Abstract. Accurate prediction of groundwater table is important for the efficient management of groundwater resources. Despite being the most widely used tools for depicting the hydrological regime, numerical models suffer from formidable constraints, such as extensive data demanding, high computational cost, and inevitable parameter uncertainty. Artificial neural networks (ANNs), in contrast, can make predictions on the basis of more easily accessible variables, rather than requiring explicit characterization of the physical systems and prior knowledge of the physical parameters. This study applies ANN to predict the groundwater table in a freshwater swamp forest of Singapore. The inputs to the network are solely the surrounding reservoir levels and rainfall. The results reveal that ANN is able to produce an accurate forecast with a leading time of 1 day, whereas the performance decreases when leading time increases to 3 and 7 days.
IntroductionPhysical-based numerical models are widely used in groundwater table simulation. Different numerical models have been developed for different regions with different objectives, such as to describe regional groundwater flow patterns, and to understand local hydrological processes. (e.g. Matej et al., 2007;Pool et al., 2011;Yao et al., 2015). Numerical models solve the deterministic equations to simulate the groundwater systems based on the knowledge of the system characteristics, initial conditions, system forcings, etc. To develop a groundwater numerical model, essential data include: topography, geological coverage, soil properties, land use map, vegetation distribution, evapotranspiration information, hydrologic and climatic data, etc. Extensive data demanding makes numerical models highly data dependent and data sensitive. Fitting a physical model is not possible when data are not sufficient; the accuracy of the numerical model to a great extent depends on how accurate the model inputs are. Numerical models are also less competent in forecasting as most of the system forcings (e.g. evapotranspiration, rainfall) are less predictable. As a result of aforementioned constraints, numerical models tend to produce imperfect results in spite of the perfect knowledge of the governing laws (Sun et al., 2010).To combat the deficiencies of the numerical models, artificial neural networks (ANNs) have emerged as an alternative modelling and forecasting approach with a variety of applications in hydrology research (e.g. French et al., 1992;Maier and Dandy, 2000). Unlike the traditional physicalbased models, the ANN-based approach does not require explicit characterization of the physical properties, or accurate representation of the physical parameters, but rather simply determines the system patterns based on the relationships between inputs and outputs mapped in the training process. ANNs typically use input variables that are more accessible to make predictions, and therefore circumvent the data reliance inherent to the numerical models. As compared to classical regression techni...