Sediment Yield Estimation Using SWAT, Case Study of Upper Awash Basin, Ethiopia
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Date
2018-06
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Publisher
AAU
Abstract
Sediments are very important parameter component in many water resource projects for
studies of reservoir sedimentation, river morphology, soil and water conservation
planning, water quality modelling and design of efficient erosion control structures. High
sediment rates leads to filling of reservoirs and loss of live storage, which eventually
commanding to loss of production potential. Furthermore, evacuation of sediments from
reservoirs is a costly process that can have large environmental impacts. The Soil and
Water Assessment Tool model, a physically based distributed hydrological model, was
used to estimate sediment yield and runoff in the upper awash basin measuring of
11073 km
2
catchment area. The basin shows large heterogeneity in terms of hydrological
parameters, land use land cover and soil features. This research has been undertaken to
analyse the sediment yield at the outlet of the catchment and effects of LULC changes on
sediment yield and flow values. The model has been calibrated and validated using
observed runoff and sediment yield data of 11 years at the basin outlet. The average
values for RSR and
Nash-Sutcliffe efficiency (NSE) for sediment yield are found to be
0.67 and 0.66 and the average values for RSR and
Nash-Sutcliffe efficiency (NSE) for
run-off are found to be 0.71 and 0.71, which are within good limits for sediment and
good limits for runoff respectively. So the overall average annual output for sediment at
the out let point was estimated, which is 5167400Met ton/month or 0.046667
ton/ha/month is model monthly output. High sediment reduction was observed when
agricultural land changed to cropland/savanna/bush land and the value of sediment is
0.03182 ton/ha from overall catchment because cropland/savanna/bush lands are denser
than agricultural land. Here appropriate mitigation measures were recommended to
reduce sediment yield of the catchment. As land development is a continuous process, for
the optimum use of the land and water resources of the area, it is recommended that soil
and watershed conservation practice should be undertaken in order to keep the
sustainability of the reservoir conserning sediment reduction.
Description
Keywords
Sediment Yield, runoff, land use/land cover change, SWAT Model, Upper awash watershed, Ethiopia