Editing IPCC:AR6/WGI/Chapter-11 (section)

==== 11.6.2.4 Hydrological Deficits ====

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There is evidence based on streamflow records of increased hydrological droughts in East Asia (D. [[#Zhang--2018|]] [[#Zhang--2018|]] [[#Zhang--2018|Zhang et al., 2018]] ) and southern Africa ( [[#Gudmundsson--2019|Gudmundsson et al., 2019]] ). In areas of Western and Central Europe and Northern Europe, there is no evidence of changes in the severity of hydrological droughts since 1950 based on flow reconstructions ( [[#Caillouet--2017|Caillouet et al., 2017]] ; [[#Barker--2019|Barker et al., 2019]] ) and observations ( [[#Vicente-Serrano--2019|Vicente-Serrano et al., 2019]] ). In the Mediterranean region, there is ''high confidence'' in hydrological drought intensification ( [[#11.9|Section 11.9]] ; [[#Giuntoli--2013|Giuntoli et al., 2013]] ; [[#Lorenzo-Lacruz--2013|Lorenzo-Lacruz et al., 2013]] ; [[#Gudmundsson--2019|Gudmundsson et al., 2019]] ). In south-eastern South America there is a decrease in the severity of hydrological droughts ( [[#Rivera--2018|Rivera and Penalba, 2018]] ). In North America, depending on the methods, datasets and study periods, there are differences between studies that suggest an increase ( [[#Shukla--2015|Shukla et al., 2015]] ; [[#Udall--2017|Udall and Overpeck, 2017]] ) versus a decrease in hydrological drought frequency ( [[#Mo--2018|Mo and Lettenmaier, 2018]] ), but in general there is strong spatial variability ( [[#Poshtiri--2016|Poshtiri and Pal, 2016]] ). Streamflow observation reference networks of near-natural catchments have also been used to isolate the effect of climate trends on hydrological drought trends in a few regions, but these show limited trends in Northern Europe and Western and Central Europe ( [[#Stahl--2010|Stahl et al., 2010]] ; [[#Bard--2015|Bard et al., 2015]] ; [[#Harrigan--2018|Harrigan et al., 2018]] ), North America ( [[#Dudley--2020|Dudley et al., 2020]] ) and most of Australia, with the exception of Eastern and Southern Australia (X.S. [[#Zhang--2016|Zhang et al., 2016]] ). Given the low availability of observations, there are few studies analysing trends of drought severity in the groundwater. Nevertheless, some studies suggest a noticeable response of groundwater droughts to climate variability ( [[#Lorenzo-Lacruz--2017|Lorenzo-Lacruz et al., 2017]] ) and increased drought frequency and severity associated with warming, probably as a consequence of enhanced ET induced by higher AED ( [[#Maxwell--2016|Maxwell and Condon, 2016]] ). This is supported by studies in Northern Europe ( [[#Bloomfield--2019|Bloomfield et al., 2019]] ) and North America ( [[#Condon--2020|Condon et al., 2020]] ).

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