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The 20 km2 Galabre catchment belongs to the French network of critical zone observatories (OZCAR; Gaillardet et al., Vadose Zone Journal, 2018, 17(1), 1–24). It is representative of the sedimentary lithology and meteorological forcing found in Mediterranean and mountainous areas. Due to the presence of highly erodible and sloping badlands on various lithologies, the site was instrumented in 2007 to understand the dynamics of suspended sediments (SS) in such areas. Two meteorological stations including measurements of air temperature, wind speed and direction, air moisture, rainfall intensity, raindrop size and velocity distribution were installed both in the upper and lower part of the catchment. At the catchment outlet, a gauging station records the water level, temperature and turbidity (10 min time‐step). Stream water samples are collected automatically to estimate SS concentration‐turbidity relationships, allowing quantification of SS fluxes with known uncertainty. The sediment samples are further characterized by measuring their particle size distributions and by applying a low‐cost sediment fingerprinting approach using spectrocolorimetric tracers. Thus, the contributions of badlands located on different lithologies to total SS flux are quantified at a high temporal resolution, providing the opportunity to better analyse the links between meteorological forcing variability and watershed hydrosedimentary response. The set of measurements was extended to the dissolved phase in 2017. Both stream water electrical conductivity and major ion concentrations are measured each week and every 3 h during storm events. This extension of measurements to the dissolved phase will allow progress in understanding both the origin of the water during the events and the partitioning between particulate and dissolved fluxes of solutes in the critical zone. All data sets are available at https://doi.osug.fr/public/DRAIXBLEONE_GAL/index.html. [ABSTRACT FROM AUTHOR]

Purpose: There is a growing interest in the characterization of the particle size of sediment due to its impact on particle dynamics, especially for connectivity purpose. This study determined the particle size distribution of suspended sediment in a mountainous catchment, with the aim to evaluate the variability of particle size during floods, the main controlling factors, and if indirect information from hillslopes was useful for the interpretation of particle size measured at the catchment outlet. This work involved the development of a measurement protocol. Material and methods: Samples were collected automatically from streamwater during flood events using an ISCO 3700 sampler. Five events were analyzed for their particle size distributions using a Malvern Mastersizer 2000. Because the samples were too concentrated, two different protocols were tested to address the errors made during the subsampling step: using a pipette and a home-made device with successive dilution phases. Results and discussion: High errors occurred when using a pipette to extract particles within a stirred sample. The maximum errors were reduced from 1,600 to 30 % using the device described within this study. Particles were found to be aggregated at various levels regardless of the discharge they were sampled at. Their size was found to be either variable or stable at the event scale, and statistical analyses revealed that discharge was the factor that best correlated with particle size. The results obtained in this study are in agreement with the few other studies in comparable environments. Some hypothesis are put forward and discussed to explain the positive relationship between particle size and discharge. Input from hillslopes seems to have a measureable effect in this headwater catchment. Conclusions: While the need for in situ measurements has long been stressed in lowland rivers, estuaries, and coastal environments, it was shown that the use of an accurate dilution protocol could provide some physically interpretable measurements on the particle size distributions of suspended sediment transported in a mountainous catchment. It also appears that hillslope information has to be considered when studying particle size measured at the catchment outlet. [ABSTRACT FROM AUTHOR]

In agricultural fields, soil erosion is usually associated to surface runoff. However, in drained fields, tile drains are additional pathways for soil particles. Few studies have quantified erosion in drained fields and they mainly focused on tile drained fields, without considering fields combining surface and tile drainage. These studies show high inter-site and inter-annual variabilities that highlight the need for more annual quantifications of erosion in drained fields. Consequently, it is still difficult to quantify the relative importance of the factors affecting soil erosion in drained fields. In addition to a comprehensive review of the existing studies of erosion through drainage, this study aims at quantifying surface and subsurface erosion in a 5 ha cultivated field combining surface and tile drainage. Suspended sediments (SS) and water fluxes have been monitored during two years (2019–2020 and 2020–2021) at a high temporal resolution (1 min), both at the outlet of the tile drain network and at the outlet of the surface drainage rill. SS yield was 0.49 t ha−1 and 1.08 t ha−1 in 2019–2020 and 2020–2021, respectively. During 2019–2020 and 2020–2021, tile drainage contribution to the total runoff was 46% and 21%, respectively and its contribution to SS yield was 9% and 11%, respectively. High temporal resolution measurements of runoff and SS concentrations showed the suspended sediment concentration in the surface drain runoff only increase by 17% from the first to the second study year. Conversely, for tile drainage, average suspended sediment concentrations increased by 260%. These variations and the increase of surface runoff rate suggest a shift in water and sediment connectivity at the field scale. Cropping practices could have generated a slumping of the soil surface during the second year and, at the same time, the development of a macropore network in the subsoil. Cropping practices induced changes of surface horizon characteristics and their impact on the hydrosedimentary behavior of drained soils need to be further studied. This study confirms previous results concerning the temporal dynamics of SS exports in a drained context under temperate climate and adds a new quantification of hydrosedimentary fluxes in a surface and tile drained field separating surface drains and tile drains contributions. • High temporal resolution monitoring of surface and tile drain hydrosedimentary fluxes. • Suspended sediment yield was 0.49 t ha−1 and 1.08 t ha−1, in 2019–2020 and 2020–2021. • Tile drains contribute up to 11% of the suspended sediment load. [ABSTRACT FROM AUTHOR]