TITLE:
Validation of PSIAC Model for Sediment Yields Estimation in Ungauged Catchments of Tanzania
AUTHORS:
P. M. Ndomba
KEYWORDS:
Calibration; PSIAC Model; Sediment Yields; Tanzania; Validation
JOURNAL NAME:
International Journal of Geosciences,
Vol.4 No.7,
September
27,
2013
ABSTRACT: The main objective of
this paper is to report on preliminary validation results of the newly applied
sediment yields estimation model in Tanzania, the Pacific Southwest
Inter-Agency Committee (PSIAC). This is a follow-up research on the call to customize
simple and/or multi-processes sediment yields estimation models such as PSIAC
in the region. The PSIAC approach is based on a sediment yield classification
scheme employing individual drainage basin characteristics: surface geology,
soils, climate, runoff, topography, ground cover, land use, upland erosion,
channel erosion, and sediment transport. In this study, PSIAC model is built from readily
available environmental variables sourced from Government ministries/agencies
and public domain global spatial data. The sediment classification exercise was
verified with field observations. The set up model was then validated by 31
small dams’ siltation surveys and previous sedimentation study findings. PSIAC
model performance for major part of central Tanzania was good during
calibration (BIAS = 7.88%) and validation (BIAS = 18.12%). Another observation
was that uncalibrated model performs fairly well, though performance improves
with calibration. The extension of the uncalibrated PSIAC model to 3 selected
large basins of Tanzania,
with drainage areas size up to 223,000
km2, registered a satisfactory performance in one of
them with fair performance in the rest. For large basins, the performance seems to correlate
with general ground slope. The higher the slope, the better the performance. It is,
however, not apparent from this study on the threshold drainage area and slope
requirements for better performance of the model. Notwithstanding, the PSIAC
model has improved previous sediment yields estimates based on simple
regressive models. Finally, the paper proposes two main further research works: use of high resolution geospatial
data and additional validation dams siltation data even beyond the central part
of Tanzania, and carries out rigorous study on spatial scale model application limitations.