天山中部流域尺度森林变化水文响应定量分析——以乌鲁木齐河流域为例

为了对天山中部流域尺度森林变化水文响应进行定量分析,论文以乌鲁木齐河流域为研究区,基于流域1980—2013年水文气象资料,在分析流域径流变化规律的基础上,使用SWAT模型,根据天山云杉分布的生境限制因素,设定了5种不同的云杉分布情景,据此,确定不同丰枯年份云杉林变化对径流的影响。结果表明:1)SWAT模型能较好地模拟乌鲁木齐河流域月径流过程,在林地状况恒定的前提下,影响模型模拟的最敏感的参数为地表径流参数CN2,率定期与验证期R2和Ens均高于0.85,相对误差|Re|均小于5%,模型模拟精度较高;2)在相同气象条件下,丰水年、平水年、枯水年云杉林变化与径流呈线性相关,云杉林面积每增加1%,三种年份径流深分别减少0.06、0.05、0.04 mm,且在丰水年和平水年径流增加更显著;3)随着云杉林面积的减少直至消失(林地覆盖率由17.73%到0%),情景间径流差异的变异系数、波动范围变化逐渐增大,其波动范围扩大5.1倍。山区云杉林的分布,可有效减少地表径流及其波动范围,这对年内径流分配不均的流域水资源稳定、对森林水源涵养功能的定量研究以及林区水资源科学调控和管理都具有重要意义。

Quantitative Analysis of Hydrological Response to ForestChanges in the Middle of the Tianshan Mountains:A Case Study of the Urumqi River Basin

Taking the Urumqi River Basin as a research area, this paper quantitatively analyzed the hydrological response to forest changes in the middle of the Tianshan Mountains. Based on the analysis of runoff change with hydrological and meteorological data (1980-2013), and using SWAT model and habitat limiting factors of spruce distribution, the influence of the change of spruce forest on runoff in different dry years was determined in five different distribution scenarios of spruce. The result shows that: 1) The calibrated SWAT model can simulate the monthly flows well and has high simulation precision, and the most sensitive parameters influencing model was CN2 according to the actual condition of forest land. The R² and Ens of calibration and validation periods were all higher than 0.85, and the relative errors |Re| were all less than 5%. 2) In the same climate condition, the spruce forest changes in wet year, normal year, dry year showed linear correlation with runoff, 1% increase of spruce forest area resulting in runoff depth reduction of 0.06, 0.05 and 0.04 mm, respectively; and the runoff increased more significantly in wet year and normal year. 3) With the decrease of spruce forest area (the forest land cover reduced from 17.73% to 0%), the difference of the runoff variation coefficient and the fluctuation range between scenarios increased gradually, and the range of the runoff fluctuation can expand 5.1 times. The spruce forest in mountain area can effectively reduce the surface runoff and its fluctuation range. It has important significance for the stability of water resources (the uneven distribution of runoff), the quantitative research of forest water conservation, and the scientific regulation and management of water resources in forest regions.