Wan Chengwei, Gibson J J, Shen Sichen, Yi Yi, Yi Peng, Yu Zhongbo
State Key Laboratory of Hydrology - Water Resources and Hydraulic Engineering, Nanjing 210098, China; College of Hydrology and Water Resources, Hohai University, Nanjing 210098, China; Department of Geography, University of Victoria, P.O. Box 3060, STN CSC, Victoria, BC V8W 2Y2, Canada; InnoTech Alberta, 3-4476 Markham Street, Victoria, BC V8Z 7X8, Canada.
Department of Geography, University of Victoria, P.O. Box 3060, STN CSC, Victoria, BC V8W 2Y2, Canada; InnoTech Alberta, 3-4476 Markham Street, Victoria, BC V8Z 7X8, Canada.
Sci Total Environ. 2019 Nov 1;689:1276-1292. doi: 10.1016/j.scitotenv.2019.06.427. Epub 2019 Jun 30.
A spatially distributed network of thermokarst lakes undergoing significant environmental changes was sampled in 2014 and 2016 to develop a comprehensive understanding of lake water balances in lakes across a gradient of frozen ground conditions. Frozen ground ranges from seasonally frozen ground (SFG) to sporadic discontinuous permafrost (SDP) to extensive discontinuous permafrost (EDP), and is representative of complex conditions in the Source Area of the Yellow River, northeastern part of Qinghai-Tibet Plateau. Radioactive and stable water isotopes in reference lakes (non-thaw lakes), thermokarst lakes, precipitation, wetlands, ground ice and supra-permafrost groundwater are analyzed to characterize systematic variations and to assess lake water balances using stable isotope mass balance (IMB). IMB, paired with analysis of tritium decay gradients, is shown to be a valid approach for detecting short-term shifts in lake water balance, which allows evaluation of the proportion of precipitation-derived versus permafrost-derived water inputs to lakes. All lakes except EDP thaw lakes are evaporation-dominated (E/I > 0.5). Negative water balances occurred most frequently in reference lakes due to hydrological connectivity with rivers. Precipitation-derived water inputs result in positive water balances in SFG and SDP thermokarst lakes, but negative-trending water balances are found in SDP thermokarst lakes due to substantial reduction in water yield. Increasing contributions from thawing permafrost in EDP thermokarst lakes result in strong positive water balance. Permafrost degradation may also lead to the changes in hydrological connectivity between precipitation and wetlands or thermokarst lakes. Based on these findings, a conceptual model of the hydrological evolution of thermokarst lakes under the influence of permafrost degradation is proposed.
2014年和2016年对一个经历显著环境变化的热喀斯特湖空间分布网络进行了采样，以全面了解不同冻土条件梯度下湖泊的水平衡情况。冻土范围从季节性冻土（SFG）到零星不连续多年冻土（SDP）再到广泛不连续多年冻土（EDP），代表了青藏高原东北部黄河源区的复杂条件。分析了参照湖（非解冻湖）、热喀斯特湖、降水、湿地、地下冰和多年冻土上限地下水的放射性和稳定水同位素，以表征系统变化，并使用稳定同位素质量平衡（IMB）评估湖泊水平衡。结果表明，IMB与氚衰变梯度分析相结合是检测湖泊水平衡短期变化的有效方法，可用于评估湖泊降水来源与多年冻土来源的水输入比例。除EDP解冻湖外，所有湖泊均以蒸发为主（E/I＞0.5）。由于与河流的水文连通性，参照湖最常出现负水平衡。降水来源的水输入导致SFG和SDP热喀斯特湖出现正水平衡，但由于产水量大幅减少，SDP热喀斯特湖出现负趋势水平衡。EDP热喀斯特湖解冻多年冻土的贡献增加导致强烈的正水平衡。多年冻土退化还可能导致降水与湿地或热喀斯特湖之间水文连通性的变化。基于这些发现，提出了一个多年冻土退化影响下热喀斯特湖水文演化的概念模型。
