This database presents the particle size, elemental geochemistry and radionuclide analyses carried out on the 19CO3 core (IGSN number: 10.58052/IEFOU0009) collected in June 2019 in the Poechos reservoir (Peru). These results are part of the publication " El Niño-Southern Oscillation (ENSO)-driven hypersedimentation in the Poechos Reservoir, northern Peru " available via the following link: http://dx.doi.org/10.5194/egusphere-2022-1233 Corresponding authors: anthony.foucher@lsce.ipsl.fr Particle size analysis was performed using a laser grain sizer Malvern Mastersizer 3000 allowing to measure the grain size distribution between 10 nm and 3.5 mm. Particle size was measured on the sandy layers identified along the core (n=19) Grain size parameters such as d10, d50, d90 and raw are present on the file: Particle_size_POECHOS-reservoir_Foucher-et-al Sediment core sections were analyzed with an Avaatech X-Ray Fluorescence core scanner (XRF) available at the Laboratoire des Sciences du Climat et de l’Environnement (Gif-sur-Yvette, France) with a 0.5 cm resolution. These data are available on the file: XRF_core_scanner_POECHOS-reservoir_Foucher-et-al Gamma spectrometry measurements were obtained using HPGe detectors (Canberra/Ortec) available at the Laboratoire des Sciences du Climat et de l’Environnement. Short-lived radionuclides (e.g., caesium-137 (137Cs) and excess of lead-210 (210Pbex)) were measured in 12 samples of dry sediment (≈10g) collected along the sedimentary sequence (approximatively every 40 cm). The data are available on the file: Radionuclides_POECHOS-reservoir_Foucher-et-al