Hydroclimatology of extreme river flows

Abstract

1. Floods and droughts are recurrent events with characteristics of frequency, magnitude, duration and timing occupying the opposing extremes of natural river flow regimes. This hydrological variability, driven by climate and meteorology and modified by river basin processes, is a key determinant of physicochemical river habitat influencing the structure and function of freshwater communities. 2. A changing (warming) climate is projected to alter water and heat inputs to river systems that drive river flow, and thus, hydrological processes may be subject to unprecedented future change, resulting in potentially unprecedented river flow extremes. 3. We review the hydroclimatology of extreme river flows in changing climates and draw case studies from the European temperate regions. 4. Specifically, we adopt a 'catchment perspective', in which an understanding of meteorological and hydrological processes is used to (i) conceptually define extreme river flows, (ii) explain the (natural) climatic and catchment processes that drive extreme river flows, (iii) discuss future potential changes driven by an anthropogenically modified climate and (iv) identify uncertainties associated with projections of future climate-driven hydrological shifts.

Drought intensification alters the composition, body size, and trophic structure of invertebrate assemblages in a stream mesocosm experiment

“…These trends were accompanied by increasing temperature variability, with the maximum annual water temperature range in each channel varying from 6 to 40°C. Groundwater‐dominated systems, such as many chalk stream reaches across southern England, typically maintain moderate to high flows throughout the year (Garner, Van Loon, Prudhomme, & Hannah, ; Sear et al., ), but protracted dry weather and groundwater abstraction can give rise to supra‐seasonal droughts, during which prolonged but patchy fragmentation and drying of the streambed can occur (Folland et al., ; Kendon, Marsh, & Parry, ; Westwood, Teeuw, Wade, & Holmes, ).…”

High‐frequency monitoring of catchment nutrient exports reveals highly variable storm event responses and dynamic source zone activation

“…Such information is also needed to generate predictions of how river nutrient loads and catchment exports are likely to change under future climate regimes. This latter point is particularly important given that most climate change scenarios suggest an increase in the magnitude and frequency of episodic precipitation events and soil drying through drought across many areas of the world [Kendon et al, 2014;Mann et al, 2017], particularly where local temperatures are <25°C [Wang et al, 2017], which in turn are likely to drive changes in other hydrological variables that influence nutrient flux and in-channel processing through river catchments [Garner et al, 2015].…”

Waning habitats due to climate change: the effects of changes in streamflow and temperature at the rear edge of the distribution of a cold-water fish

“…However, despite these strong evolutionary responses, the current combination of warming and streamflow reduction scenarios is likely to exceed the capacity of many populations to adapt to new conditions (Ayllón et al, 2016). Consistent with regional predictions (Rojas et al, 2012;Garner et al, 2015), significant flow reductions are expected during summertime in most of the studied rivers and streams at the end of the century, and this may mean, in turn, the reduction in the suitable habitat (i.e. the available water volume) (Muñoz-Mas et al, 2016).…”