Spatiotemporal variability of hydrochemistry in a tropical glacierized watershed in the Andes
Abstract
With climate change, some of the highest rates of warming are occurring in tropical glacierized mountainous watersheds, 99% of which located in the Andes . Extensive glacier retreat throughout the Andes will not only impact the glacier meltwater contribution to the streamflow, but it may also alter the hydrochemistry of watershed s . This is because hydrological changes triggered by glacier retreat can affect c hemical weathering, dilution, and transport - all of which control solute concentrations. Here, we examine how the spatiotemporal distribution of solutes within a watershed and the export of solutes out of a watershed will respond to glacier retreat due to both hydrological and geochemical process es . To do so, we implement the model RT-Flux-PIHM, which integrates multicomponent reactive transport with hydrologic and land-surface processes, for a 7.2 km 2 tropical watershed on Volcán Chimborazo, Ecuador that is currently 34 % glacierized . For model inputs, soil parameters are constrained by observed groundwater and surface water chemistry as well as stream discharge . M ineral compositions in the watershed are determined using X- R ay Diffraction (XRD) a nalysis . Reaction rate and specific surface area (ssa) parameters are based on literature values for the observed mineral phases. Preliminary results indicate that the spatiotemporal variability of the hydro chemistry in the watershed is controlled by both hydrological processes , particularly evapotranspiration and length of flow paths, and geo chemical processes, mainly mineral dissolution. Further, sensitivity tests have been implemented to evaluate the role of meltwater in controlling geochemical conditions. The results suggest that without glaciers, flux of reactive solutes (mineral dissolution products) out of the watershed would be 30% lower while stream discharge would be 45% lower, correspond ing to a greater solute concentration without glacier melt than with it . This finding indicate s that glacier melt water produces a n overall dilution effect by increasing the surface runoff contribution to the streamflow. A better understanding of the influence of meltwater on hydrochemical processes can provide insights into potential biogeochemical impacts of future glacier retreat in downstream portions of the Amazon basin.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H21J1883S
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 0466 Modeling;
- BIOGEOSCIENCES;
- 1828 Groundwater hydraulics;
- HYDROLOGY;
- 1849 Numerical approximations and analysis;
- HYDROLOGY