Effect of Dam Construction on Spatial-Temporal Change of Land Use: A Case Study of Manwan, Lancang River, Yunnan, China

Selecting Manwan Dam as a study case, we studied the spatial-temporal change of land use during 1974, 1991 and 2004 based on the application of RS interpretation and GIS buffer analysis. Land use indices within three buffer distances from dam centre were calculated to quantify the effects of dam construction. The results showed that land use structure changed greatly during and after dam construction. Forestland and grassland were two main types of land use, which occupied over 79.70% of total area in 10000 m buffer. The main conversion of land use types took place from forest land to grass and farm land between 1974 and 1991, and that was almost consistent between 1991 and 2004. During 1974-1991, spatial dynamics of grass, farm and construction land were much larger than water body and forest land, and had an increasing tendency and the balanced state decreased with the increased off-dam distances which indicated that conversion of input and output were frequently between the three land use types. During 1991-2004, water body had the largest value of Rss, in a state of extreme non-balanced with its Ps reached 0.96, 0.96 and 0.99 in 10000, 5000 and 1000 m buffer, respectively. Further studies showed that direct effect was limited in the 1000 m buffer region based on the land use indices including temporal dynamics of land use change (Rs), spatial dynamics of land use change (Rss,) and tendency and state index (Ps). Generally, three indices of each land use type decreased with the increased off-dam distances.