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Revisiting lake sediment budgets: How the calculation of lake lifetime is strongly data and method dependent

Hanibal Lemma Gebrekidan UGent, Teshager Admasu, Mekete Dessie, Derbew Fentie, Jozef Deckers, Amaury Frankl UGent, Jean Poesen, Enyew Adgo and Jan Nyssen UGent (2018) EARTH SURFACE PROCESSES AND LANDFORMS. 43(3). p.593-607
abstract
Lake sedimentation has a fundamental impact on lake lifetime. In this paper, we show how sensitive calculation of the latter is to the quality of data available and assumptions made during analysis. Based on the collection of a large new dataset, we quantify the sediment masses (1) mobilized on the hillslopes draining towards Lake Tana (Ethiopia), (2) stored in the floodplains, (3) transported into the lake, (4) deposited in the lake and (5) delivered out from the lake so as to establish a sediment budget. In 2012-2013, suspended sediment concentration (SSC) and discharge measurements were made at 13 monitoring stations, including two lake outlets. Altogether, 4635 SSC samples were collected and sediment rating curves that account for land cover conditions and rainfall seasonality were established for the 11 river stations, and mean monthly SSC was calculated for the outlets. Effects of the floodplain on rivers' sediment yield (SY) were investigated using measurements at both sides of the floodplains. SY from ungauged rivers was assessed using a model that includes catchment area and rainfall, whereas bedload and direct sediment input from lake shores were estimated. As a result, the gross annual SY was c. 39.55 (+/- 0.15) Mt, dominantly from Gilgel Abay and Gumara Rivers. The 2.57 (+/- 0.17) Mt sediment deposited in floodplains indicate that the floodplains serve as an important sediment sink. Moreover, annually c. 1.09 Mt of sediment leaves the lake through the two outlets. Annual sediment deposition in the lake was c. 36.97 (+/- 0.22) Mt and organic matter accumulation was 2.15 Mt, with a mean sediment trapping efficiency of 97%. Furthermore, SSC and SY are generally higher at the beginning of the rainy season because soils in cultivated fields are bare and loose due to frequent ploughing and seedbed preparation. Later in the season, increased crop and vegetation cover lead to a decrease in sediment production. Based on the established sediment budget with average rainfall, the lifetime of Lake Tana was estimated as 764 to 1032 years, which is shorter than what was anticipated in earlier studies. The sedimentation rate of Lake Tana (11.7 +/- 0.1kg m(-2)yr(-1)) is in line with the sedimentation rates of larger lakes in the world, like Lake Dongting and Lake Kivu. Copyright (C) 2017 John Wiley & Sons, Ltd.
Please use this url to cite or link to this publication:
author
organization
year
type
journalArticle (original)
publication status
published
subject
keyword
NORTHERN ETHIOPIAN HIGHLANDS, BLUE-NILE, SOIL-EROSION, TANA BASIN, OVERBANK SEDIMENTATION, BEDLOAD TRANSPORT, LATE PLEISTOCENE, MANAGEMENT, TOOL, RATING CURVES, AMAZON RIVER, suspended sediment concentration, floodplain deposition, lake, sedimentation, sediment budget, Lake tana, Ethiopia
journal title
EARTH SURFACE PROCESSES AND LANDFORMS
Earth Surf. Process. Landf.
volume
43
issue
3
pages
15 pages
publisher
Wiley
place of publication
Hoboken
Web of Science type
Article
Web of Science id
000427007100003
ISSN
0197-9337
1096-9837
DOI
10.1002/esp.4256
language
English
UGent publication?
