The Manso River Drainage System in the Northern Patagonian Andes: Hydrological, Hydrochemical and Nutrient Dynamics

LECOMTE KARINA; PASQUINI ANDREA; SEPÚLVEDA LAURA DANIELA; TEMPORETTI P.; PEDROZO FERNANDO; DEPETRIS PEDRO

Environmental Assessment of Patagonia's Water Resources

Springer

Año: 2021; p. 27 - 55

The Manso River system is a mountainous basin fed by rain, snow and glacier meltwater from thePatagonian Andes. Glaciers located in the uppermost basin have shown a significant retreat though the last decades. Most of the annual precipitation occurs during austral winter and, together with meltwater, generates a bimodal annual hydrograph. Mean annual discharge increases from 12.5 m3 s−1 in the upper basin, to ~80 m3 s−1 in the lower basin. The historical discharge of the Manso Superior (i.e. Upper) River shows a significant positive trend due to meltwater discharge increase, generating the growth of the Proglacial lake. Lake Mascardi and the Manso Inferior (i.e. Lower) River show a negative statistical trend in their respective mean discharges. The hydrochemical signal of the Manso River is determined by dominating geochemical processes along the basin: the upper basin is highly influenced by the Manso Glacier dynamics, where pyrite oxidation generates sulfate-calcic waters, and it is responsible for the scavenging of phosphorous from the solution, causing a low soluble reactive phosphorous/total phosphorous ratio. The low N:P ratio indicates that nitrogen limits algal growth. In the middle and lower basin, the silicate hydrolysis is the dominant process, generating bicarbonate waters. The Manso River system appears to be highly sensitive to climate change, which is an attribute influencing both, the hydrological and geochemical signals.