Water quality modelling of an impacted semi-arid catchment using flow data from the WEAP model
The continuous decline in water quality in many regions is forcing a shift from quantity-based water resources management to a greater emphasis on water quality management. Water quality models can act as invaluable tools as they facilitate a conceptual understanding of processes affecting water...
Main Authors: | , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2018-04-01
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Series: | Proceedings of the International Association of Hydrological Sciences |
Online Access: | https://www.proc-iahs.net/377/25/2018/piahs-377-25-2018.pdf |
Summary: | The continuous decline in water quality in many regions is forcing a shift
from quantity-based water resources management to a greater emphasis on
water quality management. Water quality models can act as invaluable tools
as they facilitate a conceptual understanding of processes affecting water
quality and can be used to investigate the water quality consequences of
management scenarios. In South Africa, the Water Quality Systems Assessment
Model (WQSAM) was developed as a management-focussed water quality model
that is relatively simple to be able to utilise the small amount of
available observed data. Importantly, WQSAM explicitly links to systems
(yield) models routinely used in water resources management in South Africa
by using their flow output to drive water quality simulations. Although
WQSAM has been shown to be able to represent the variability of water
quality in South African rivers, its focus on management from a South
African perspective limits its use to within southern African regions for
which specific systems model setups exist. Facilitating the use of WQSAM
within catchments outside of southern Africa and within catchments for which
these systems model setups to not exist would require WQSAM to be able to
link to a simple-to-use and internationally-applied systems model. One such
systems model is the Water Evaluation and Planning (WEAP) model, which
incorporates a rainfall-runoff component (natural hydrology), and reservoir
storage, return flows and abstractions (systems modelling), but within which
water quality modelling facilities are rudimentary. The aims of the current
study were therefore to: (1) adapt the WQSAM model to be able to use as input
the flow outputs of the WEAP model and; (2) provide an initial assessment of
how successful this linkage was by application of the WEAP and WQSAM models
to the Buffalo River for historical conditions; a small, semi-arid and
impacted catchment in the Eastern Cape of South Africa. The simulations of
the two models were compared to the available observed data, with the
initial focus within WQSAM on a simulation of instream total dissolved
solids (TDS) and nutrient concentrations. The WEAP model was able to
adequately simulate flow in the Buffalo River catchment, with consideration
of human inputs and outputs. WQSAM was adapted to successfully take as input
the flow output of the WEAP model, and the simulations of nutrients by WQSAM
provided a good representation of the variability of observed nutrient
concentrations in the catchment. This study showed that the WQSAM model is
able to accept flow inputs from the WEAP model, and that this approach is
able to provide satisfactory estimates of both flow and water quality for a
small, semi-arid and impacted catchment. It is hoped that this research will
encourage the application of WQSAM to an increased number of catchments
within southern Africa and beyond. |
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ISSN: | 2199-8981 2199-899X |