A Hydrological and Biogeochemical Appraisal of Patagonia?s Río Gallegos

P. J. DEPETRIS,; , DM GAIERO; COSENTINO, N.J.

A. I. Torres and V. A. Campodonico (eds.), Environmental Assessment of Patagonia?s Water Resources, Environmental Earth Sciences

SPRINGER

Año: 2021; p. 241 - 259

The Gallegos is the southernmost river of continental Patagonia. It has2 the smallest drainage basin of all the main rivers in the region. Moderate atmosphericprecipitations (~500 mm y−1 in the uppermost catchments) determine 34 discharge maxima in austral winter (rainfall/snowfall) and spring (snowmelt), delivering~0.573 km3 y−1 of freshwater (i.e. ~57 L m2 y−1) into an ample estuary in 56 the SW Atlantic Ocean. The Gallegos stands out among the remaining Patago7nian rivers for its connection (~18-month significant squared coherency) with the8 Southern Annular Mode, and due to its biogeochemistry, which appears affected by9 groundwater and debris, both associated to some degreewith Eocene bituminous coalbeds. The relevant factors seem to be: (a) the marked prevalence of NO3−10 ?N amongnutrients (N:P = 50:1?60:1); (b) the mean DOC concentration (~500 μmol L−1), 11higher than all remaining Patagonian rivers (mean of ~300 μmol L−1), and linked 1213 to river discharge; (c) high DIC, correlated with high pCO2 (probably groundwater14supplied); (d) mean POC/PN molar ratio of ~8:1 (the highest in Patagonia?s rivers),15 leading to infer a terrigenous source with some planktonic contribution. High DOCconcentrations (~1000 μmol L−1) are associated with low?13CDIC (~−11 per mil), 1617 probably controlled by carbonate dissolution. Mean TOC in the Gallegos River is~700 μmol LAQ1 −1, 70% of which is accounted for by DOC.