D4.1 Review of Environmental Models - SEAT Global

now follows the material flows through a system. It is now a stock and flow model as it is
built in STELLA and can provide a visual aid for pollution flows (Schaffner et al, 2009).
The MMFA has been used in conjunction with WASP in Thailand on a catchment known as
the Thachin River Basin (Schaffner et al., 2007), which is perceived as the most polluted river
in Thailand (Simachaya, 2003). The MMFA was used to quantify the nutrient loading and
consequent carrying capacity of the river, by taking into account both agriculture and
aquaculture activities simulating the loading from each to determine the largest polluter in
terms of nitrogen and phosphorus (Schaffner et al., 2009). The model confirmed that
aquaculture was the most significant nutrient polluter in the Thachin River (Schaffner et al,
2009). The benefit of this mode was simulations could be carried out using whatever data
was available (Schaffner et al., 2007). This is a clear advantage as there is often a paucity of
data in such systems. It is also advantageous as the model can be easily adapted for use in
other similar aquatic systems and where data is limited.
It is unadvisable to use the MMFA model on its own for any decision on catchment
management. It is desirable to use it in combination or to complement a system dynamics
model to provide a wider understanding of the workings and carrying capacity for any
aquatic system (Schaffner et al., 2007).
1.3.7 SWAT (Soil and Water Assessment Tool)
SWAT is a long-term assessment tool for simulations of watershed dynamics (Ullrich & Volk,
2009). The basic design of SWAT is in three layers: the sub-basin, reservoir routing and
channel routing (Spruill et al., 2000). SWAT was originally developed for use with nutrient
loading of water sources from land based activities (Huang et al, 2009), and has been used
for estimating nutrient loads to local watersheds in relation to salmon farming.
SWAT2000 was used in the Cannonsville reservoir in New York to simulate nutrient loading
of agricultural practices on the surrounding land, taking into consideration sediment flows
(Tolson & Shoemaker, 2004). Although the model was effective in showing some useful
findings, it was not effective in showing phosphorus loading as a validation method. There
were significant errors between empirical data and simulations (Tolson and Shoemaker,
2004). However, the model demonstrated that agricultural land used for corn was the main
contributor to phosphorus loading to the reservoir, even though the land used for this
purpose only took up approximately 1.2% of the survey area (Tolson & Shoemaker, 2004).
SWAT is a popular model as it has been used in a number of further studies:
In Kentucky to determine monthly runoff in karst areas and was found to have
effective analysis and simulation results for the system in this respect (Spruill et al.,
2000)
In the Vantaanjoki basin in Finland (Barlund & Kirkkala, 2008) to determine
management efficiency in simulating the nitrogen and phosphorus flow in
catchment and water bodies under the Water Framework Directive (WFD) (Barlund
& Kirkkala, 2008). In this case the model did not allow for nitrogen input from
forestry, which is significant and thus limited the model’s use for the present.
However, this can be adapted and used more effectively for management under the
WFD in future (Barlund et al, 2007).
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