Determining the influencing distance of dam construction and reservoir impoundment on land use: A case study of Manwan Dam, Lancang River

摘要

Based on Landsat MSS and TM images from 1974,1988, and 2004, we conducted a case study of the Man-wan Dam along the Lancang (Mekong) River to determine the influencing distance of dam construction and reservoir impoundment on land use. Spatio-temporal variation in land use was analyzed within 14 adjacent buffer zones around the dam site (concentric rings) and in upstream and downstream areas along the riverway (linear tract). Grassland increased with the greatest dynamic degree in the 1974-1988 period, whereas water area increased extensively in the 1988-2004 period. The integrated dynamic degrees of forestland were low in both periods. The integrated land use dynamics in the 14 concentric rings showed that the impact of dam construction extended to a threshold distance of 5000-6000 m from the dam site during the 1974-1988 period and to 2000-3000m during the 1988-2004 period. The transformational patch density in the 14 linear buffer zones indicated that the impact of reservoir impoundment on land use conversion exhibited a threshold distance of 3000 m from the riverway. The impact intensity of dam construction in the concentric rings and linear buffer zones tended to decline with increasing distance from the dam site or riverway. The impacts of dam construction and reservoir impoundment were larger in upstream locations than in downstream ones. Our results enhance our understanding of the threshold of dam construction and may guide the management of dam construction on a regional landscape level.