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also likely to affect the surface and groundwater of Nee Soon freshwater swamp forest, 
both locally and in its surroundings. 
A numerical model, which can anticipate the likely changes in surface and 
groundwater, and their impacts on fauna and flora, is highly important to any area, 
and to the Nee Soon catchment in particular, considering the national conservation 
significance of this, the last pristine freshwater swamp forest in Singapore (Sun et 
al., 2015). The Mike-SHE eco-hydrological modelling system, as a multi-physics 
modelling package, is well suited to simulate integrated catchment hydrology (DHI, 
2014). Mike-SHE simulates water flow over the entire land surface based on different 
phases of the hydrological cycle from rainfall to river flow, via various flow processes, 
such as overland flow, infiltration into soil, evapotranspiration, and groundwater flow. 
It is thus an ideal tool for simulating the hydrology of wetlands. Such a modelling 
system, however, requires model inputs. Essential input data include: topography, 
geological coverage, soil properties, land use maps, hydro-meteorological data, 
evapotranspiration information, vegetation distribution, etc. For the Nee Soon 
freshwater swamp forest, the complex hydro-geological characteristics and the strict 
requirements for conservation hinder the installation of monitoring stations to acquire 
the necessary information. This study, therefore, adopted a combined approach to 
develop the numerical model, which makes use of field survey data and the alternative 
remote sensing data. 
The numerical model is calibrated based on groundwater table and water level 
measurements; it is then combined with the future projected rainfall from the Regional 
Climate Model (RCM) to assess the hydrological impacts that might result from future 
climate change. A few possible management strategies are suggested corresponding to 
the severe drought and flood scenarios in order to maintain favourable hydrological 
conditions for conserving the local ecosystem. 
Modelling Scheme 
Study area 
Fig. 1 shows the geographical location of the Nee Soon freshwater swamp forest in 
Singapore. Details are given by Chong et al. (2018), Clews et al. (2018), Davison et al. 
(2018) and Nguyen et al. (2018). 
With an estimated area of about 485 ha, the catchment of the freshwater swamp 
forest covers the lower parts of shallow valleys with slow-flowing streams and a little 
higher ground supporting dryland forest. The elevation of the Nee Soon catchment 
ranges between 1 m to 80 m above mean sea level (MSL). The aquifer depth in the 
Nee Soon catchment is from 20 m to 40 m, and the major soil type features silty sand 
with a hydraulic conductivity of 4.05 x 10 5 m/s. The boundary of the study area on 
the east is defined by catchment delineation based on the catchment topography, the 
administrative boundary of the Central Catchment Nature Reserve, and the physical 
barrier formed by a major highway. The boundary on the west and south is defined by 
