黄河源区地表水资源变化及其影响因子

利用1955～2005年黄河源区玛多气象站和黄河沿水文站气象、水文资料,分析了该区域地表水资源、气候及冻土演变规律,揭示了地表水资源变化的成因.研究表明:近51年黄河源流量丰枯转化频繁.但在总体上特别是进入20世纪90年代以来黄河源流量呈减少趋势.流量年内分配表现为单峰型;降水量对流量有着较为显著的影响,且具有一定的持续性;黄河源区气温的显著升高对于加大流域蒸发量导致流量补给的减少作用要大于其升高致使冰雪融水的补给作用.其中春季气温回升的这一效应更为显著;黄河源区冻土呈现出显著的退化趋势.冻土厚度与流量总体上呈显著的正相关关系,其不断减小削弱了自身天然隔水层的作用;黄河源区蒸发量呈现出显著的增大趋势,并导致流量的减少;气候变化导致流量的减少量占总减少量的70%.其余30%可能是由人类活动加剧造成的.气候及冻土因子对流量的作用大小依次为冻土、降水、蒸发和气温,显然多年冻土对于黄河源区地表水资源的形成和发育有着至关重要的作用.

Changes and Influencing Factors of Surface Water Resources in the Source Region of the Yellow River

Taking the source region of the Yellow River as a study area and based on the data from Madoi Meteorological Station and Huangheyan Hydrological Station covering the period 1955-2005 in the study area, this paper analyses the changing trends of surface water resources, climate and frozen ground and reveals their causes. Some conclusions can be drawn as follows: (1) Results show there exist frequent fluctuations from high to low water flow in recent 51 years. Generally speaking, the discharge has shown a declining trend in the 51 years especially since the 1990s. The annual distribution shows one peak which, year on year is getting smaller. (2) Precipitation has a significant and sustained influence on discharge. (3) A sharp rise of temperature in the source region resulted in the increase of evaporation and the decrease of discharge supply, which has a greater effect than on ice-snow melting, as indicated by the fact that the rising spring temperatures played the most important role in this process. (4) Frozen ground tends to be degraded markedly. Permafrost is impermeable so there is a negative correlation between the thickness of the active layer and permeability, whereas there is a significant positive correlation between the permafrost thickness and the discharge. (5) Evaporation rates are significantly increasing, leading to the decrease of discharge. (6) 70% of the discharge reduction resulted from climate change, and the remaining 30% may have been caused by intensified human activities. The major factors influencing the discharge are, in the order of their effects, frozen ground, precipitation, evaporation and temperature. It is evident that permafrost is of utmost importance in the formation and development of surface water resources in the source region of the Yellow River.