Preprints
https://doi.org/10.5194/nhess-2020-265
https://doi.org/10.5194/nhess-2020-265

  19 Aug 2020

19 Aug 2020

Review status: a revised version of this preprint was accepted for the journal NHESS and is expected to appear here in due course.

Soil moisture and streamflow deficit anomaly index: An approach to quantify drought hazards by combining deficit and anomaly

Eklavyya Popat1 and Petra Döll1,2 Eklavyya Popat and Petra Döll
  • 1Institute of Physical Geography, Goethe University Frankfurt, Germany
  • 2Senckenberg Leibniz Biodiversity and Climate Research Centre Frankfurt (Sbik-F), Frankfurt, Germany

Abstract. Drought is understood as both a lack of water (i.e., a deficit as compared to some requirement) and an anomaly in the condition of one or more components of the hydrological cycle. Most drought indices, however, only consider the anomaly aspect, i.e., how unusual the condition is. In this paper, we present two drought hazard indices that reflect both the deficit and anomaly aspects. The soil moisture deficit anomaly index, SMDAI, is based on the drought severity index, DSI, but is computed in a more straightforward way that does not require the definition of a mapping function. We propose a new indicator of drought hazard for water supply from rivers, the streamflow deficit anomaly index, QDAI, which takes into account the surface water demand of humans and freshwater biota. Both indices are computed and analyzed at the global scale, with a spatial resolution of roughly 50 km, for the period 1981–2010, using monthly time series of variables computed by the global water resources and the model WaterGAP2.2d. We found that the SMDAI and QDAI values are broadly similar to values of purely anomaly-based indices. However, the deficit anomaly indices provide more differentiated, spatial and temporal patterns that help to distinguish the degree of the actual drought hazard to vegetation health or the water supply. QDAI can be made relevant for stakeholders with different perceptions about the importance of ecosystem protection, by adopting the approach for computing the amount of water that is required to remain in the river for the well-being of the river ecosystem. Both deficit anomaly indices are well suited for inclusion in local or global drought risk studies.

Eklavyya Popat and Petra Döll

 
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Eklavyya Popat and Petra Döll

Eklavyya Popat and Petra Döll

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Short summary
Two drought hazard indices are presented that combine the drought deficit and anomaly aspects: one for soil moisture drought (SMDAI), where we simplified the DSI and the other for streamflow drought (QDAI), to our knowledge, is the first-ever deficit-anomaly drought index including surface water demand. Both indices are tested at the global scale with WaterGAP 2.2d outputs, provides more differentiated, spatial and temporal patterns distinguishing the actual degree of respective drought hazards.
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