Defining Dry Rivers as the Most Extreme Type of Non-Perennial Fluvial Ecosystems

Abstract

We define Dry Rivers as those whose usual habitat in space and time are dry channels where surface water may interrupt dry conditions for hours or a few days, primarily after heavy rainfall events that are variable in time and that usually lead to flash floods, disconnected from groundwater and thereby unable to harbor aquatic life. Conceptually, Dry Rivers would represent the extreme of the hydrological continuum of increased flow interruption that typically characterizes the non-perennial rivers, thus being preceded by intermittent and ephemeral rivers that usually support longer wet phases, respectively. This paper aims to show that Dry Rivers are ecosystems in their own right given their distinct structural and functional characteristics compared to other non-perennial rivers due to prevalence of terrestrial conditions. We firstly reviewed the variety of definitions used to refer to these non-perennial rivers featured by a predominant dry phase with the aim of contextualizing Dry Rivers. Secondly, we analyzed existing knowledge on distribution, geophysical and hydrological features, biota and biogeochemical attributes that characterize Dry Rivers. We explored the capacity of Dry Rivers to provide ecosystem services and described main aspects of anthropogenic threats, management challenges and the conservation of these ecosystems. We applied an integrative approach that incorporates to the limnological perspective the terrestrial view, useful to gain a better understanding of Dry Rivers. Finally, we drew main conclusions where major knowledge gaps and research needs are also outlined. With this paper, we ultimately expect to put value in Dry Rivers as non-perennial rivers with their own ecological identity with significant roles in the landscape, biodiversity and nutrient cycles, and society; thus worthy to be considered, especially in the face of exacerbated hydrological drying in many rivers across the world.

Desiccation time and rainfall control gaseous carbon fluxes in an intermittent stream

“…The duration of the dry period, seen as a proxy of desiccation severity, is recognized to greatly shape biogeochemical cycling in intermittent streams (Muñoz et al 2018;Arce et al 2019;Vidal-Abarca et al 2020). Desiccation induces changes in the structure and functioning of microbial communities (Febria et al 2012;Romaní et al 2017) and in the physico-chemical conditions of sediments (von Schiller et al 2017;Casas-Ruiz et al 2016;Harjung et al 2019a).…”

Explorando los beneficios de los ríos secos para el bienestar humano: una perspectiva social

“…En primer lugar, se pretende revisar la capacidad de los ríos secos para proveer servicios ecosistémicos a la sociedad a través de la información aportada por publicaciones científicas. A excepción de dos trabajos previos realizados por Datry et al (2017b) y Koundouri et al (2017) para los ríos intermitentes y algunos datos aportados por Vidal-Abarca et al (2020) para los ríos secos, no existe un análisis global sobre los beneficios potenciales que estos ecosistemas pueden suministrar a la sociedad. Probablemente el desconocimiento de la población humana sobre los beneficios de los ríos secos para el bienestar humano sea una de las razones para ignorarlos o considerarlos sistemas baldíos y degradados.…”

“…Las contribuciones de regulación están ligadas al funcionamiento de los ecosistemas y, en el caso de los ríos secos, aún se desconocen muchos de los procesos biogeoquímicos que los sustentan(Arce et al, 2019). Ni siquiera se tiene certeza de a qué escala espacial o temporal ocurren, o cuál es el papel funcional de las avenidas en la reactivación y/o desorganización de los cauces que son la base física que sustenta la provisión de estas contribuciones(Vidal-Abarca et al, 2020).…”

Drought in intermittent river and ephemeral stream networks

“…Flow cessation by itself is not an anomaly in IRES. On the contrary, water flows for only a few weeks or days every year in many non‐perennial rivers (Vidal‐Abarca et al, 2020). Dryland stream catchments typically exhibit great intra‐ and inter‐annual variability in rainfall (Tooth, 2000), so flow does not necessarily follow regular seasonal patterns in non‐perennial rivers—further invalidating the relevance of the term seasonal drought.…”