yes
classification
U
id
8562177
handle
http://hdl.handle.net/1854/LU-8562177
date created
2018-05-18 07:32:53
date last changed
2018-05-18 07:32:53
@article{8562177,
  abstract     = {Lake sedimentation has a fundamental impact on lake lifetime. In this paper, we show how sensitive calculation of the latter is to the quality of data available and assumptions made during analysis. Based on the collection of a large new dataset, we quantify the sediment masses (1) mobilized on the hillslopes draining towards Lake Tana (Ethiopia), (2) stored in the floodplains, (3) transported into the lake, (4) deposited in the lake and (5) delivered out from the lake so as to establish a sediment budget. In 2012-2013, suspended sediment concentration (SSC) and discharge measurements were made at 13 monitoring stations, including two lake outlets. Altogether, 4635 SSC samples were collected and sediment rating curves that account for land cover conditions and rainfall seasonality were established for the 11 river stations, and mean monthly SSC was calculated for the outlets. Effects of the floodplain on rivers' sediment yield (SY) were investigated using measurements at both sides of the floodplains. SY from ungauged rivers was assessed using a model that includes catchment area and rainfall, whereas bedload and direct sediment input from lake shores were estimated. As a result, the gross annual SY was c. 39.55 (+/- 0.15) Mt, dominantly from Gilgel Abay and Gumara Rivers. The 2.57 (+/- 0.17) Mt sediment deposited in floodplains indicate that the floodplains serve as an important sediment sink. Moreover, annually c. 1.09 Mt of sediment leaves the lake through the two outlets. Annual sediment deposition in the lake was c. 36.97 (+/- 0.22) Mt and organic matter accumulation was 2.15 Mt, with a mean sediment trapping efficiency of 97\%. Furthermore, SSC and SY are generally higher at the beginning of the rainy season because soils in cultivated fields are bare and loose due to frequent ploughing and seedbed preparation. Later in the season, increased crop and vegetation cover lead to a decrease in sediment production. Based on the established sediment budget with average rainfall, the lifetime of Lake Tana was estimated as 764 to 1032 years, which is shorter than what was anticipated in earlier studies. The sedimentation rate of Lake Tana (11.7 +/- 0.1kg m(-2)yr(-1)) is in line with the sedimentation rates of larger lakes in the world, like Lake Dongting and Lake Kivu. Copyright (C) 2017 John Wiley \& Sons, Ltd.},
  author       = {Gebrekidan, Hanibal Lemma and Admasu, Teshager and Dessie, Mekete and Fentie, Derbew and Deckers, Jozef and Frankl, Amaury and Poesen, Jean and Adgo, Enyew and Nyssen, Jan},
  issn         = {0197-9337},
  journal      = {EARTH SURFACE PROCESSES AND LANDFORMS},
  keyword      = {NORTHERN ETHIOPIAN HIGHLANDS,BLUE-NILE,SOIL-EROSION,TANA BASIN,OVERBANK SEDIMENTATION,BEDLOAD TRANSPORT,LATE PLEISTOCENE,MANAGEMENT,TOOL,RATING CURVES,AMAZON RIVER,suspended sediment concentration,floodplain deposition,lake,sedimentation,sediment budget,Lake tana,Ethiopia},
  language     = {eng},
  number       = {3},
  pages        = {593--607},
  publisher    = {Wiley},
  title        = {Revisiting lake sediment budgets: How the calculation of lake lifetime is strongly data and method dependent},
  url          = {http://dx.doi.org/10.1002/esp.4256},
  volume       = {43},
  year         = {2018},
}

Chicago
Gebrekidan, Hanibal Lemma, Teshager Admasu, Mekete Dessie, Derbew Fentie, Jozef Deckers, Amaury Frankl, Jean Poesen, Enyew Adgo, and Jan Nyssen. 2018. “Revisiting Lake Sediment Budgets: How the Calculation of Lake Lifetime Is Strongly Data and Method Dependent.” Earth Surface Processes and Landforms 43 (3): 593–607.
APA
Gebrekidan, H. L., Admasu, T., Dessie, M., Fentie, D., Deckers, J., Frankl, A., Poesen, J., et al. (2018). Revisiting lake sediment budgets: How the calculation of lake lifetime is strongly data and method dependent. EARTH SURFACE PROCESSES AND LANDFORMS, 43(3), 593–607.
Vancouver
1.
Gebrekidan HL, Admasu T, Dessie M, Fentie D, Deckers J, Frankl A, et al. Revisiting lake sediment budgets: How the calculation of lake lifetime is strongly data and method dependent. EARTH SURFACE PROCESSES AND LANDFORMS. Hoboken: Wiley; 2018;43(3):593–607.
MLA
Gebrekidan, Hanibal Lemma, Teshager Admasu, Mekete Dessie, et al. “Revisiting Lake Sediment Budgets: How the Calculation of Lake Lifetime Is Strongly Data and Method Dependent.” EARTH SURFACE PROCESSES AND LANDFORMS 43.3 (2018): 593–607. Print.