Suspended sediment and dissolved load budgets of

IRD GET - Toulouse Université de Toulouse IGP Lima INAMHI Quito SENAMHI Lima

UNALM Lima SENAMHI La Paz UMSA La Paz ANA Brasilia UnB Brasilia UFAM Manaus

Suspended sediment and dissolved load budgets of Peruvian and Ecuadorian Pacific Andeans rivers Preliminary results

Moquet Js., Morera S.B., Crave A., Vauchel P., Pombosa R., Lavado W.C., Guyot J.L., Martinez J.M.

Motivations Relationship Erosion vs weathering (silicate) in orogenic context

Integrator of critical zone behavior

Andes

Pacific Oceans

Characterisation of pacific river quality Mass balance budget to Pacific rivers

 Low knowledge of Pacific solids and chemical inputs

Studied area

Studied area

Esmeraldas Volcanos

Tumbes

2008-2011

Santa

 2008-2011 period : no extrem events

Area : 6000-16000km² Lithology : Mixed lithology : volcanic, plutonic and metamorphic, sedimentary Esmeraldas : active volcanos.

Canete Ocona

Material and method

5 monitored stations (2008-2011-HYBAM) : - Daily discharge - 10 days frequency surface suspended matter concentration -Monthly major elements concentration

+ 14 discrete rivers sampling : Major elements Annual discharge (Lavado et al., 2012)  Flux calculation (Concentration x discharge)

Material and method Distribution of daily discharge for suspended matter and dissolved solids sampling

 Allows the estimation of annual suspended and dissolved matter fluxes

Erosion budget

Weathering budget Suspended matter dynamic Tumbes

 Morera et al., 2013 and the next presentation

Erosion vs weathering

Erosion budget Erosion flux (Mt/yr)

Weathering budget Erosion yield (t/km²/yr)

Armijos et al., 2013

Mining activity (Morera et al., 2013)

Erosion vs weathering

Erosion budget

Weathering budget

Erosion vs weathering

TDS (mg/l)

S

TDS sources :  Atmosphere  Silicates  Carbonates  Evaporites  Pyrite

Erosion budget

Weathering budget

Erosion vs weathering

Dissolved solids vs runoff

South

North

Erosion budget

Weathering budget

Erosion vs weathering

Dissolved solids vs runoff

evaporite influence

South

North

 TDS gradient associated to evaporites inputs gradient

Erosion budget

Weathering budget Silicates weathering : Dissolved Si as a first index

Low runoff : high dissolved Si variability  Source of SiO2 in semi arid context?

Erosion vs weathering

Erosion budget

Weathering budget

Erosion vs weathering

TDS = 0.1 TZ+ (r²=0.97) ?

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Erosion budget

Weathering budget

Erosion vs weathering

 Discharge variability : first order parameter controlling the TDS flux variability along hydrological cycle

Erosion budget

Weathering budget Dissolved solids flux and yield

Erosion vs weathering

Erosion budget

Weathering budget Total flux budget

Dissolved solids  5-56% of the total fluxes

Erosion vs weathering

Erosion budget

Weathering budget

Erosion vs weathering

Total dissolved solids discrimination (Garrels and Mackenzy, 1972; Ca/Na and Mg/Na coefficients from Gaillardet et al., 1999)

Scenario 1 : SO4 from evaporites

Scenario 2 : SO4 from pyrite

Atmospheric inputs