Stable isotope tracing internal recycling and evaporation losses in saline lakes on the Qinghai-Tibet Plateau

Direct measuring of internal lake recycling and evaporation losses remains challenging for lakes on the QinghaiTibet Plateau (QTP). Stable isotope techniques provide an effective approach for estimating water vapor cycling ratios and evaporation losses of lakes on the QTP. In this study, the stable isotope values of saline lakes on the QTP were modeled using the stable isotope values of the sampled lake water and their influencing factors. The water vapor recycling ratio and evaporation loss (E/I) of 135 saline lakes on the QTP were evaluated and their influencing factors were revealed. The results showed that stable isotopes in saline lakes on the QTP showed significant spatial variability. Their stable isotopes were affected by the source of water vapor, recharge patterns, and local evaporation conditions. It's worth noting that the average water vapor recycling ratio of saline lakes on the QTP was 20.16 %, one-fifth of the saline lakes had a water vapor recycling ratio beyond 30 %. Saline lakes lose 26 % of their water through evaporation. 26 % of the saline lakes experienced high evaporation losses of >40 % of the total inflow. We found that the main factors controlling the water vapor recycling ratio and evaporation loss in saline lakes on the QTP were precipitation and altitude, respectively. Interestingly, the control factors of water vapor recycling ratio and evaporation loss in saline lakes with elevation above 4500 m showed significant differences compared to saline lakes with elevation below 4500 m. Therefore, the strengthening of lake system monitoring can provide reliable data support for security assessment and effective management of water resources on the QTP.

Automated summary

This study used stable isotope techniques to investigate saline lakes on the Qinghai-Tibet Plateau (QTP) and found significant spatial variability in their stable isotopes due to the source of water vapor, recharge patterns, and local evaporation conditions. The average water vapor recycling ratio of saline lakes on the QTP was 20.16%, with some lakes exceeding 30%. Saline lakes lose 26% of their water through evaporation, with 26% experiencing high evaporation losses of over 40% of the total inflow. Precipitation and altitude were identified as the main factors controlling the water vapor recycling ratio and evaporation loss, respectively, with significant differences found between saline lakes above and below 4500 m elevation.