Dataset of Disentangling lithological control from drought-induced flushing in a Mediterranean river basin

This dataset contains the results of the physicochemical and hydrochemical parameters obtained from the sampling and analyses conducted as part of the study “Disentangling lithological control from drought-induced flushing in a Mediterranean river basin.”. A total of 88 water samples were collected from 23 sampling sites distributed throughout the Upper Llobregat River Basin (Figure 1) in four field campaigns. The first campaign was conducted at the end of the drought periods, right after the first spring rainfalls (April 2024), while the subsequent three campaigns were carried out after this initial post-drought period (June 2024, September 2024, and May 2025), enabling the assessment of temporal changes in water chemistry associated with hydrological recovery. Of the total samples, 24 were surface water samples collected from six sites on the Llobregat River notated as L, where the distances from the birth point are 0.14 km (L1), 4.59 km (L2), 13.1 km (L3), 16.2 km (L4), 21.9 km (L5), and 29.1 km (L6). Moreover, 16 additional surface water samples were collected from four tributaries, designated as T: the Aritja River (T1), Grèixer River (T2), Saldes River (T3), and Demetge River (T4). Groundwater was sampled from four piezometers (P), two located in the “Les Fonts del Llobregat” area (Castellar de n’Hug; P1 and P2), one in the Gisclareny sector (P3), and one in the Cercs sector (P4), yielding 14 samples in total. A total of 32 samples were obtained from eight natural springs, designated as S1 to S8. Finally, a total of 2 rainwater samples were collected from Tosa d’Alp (R1) during the last two sampling campaigns, serving as a reference for rainwater chemistry inputs.