黄河流域多尺度水系统结构变化特征

大河流域的水系统是支撑社会-生态系统的基础，理解水系统的结构变化是深入揭示区域系统演化的关键。基于自然-社会水系统视角，从黄河全流域和二级水资源分区尺度，利用1998—2018年降水、蒸发、径流、社会经济耗水等水系统变量，通过Mann-Kendall趋势检验和线性回归分析方法，分析了水系统要素的变化趋势及结构演变特征。结果表明：在全流域尺度，降水、蒸发分别以4.25 mm·a^-1、4.09 mm·a^-1的速率上升，但蒸发在空间上的变化更显著；径流量呈现先减少再上升后急剧下降的趋势，且与降水量显著正相关。社会系统耗水量呈现增速减缓的特征，农业灌溉占耗水结构的比例以0.50%的速率逐年下降；城镇公共、居民生活和生态环境耗水比例分别以0.07%、0.29%、0.11%的速率上升。在二级水资源分区尺度，各水系统分异特征明显，兰州至头道拐段及花园口以下区域水系统所支撑社会经济发展的功能已经出现了超载。各水系统要素间具有不同程度的协同演变趋势，在湿润区域，蒸发相较于降水具有明显的滞后现象，但在干旱区域两者变化趋势基本一致。黄河流域水系统要素在时空上均存在明显的异质性，未来人口和经济的进一步发展可能会使区域的水资源压力加剧。

Multi-scale analysis of water system structure changes in the Yellow River Basin

Water system of river basin is the basis of supporting the socio-ecological system. Thus， understanding the structural change of water system is essential to reveal the evolution of regional system. To address this， we investigated the changing trends and structural evolutions of water system elements in the whole Yellow River basin and its secondary water resource divisions. Specifically， water system variables from 1998 to 2018， such as precipitation， evaporation， runoff， socio-economic water consumption， were analyzed using Mann-Kendall trend test and linear regression， in the perspective of nature-social water system. The results showed that precipitation and evaporation increased at a rate of 4.25 mm·yr^-1 and 4.09 mm·yr^-1 at the whole basin scale， respectively， in which the increase of evaporation was more significant. Runoff showed a significantly positive correlation with precipitation， and presented a decreasing-increasing-sharply decreasing trend during the whole period. The water consumption of social system was characterized by slow growth. In detail， the proportion of consumption in agricultural irrigation decreased at a rate of 0.50% per year， whereas the consumption of urban public， residential and ecological environment increased at the rate of 0.07%， 0.29% and 0.11%， respectively. Based on secondary divisions of water resources， the water system is highly heterogeneous， both spatially and temporally. Functions supported by the water systems have overloaded in Lanzhou-Toudaoguai and Huayuankou-Lijin section. Moreover， all the water system elements had co-evolution trend of different degree. In the humid region， evaporation had obvious lag phenomenon compared with precipitation， but the change trends were the same in the dry region. Water system elements in the Yellow River Basin had an obvious spatial and temporal heterogeneity. Further development of population and economy may aggravate the regional water resources pressure in the future. This study provided an important reference for scientific regulation of water resources and high-quality development of the basin.