Quantifying the anthropogenic and climatic impacts on water discharge and sediment load in the Pearl River (Zhujiang), China (1954-2009)

SummaryAnthropogenic and climate influences on temporal changes in water discharge and sediment load were examined in the Pearl River in China. Increasing, undulating, and decreasing phases were found in the years 1954-1983, 1984-1993, and 1994-2009, respectively. Between 1954 and 1983, water discharge and sediment load increased by 18% and 32%, respectively. During an undulating phase between 1984 and 1993, a marked up in water discharge and sediment load was followed by suddenly rebounded discharge. From 1994 to 2009, water and sediment decreased by 32% and 83%, respectively. These trends were generally in agreement with changes in precipitation, suggesting climatic influences on a decadal timescale, although the changes in sediment load were also related to human activities. Human impact on sediment load can also be identified as three major phases. In the 1950-1970s, deforestation in the catchment was balanced by dam construction, resulting in no significant net change in sediment load. In the 1980s, however, the influence of the deforestation outweighed dam construction, resulting in an increase in sediment load. Since the 1990s, dam construction and soil preservation have decreased sediment load quickly, and the monthly sediment loads were lower in post-dams period than in the pre-dams period. Since the closure of the Longtan and Baise Dams in 2006, the sediment load in the Pearl River has decreased by ∼70% relative to the level of the 1950-1980s. Of this change, ∼90% was caused by dam construction and ∼10% was due to by climate change. In the coming decades, the sediment load in the Pearl River will probably continue to decrease as the new dams are built within the watershed.

► Three phases of significant changes in water and sediment discharges were identified. ► Anthropogenic and climatic impacts on water and sediment discharges were separated. ► Sedimentary impacts of major dams recently constructed in the river were examined.