Climate Drivers and Sources of Sediment and Organic Matter Fluxes in Intermittent Rivers and Ephemeral Streams (IRES) of a Subtropical Watershed, USA

Janet Dewey,Byoungkoo Choi,Ying Ouyang,Jeff Hatten,Clay Mangum

doi:10.3390/cli8100117

Janet Dewey, Byoungkoo Choi + Show 3 more

Open Access

https://doi.org/10.3390/cli8100117

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Journal: Climate	Publication Date: Oct 16, 2020
Citations: 5	License type: CC BY 4.0

Affiliation: US Forest Service, University of Wyoming

Abstract

Climate-driven hydrological models rarely incorporate intermittent rivers and ephemeral streams (IRES) due to monitoring difficulties and their perceived minor effect on river networks. Worldwide, IRES represent approximately 50% of river networks and up to 60% of annual flow and are recognized as conduits and processors of organic matter (OM). Climate induced changes in precipitation and discharge (Q) may impact OM fluxes from IRES. We assessed storm-driven source and flux of total suspended solids (TSS) and OM from small IRES in Mississippi, USA. We used linear Pearson correlations to evaluate relationships between water and storm characteristics (e.g., discharge). Stepwise regression was used to predict change in flux. Dissolved OM was derived from saturated flow through soil whereas particulate OM was derived from channel extension during storms. A power log relationship between Q and materials flux indicated that Q was the driver for flux. A 5% increase in Q within IRES may result in flux increase of 2% TSS and 1.7–2.8% OM. Climate change projections of increased storm intensity over a shorter water year will increase channel extension and soil water transfer resulting in higher material flux to downstream reaches. Climate-driven hydrological models of OM flux should incorporate IRES.

Highlights

Intermittent rivers and ephemeral streams (IRES) have long been perceived as peripheral in their effect on river networks because they only flow in response to rainfall [1,2]
Our research was guided by two questions: (1) what are the sources of sediment and organic matter (OM) in IRES and (2) what are the controls on the flux of sediment and OM from very small (
Our first question was: what are the sources of sediment and OM in ES? dissolved organic matter (DOM) was derived from

Summary

Introduction

Intermittent rivers and ephemeral streams (IRES) have long been perceived as peripheral in their effect on river networks because they only flow in response to rainfall [1,2]. It has been estimated that headwater IRES account for 60% of total mean annual flow (for streams and rivers in the northeastern US) [3]. Intermittent rivers and ephemeral streams drain and connect with much of the Earth’s critical zone, so they have considerable potential to release, transport, transform, or sequester organic matter (OM) (e.g., [5,6]); this, in turn, can be released into the atmosphere in the form of CO2 [7,8]. 36% of the CO2 outgassed by river networks can be attributed into headwater streams [8]. Climate change can affect the timing, duration, frequency, and severity of storm events—all of which have the potential to control sediment and OM exports from IRES [9].

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