Land Cover Changes and Drivers in the Water Source Area of the Middle Route of the South-to-North Water Diversion Project in China from 2000 to 2015

The Middle Route of the South-to-North Water Diversion Project (MR-SNWDP) in China, with construction beginning in 2003, diverts water from Danjiangkou Reservoir to North China for residential, agriculture and industrial use. The water source area of the MR-SNWDP is the region that is most sensitive to and most affected by the construction of this water diversion project. In this study, we used Landsat Thematic Mapper (TM) and HJ-1A/B images from 2000 to 2015 by an object-based approach with a hierarchical classification method for mapping land cover in the water source area. The changes in land cover were illuminated by transfer matrixes, single dynamic degree, slope zones and fractional vegetation cover (FVC). The results indicated that the area of cropland decreased by 31% and was replaced mainly by shrub over the past 15 years, whereas forest and settlements showed continuous increases of 29.2% and 77.7%, respectively. The changes in cropland were obvious in all slope zones and decreased most remarkably (−43.8%) in the slope zone above 25°. Compared to the FVC of forest and shrub, significant improvement was exhibited in the FVC of grassland, with a growth rate of 16.6%. We concluded that local policies, including economic development, water conservation and immigration resulting from the construction of the MR-SNWDP, were the main drivers of land cover changes; notably, they stimulated the substantial and rapid expansion of settlements, doubled the wetlands and drove the transformation from cropland to settlements in immigration areas.