The Manso River D rainage System in the Northern Pa tagonian Andes: Hydrological, Hydrochemical and Nutrient D ynamics

LECOMTE KARINA; PASQUINI ANDREA; SEPULVEDA LORENA; TEMPORETTI PEDRO; PEDROZO FERNANDO; DEPETRIS PEDRO

Environmental Assessment of Patagonia?s Water Resources

Springer Nature Switzerland AG

Año: 2021; p. 27 - 55

The MansoRiver system is a mountainous basin fed by rain, snow and glacier meltwaterfrom the Patagonian Andes. Glaciers located in the upper mostbasin have shown asignificant retreat though the last decades. Most of the annual precipitationoccurs during austral winter and, together with meltwater, generates a bimodalannual hydrograph. Mean annual discharge increases from 12.5 m3 s−1 in theupper basin, to ~80 m3 s−1 in the lower basin. The historical discharge of theManso Superior (i.e. Upper) River shows a significant positive trend due to meltwaterdischarge increase, generating the growth of the Proglacial lake. Lake Mascardiand the Manso Inferior (i.e. Lower) River show a negative statistical trend intheir respective mean discharges. The hydrochemical signal of the Manso Riveris determined by dominating geochemical processes along the basin: the upperbasin is highly influenced by the Manso Glacier dynamics, where pyriteoxidation generates sulfate-calcic waters, and it is responsible for thescavenging of phosphorous from the solution, causing a low soluble reactivephosphorous/total phosphorous ratio. The low N:P ratio indicates that nitrogenlimits algal growth. In the middle and lower basin, the silicate hydrolysis isthe dominant process, generating bicarbonate waters. The Manso River systemappears to be highly sensitive to climate change, which is an attributeinfluencing both, the hydrological and geochemical signals.