Climate and hydrological variability: the catchment filtering role

Abstract

Abstract. Measuring the impact of climate change on flood frequency is a complex and controversial task. Identifying hydrological changes is difficult given the factors, other than climate variability, which lead to significant variations in runoff series. The catchment filtering role is often overlooked and thus may hinder the correct identification of climate variability signatures on hydrological processes. Does climate variability necessarily imply hydrological variability? This research aims to analytically derive the flood frequency distribution based on realistic hypotheses about the rainfall process and the rainfall-runoff transformation. The annual maximum peak flow probability distribution is analytically derived to quantify the filtering effect of the rainfall-runoff process on climate change. A sensitivity analysis is performed according to typical semi-arid Mediterranean climatic and hydrological conditions, assuming a simple but common scheme for the rainfall-runoff transformation in small-size ungauged catchments, i.e. the CN-SCS model. Variability in annual maximum peak flows and its statistical significance are analysed when changes in the climatic input are introduced. Results show that depending on changes in the annual number of rainfall events, the catchment filtering role is particularly significant, especially when the event rainfall volume distribution is not strongly skewed. Results largely depend on the return period: for large return periods, peak flow variability is significantly affected by the climatic input, while for lower return periods, infiltration processes smooth out the impact of climate change.

If Precipitation Extremes Are Increasing, Why Aren't Floods?

“…The primary problem in the conceptualization that precipitation increases lead to increased flooding is that it assumes that catchment specific conditions are invariant and streamflow is generated from precipitation alone. In fact, floods are influenced by the location, pattern, duration and rarity of precipitation, as well as the wetness state of the catchment prior to the event, with the streamflow response dependent on the hydraulic characteristics of the catchment, among other factors (Andrés-Doménech et al, 2015;Johnson et al, 2016). Additionally, there exist multiple flood types, with many of these (such as coastal floods) attributable to factors independent of precipitation change (Zheng et al, 2013).…”

Hydroclimatology of extreme river flows

“…Thus, river flow is the integrated catchment hydroclimatological response (Hannah et al ., , ). Not all meteorological anomalies will produce an extreme river flow response because of the moderating influence of terrestrial hydrological processes (Van Loon & Van Lanen, ; Andrés‐Doménech et al ., ). Consequently, hydrologists typically adopt a ‘catchment perspective’ and consider catchment and meteorological processes together (after Merz & Blöschl, ) when attempting to understand the processes driving flood and drought events.…”

The compensating effect of glaciers: Characterizing the relation between interannual streamflow variability and glacier cover

“…Streamflow variability is related to climate variability, for instance heat waves, seasonality of precipitation and temperature, and climate modes (e.g., Barlow, Nigam, & Berbery, 2001;Dettinger & Diaz, 2000), and moderated by catchment storages, such as lakes, groundwater and soil characteristics (e.g., Andrés Doménech, García Bartual, Montanari, Segura, & Bautista, 2015;Milly & Wetherald, 2002). In mountain regions, snow and particularly glaciers represent such storages that can modify the streamflow response to climate input (e.g., Collins, 2006a;Dahlke, Lyon, Stedinger, Rosqvist, & Jansson, 2012;Fleming & Dahlke, 2014;Jansson, Hock, & Schneider, 2003;Jenicek, Seibert, Zappa, Staudinger, & Jonas, 2016, Viviroli et al, 2011.…”