Understanding the variation of water availability along elevation gradients is essential for predicting the response of mountain ecosystems to global warming. However, it is challenging to precisely quantify water availability in dry mountains, especially in remote areas where climate records are limited. In dry habitats, leaf delta C-13 is highly sensitive to water availability. Here, we demonstrated how leaf delta C-13 of a widespread species could be used as an indicator of water availability in dry mountainous regions. We measured leaf delta C-13 and nitrogen content in one dominant forb and two cushion species along two elevational transects in the central Himalayas, Nepal. The Thornthwaite climatic moisture index was determined for each elevation site based on the 1-km(2) WorldClim data of monthly mean temperature and precipitation. We found that the elevational variation of delta C-13 in each of the three species was associated with precipitation, in which growing-season moisture index and annual precipitation were negatively correlated with delta C-13, regardless of elevation and temperature. Elevation and leaf nitrogen showed no significant relationship with leaf delta C-13. Thus, within-species leaf delta C-13 promises to be a simple and reliable indicator of environmental severity along elevation gradients, which can be easily quantified in remote high-mountain environments. Leaf delta C-13 would be a useful predictor of the change in water availability induced by warming in dry mountainous regions like the Himalayas