Towards improved parameter estimation in streamflow predictions using the ACRU model.
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Date
2002
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Abstract
An unresolved problem in hydrology has been to establish relationships between
catchment attributes and the flow characteristics of the stream. Such information is
commonly sought to improve streamflow predictions, often in a process of
extrapolating research results obtained from relatively few, but intensively studied
catchments, to a broader region. This study has attempted to clarify terminology
related to streamflow generation processes and mechanisms, and to investigate
relevant physiographic and climatic characteristics which critically influence the
hydrological responses of catchments. Fourteen catchments were selected for this
study. They comprised both operational and research catchments. These catchments
were selected to be representative of variations in climate, topography, vegetation
and geology occurring throughout the Republic of South Africa (RSA). The selection
of catchments was also restricted to areas less than 100 krrr', and to the higher
rainfall regions of the country, where runoff is significant and any land use changes
may lead to marked changes in evapotranspiration and streamflow. A catchment was
also selected from an arid zone in the USA, to capture the flow characteristics that
are typical of such areas. A frequently applied simulation model on RSA catchments
is the ACRU model. While physical-conceptual in structure it contains some
parameters which, while not determining total streamflow magnitudes, governs the
time distribution of the streamflows generated. Two such parameters from the ACRU
model selected were the coefficient of baseflow response (COFRU) and the
quickflow response fraction of the catchment (QFRESPj. These parameters are not
explicitly physically based, and therefore improved guidelines of initial parameter
values are required. Relationships between catchment characteristics and these two
parameters were sought to provide guidelines for effective parameterisation of these
parameters in future studies. Trends between QFRESP and COFRU, and catchment
physical and climatic attributes such as catchment area, average depth of the soil
profile, maximum basin relief, MAP and profile plant available water were identified,
and could prove useful to future users of the ACRU model and guide experimentation
in estimating initial parameter values. However, only a single significant multiple
regression model was obtained for the baseflow release fraction COFRU from a
catchment using MAP, catchment area and profile plant available water.
Description
Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2002.
Keywords
Streamflow., Streamflow--South Africa--Computer simulation., Hydrologic models., Theses--Bioresources Engineering and Environmental Hydrology.