FACTORS OF RUNOFF FORMATION AND THE STATE OF THE LENA RIVER ECOSYSTEM IN THE 21ST CENTURY. PART 1: NATURAL, CLIMATIC, AND ANTHROPOGENIC FACTORS OF THE LENA RUNOFF FORMATION IN THE 21ST CENTURY

The main runoff formation factors and their temporal and spatial variations in the Lena River basin in 2000-2023 and the years with typical water content during this period are considered in comparison with the normal conditions of the middle and end of the 20th century. The problems of quantification of these variations are discussed. The methodological approach and initial data are described. The impact of the northern position of the basin, geographic zoning, orography, changes in air temperature, precipitation, permafrost, ice jams, and anthropogenic factors on the runoff are analyzed.