devanmini Halwatura et al.
Devanmini Halwatura et al.

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Short summary
Droughts indices that only use rainfall/evaporation may not reliably detect soil moisture droughts. Few comparative studies have been published to guide the decision on the most appropriate method for describe soil moisture droughts. We evaluate the performance of drought indices in predicting soil moisture droughts by comparing drought indices with soil water pressure. The failure and false alarm rates of drought indices showed, indices performed reasonably well in detecting soil moist drought.
Droughts indices that only use rainfall/evaporation may not reliably detect soil moisture...
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