土地利用与土地覆被变化(Land Use and Land Cover Change,LUCC)及气候变化对流域的径流变化影响巨大.为揭示龙川江流域LUCC和气候变化对径流变化的影响,基于SWAT模型,通过设置不同情景,定量分析了不同土地利用类型和气候要素对流域内径流的影响,并结合RCP4.5、RCP8.5两种气候情景对流域未来径流的变化进行了预估.结果显示,(1) SWAT模型在龙川江流域径流模拟中具有较好的适用性,可用SWAT模型进行流域的径流模拟,率定期的模型参数R~2、Ens分别达到0.73、0.71,验证期的模型参数R~2、Ens分别达到0.75、0.74.(2)从土地利用方面考虑,将农业用地转化为林地或草地,均会导致流域径流量的减少,而将林地转化为草地则会引起流域径流量的增加,农业用地、林地、草地三者对径流增加的贡献大小顺序为农业用地˃草地˃林地.从气候变化方面考虑,流域径流量与降雨量呈正比,与蒸发量呈反比.(3) 2006-2015年间龙川江流域LUCC引起的月均径流增加幅度小于气候变化引起的月均径流减少幅度,龙川江径流的变化由气候变化主导,月均径流量总体上减少1.59 m~3·s~(-1).(4)预估结果显示,RCP4.5和RCP8.5气候情景下,2021-2050年间龙川江流域径流减少趋势明显,分别为1971-2015年减速的2.65倍、3.43倍.
英文摘要:
Land use and land cover change (referred to as LUCC) and climate change has a significant influence on runoff variation in a river watershed, which is a hotspot in the study of variation of watershed water resources. Based on SWAT model and quantitatively analyses, the impact of different land use types and climatic factors on watershed runoff in different scenarios were studied to reveal the influence of LUCC and climate change on watershed runoff variation. Combined with RCP4.5 and RCP8.5 climate scenarios, the future runoff change of the Longchuan River Watershed was predicted. Results were as follows: (1) SWAT model performed well in simulating Longchuan River Watershed runoff. The model parameter R~2 and Ens was 0.73 and 0.71 respectively in parameter calibration period, and 0.75 and 0.74 respectively in model verification period. (2) Considering the aspect of LUCC, the conversion of farmland into woodland or grassland would decrease watershed runoff, however, the conversion of forest to pasture would increase watershed runoff. The three types of land contributed to the rise of runoff in the order from the largest to the smallest, followed by cultivated land, grassland and forest land. Regarding climate change, runoff was directly proportional to rainfall and inversely proportionate to evaporation. (3) The average monthly runoff increase caused by LUCC was lower than the average monthly runoff reduction caused by climate change in the Longchuan River Watershed in 2006-2015. The evolution of Longchuan River runoff was dominated by climate change, and the average monthly runoff was reduced by 1.59 m~3·s~(-1). (4) Under the climate scenarios of RCP4.5 and RCP8.5, the runoff of the Longchuanjiang River Watershed would decrease naturally from 2021 to 2050, which was 2.65, 3.43 times of the deceleration from 1971 to 2015 respectively.