Determining tributary sources of increased sedimentation in East-African Rift Lakes

Area of Science:

• Environmental Science
• Geology
• Hydrology

Background:

• Lake Manyara, Tanzania, faces challenges from sediment dynamics.
• Understanding sediment sources is crucial for water resource management in East African Rift Lakes.

Purpose of the Study:

• To evaluate temporal and spatial sediment dynamics in Lake Manyara.
• To identify key tributary sources contributing to lake sedimentation.
• To link land degradation to downstream ecosystem health.

Main Methods:

• Radioactive dating of sediment cores to assess sedimentation rates.
• Geochemical analysis of sediment for elemental profiling.
• Bayesian mixing models for source attribution of sediment.

Main Results:

• Lake Manyara shows an increasing sedimentation trend over the past 120 years.
• Sedimentation rates peaked in the 1960s and 2010, linked to land cover changes and rainfall.
• Two tributaries were identified as major contributors (58% and 38%) to recent sediment load.
• Sedimentation impacts varied spatially across the lake.

Conclusions:

• Upstream land degradation and rainfall fluctuations drive increased sedimentation in Lake Manyara.
• Source-tracing successfully linked specific tributaries to sedimentation issues.
• Findings support targeted land and water management for ecosystem health and water security.