黄土高原典型流域土地利用变化对蒸散发影响研究

Relationship between ET and LUCC in a typical watershed of Loess Plateau over the past 20 years

选取黄土高原典型流域罗玉沟流域为研究区,以2006年和1986年两个时段的TM影像为原始数据,通过SEBAL模型估算蒸散量,采用地面实测资料对估算结果进行验证,表明SEBAL模型在该流域较为适用。同时,得到该流域蒸散发的空间变化规律,并结合该流域相应时段的土地利用变化进行对比分析。结果表明:(1)遥感反演日蒸散量平均为2.41 mm和2.96 mm,平均误差为12.38%和13.14%,反演精度较高。(2)流域内蒸散量呈现西北高、东部低的空间分布规律,尤其在高植被覆盖区蒸散量比较大。(3)流域内土地利用变化明显,主要为坡耕地向梯田和林地转移,ET的空间分布与土地利用/覆盖类型有关,土地利用/覆盖的特点基本控制了研究区域ET的分布特点。(4)对比两期日蒸散量图,ET显著增大的区域占到罗玉沟总面积的47.6%,显著减小的占到13.2%,并且2006年各个土地类型的日ET量均大于1986年的日ET量。研究流域内蒸散发分布规律可为罗玉沟流域土地利用规划、环境规划提供科学支持。

the Luoyugou valley was selected as a typical Loess Plateau watershed for this study.The TM image data from 1986 to 2006 was used for calibration and the record from 1954 to 2008 for validation.Through SEBAL model estimating ET;it demonstrates SEBAL model in the basin is more applicable.At the same time,ET spatial variation distribution was gotten over the past 20 years,combined with the corresponding periods of the land-use changes for analysis.The results show as follows:(1) The daily average evapotranspiration based on remote sensing inversion are 2.41 mm and 2.96 mm.The average errors are 12.38% and 13.14% respectively with high inversion precisions.The simulated daily ET values satisfactorily match the observed values.(2) The ET values in the northwest of the basin are higher than that in the east dealing with their spatial distribution,especially in the high vegetation coverage areas.(3) Land use types significantly changed in the watershed over the past 20 years,mainly being transferred from the cultivation-on-slopes to the cultivation-on-terraces and woodland.Results show that the change in land use/cover is considerably obvious,whose changed area accounts for 87.03% of the total area.The areas of terraced fields,natural vegetation lands and construction lands were increased in varying ratios(increased by 275.0%,17.05% and 14.32% respectively);Meanwhile,the areas of land used for cultivation-on-slopes and bare land decreased sharply(decreased by 76.5% and 20.31% respectively).ET spatial distribution is related to landuse/cover characteristics,which control the ET distribution characteristics in the study area.(4) The ET value images of 1986 and 2006 were compared.The ET values significantly increased and conspicuously reduced areas accounted for 47.6% and 13.2% of the total area respectively in 2006,the ET daily values for various landuse types are larger in 2006 than in 1986.The reaserch on the distribution laws of evapotranspiration can put forward the scientific supports for landuse planning and environmental construction of Luoyugou Watershed.