Particle and nutrient budgets for Kariba Reservoir (Zambia/Zimbabwe)
Abstract
Flow in the Zambezi River Basin, the fourth largest river basin in Africa, is highly regulated by several large hydropower structures. However, only 30% of the river's hydropower potential is currently being utilized and multiple new hydropower schemes are planned. While the hydrology of this system has been explored in some detail, there has been limited investigation of how the existing hydropower schemes affect downstream transport of particles and the cycling of carbon and nutrients. We are exploring the impacts of Kariba Reservoir on suspended sediments and biogeochemistry of the middle Zambezi River. Kariba Reservoir (A= 5400 m2, V = 160 km3, zmax>90 m) was completed in 1959 and regulates approximately 40% of the Zambezi River's flow. In July 2007 and May 2008 sediment cores were collected in Kariba's four basins to characterize sediment accumulation rates, sources of sediments, and chemical composition. Lead-210 dating of sediment cores indicates sedimentation rates on the order of 1 cm/year. Event driven sedimentation (e.g., high flow) appears important in Kariba Reservoir: visual inspection of sediment cores reveals distinct sediment layers, with thin dark layers separated by sporadic light layers. Chemical measurements support the visual inspections, with elevated OC, N, and P measured in the dark layers, which are presumably enriched in autochthonous OC. A preliminary P budget of Kariba's furthest downstream basin suggests that >80% of P entering the system is removed by sedimentation. This presentation will explore sediment accumulation and chemistry in Kariba Reservoir and the implications for C, nutrient, and particle budgets.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.H53C1085K
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling (0412;
- 0793;
- 1615;
- 4805;
- 4912)