Temporal and Spatial Snow Variability in the Mountainous Region of the Upper Euphrates Basin

Human-induced greenhouse gas emissions have driven climate change, leading to rising global temperatures and significant disruptions in natural ecosystems. These changes have particularly affected sensitive areas such as the Upper Euphrates Basin in eastern Turkey, and these effects have intensified over the past century. Since the Euphrates River is transboundary water, it is important to monitor the water availability of the river for Syria, Iraq, and Tu ̈rkiye. The basin’s reliance on snow melt for water resources makes it particularly vulnerable to climate change, as rising temperatures shift snow melt timing, reduce snowfall threatening water availability for agriculture, energy production, and ecological balance. This study investigates changes in snow depth and snow cover patterns in the Upper Euphrates Basin from 1985 to 2021, using the Copernicus European Regional Reanalysis for Land (CERRA-Land) dataset. With a high spatial resolution (5.5 km x 5.5 km) and advanced surface modeling, the dataset integrates observational and modeled data, offering a detailed reconstruction of surface and soil variables. We focused on variations in snow depth during the snow season, spanning from November to April. During the study period, specific years, including the early 2000s and mid-2010s, experienced a marked reduction in maximum snow depth. Trend analysis for March and April reveals significant decreases in snow depth, with declines exceeding 30 cm per decade. The most pronounced decreases in snow depth are observed at grid points between 1250 m to 2000 m in the Upper Euphrates Basin. Snow cover decreased remarkably in November, and in the 2012–2021 period, compared to 1985–1994, it remained below 20%, particularly at grid points between 1000– 1500 m altitude. These analyses indicate that the earlier snow melt, the reduction of the snow cover duration, and the decreasing trend in snow depth have considerable impacts on water resources in the countries where the Euphrates basin is located.