16 Sep 2019

16 Sep 2019

Review status: this preprint was under review for the journal HESS but the revision was not accepted.

The impact of elevation and flow dynamics on hydrological drought and wet spell characteristics in semi-arid southeast Arizona

Mengtian Lu1,2, Pieter Hazenberg2,a, Xiaohui Lei3, and Hao Wang3 Mengtian Lu et al.
  • 1College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, China
  • 2Department of Hydrology and Atmospheric Sciences, P.O. Box 210011, Tucson AZ 85721-0011, USA
  • 3State Key Laboratory of Simulation and Regulation of Water Cycles in River Basins, China Institute of Water Resources and Hydropower Research, Beijing 100038, China
  • anow at: Deltares, Postbus 177, 2600 MH Delft, the Netherlands

Abstract. Identification and understanding of the dominant control mechanisms of hydrological extremes has drawn worldwide attention in recent decades. However, detailed understanding of drought and wet spells within semi-arid regions has been hampered by the fact that identification is difficult for no flow conditions. Classification methods that have been developed for regions with perennial flow, do not work for ephemeral semi-arid rivers, while approaches for arid environments have difficulties to deal with seasonal runoff. Recently, a method was presented to identify hydrological extremes within semi-arid regions, by combining approaches developed for perennial flow and arid environments. However, this combined approach shows difficulties to identify drought and wet spells within semi-arid domains with a yearly precipitation cycle (e.g. monsoon). The current paper proposes to modify the combined method and make it suitable for these domains.

The modified combined approach presented here to identify hydrological extremes was applied to decade-long discharge observations from 12 different locations within the San Pedro basin in southeastern Arizona. These locations correspond to catchments covering multiple elevation bands and runoff characteristics. Southern Arizona receives the majority of its rainfall from the summertime North American Monsoon (NAM), with frontal systems providing additional precipitation in winter.

Using the modified method, the identified droughts and wet spells last longer compared to the previously defined combined procedure, and drought generally does not only start in spring at the end of the dry season. Furthermore, results show that if a drought or wet spell starts during the NAM or post-NAM season, it will generally last longer as compared to one that starts in winter or spring. This specifically holds for catchments with no perennial flow. By increasing the flow averaging interval, the new method also enables to observe multi-year drought and wet spells patterns. For the precipitation limited semi-arid San Pedro basin results show that multi-year wet spell and drought are rare. This is caused by the strong impact of the summertime NAM that generally acts both as a start and reset button for both types of hydrological extremes.

Mengtian Lu et al.

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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Mengtian Lu et al.

Mengtian Lu et al.


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Short summary
Using a newly developed identification procedure, this work identifies the occurrence and duration of observed hydrological extremes (drought and wet spells) within the semi-arid San Pedro basin that experiences a yearly precipitation season. Results, shows that the summertime North American Monsoon a start and reset button, with very few extremes lasting multiple years, and duration dependent on the time until the following monsoon.