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Program |
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Special Session 2: Changing ocean environment: from the sedimentary perspective -- processes and records |
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A numerical investigation of freshwater and sediment discharge variations of Poyang Lake catchment, China over the last 1000years
SS2-09-S
Qidong Shi* , Ministry of Education Key Laboratory for Coast and Island DevelopmentNanjing UniversityChina
Jianhua Gao, Ministry of Education Key Laboratory for Coast and Island DevelopmentNanjing UniversityChina
Presenter Email: 819230211@qq.com
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| The Poyang Lake catchment, an important sub-catchment of Changjiang, experienced Little Ice Age(LIA) and accelerating intensity of human activities
during the last 1000 years. As such, the area and time period serve as a perfect case to study the variations in water and sediment discharge under
combined natural and anthropogenic impact. Simulation results of the model HydroTrend indicate that the annual average cumulative water discharge
of the five rivers entering Poyang Lake over the last 1000 years is 103.65±1.80 km3, and climate change is the dominating factor determining water
discharge variations over time. Influenced by the LIA (AD 1451–1850), the total water discharge of the five rivers was reduced by 10%. Sediment load
discharging into Poyang Lake by the five rivers was only 9.21±0.43Mt yr−1 between AD 1000 and 1700, when the anthropogenic impact on the landscape
was still low. However, with the human activities accelerating during the past 300 years, the sediment load entering Poyang Lake underwent a drastic
change. Because of intensified soil loss, the total sediment load entering Poyang Lake during AD 1800–1950 increased by 58.7%, compared with AD
1000–1700. After AD 1950, the sediment load variation is mainly reflected by the combined impact of dam emplacement and soil erosion. As sediment
interception by dams continuously increased over time, the total sediment load entering Poyang Lake during AD 1990–2000 is only 60.9% of that of
the highest riverine sediment flux during AD 1951–1980, which is almost equal to that of the lowest level during AD 1000–1700. The sediment load of
many rivers in the world exhibited similar variation trends as that of Poyang Lake under combined impact of climate change and human activities. Better
understanding the mechanisms of these variation trends is helpful to analyzing the formation and evolution of an estuary-shelf sedimentary system over
the Holocene. |
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