Role of reservoir construction in regional land use change in Pengxi River basin upstream of the Three Gorges Reservoir in China

The impact of the Three Gorges Reservoir (TGR) construction on land use change has attracted worldwide concern. However, quantitative evidence is lacking for the drivers of land use change resulting from the TGR during and after construction. We used the Pengxi River basin, located upstream of the Three Gorges dam, to evaluate the effects of large-scale hydrological engineering on land use. Landsat remote sensing images from 1995, 2000, 2005 and 2010 covering the main construction period of the TGR were obtained. The largest changes were the conversion of land to water bodies and built-up areas, corresponding to reservoir impoundment and population resettlement during TGR construction. These changes were more intensive downstream of the TGR and closer to the river. Compared with 2000-2005, the expansion in water bodies during 2005-2010 moved from lower to higher elevations. The distribution of built-up land during the two periods was similar, mainly because the planned resettlement zones were fixed and spatially concentrated. Geographical and environmental factors, such as elevation, slope, location, soil type and precipitation, still controlled land use patterns. Land use pattern in 2020 under two scenarios was simulated using a multi-criteria evaluation cellular automata-Markov model. Scenario 2 was more realistic and helpful for management decisions. The scenarios highlighted the indirect influences of TGR construction on land use change after 2010. Indirect driving forces were mainly reflected through related policies or plans, especially from the perspective of water conservation in the newly built reservoir.