SWAT模型参数对土地利用变化的响应及其对不同时间尺度径流模拟的影响

Response of SWAT model parameters to land use change and its effects on the simulation of runoff with different time scales

SWAT模型广泛应用于土地利用变化的水文效应评估研究,但土地利用变化是否对模型参数产生影响,进而影响径流模拟效果还有待于进一步分析。以东南沿海福建省山美水库流域为研究区,基于SWAT模型,分别模拟1995年、2005年、2015年土地利用条件下的年、月、日尺度径流过程,采用SWAT-CUP进行参数敏感性分析与自动率定,分别获取1995年、2005年、2015年3种土地利用条件下径流过程模拟的最优参数集,比较参数差异;将3组参数集分别应用到不同土地利用条件,分析参数变化对不同时间尺度径流模拟的影响。结果表明:(1)1995—2015年间,研究区土地利用格局发生了较大变化,主要表现为林地转向园地和建设用地;3期土地利用条件下率定的SWAT模型都能较好地模拟山美水库流域年、月、日尺度径流,其效率系数NS和决定系数R^(2)分别大于0.62和0.78。(2)不同土地利用条件下敏感参数基本一致,敏感参数分别为CN2、SOL_AWC、SOL_K、CANMX、ESCO、GW_DELAY、OV_N,但敏感参数取值随着土地利用变化而变化,其变化规律符合敏感参数的物理意义,变化率基本与土地利用变化强度正相关。(3)由土地利用变化引起的参数变化,对年、月径流模拟的影响较小,对日径流影响显著,且随着土地利用变化强度的增加而增加。

The distributed hydrological model provides an effective means for runoff simulation and hydrological response to land use change.SWAT model is widely used to evaluate the hydrological response of land use change.However,the response of model′s parameters to land use change and its effects on the simulation of runoff have not been well investigated.In this study,Shanmei Reservoir watershed located in the southeastern China was took as a research area and SWAT models for the simulation of the annual,monthly,daily runoff were constructed under the land use conditions of 1995,2005 and 2015,respectively.The optimal values set for the sensitive parameters under three land use conditions were determined with the method of SWAT-CUP,respectively.The three optimal values sets of parameters then were applied to analyze the effects of land use change on the simulation of different time scales runoff.The results showed that:(1)the land use pattern in the study area changed greatly from 1995 to 2015.The garden and urban land were increased while the forest was reduced significantly.The SWAT models well simulated the different time scales runoff process for the three land use conditions of 1995,2005 and 2015 with the Nash-Suttcliffe(NS)was above 0.62 and the coefficient of determination(R^(2))above 0.78.(2)The sensitive parameters were same for the three land use conditions which included CN2,SOL_AWC,SOL_K,CANMX,ESCO,GW_DELAY and OV_N.The values of the sensitive parameters were varied with the change of land use and the variation was coincident with the physical meaning of sensitive parameters.The values of CN2,SOL_K,CANMX,ESCO and OV_N in the study area were gradually increased from 1995 to 2015,while the values of SOL_AWC and GW_DELAY gradually decreased.The reason for the changing trend of sensitive parameters was that the land use in the study area was changed partly from forest to garden,pasture,orchard and urban land from 1995 to 2015,resulting in the decrease of the forest area.(3)The change of the value of sensitive parameters,caused by land use change,had little influence on the simulation of the annual and monthly runoff but significantly on the daily runoff.The influences on the daily runoff increased with the increase of the amplitude of land use change.