2.2 Observed data at St. Andre MAR facility
Temperature and groundwater elevation data were obtained from the
monitoring wells using the transducers. The monitoring wells are
represented as WP, which is the abbreviation of Dutch words “Waarneming
Putten”, meaning observation wells. The convention used for numbering
the wells are shown in fig. 3. All monitoring wells have a series of 4
levels of well with screen openings at different depths. The level 1
wells have screens at -20 mTAW, which are the deepest wells and level 4
wells are the shallowest wells having screens at 3.55 mTAW. Level 2
wells are located at a depth of -5 mTAW and level 3 wells are at 0.55
mTAW. The negative mTAWs indicate that they are below the standard
reference of low tide sea level and the positive mTAWs are above the
reference elevation. The ground elevation around the pond is 7.1 mTAW
and the pond bed elevation is 6.2 mTAW. However, the obtained data had
periods of missing information. To combat this problem, Genetic
Programming (GP) was employed. GP is a form of evolutionary algorithm,
which is a component of machine learning. GP is a powerful tool, which
employs non-linear regression to develop a relationship between
variables with very little domain knowledge (Koza, 1994). The
statistical indices used for evaluating the efficiency of the model are
coefficient of determination (R2) and Nash-Sutcliffe
Efficiency (NSE). Temperature data of water in the infiltration ponds
are available from January 2014 to June 2015 and from April to June
2016. For the missing period, Genetic Programming (GP) was employed to
develop a non-linear relationship between minimum and maximum air
temperatures with water temperature in the infiltration ponds. Fig 4
shows the equation tree consisting of numeric operators and 2 variables,
X1 and X2. X1 is the
minimum air temperature, X2 is the maximum air
temperature and Y is pond water temperature.
Fig. 3 Schematic reference of well screen depths at St-André
MAR site
Fig. 4 Genetic Programming equation tree for prediction of pond
water temperature. X1 is the minimum air temperature, X2 is the maximum
air temperature and Y is pond water temperature