The compound-specific hydrogen isotopic composition (δ2H) of n‑alkanes is a valuable proxy to investigate hydrological conditions in lake sediments. While terrestrial n-alkanes reflect the isotopic signal of the local precipitation, aquatic n-alkanes incorporate the isotopic signal of the lake’s water, which can be strongly modulated by evaporative enrichment. So far, the spatial distribution of the terrestrial and aquatic δ2H signal within lakes have not systematically been investigated. We present compound-specific δ2H results of terrestrial (δ2HC31) and aquatic (δ2HC23) n‑alkanes of surface sediment samples from Lake Khar Nuur, a semi-arid, high-altitude lake in the Mongolian Altai, and additionally investigate the δ2H signal of the catchment plants and topsoils. Our results show only a small variability of δ2HC31 in the surface sediments which well-reflect δ2H values from catchment plants and topsoils, andsummer (growing season) precipitation. δ2HC23 in surface sediment samples from the central and deepest parts of the lake, i.e., the lake’s sediment accumulation zones, shows distinctly more positive δ2HC23 values due to evaporative lake water 2H-enrichment. By contrast, δ2HC23 in samples closer to the shore is likely biased by 2H-depleted meltwater. Consequently, Δaq‑terr, which is the isotopic offset between δ2HC23 and δ2HC31, indicates distinct lake water enrichment in the lake’s accumulation zones and is a valuable proxy to investigate past hydrological changes. Therefore, sediment retrieval for paleoenvironmental and -hydrological studies should hence carefully be figured out and be related to the sediment accumulation zones of the lake.