Abstract
Intermittent rivers are prevalent in many countries across Europe and in
Mediterranean countries outside Europe, but little is known about the
temporal evolution of intermittency characteristics and their
relationships with climate variability. In this study, a trend analysis
is performed on the annual and seasonal number of zero-flow days, the
maximum duration of dry spells and the mean date of the zero-flow
events, on a database of 452 rivers in European and in Mediterranean
countries outside Europe, with varying degrees of intermittence. In
addition, the relationships between flow intermittence and climate are
investigated using the Standardized Precipitation Evapotranspiration
Index (SPEI) and six climate indices describing large scale atmospheric
circulation. Results indicated a strong spatial variability of the
seasonal patterns of intermittence and the annual and seasonal number of
zero-flow days, which highlights the controls exerted by local catchment
properties. Most of the detected trends indicate an increasing number of
zero-flow days which also tend to occur earlier in the year, in
particular in Southern Europe. The SPEI is found to be strongly related
to the annual and seasonal zero-flow day occurrence in more than half of
the stations for different accumulation times between 12 and 24 months.
Conversely, there is a weak dependence of river intermittence with
large-scale circulation indices. Overall, these results suggest
increased water stress in intermittent rivers that may affect their
biota and biochemistry and also reduce available water resources.