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. Here, we present compound-specific δ²H results of terrestrial (δ²H_C31) and aquatic (δ²H_C23) n-alkanes of surface sediment samples from Lake Khar Nuur, a semi-arid and high-altitude lake in the Mongolian Altai, and additionally investigate the δ²H signal of topsoils from the catchment. Our results show that the majority of the n-alkane δ²H values from the catchment topsoils correspond well with modeled local growing season precipitation (JJAS). However, few samples in the northern catchment show more positive δ²H values possibly due to increased evapo(transpi)ration by southward exposition and shallower soils there. The only small variability of δ²H_C31 in the surface sediments is in the range of most topsoils δ²H from the catchment, and thus, well reflects local growing season precipitation. δ²H_C23 in surface sediment samples from the central and deepest parts of the lake, that is, the lake's sediment accumulation zones, shows distinctly more positive δ²H_C23 values due to evaporative lake water enrichment. Consequently, Δ_aq-terr, which is the isotopic offset between δ²H_C23 and δ²H_C31, indicates distinct lake water enrichment in the lake's accumulation zones and is a valuable proxy to investigate past hydrological changes.