环青海湖地下水补给来源及对湖水补给量估算研究

Groundwater's contribution to the lake system directly affects the lakes and the surrounding ecological environment security. So the interaction between groundwater and lake water has been listed as major fundamental frontier science issues in the fields of earth system, resources and environment. Qinghai Lake is one of China's national nature reserves and an important water body for the ecological security of the Northeast Qinghai-Tibet Plateau. At present, the recharge source and refresh rate of groundwater around the Qinghai Lake, as well as the interaction between groundwater and lake water, are not clear, and these are essential and contribute to the planning strategies and recommendations for the rational use of groundwater resources. This research selects the Qinghai Lake as a study area. Observatories for ground water level and flow direction are set up around the Qinghai Lake. We use ArcGIS software to simulate and reveal the spatio-temporal variations of ground water level around the Qinghai Lake. We analyze the spatio-temporal characteristics of stable isotope and hydrochemistry of precipitation, river water, ground water and lake water to investigate the recharge source of ground water around the Qinghai Lake. The age and refresh rate of ground water are estimated by using isotopic dating method. Supply amount of groundwater to the Qinghai Lake are estimated by using the darcy law method and the sable isotope mass balance equation. Based on the Visual Modflow software, we use the finite difference model (MODFLOW) to simulate the interaction between groundwater and the Qinghai Lake water, and construct the sketch map of supply pattern between groundwater and lake water in different seasons and throughout the year. Meanwhile, we discuss the impact of supply amount of ground water to the lake level change. This study would provide scientific base for analyzing the water resources changes and discussing the causes of lake level change. Meanwhile, it is expected that the results will provide insight into the hydrological process of cold and alpine groundwater in addition to water resource management in the Qinghai Lake Basin and the Qinghai-Tibet Plateau.

地下水对湖泊系统的贡献直接影响湖泊及周边生态环境安全及存亡，地下水与湖水相互作用研究已被列为地球系统和资源环境领域的重大基础性前沿科学问题。青海湖是维系青藏高原东北部生态安全的重要水体，其地下水与湖水相互作用规律及机制尚不清楚。本研究拟通过全年度观测环青海湖地下水水位及流向，揭示环湖地下水水位的时空变化规律；采用环境同位素和水化学示踪技术，分析不同水体同位素及水化学的时空变化特征，揭示环湖地下水补给来源，运用同位素测龄法估算地下水的年龄及更新速率；采用断面法和同位素水量平衡模型估算地下水对青海湖的补给量及时空分布特征；利用有限差分模型模拟青海湖地下水与湖水的相互作用规律，构建不同季节及全年的地下水-湖水补给模式图，探讨气候变化背景下地下水对青海湖水位的影响。为定量研究青海湖流域水资源和青海湖水位变化的原因等提供科学依据，并为高寒区域地下水与湖泊相互作用及区域水循环研究提供借鉴。

地下水对湖泊系统的贡献直接影响湖泊及周边生态环境安全及存亡，地下水与湖水相互作用研究已被列为地球系统和资源环境领域的重大基础性前沿科学问题。青海湖是维系青藏高原东北部生态安全的重要水体，其地下水与湖水的相互作用规律及机制尚不清楚。本研究通过全年度观测环青海湖地下水水位及流向，揭示了环湖地下水水位的时空变化规律；采用环境同位素和水化学示踪技术，分析了不同水体同位素及水化学的时空变化特征，揭示了环湖地下水补给来源，运用同位素测龄法估算了地下水的年龄及更新速率；采用同位素水量平衡模型估算了地下水对青海湖的补给量及时空分布特征；构建了不同季节及全年的地下水-湖水补给模式图，探讨气候变化对青海湖水位的影响。主要结果如下：（1）环湖地下水水位埋深介于1~16.7m，地下水水面与青海湖湖水水面的相对高程值介于-0.41~141.25m，水力梯度介于-0.06 ~13.47‰，环湖地下水补排方式为地下水补给湖水。（2）浅层地下水平均滞留时间介于1.64年-4.11年之间，平均值为2.70年。（3）2019年湖泊水位由3195.71m上升至3196.11m，上升40cm，即青海湖水量增加17.94×108m3。输入项包括湖面降水、河水径流、地下水径流，分别为：18.52×108m3、26.62×108m3、7.02×108m3；输出项为湖面蒸发，34.22×108m3。（4）2004年之后青海湖水位上升的主要原因为：流域内风速降低，致使蒸发量减少；流域内降水量增加，致使湖面降水、地表河流、地下水入湖水量增加。相关结果为定量研究青海湖流域水资源和青海湖水位变化的原因等提供科学依据，并为高寒区域地下水与湖泊相互作用及区域水循环研究提供借鉴。