Wednesday 25 Jan 2017
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Yellow River Basin

Updated Land Cover Classification for the Yellow River Basin, 2003-2013

Based on time series of MODIS satellite imagery a land cover classification for the whole Yellow River Basin was generated for the years 2003 and 2013. MODIS NDVI time series were analyzed and several phenologic and seasonal parameters, such as start and end of vegetation period, were derived for further processing of the data under the utilization of well-known classification approaches. The result is a regionally adapted land cover map with a spatial resolution of 250m. Agricultural encroachment, urban expansion, and large scale vegetation restoration programs have been the most prominent influencing factors during the last decade.

12-year analysis of basin-wide NDVI changes based on EO data, 2002-2014

Based on a MODIS NDVI time series, the annual NDVI sums have been calculated since 2002 with a spatial resolution of 250 m. The Normalized Differenced Vegetation Index (NDVI) is an often used proxy, describing the prevailing productivity and vegetation density. In order to identify NDVI changes during the last decade, we performed a trend analysis using the annual NDVI sums. The statistically significant trends are depicted in the following figure, showing large areas with positive NDVI changes.

Modeling Net Primary Productivity

Net Primary Productivity (NPP) describes the CO2 uptake by vegetation for a given area and time unit and thus provides information on plant growth, CO2 storage and CO2 release. The used model BETHY/DLR is a soil-vegetation-atmosphere-transfer (SVAT) model (Wißkirchen et al. 2013). It is based on meteorological and remote sensing derived input data. The temporal resolution of input data allows for daily modelling of NPP.

Mean Precipitation and Temperature

Map Precipitation:

This map depicts the precipitation distribution within the Yellow River Basin. The rainfall is unevenly distributed in space and time. It shows a decreasing trend from southeast to northwest and is mainly concentrated from July to September. The basin´s mean annual precipitation is around 520 mm. The lowest precipitation values can be found in Ningxia/Inner Mongolia plains and the Gobi desert, the highest in the lower reaches of the Yellow River.

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