This data set presents the reconstructed water level for AL1 sediment core based on subfossil Chironomidae data. The core was collected in July 2019 from from the lower alas level, approximately 1.5 km north of the Berelekh River (70.84057° N, 147.48369° E). It was taken from the active layer as a monolith using a Russian auger and was subsequently cut into 1-cm slices in the laboratory of the Chokurdakh Scientific Tundra Station. Water depth was reconstructed using the East-Siberian chironomid-based inference model (WA-PLS, 1 component; r2 boot = 0.62; RMSEP = 0.35) based on a modern calibration dataset of 150 lakes from Yakutia (Nazarova et al., 2011). To determine whether the modern calibration model had adequate analogues for the fossil assemblages, the modern analogue technique (MAT) was performed using C2 version 1.7.7 (Juggins, 2007) on percentage, square-root-transformed data. The distance between each fossil sample and its most similar modern assemblage was compared, and the 5th percentile of all squared-chord distances of the modern data was used to define the cut-off for a good analogue (Plikk et al., 2019).