A global evaluation of streamflow drought characteristics

Abstract

Abstract. How drought is characterised depends on the purpose and region of the study and the available data. In case of regional applications or global comparison a standardisation of the methodology to characterise drought is preferable. In this study the threshold level method in combination with three common pooling procedures is applied to daily streamflow series from a wide range of hydrological regimes. Drought deficit characteristics, such as drought duration and deficit volume, are derived, and the methods are evaluated for their applicability for regional studies. Three different pooling procedures are evaluated: the moving-average procedure (MA-procedure), the inter-event time method (IT-method), and the sequent peak algorithm (SPA). The MA-procedure proved to be a flexible approach for the different series, and its parameter, the averaging interval, can easily be optimised for each stream. However, it modifies the discharge series and might introduce dependency between drought events. For the IT-method it is more difficult to find an optimal value for its parameter, the length of the excess period, in particular for flashy streams. The SPA can only be recommended as pooling procedure for the selection of annual maximum series of deficit characteristics and for very low threshold levels to ensure that events occurring shortly after major events are recognized. Furthermore, a frequency analysis of deficit volume and duration is conducted based on partial duration series of drought events. According to extreme value theory, excesses over a certain limit are Generalized Pareto (GP) distributed. It was found that this model indeed performed better than or equally to other distribution models. In general, the GP-model could be used for streams of all regime types. However, for intermittent streams, zero-flow periods should be treated as censored data. For catchments with frost during the winter season, summer and winter droughts have to be analysed separately.

Future discharge drought across climate regions around the world modelled with a synthetic hydrological modelling approach forced by three general circulation models

“…Some attempts have been made to derive hydrological drought characteristics at the global or continental scale under future climate. Forzieri et al (2014) project an increase in deficit volume of river flow for vast areas of Europe, except the Scandinavian countries and North Russia. Hirabayashi et al (2008) and Feyen and Dankers (2009) project a substantial increase in the number of drought days (PDY) or flow deficit volume for the period 2071-2100 in some regions, whereas in contrast, wide areas will benefit from a decrease in drought days.…”

“…Arnell, 2003;Milly et al, 2005;Hagemann et al, 2013;Schewe et al, 2014). Other studies also focus on low water availability and include minimum flow or flow deficits to investigate future drought (e.g Feyen and Dankers, 2009;Forzieri et al, 2014). Few large-scale studies test hydrological model performance by comparing GCM forcing against observed forcing.…”

“…At the continental scale, Andreadis et al (2005) investigated runoff drought in the United States and Prudhomme et al (2011) studied European runoff drought. Forzieri et al (2014) project for the A1B scenario that future drought in streamflow will increase in many European regions, except for North and Northeast Europe. Corzo Perez et al (2011b), Van Huijgevoort et al (2012) and Wanders et al (2015) showed the changes in hydrological drought characteristics at the global scale.…”

“…The Q 80 has been used in multiple studies where drought is studied (e.g. Fleig et al, 2006;Parry et al, 2010). A monthly threshold was applied, where the Q 80 is derived for every month of the year in the control period.…”

A systematic assessment of drought termination in the United Kingdom

“…Low flow thresholds such as Q 70 (Hisdal et al, 2001) and Q 80 (e.g. Tallaksen et al, 2009) have been widely used in the literature, and threshold levels between Q 70 and Q 90 are generally considered appropriate (Fleig et al, 2006). The use of an average flow threshold would be expected to increase the overall duration of drought (as illustrated by Tallaksen et al, 1997) as well as the drought development and drought termination phases.…”