青藏高原高寒草甸浅层地下水位对环境因子的响应特征——以青海海北站为例

The Response of Shallow Groundwater Level to Environmental Factors on Alpine Meadow in Qinghai-Tibet Plateau: A case study on Qinghai Haibei Station

青藏高原水资源丰富,浅层地下水位是水源涵养功能的重要表征,但其对全球气候变暖的响应特征尚不清楚。基于青海海北站高寒草甸2012—2016年浅层地下水位自动观测连续数据,采用优势分析方法定量评估了降水、风速、水面蒸发、50 cm土壤温度和气温等5个主要环境因子对地下水位的影响。结果表明,(1)季节尺度上,地下水位表现为双峰双谷曲线趋势,5—8月(生长季)为丰水期,8月达到最高值(4.25±0.13)m,1—4月和9—12月(非生长季)为枯水期,5月达到最低值(4.78±0.06)m;年际尺度上,地下水位总体呈逐渐下降趋势,且在2014年达到最高值(4.18±0.27)m。(2)风速是影响地下水位变化最重要的环境因子,占总贡献的36.8%,其次依次是蒸发(27.7%),气温(16.6%)和50 cm土壤温度(9.5%),而降水对地下水位影响微弱,仅占总贡献的9.3%;除降水外,各环境因子与地下水位均呈显著负相关(P<0.05)。(3)地下水位与降水的年内和年际变异规律差异较大,降水的季节和年际变异均大于地下水位。综上,青藏高原东北隅高寒草甸浅层地下水位的变异与降水关联较小。研究结果可为青藏高原水资源合理管理和利用提供理论依据。

The water resources in Qinghai-Tibet plateau are abundant,and shallow groundwater plays an important role in plateau hydrologic cycle.However,few studies had conducted on the responses of shallow groundwater level to global warming in this special region.Our research conducted on alpine meadow in the northeast corner of Qinghai-Tibet plateau,and applied dominance analysis to quantitatively evaluate the contributions of rainfall,wind speed,evaporation,50 cm soil temperature and air temperature to groundwater level.The results showed that,(1)On a seasonal scale,the groundwater level was characterized by a double peak and double valley relationship within a year,which decreased significantly during the non-growth season(January to April,October to December)and increased during growth season(May to September),with the maximum and minimum value of groundwater level occurred in May(4.78±0.06)m and August(4.25±0.13)m,respectively.On a interannual scale,the groundwater level showed a show slightly downtrend from 2012 to 2016,with the highest value occurred in 2014(4.18±0.27)m.(2)The wind speed was the most important factors affecting the variation of groundwater level among five environmental factors,which accounted for 36.8%of total variation,then followed by evaporation(27.7%),air temperature(16.6%),50 cm soil temperature(9.5%).However,rainfall exerted little impact on the variation of groundwater level,which only accounted for 9.3%of total variation.Moreover,all environmental factors were significantly negative relate to groundwater level except rainfall.(3)The groundwater level was more stable than rainfall,and the variation of rainfall was larger than groundwater both on a seasonal scale and inter-annual scales.Our studies suggested that the shallow groundwater level would be less affected by rainfall on alpine meadow in Qinghai-Tibet plateau,which could provide scientific proofs to manage and utilize water resources in Qinghai-Tibet plateaus in future.