Calculating the sediment budget of a tropical lake in the Blue Nile basin: Lake Tana
Other literature type
Zimale, F. A.
Mogus, M. A.
Alemu, M. L.
Ayana, E. K.
Demissie, S. S.
Tilahun, S. A.
Steenhuis, T. S.
(issn: 2199-398X, eissn: 2199-398X)
Soil erosion decreases soil fertility of the uplands and causes siltation of lakes and reservoirs. However, very little
data exists to quantify accurately the impact of sediment on lakes in tropical monsoonal areas in the African highlands. Lake
Tana is one of these lakes in Ethiopia. The objective of this study is to quantify the sediment budget for Lake Tana watershed
with limited observational data. To overcome these limitations we use the Parameter Efficient Distributed (PED) model that
has shown to perform well in the Ethiopian highlands. PED model parameters are calibrated using daily discharge data and
sediment concentration infrequently measured for establishing sediment rating curves for
the major rivers. The calibrated
model parameters are then used to predict the sediment budget for the period 1994–2009. Sediment retained in the lake is
calculated from two bathymetric taken 15 years apart and the sediment leaving the lake is based on
measured discharge and
observed sediment concentrations. Results show that annually on average 34 Mg/ha/year of sediment is removed from the
gauged part of the Lake Tana watersheds. Depending on the
method, 14 to 32 Mg/ha/year is transported from the
watershed of which 82% to 96% (with the upper estimate more likely) is trapped on the floodplains and in the lake.