| Water is the irreplaceable resource for human’s life, which is also the basis for the sustainable development of economy and society. Different management measures in a basin result in diversification characteristics on the influence of water resources, due to the large heterogeneity, climate variability and human activities factors overlap and coupling in the basin. In this paper, Chaohe basin was chosen as the case study area. Based on the MODIS dates, hydrometeorology dates and vegetation distribution, using the ENVI, ArcGIS software, the vegetation dynamic change and its response to climate change were analyzed. Actual evapotranspiration was reckoned by MODIS, Water Use Efficiency (WUE) and Zhang L. model and results were verified by explored the secular annual basin actual evapotranspiration which was calculated from water model. The annual water yield spatial distribution in Chaohe basin during 2001-2012 was discussed. We have also analyzed the changes of landscape pattern and relevance among landscape index and runoff. The results revealed that:(1)The average Leaf Area Index (LAI) showed a significant tendency of increasing (R2=0.59, P<0.05) on the whole basin and the rate was 0.01/a. While in some areas, the LAI falling which caused by human activities, such as urban construction and road building. The annual Gross Primary Productivity (GPP) showed a no significant tendency of increasing (R2=0.02, P>0.05) at a rate of 0.02*106 tons/a. Spatial variation of GPP showed a similar trend as the LAI. Not only LAI but also GPP showed significant correlation with precipitation factor and no significant correlation with temperature factor on year scale.(2)Precipitation exhibited an obvious rising tendency in Chaohe watershed(R2=0.02, p=0.22), the rising speed was 2.72mm·year-1, causing the unbalanced spatial distribution between the northern and southern areas, the northern rained more than southern, the precipitation range from 400mm-600mm; In yearly distribution, the precipitation was the heaviest in July and the least in January. Mean annual temperature rise at a rate of 0.215℃/10a, water yield reduced significantly in Chaohe watershed, the conversion between high flow years and low flow years run on a 28-year cycle.(3)According to MODIS data, Zhang L. formulation and the relationship between WUE and GPP, the spatial distribution of actual evaporation was calculated, compared with the total evaporation which was the result of water balance, Zhang L. formula had the best correlation, the model fitting efficiency reached 90%; MODIS ranked the second, the model precision was the lowest by using WUE and GPP the fitting degree only reached 20%.(4)Water yield exhibited an obvious decrease tendency in chaohe watershed from 2001 to 2012 (R2=0.02,P<0.1), the rate of reduction was 0.096mm · year-1. Interannual difference was obvious, the annual average water yield was 18.7±15.5 mm · year-1, different vegetation types from more to less in proper order were:Cultivated land> grassland> shrub forest land> forest land, the water discharge in Chaohe mainly occurs in the middle area of upstream and downstream.(5) A steady increasing plaque number with decreasing area with more simplicity caused Chaohe basin become weak. Runoff was decreased with increasing landscape shape index. When the mean plaque perimeter was 1050m, the number of plaques was 110000 with Shannon’s diversity index of about 1.33. Therefore, the comprehensive intercepting ability of plaque was strongest and the watershed runoff capacity was weakest. |
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