泾河流域土地利用/覆被变化对径流情势的影响

Influence of land use and land cover changes on runoff regime in Jinghe Basin

通过建立泾河流域SWAT分布式水文模型,重点模拟分析了河流径流情势对土地利用/覆被变化的响应,对比了不同气候条件及人类活动综合影响下研究区水文过程的变化。结果表明:1996年以前土地利用/覆被变化是影响水文过程的主要人类活动影响源,径流量年际变化平稳,属有小幅增加的正偏;年内影响以枯水季节为主,年内分配更趋均匀,径流集中度降低,集中期略有滞后,且趋于平稳;土地利用/覆被变化导致流域蒸散发量、冠层和落叶层截留量减小,入渗量增加,河川基流量和地表径流量相应增大,并在时域上耦合形成了水文过程的新变化;1996年以后,气候条件驱动下泾河年径流量呈现明显的增大趋势,人类活动亦从以土地利用/覆被变化为主转变为以人类水事活动为主的综合影响模式,且人类水事活动超过气候变化和土地利用/覆被变化成为影响水文过程变化的主因。

In order to analyze the influence of land use and land cover changes on runoff regimes, a distributed hydrological model in the Jinghe Basin was built based on the SWAT model. The synthetic influence of climate change and human activities on the hydrological processes in the study area was also investigated. The results show that, before 1996, land use and land cover changes were the main human activities affecting hydrological processes; under those influences, inter-annual fluctuations of runoff were stable, showing a significant positive skew. At the intra-annual scale, the main influence was runoff in dry seasons, and the flow was more uniformly distributed than before. Meanwhile, the concentration ratio of runoff decreased, and the concentration period lagged and tended to be stable. The analysis of the physical causes of the runoff change indicates that land use and land cover changes lead to decreasing evapotranspiration, a decreasing amount of rainfall intercepted by the canopy and litter layer, and increasing infiltration in the basin, all of which cause the increase of the baseflow and surface runoff in the channel, leading to new variations of hydrological processes. The results also show that the runoff increased after 1996 due to climate change, and the main human activities changed from single land use and land cover type to land use and land cover coupled with other water-related activities. Also water-related activities, rather than climate change and land use and land cover changes, became the principal factor in the variation of hydrological processes.