Hydro-sedimentary data collected between 2010 and 2017 within the framework of the Critical Zone Observatory HYBAM* in the Amazonian foreland of Peru

The hydrological data were collected within the international framework of the Critical Zone Observatory HYBAM (Hydrology of the Amazon Watershed). A Franco-Peruvian team from the IRD (Institut de Recherche pour le Développement) and the SENAMHI (SErvicio NAcional de Meteologia e HIdrologia) operates the 8 gauging stations of the HYBAM hydrological network in Peru; of these, 4 stations control the Andean piedmonts fluxes, and 4 stations control the lowlands. The three major Peruvian tributaries of the Amazonas (Solimões) River, i.e., the Ucayali River, the Marañon River and the Napo River, are monitored. The studied sites cover drainage areas ranging from approximately 22,000 km² to 720,000 km² and have mean discharges ranging from 2,100 m3 s-1 to 30,300 m3 s-1. 44 measurement campaigns were conducted during the 2010-2017 period. These campaigns included the collection of 494 discharge measurements, 249 sediment concentration profiles and 1330 water samples. This dataset is also partly available on the CZO HYBAM website: https://www5.obs-mip.fr/hybam. Extra data (e.g. water levels, surface SSC series ...) are also available from the corresponding author upon request. A 600 kHz Teledyne RDI Workhorse Acoustic Doppler Current Profiler (ADCP) was used and coupled with a 5 Hz GPS sensor to correct for the movable bed error. A point sampling method was used to estimate the cross-sectional average concentration. The sampling for concentration determination was usually performed at the following height (h) from the bed: ~0.98 h, 0.75 h, 0.5 h, 0.25 h, sometimes at ~0.15 h, and finally at ~0.1 h, at three verticals that divided the cross-section according to the river width or the flow rate. Sampling was performed from a boat drifting on a streamline immediately after the ADCP measurements were collected. The sampler capacity was 650 mL, with a filling time of ~10 seconds, which allowed for a short time integration along the streamline passing by the sample point. Considering the waves at the free surface, the boat’s pitch and roll and the bedforms, the accuracy of the vertical position of the sampler may be evaluated as ± 0.5 m. The operation time was approximately 2-5 hours, depending on the river sites. Steady conditions were observed during the sampling operation. The concentrations of the two main grain size fractions were further determined: the sand fraction was separated from the silt/clay/aggregates fraction using a 63-µm sieve (cf. Standart Methods ASTM D3977), according to the Wentworth (1922) grain size classification for non-cohesive particles. The water samples were filtered using 0.45-µm cellulose acetate filters (Millipore) that were then dried at 50°C for 24 hours. Particle size analysis was performed with a Horiba LA920-V2 laser diffraction sizer.