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Plants vs. Streams: Their groundwater-mediated competition at “El Morro”, a developing catchment in the dry plains of Argentina
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  • Esteban Jobbágy,
  • Santiago Lorenzo,
  • Ricardo Páez,
  • Nicolás Buono,
  • Yésica Díaz,
  • Victoria Marchesini,
  • Marcelo Nosetto
Esteban Jobbágy
Instituto de Matematica Aplicada San Luis
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Santiago Lorenzo
Instituto Nacional de Tecnología Agropecuaria
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Ricardo Páez
Instituto de Matematica Aplicada San Luis
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Nicolás Buono
Universidad Nacional de la Plata
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Yésica Díaz
Instituto de Matematica Aplicada San Luis
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Victoria Marchesini
Instituto de Matematica Aplicada San Luis
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Marcelo Nosetto
Instituto de Matemática Aplicada San Luis
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Abstract

Our understanding of the mechanisms routing precipitation inputs to evapotranspiration and streamflow in catchments is still very fragmented, particularly in the case of saturated flows. Here we explore five mechanisms by which plants and streams compete with each other for water, based on multiple scales of observations in a flat semiarid sedimentary catchment of central Argentina subject to abrupt hydrological transformations. Since the 80s, the “El Morro” catchment (1334 km2, -33.64°, -65.36°) experienced a fast expansion of crops over native forests and grasslands, rapid water table level rises (~0.3 m y-1), spontaneous expansion of wetlands and permanent streams by groundwater sapping. Based on episodic and continuous groundwater level, stream flow, and remote sensing data we show that plants not only take away water from streams by drying the unsaturated zone (mechanism 1), but by tapping the saturated zone in the expanding waterlogged environments (mechanism 2) and in the upland environments that remain uncultivated and display increasing tree cover (mechanism 3). Conversely, streams take away water from plants through pulsed bed-deepening and water table depression (mechanism 4), and riparian and wetland zones burying with fresh sediments (mechanism 5). While earlier work established widespread support for mechanisms 1 preventing stream formation, diurnal and seasonal fluctuations of water table levels and base streamflow records in this study proved the importance of mechanisms 2 and 3 under the current high-water table conditions. These data together with remotely-sensed greenness showed a growing but localized relevance of mechanism 4 and 5 as the stream network developed. The distinction of recharge- vs. topography-controlled groundwater systems is useful to organize the interplay of these concurrent mechanisms. Findings point to the unsaturated-saturated contact zone as a crucial and dynamic hub for water partition and for ecological, geomorphological, and hydrological knowledge integration.

Peer review status:Published

09 Oct 2020Submitted to Hydrological Processes
09 Oct 2020Submission Checks Completed
09 Oct 2020Assigned to Editor
09 Oct 2020Reviewer(s) Assigned
02 Dec 2020Review(s) Completed, Editorial Evaluation Pending
08 Dec 2020Editorial Decision: Revise Major
22 Jan 20211st Revision Received
23 Jan 2021Assigned to Editor
23 Jan 2021Submission Checks Completed
23 Jan 2021Reviewer(s) Assigned
28 Mar 2021Review(s) Completed, Editorial Evaluation Pending
31 Mar 2021Editorial Decision: Revise Minor
09 Apr 20212nd Revision Received
10 Apr 2021Submission Checks Completed
10 Apr 2021Assigned to Editor
10 Apr 2021Reviewer(s) Assigned
20 Apr 2021Review(s) Completed, Editorial Evaluation Pending
21 Apr 2021Editorial Decision: Accept
25 Apr 2021Published in Hydrological Processes. 10.1002/hyp.14188