关键词: 氢氧同位素;海拔效应;水体滞留;大渡河;

Abstract: Dadu River is a large river located on the south-east slope of the Qinghai-Tibet Plateau, with a large change in elevation from its source to its estuary. There are abundant hydropower resources in this river, with 29 cascade hydropower stations planned in the main stream, and 13 have been constructed. In order to understand the influence of environment and hydropower development on the stable isotope composition of river water in the Dadu River, mathematical statistic was applied to analyze the δ18O and δD of river water and related hydrological data collected in Dadu River in September 2020. The results indicated that: ① the range of δD and δ18O were -120.60‰ ~ -77.98‰ and -16.67‰ ~ -11.90‰ respectively. The relationship between δD and δ18O of river water was δD = 8.01δ18O + 14.3(R2=0.97, ρ<0.01). ② The d-excess values varied from 11.72‰ to 18.15‰, and all of the values were positive, indicating the Dadu River was recharged by melting water of ice and snow. ③ δD and δ18O increased along the river, suggesting that heavy isotopes were gradually enriched from upstream to downstream, which was likely to result from the “altitude effect” of hydrogen and oxygen isotopes in this area. ④ Dam interception had an impact on the hydrogen and oxygen isotope composition of the river water. The long residence time of water in the reservoir will lead to the enrichment of water isotopes before the dam.

Key words: hydrogen and oxygen isotopes; altitude effect; water residence; Dadu River